Chrysler 300M Overheating mystery

becarisbecaris Member Posts: 3
I have a 1999 Chrysler 300M. It is overheating in a strange way. After driving 3 miles it begins to overheat. Sometimes it will overheat, then quickly drop back down to normal temperature, but then overheat again. When going up any grade it definitely overheats.

I have had the car in for repair at two mechanics. Both have GIVEN UP on fixing the problem. Here is what they tried: Replacing the radiator, replacing both radiator fans, replacing the thermostat, replacing the water pump. The car does not lose coolant. None of these repairs has helped the problem what-so-ever. It's a mystery.


  • quietflyerquietflyer Member Posts: 33
    Given how fast you say it overheats and goes back to normal it sounds more like the electronic temperature sensor to the gauge is going bad. I have seen this with the fuel sensor. I would have a full tank and suddenly the low fuel light comes on and the gauge drops to empty. Then it would just as quickly go back to full. On my '99 300M the temperature gauge barely comes off the cold mark in three miles. Does your car act different when the gauge indicates overheating?
  • becarisbecaris Member Posts: 3
    To answer your question, I'm not noticing it acting differently, but I haven't let it overheat to any extreme amount. I stop the car if it gets to about 3/4 of the guage so that I don't hurt the engine. I have never let it get all the way into the red.

    I don't know that the problem is the sensor because it overheats when you go up a grade... every time. It is slower to overheat on a level street or going downhill. If I get on a freeway and go 70+ mph it overheates, if I back off to 50 mph it cools back down somewhat.
  • tayl0rdtayl0rd Member Posts: 1,926
    That's some weird stuff happening. Maybe you have air in the cooling system? Take it to a shop and have them bleed the cooling system, or do it yourself.

    Now that I think about it, air in the system seems to be the most logical problem. You say it happens every time you go uphill. That would indicate (to me) that an air bubble is traveling forward to the water pump, in which case the coolant isn't going to be pushed through efficiently, if at all. You also say it happens when you're traveling at highway speeds. Again, that would indicate air is getting to the pump. The inherent cavatation of the pump at those speeds only exacerbates the problem and brings coolant circulation to pretty much a trickle. When you slow down, the cavatation is reduced and coolant flows more efficiently.

    In closing, just get the air out of the system and you'll be fine. ;) Good luck! :)
  • becarisbecaris Member Posts: 3
    Thanks for the suggestion, and I'll certainly take a look to make sure there is no air in the system. However, you would think that after the radiator and water pump were replaced by a mechanic that they would have gotten the air out of the system since they had to fill it again. It overheated before the change of water pump, and afterwards, with no improvement.
  • tayl0rdtayl0rd Member Posts: 1,926
    They may have forgotten to bleed the air out. Another possibility is that you have a small crack in one of your radiator hoses. Has your coolant level remained the same?
  • brendalou22bbrendalou22b Member Posts: 1
    Question...did you ever find out what caused this overheating? I have a 2002 300m and it is doing the same thing. We thought it might be the thermostat? the car is torn apart right now so if it is something else would you let me know???
  • rider62rider62 Member Posts: 13
    I have 1999 300m and it just started over heating.
    I rotated radiator flush in the system after it cooled down.
    I will began to drain after a days down time.
    Some things that I've noted is that the antifreeze was broken down and the last filler used prestone dex-cool with silicate. I am thinking that this may have cause slugging or just broke down the coolant's ability to perform.
    Q. Since I have opened a manual, although I do have some mechanical attitude, how to access the radiator drain plug and what bolts on the engine mount to remove to rock up the engine?
  • rider62rider62 Member Posts: 13
    Q.1. Is it a good idea to cut into cooling system hoses to add a flush kit with the tee, like the one sold at auto stores?
    2. Where is the easiest access to the radiator drain plug?
    3. What bolts are to be removed to rock up the engine to replace the pulley compressor belts and serpentine belt?

