Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Chrysler 300M Overheating mystery



  • 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 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?
  • 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".
  • 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 Posts: 68
    edited November 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 ( 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.
  • Hello!

    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
  • The manuals I am offering are free of charge on CD , mailed FREE. They only cover 2000~2004 300M / Intrepid & Concorde vehicles.
  • 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 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 :
  • mbelanombelano 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
  • gking101gking101 Posts: 1
    I can use the Cd. Email me at
  • littleearllittleearl 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!
  • 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 : - 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 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 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.
Sign In or Register to comment.