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Cooling Systems -- Problems & Solutions (Radiator, Fan, etc)



  • My Jeeps Temp. has been running a little on the hot side the past couple of days. After I turn the vehicle off, the electric fan continues to run. I had to pull one of the teminals off the battery to get it to stop ?
  • leverlever Posts: 3
    Have 01 sebring has no heat at idle. Replaced thermostat was fine for a week then same problem Coolant levels are fine no leaks. System is very clean. Do I need to bleed this system if so how is this done? Could thermostat gone bad already? Any help appreciated, THANKS.
  • leverlever Posts: 3
    Bump, Can anybody help? Thanks Lever
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Yep could be air blockage.

    Is this of any help?
  • leverlever Posts: 3
    Yes I'll work on it tomorrow. Thanks
  • The radiator drain plug on my wife's 1995 Jeep Grand Cherokee is leaking. It's threaded with the hole in the middle of the plug as the drain. I've tightened it but this doesn't help. Is there a seal inside of these types of plugs that could be bad? Thanks.
  • My son owns a 98 Ford Probe. The car runs fine until the temperature outside goes down below 32 degrees, then the car runs hot. He turns on the a/c and that helps. Three new thermostats have been put on, two by mechanics. He has been told by a recent mechanic that it is the head gasket. But it has no symptoms that go with that problem. The temp stays at 271 hot and cold. The temp is supposed to be at 190. We are thinking maybe a sensor is bad. Anyone out there know what could cause this problem?
  • philzyphilzy Posts: 4
    Can anyone tell me where the coolant temp sensor is located on a 2003 dodge neon sxt?
  • I have a 1998 Nissan Sentra with 78,000 miles. A few months ago I noticed that my coolant reservoir was empty and I filled it up. Three weeks later it was back to empty. Previous owner told me the car had overheated on them a few months back. I went to my mechanic who told me that my radiator cap was broken. Of course three weeks later I found out it wasnt since I was still losing coolant. There are no signs of external leaking and this time my mechanic told me it was an internal leak and that the coolant is leaking but is being burned off. Also he mentioned that it would not be worth it to fix so I should just fill up the reservoir every few weeks. I bought Stop Leak powder and put half into my radiator without any success. A few weeks after I did that, I noticed that my coolant reservoir became very dirty and contained some oil and I was still losing coolant. Should I put the other half of the Stop Leak into the radiator? Will I be fine continually refilling my coolant reservoir with coolant? What will happen if I continue this pattern?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Why don't you have a test run for a bad head gasket and then you can make a more informed decision as to what to do next?
  • I have a 98 Sunfire/2.4 motor
    There is no flow to or from the radiator...
    I've already done the following....
    replaced thermostat
    replaced water pump
    radiator rod out
    block check for combustion gases
    still.....nothing... anybody know about this car...?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Well gee...that's kind of impossible as you've stated it...if you hook a water pump with two hoses to a tank of water, it's pretty much gotta flow...

    I wonder if someone put your thermostat in backwards?
  • Problem solved!
    air in the line....I guess...flows now
    Seems that the fan wants to stay running, once it kicks a clue, please let me know
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    most cars have a sensor for the "turn-on" temperature for the fan and oen for the "turn-off" temperature. Maybe one of those leads is grounded or the sensor is bad.

    GEEZ you must have had a boatload of air in there...maybe someone forgot to fill it at all? The pump sucks water up from the bottom of the radiator.
  • After all the repairs....
    Heres what its doing now....
    Got the flow ok, and after running the car, everything seams fine.... but..... the gauge says its hot, and it isnt, and the fan is staying on. I think the fan/gauge sensor is one in the same. Is that where you would go first.....?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    yeah you could replace the temp gauge sensor and see what happens from there. That's a relatively easy experiment.
  • Thanks...
    I will let you know how it turns out!
  • Hello,

    The car overheated for the 3rd time this morning. The first time the car overheated was after a very cold night (below 10 degrees F) and it occured within 15 minutes after letting the car warm up. I felt the top and bottom radiator hoses and they were cold. I also noticed that the car left a trail of coolant behind it.
    I decided to replace the thermostat and water heater. I then refilled the system with coolant and water (estimated a 50/50 mix). The car started and ran fine for the next 2-3 days. Then one morning (after another night of below 10 degree F temps), the car overheated again. Once again, it occured about 15 minutes down the road after I let the car warm up.
    This time I had the car towed to a garage. They said that they ran a pressure test and everything turned out fine. They refilled the coolant and away I went ($150 later). The car started and ran fine for about 6 days. During this time, there were some very cold nights so I thought the solution was that I did not have the correct concentration of coolant to water in the system. Problem solved!
    Not quite. This morning, after SUB ZERO temperatures overnight, I went outside and warmed up the car. I got in after 10 minutes and drove for about 10 minutes down the road. I began to hear gurgling noises from behind the heater controls and I feared for the worst. My fears were confirmed when I began to notice the tell-tale symptoms of overheating. The heat began to get luke warm and the dummy TEMP light appeared. Frustrated, I pulled over and left the car on a the side of a small side-street. I looked in the snow under the car and saw coolant drips. When I pulled over, I could heat the coolant boiling in the overflow container. I went to open the hood and it was frozen shut. I then pulled the hood release lever quite hard and stretched the metal wire so I now cannot open the hood.
    As I hope you can see, I would like to blow this vehicle up, but it has run so well for the short time that I have owned and it was a Florida car so there is not rust. Maybe that is the problem... it is just not used to Connecticut winters!
    Anyway, I should note, if you have not already figured out, I chose not to garage this car. I can kick the Mazda Miata out of the garage for the winter, but I would rather not do that. I see other "older" cars driving on very cold mornings and I notice snow on their hoods and trunks so, I gather that "their" cars were out in the cold all night too. Why can this Buick not tolerate cold temps?