  • rider62rider62 Member Posts: 13
    I found the problem, got it fixed. After I did the coolant flush, I started the car and notice one of two cooling fans not working. That also explains while the A/C didn't turn out cold air, nevertheless, I used a simple hand held diagnostic and it gave a code for "fan relay."
    They are located under the hood on the drivers side with the fuse box. Found blown fuse and the fuse was blown because of the fan motor seizing.
    Dual or combo fans cost about $300 new from MANUFACT. but I saw online for as little as $150. The labor is about $65-$70 hrly with about 2-2 1/2 hrs to do it right.
  • cmitchell18cmitchell18 Member Posts: 1
    I have been having the same ongoing problem for a year and a half now. What ended up being the problem? I have changed the radiator, thermostate, therostat houseing, bleed the system, changed hoses and the feels like everything.
  • phaex11phaex11 Member Posts: 2
    My 99 300m did the same thing. It started with a loud vibrating noise coming from under the hood which was intermittent at first. Eventually the noise went away and the temperature was reading close to red. I parked the car and looked under the hood. The 40 amp hi / low fan fuses both were blown. I assumed one of the two fans siezed and blew the fuses. The A/C stopped working at that time also. I ordered a replacement fan from which has an ebay store. I got the fans and shroud for $123.00 with shipping! UPS tracking shows I will receive it on 7/8/08. My local mechanic will install it for $100.00.
  • quietflyerquietflyer Member Posts: 33
    I had the same problem a few years ago. The fuse for the fans also provides power to the A/C compressor clutch. They did not want the A/C to run with no fans. When you get the fans replaced and new fuses the A/C will work again.
  • davemc2davemc2 Member Posts: 2
    I have a 2001 300m with the 4 CD in-dash changer. 95% of the time I cannot change to the CD either from the steering wheel or the stereo console. Every once in a while, I can. When it is in this failure mode, I cannot control anything (even the volume) from the steering wheel. I have pulled both the radio/tape player and the changer from the dash to look for loose cable etc. but no luck. With a tape in the player, I can play a tape but still cannot control from steering wheel. On the rare occasion it is working, everything works from the steering wheel.
    Any ideas ?
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    Overheating can be caused by things as seemingly unrelated as sparkplugs. Cars from the 60's are a testiment of that fact , in that you will definately notice the engine's normal operating temperature variances , especially if you install the wrong sparkplugs.

    It's best to stick with the manufacturers suggested spark plugs , as the entire car's components are calibrated to both their performance and heatrange. If a spark plug is running too hot , it will make the engine run too hot. To the contrary , a spark plug that is running too cool , which means it is actually hardly sparking at all , your engine will show stalling characteristics. (ie: poor heat for defrosting , or hard starting). Bear in mind that the manufacturer has calibrated every component under the hood to a specific type of sparkplug , which promotes the best possible performance and reliability. You should always refer to any decal that has been fixed to the radiator cover or frame , where specific updates for your engine are posted.

    In the case of the 300m - 3.5L V6 , the proper sparkplug is an NGK ZFR5LP-13G [Laser/Platinum/Premium]. As a matter of fact , I just bought a 2002 300m Special with 230,000km on it , where the original sparkplugs were still in it. The engine was starting and running fine , while the temperature was approx. 50% max. on the gauge scale at highway speeds , until I changed the plugs with 6 new NGK's as above. That 1 change I made , made it so that the temperature gauge showed a 50% decrease , and the only time the temperature rose was when I was stopped at a light or stopsign. In other words the temperature began to fluctuate where it wasn't before.

    Especially important is the radiator water/coolant mixture. I am 1 of those guys who doesn't pay attention to the specifications on coolant labels , especially since there are so many different brands available these days. I use the in-dash temperature gauge to tell me how to set the mixture , although there are many rules of thumb when it comes to filling a radiator. As I said above , the sparkplugs play a major role , and they do effect how you set the radiator mixture as well. So .. once you have the right sparkplugs , you simply drain the radiator and start from scratch (best case scenario) , and add the recommended mixture to the radiator , which you are going to adjust right afterwards with either water or coolant/antifreeze - using the in-dash gauge as your meter.

    This adjustment can be confusing , especially since etholene glycol can be called coolant or anti-freeze because it actually does both. #1 rule of thumb is NOT to add too much anti-freeze to the radiator : you can go with 50/50 (BCS) , 60/40 or whatever is suggested on the product , but 50/50 is the best. 50/50 makes it so that you can adjust up or down more easily and accurately , using either water or more coolant/anti-freeze to achieve the correct balance : in accodance with your in-dash temperature gauge.

    #2 rule of thumb is to NOT add too much water. Make sense? With a 50/50 mixture (where the radiator is not yet completely full) , [leave out approx. 2 to 3 Litres of room] , more on larger engines , you start the engine to get a reading from the in-dash temperature gauge at idle. The best way to fill any radiator is to use the empty coolant jug , as your waterjug , by filling it with the exact same amount before pouring the water into the coolant in the radiator. Guessing , by using a garden hose is not recommended nor accurate.

    #3 rule of thumb , never fill a radiator with coolant or water by themselves. NEVER ! Either one will cause an extreme overheating condition , except in winter conditions where you might be driving in the area of the North Pole (they use more etholene glycol as "anti-freeze".) The reasons are , that water boils quickly - which turns the water into steam. And coolant/anti-freeze boils at a much higher temperature , but takes alot longer than water to cool off [ coolant holds the heat like red hot iron does ] , where too much can make it so that the radiator or cooling system is overwhelmed by the time it takes for the coolant to be effected to any degree where overheating will not occur.

    Depending on what your in-dash temperature gauge results are with the engine running at idle only (rad is not full yet) , you can determine what has to be added to finish the job properly and accurately. Most gauges should show a reading at the exact half-way mark on the gauge , so you have to determine which side of the gauge the reading is , and fill accordingly. If the guage shows a little below halfway after 5 minutes of the engine running at idle : that means it is running cool. If the gauge shows a low reading (cooler) , this is where the adjustment gets tricky.

    #4 rule of thumb : to make the engine run cooler , add coolant/anti-freeze ; to make the engine run hotter , add water. Consequently , if your intitial fill test , shows that the engine runs slightly hot , you will want to adjust your radiator with a mixture of more coolant/antifreeze.

    While the radiator only has approx. 2 litres of space remaining , you can pour in either water or coolant/anti-freeze as needed by themselves , and re-use the gauge after having increased either one to tell you when to stop. [But you must run the engine for 5 minutes and increase the revs slightly to highway rpm's , and let the engine run until the temperature gauge needle has stopped moving , usually 7 minutes]. Primarily , by using the in-dash gauge , you want to have the temperature gauge needle positoned in the center. Once you have achieved that , you can complete the fill with the 50/50 mixture , as you are only filling the space in terms of volume within any sized radiator. So.. you can use this method to properly and safely fill your radiator in less than 15 minutes.

    I have personally used this method to drive in a variety of both cold and hot conditions , from Maine to California , through the desert heat especially , where : if you don't have a balanced radiator mixture , you will soon see the warning lights come on in the dash - when climbing long hills or mountains.

    [Best Case Scenario's] : #1
    You are driving in the Mojave Desert , or any environment where the temperature is hot , and you see the in-dash temperature gauge rising to the 3/4 area on your gauge. What do you do? You stop , and let the engine cool down. Open the radiator cap when it is safe , and so that you don't lose any coolant at all. Being too hot , in a hot environment , you need to add coolant , which means less water will boil in your radiator. Then you can proceed and note that the in-dash temperature gauge shows that you are running much cooler and safer. You will have to use a hose to remove some of the existing mixture from the radiator , and judge how much by the intensity of the temperature increase you experience prior to deciding to adju
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    As is with most luxury cars , in the past , where you have a much wider variety of electronic connections and options , the battery is of utmost concern compared to vehicles that don't have nearly as many. With the 300m , it is no different , but in fact , a little more common , due to where the battery is actually located - not to mention that the passenger side inner fender has a rather large vent incorporated there , where water , ice , salt , snow , and road debris can accumulate and also , most importantly increase the period over which the battery terminals can become corroded - where the PCM is not receiving ample power etc.

    The 300m requires that you remove the passenger side wheel , the inner fender portion which includes the vent , and is also the hatch where the battery can be removed. The battery can't be removed through the top , it slides out towards the passenger side wheel. Bear in mind that the 300m's PCM also calculates how much voltage is being produced at the alternator , and the computer will shut down any accessories such as interior lights , when a condition of low amperage is measured at the battery/alternator automatically by design. That means if your battery cables have a poor connection to the PCM , you might see things like the interior lights shutting off after a few minutes , even if you have a door open or the interior light on. That feature makes it so that the battery will not run down or remain in a state where the alternator/voltage regulator is running at full capacity in a constant attempt to fully charge the battery.

    In the 300m , there isn't any ammeter or voltage meter in the dash , but there is , in their place , a "check engine light" , which functions as a meter for that purpose. So ... if your battery connections are poor , you will see a check engine light come on , and/or you may see other malfunctioning lights within the dash , as a direct result of a poor connection between the PCM and it's power source (the battery). These malfunctioning dashlights , are the same as when your engine stalls while the ignition is in the RUN position while driving , all of the dash lights will come on and stay on until the ignition switch is turned off. This is also why you may see that the lights might not come on if you wait for a while before restarting your engine , but eventually come back on again after a short period of time as before.

    The ammeter or voltage meter has become a device or sensor which triggers a shutdown of some accessories , in a situation where the PCM/Battery connection is poor or lacking/short or otherwise not normal. These shutdowns can include things like stereo controls or units of particular requirements for battery /alternator power. Which could explain why a cassette deck might work , while the CD changer won't , they have different power consumption requirements and usages.

    On the 1 hand , the battery is well protected in terms of it's available performance and lifetime , while on the other , it is more difficult to service/maintain in it's exisiting location. When you weigh the differences , it is possible that the battery could last the lifetime of the vehicle in it's present design , saving enough money , to have the battery serviced from time to time without having to worry about replacing the battery 4 times during the vehicle's lifetime or more.

    While the 300m's design makes it so that the battery will outlast any other manufacturers designs by as much as 50% or more ( 10 years instead of 5 years ) , the vehicle's computer is also protected from things like shortcircuits and current overloads (including automatic sensor adjustments made by the computer fulltime) , where the computer can become little more than a sensing device for the entire vehicle , and wear out. I like the design , and I see that it is working as new , even 10 years later. I think servicing the battery is much easier even in the 300m , than buying a new computer or having everything else serviced as a result of a malfunctioning set of sensors in the vehicle , which is also effecting the performance of the vehicle full time as well. Servicing everything else , is not an option.
  • semitech27semitech27 Member Posts: 1
    ur head gaskets are blown buba get in the shop and replace them before u blow ur engine
  • hotrodmommahotrodmomma Member Posts: 1
    I have a 300m that I love bought it at 93,000 miles and now have 132,000. I have problems with it overheating. Within the past year and a half had to change the thermostat. Engine light is on also. Just overheated 2 days ago so we put another thermostat in it. Seems to be running good now. Anyone else with this problem? Thanks
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    edited June 2012
    I would say , because you had to replace the thermostat twice , something is wrong. The first thing to check when you have an overheating problem is the fill/fluid & type in the motor/radiator. You MUST use MOPAR (orange) antifreeze/coolant @ 50/50 mixtures with water. The Chrysler Service manuals stress and warn , that you MUST use orange color coolant in this all aluminum engine. You cannot mix the orange coolant with green colored coolant , and if you do , the manuals stress that if this is done in an emergency , the entire system must be flushed asap , before new proper fluid is applied. Also - the proper MOPAR coolant is not just orange in color , it has special additives in it that other coolants don't have , specifically designed for the 300M's engine.

    At the same time , it is also very important that the proper thermostat from Chrysler is installed to ensure proper operation of the system/s - but , you should be sure that the waterpump is operating properly before you do anything. The best way to check a water pump is to completely drain the system from the lower radiator hose (not the drain cock , they break , even the manuals state so) , and then reconnect the lower radiator hose and refill the system to capacity with ordinary water. With the engine running , you can determine if the proper steady flow of water is exiting either the top or bottom radiator hose in under 30 seconds. If no water is exiting either of the 2 main hoses etc. , then the waterpump is not working. This will allow you to determine the source of the problem , instead of searching.

    Another thing that can actually cause eventual overheating in a normally functioning system , is if your engine is fitted with the wrong spark plugs. If the sparkplug heatrange is wrong , then the cylinders are being allowed to get too hot , which abnormally overheats the coolant in the engine coolant galleys that will eventually force the radiator to store a higher than normal temperature coolant. Then you have an overheating condition throughout the engine/waterpump/thermostat & radiator. You should refer to the sticker on the engine front crossmember to determine the exact sparkplugs for the engine/application , and NOT disregard or use sparkplugs of other types.

    Bare in mind that the 300M also doesn't have a full time fan that runs off of a belt , it has dual electric fans , which are temperature controlled. If those 2 fans are not functioning properly , or at all , this can also be a cause of overheating. Lastly , you should be using 10W 30 engine oil in the summer , and refrain from anyone who claims that 5W 30 engine oil is adequate for yearround use. It is not. (10W 30 is the recommended yearround engine oil). The thicker the oil is , the hotter it will be full time , and the longer it will remain hot. The same is true for your coolant mixture and type. There are many more factors in determining why an engine is overheating , other than a thermostat , or a simple claim of some sort that your heatgaskets must be leaking. Any good reputable mechanic knows that the waterpump must be checked for positive flow before performing any repairs , and then work outwards from there.

    These are the things a customer must know , prior to trusting a mechanic who might be looking to tell you things , or do repairs that will likely (as they know) , eventually put your vehicle in their lot for repair repeatedly. Did they consider that you might damage your vehicle during this type of misguided and misleading information and repair practice? NO. It's all money in their pocket , while YOU are responsible for the cost/s.

    For example : Your car's engine is overheating , and the engine temperature light , and/or gauge shows that it is. You take your car to a service station , and they make a 5 minute diagnosis that you need a thermostat. WRONG ! Even if the engine needed a thermostat , if the waterpump is badly worn , to a point where only a trickle or 50% of the proper pressure is being produced by the waterpump to keep the fluid moving in the system is present , the thermostat repair will only make things worse. You can determine the condition of the waterpump , and when you remove it (even if it was slightly working) , find the blades on the waterpump badly worn to the point where there hardly are blades on the main shaft of the pump. Especially "if" the coolant / antifreeze has been ignored for years , or the wrong (cheap) type has been being used for years on end. Sure , you are out the door for less , only to have a major breakdown afterwards that will be far more costly. This is a no-brainer , like filling a gastank that has a leak in the very bottom of the tank.
  • Kirstie_HKirstie_H Administrator Posts: 11,142
    On behalf of our members, thanks a MILLION for posting such a detailed response to help diagnose overheating issues!

    Need help navigating? [email protected] - or send a private message by clicking on my name.
    Share your vehicle reviews

  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    No problem you're welcome. I have finally managed to create a link for the 10,000+ page Chrysler Technician Service Manuals for the 300M & Concorde models. To my surprise it is jumbled in reproduction and not clear , but you may be able to download it from the link , and have it appear properly in Adobe Reader , where you can view the main index and click/select any portion of the vehicle. Example : air conditioning.

    You can view the manuals (not sure of their quality , doesn't look anywhere near the originals) at :

    You may have to create a dropbox account which is free , and allows you to upload / download up to 2gb of info free. It's simple and quick with no email verification required. Hopefully it can help out those who need quick info as well. If it doesn't work out properly , I can find another place to create a link.
  • hdvideomanhdvideoman Member Posts: 1
    Yes the spark plugs will make the 3.5 overheat. After I had changed my timing belt and water pump my 300m Special started to overheat. It at first seemed like a clogged cooling system but I had replaced my radiator, thermostat, temp sending unit sensor and had bled the system about 50+ times. I had replaced mine with the Bosch +4. Their rating was an 8 which was high. The NGK are 5. Under load of the engine climbing hills or heavy acceleration is when the gage climbed. After running out of ideas besides a head gasket I put the old plugs in as a last resort and the problem is solved. Check those plugs; remember the computer will compensate the timing based on performance of the engine’s components as well as the atmospheric conditions.
  • trip03trip03 Member Posts: 1
    My 2004 Chrysler 300m 3.5L is overheating. Within about 3 to 4 miles the temperature gauge is already between half and 3/4 sometimes even closer to the red. As soon as I get to the highway and get going about 70 mph the temperature gauge goes back down to where it should be. It starts to overheat again when im going slower speeds (under 50) or when I'm sitting at a stop light. What could the problem be?
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    When considering spark plugs for any engine , no matter what mechanic / gearhead / hotrodder or even /engineer says : you have to consider that the spark plugs are "calibrated" for each specific engine. In doing so , the manufacturer has spent tons of money and time on all of the factors involved , of which - engine temperature is a major detail. If the engine overheats with certain types of spark plugs - they will NOT be a consideration. IE : Champion spark plugs , or any other aftermarket type should NOT be your goal.

    When it comes to the 3.5L engine , albeit aluminum based as per the engine block , it relies upon the twin electric fans and it's relays. Those 2 fans should be running as soon as the engine begins to warm up (after 1 minute). On my 02 300M Special Berline , the fans are running within 30 seconds of startup , and - the temperature gauge never reaches 1/2 way , while it will be at 1/4 until I reach a highway , where it climbs 1 line on the gauge. This can be achieved by using the correct coolant , which must be the orange type , not the green type. According to Chrysler , you should be using ONLY the orange/yellow type , and - you should be using the MOPAR specific coolant which has special additives for the aluminum engine , unlike aftermarket suppliers of coolant. IE : aftermarket coolants DO NOT contain the extra additives required for the engine. It's the same , NO BRAINER as the spark plugs issue. Calibrated , and specifically designed coolant. It is such an issue , that the Chrysler Service Manuals specify , that if you "top off" your coolant with GREEN coolant (in an emergency only) , you MUST flush the system as soon as possible and refill with the proper coolant.

    Any time your coolant is questionable , you should also be changing the coolant reservoir bottle cap , because it is pressure sensitive (16lb). The cap is vented to prevent overheating issues , much like those that can occur with a gas cap.

    I am still offering the entire collection of Chrysler Service Technician Manuals , which are over 10,000 pages (on CD only) , for the 2002-2004 300M's / Intrepids and Concorde vehicles - FREE , if anyone needs them. To date since last Christmas 10 people have received them from me FREE. Make no mistake , these are the actual manuals that are instructions from Chrysler , to the service technicians , on a step by step basis for diagnosis and repair of everything from the tires to the computer - including all fault codes - everything. Wiring and schematics too. These are not "owner's manuals".
  • will_dannerwill_danner Member Posts: 1
    Hello, I'd like to learn more about getting a copy of the CD and any others for all the Chrysler, Jeep, Dodge, Ram, SRT, Fiat, and Mopar lines. What do I need to do to get a hold of these CDs?
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    edited October 2012
    will danner : I can send you a copy on CD , which can be used on any computer that runs the Win XP (or later) operating system. All you have to do is : email me ([email protected]) the address you want it sent to. To date only 10 people in almost a year have taken advantage of my offer. The cost for me is approx. $3 each , while you will need Adobe Reader , or some kind of PDF file reader to open the files. There are , some , 89 PDF files contained within the Chrysler 300M/Intrepid/Concorde - 2000~2004 Service Technician Manuals I have. The way I look at it is , that this single disk contains over 10,000+ pages , which would be a huge pile if in paper form , that is just sitting around. So... why not share it?

    Believe me , you won't find a bigger collection , and not nearly as precise instructions directly from the manufacturer. These manuals sell for $80~$100 each , on each area covered : IE ; engine / wiring / fault codes etc. I have no estimate of their worth , but being authentic Chrysler Service Manuals , it could be worth $1000's.

    Just let me know where to send it. No other spam etc. or anything else is involved.
  • chryslergroupchryslergroup Member Posts: 35

    Chrysler Group LLC vehicle service manuals can be ordered through Tech Authority (Web site:

    If you need assistance with purchasing a manual, you can call Mopar's Tech Authority at 1-(800)-890-4038.

    Customer Care
    Chrysler Group LLC
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    The manuals I am offering are free of charge on CD , mailed FREE. They only cover 2000~2004 300M / Intrepid & Concorde vehicles.
  • rdelgado1rdelgado1 Member Posts: 1
    My caregiver is having the EXACT same issue with her 99 300M. Could you please send me a copy of the manual? She took her car to SEVERAL mechanics to no avail! Yesterday she took it to Firestone (against my recommendation) and they told her that they aren't sure how/why but, there is air in her coolant system. They have checked EVERYTHING that you've mentioned in your very detailed posts (thank you for that btw) and can not figure it out. They did bleed the system but the air keeps coming back. They've recommended that she take the vehicle to the dealership.
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    edited February 2013
    When you say that your caregiver's car has been fully checked , to me that means that : the thermostat was changed , the waterpump pressure was confirmed working , all hoses were checked , and the proper YELLOW Chrysler Coolant was replaced. Damage can occur from using the GREEN coolant because it does not contain the proper additives that an all aluminum engine requires. This means that the radiator could be blocked with deposits , where the radiator no longer passes heated fluid temperatures through it's fins to the outside air. If the radiator has alot of buildup inside it's cooling tubes , it becomes a hotbox to the engine , further increasing the engine's temperature as it builds up. The radiator should be fully flushed and inspected to see if there are signs of gross oxidization within it's tubes. The Chrysler Service Manuals specifically refer to the GREEN coolant as : FOR EMERGENCY USE ONLY. And "if" the GREEN coolant is used to top up or fill the system - it must be removed as soon as possible to avoid damaging the entire cooling system. In the case of older vehicles , it is NOT uncommon for radiators to be replaced due to oxidization and just because a radiator is NOT leaking - doesn't mean it's good. The quickest way to simply check a radiator , to see if it's fins are receiving and conducting heat , is to place your bare hand on the bumper side of the radiator while the engine is running or has been running 5~10 minutes. You should feel that the fins themselves are heating up , if NOT , then the radiator is NOT working. If the radiator fins remain cool or cold , the radiator is a BRICK.

    If you want a copy of the (10,000+ page) Service Manuals on CD , just send the address where you want it sent to , to : [email protected]
  • mbelanombelano Member Posts: 1
    edited March 2013
    I having same problem with my 300m 1999, can you send me the repair manual in PDF if possible pls? It would help me a lot! Thanks!my email add is [email protected]
  • gking101gking101 Member Posts: 1
    I can use the Cd. Email me at [email protected]
  • littleearllittleearl Member Posts: 1
    I see you have offered the entire collection of Chrysler Service Technician Manuals , which are over 10,000 pages (on CD only) , for the 2002-2004 300M's / Intrepids and Concorde vehicles - FREE on your Edmund's post.

    I am very interested in these as I am starting to need more in-depth instruction on repairs for my 2002 300M. Could you please send me these? Thanks so very much!
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    Due to forum abusers (who will not even refund me any postage) , the only
    way to get the CD , is to send $6 to my Paypal address : [email protected] - so that I can pay the postage (while the CD's contents are still FREE). If you send $6 , be sure to also send me an email at the same email adress , so that I will send the disk to the address you want it to be sent to. The manuals are authentic Chrysler (not altered or reprinted etc. manuals). Worth alot more than $6. I have sent about 60 of these in the last 2 years. It's a no-brainer .
  • bookiettbookiett Member Posts: 1
    I recently changed the radiator thermostat fan fan relay switch belt and the engine isn't getting hot and the internal cage is only going up to half mark but the water/antifreeze in the resevior is bubbling or should say boiling then steaming out.. Any ideas??
  • pitmanoeuvrepitmanoeuvre Member Posts: 68
    edited July 2013
    If your engine temperatures are normal , then you can assume the waterpump is OK , but you may have put the thermostat in backwards / causing the overflow reservoir to become a radiator. It is possible , that when you change a thermostat and follow how the thermostat is already installed (at which time you are also changing the thermostat because ? the engine is overheating?) , you will have repeated installing the thermostat incorrectly - if you match the direction that the thermostat is placed. Any time you change a thermostat you should be checking that the closed position is towards the engine - while the spring/open position is towards the radiator.

    In some cases boiling of the fluids indicates that the waterpump is not functioning , but your interior temperature gauge should show a maximum reading as well. Whenever there are conflicting symptoms or indications , it would be best to recheck the positioning of the thermostat in the housing. Boiling fluid in the reservoir indicates that the heated fluid has no heat outlet (radiator) , so the fluid keeps heating up until it boils. You should also be replacing the overflow reservoir cap because it is vented (@16lbs) , so if that cap's rubber seal or pressure spring is not working properly , you have no blow off (which , since it is boiling , should already be occurring).

    If nothing really makes sense , you should check that you are using a full fill of the correct coolant/antifreeze. With the all aluminum 3.5L engine , the service manual strongly requires that the "yellow" (not green) coolant is used at all times and not mixed (ever , unless it is an emergency). Aluminum engines , or even engines that only have aluminum heads , must use "ethylene glycol coolant " - as opposed to "polypropylene glycol coolant (which is green etc. for cast iron and steel engines only). Mixing these 2 is not acceptable according to the service manual for the 300M , and even if you do , you MUST flush and refill ASAP. Aluminum requires special protection , while all of the engine's other components and calibrations are set in accordance with ethylene glycol (IE : thermostat / gauge / radiator / hoses / heater etc).

    The last factor is the coolant mixture. I never buy 50/50 mix coolant , because I don't buy water , and those premixed containers are for immediate topups only. When you buy 100% coolant , you mix equal amounts of water in another container and fill from that (50/50). From there , you check the interior temperature gauge and adjust accordingly : if too hot , add coolant , if too cool , add water. Try to add 8 ounces at a time until the gauge balances just under half way. This can be a bit tricky too , when you don't really know if you have a 50/50 mix to work with. I always start by using the rule of thumb that "water" has a much lower boiling point than any coolant. From there , I know that the fluid will boil if there is too much water , or NO coolant at all - BUT , it is possible for coolant to boil as well. If you were to fill your vehicle with coolant only , once the coolant reaches it's higher than water boiling point , it will boil to where it will cool alot slower (take more time) than water. It can be a bit confusing to determine which way to go when you don't know about the actual fill. You can do so though , if you know that you can't run any engine strictly on water , as it will eventually overheat profusely. So... you could have either one of the 2 - too much coolant , or too much water.
  • meyer07meyer07 Member Posts: 1

    After approx 8 months of trying to figure out why my 2000 to 300 M was overheating at high speeds on the highway or stop and go traffic but idling it was just perfectly fine. We then change the thermostat we also changed the water pump plus a new radiator....come to find out the OEM thermostats from Dodge/Chrysler are JUNK!!!! They have that rubber flange around them that does not sit correctly so we learned from my last car which was a 1998 Cavalier let's try a Failsafe from Autozone WITHOUT that rubber flange car runs perfect!!!!  Mind you this car has only 15,000 miles on a brand new motor that I did myself ....needless to say I may keep this pain in the tutu now...

  • tschroeder1tschroeder1 Member Posts: 1
    After spending nearly $2,000 on fixes for our 2004 300M, the tech found casting sand in the coolant. It had collected at the thermostat. It overheated again and we had to clean the system again. Seems like a manufacturer's problem. I read this once before. Not sure how many times this has been the issue.
  • peteolepeteole Member Posts: 4
    trip03 said:

    My 2004 Chrysler 300m 3.5L is overheating. Within about 3 to 4 miles the temperature gauge is already between half and 3/4 sometimes even closer to the red. As soon as I get to the highway and get going about 70 mph the temperature gauge goes back down to where it should be. It starts to overheat again when im going slower speeds (under 50) or when I'm sitting at a stop light. What could the problem be?

  • peteolepeteole Member Posts: 4
    my 02 is doing the same thing, but in any gear above 3000 rpm it cools
  • peteolepeteole Member Posts: 4
    peteole said:

    my 02 is doing the same thing, but in any gear above 3000 rpm it cools

  • peteolepeteole Member Posts: 4
    peteole said:

    peteole said:

    my 02 is doing the same thing, but in any gear above 3000 rpm it cools

    peteole again, anyone with an idea?
  • kamero123kamero123 Member Posts: 2
    I just wanted to tell anyone with these cars chrysler 300m that an engine can overheat from more than waterpump, Thermostat etc, I can tell you first hand, by owning 6 of these it's always either 1 of these two things, when overheating. Has anyone on here ever thought of changing the oil pump. It would overheat Severely in pretty much any condition, but starving the engine of oil causes severe internal friction causing catastrophic engine failure. The 6 cars I rebuilt all had bad oil pumps, weird overheating thus no one could figure it out, the other issue was the fans not working. I've never believed that whole "air in the system" crappie and in 30 years have never actually seen evidence to the contrary. Believe it or not I'm just throwing some advice on here. The oil pump failure won't always trigger a warning light. It will most of the time bring up the oil pressure warning light. Just a thought. I caught that the first time, mysterious just means something you probably won't think of right away. Check oil pressure. 
    Take care
    Would love to hear some polite comments and opinions please
  • kamero123kamero123 Member Posts: 2
    When my first 300m overheated the oil pressure light came on @ first I thought it was because It was about to die, but then when I reved the car it would go off. The temperature never registered the engine overheating but when it did the oil pressure didn't pop up at all. Just another idea. The car is trying to survive by dying and not starting. It will start again. But if it's hard the engine and computer are in self preservation mode. Trying to interpret the signs is hard but just think of a car as a child who can't speak yet. If there's nothing wrong then it doesn't fuss about but if there's something going on then you'll see certain signs. Antifreeze is sweat, oil is blood and well the other fluids are just other fluids
Sign In or Register to comment.