    What can I do??

    Thank you very much for your reply,

  • I have a 03 Mitsu Outlander with two cooling fans. Normally,
    the secondary cooling fan only comes on when the A/C is switched on. Lately, the secondary fan is coming on all the time even when the A/C is off and it is cool outside, and it stays on for 10-15 seconds after the engine is turned off. The temperature gauge is at about the same place it has always been. I checked the coolant level it is fine.
    Don't seem to know what the problem is. Do i need to maybe change thermostat. Thanks for any assistance..........

  • doc25doc25 Posts: 1
    I replaced the intake gaskets and thermostat and now water comes out of my radiator cap as soon as I start the motor.
    What could cause this.
  • well i have a 1992 toyota corolla and it is overheating after 10 minutes.. the theromostat has already been replaced as well as the raditor..when the car is running i can hear the fans turn on and they stay on.. when the car gets to the overheating stage, i can hear the fluid in it boiling.. can anyone help me figure out whats going wrong with it and how do i go by fixing it?
  • well i have a 1992 toyota corolla and it is overheating after 10 minutes.. the theromostat has already been replaced as well as the raditor..when the car is running i can hear the fans turn on and they stay on.. when the car gets to the overheating stage, i can hear the fluid in it boiling.. can anyone help me figure out whats going wrong with it and how do i go by fixing it?
  • kiawahkiawah Posts: 3,666
    Is the waterpump pumping? With the engine cold, take off the cap and make sure there is water in the radiator. Start the engine, and wait for the engine to come up to temperature. You should see the fluid in the radiator begin to flow, the pump drawing fluid from the bottom of the radiator into the engine, and hot fluid coming out of the top hose into the radiator.

    If you don't see the fluid moving, the either the pump isn't pumping, the thermostat isn't opening (but you've said you replaced that) or slight possibly it is air-locked (although this would normally clear by itself).

    If I had this problem and didn't have fluid moving, I would take out the thermostat completely (for diagnostic purposes). No fluid movement now....replace the waterpump.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    That fast an overheat almost has to be a head gasket. Basically you are driving a large teapot that is making boiling water. Of course you can check the water pump but a ten minute overheat is pretty radical. The water pump would have to be shattered internally...a rare but possible occurrence.

    There are many good tests for bad head gaskets. At most auto parts stores you should be able to buy a test kit that can detect carbon monoxide gases in your engine coolant.
  • Hello all. My son broke his serpentine belt on a '95 Golf 1.8 litre, and kept on driving . . . I've now change out the pump, thermostat & thermoswitch (in rad to actuate radiator fan), but after 10-15 minutes of driving, the seemingly "perfect" cooling system (steady temp, pump outlet hose hot, heat inside car, rad fan turning on, etc.) begins to rapidly self-destruct. The heat inside the car is lost, the temp skyrockets, the reservoir blows her top, and the strange thing to me - the rad begins to cool down on one side. Any thoughts ? ? Thanks to all.

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    If the reservoir has pressure in it with a VW engine of this year, you have to suspect a bad head gasket.
  • Not sure if you've fixed yours or not, but I've just done a '95 Golf thermostat (& pump & belts & . . . ). Let me know if you need help. [email protected]
  • Thanks for the quick response Joe. Much appreciated. I picked up an ultraviolet test kit this morning and some coolant die. Do you know where I should be looking fro the "transferred" die after running the engine for awhile?? I'm thinking directly in the pan, or maybe out the tailpipe. I wasn't really sure how else to confirm head gasket trouble. Thanks again.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    That all depends on where the gasket has given could leak COMBUSTION to WATER, or COMBUSTION to OIL, or both.

    I think a better test kit is the one that tests for CO in the coolant itself.

    Also you can pressurize the cooling system, and then pull out a spark plug and see if there's coolant on the tip of it...that's a sure fire method.
  • Thanks Joe. I'll try the UV light kit since I have it, but I think that head is coming off tomorrow morning. Thanks again.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    If he drove the car while it was overheating, that engine will not tolerate too much of that...they aren't like the old Chevy cast iron blocks from 1965 unfortunately. Those heads like to bend a bit. You may need to check the head for straightness if you find a blown gasket. And if the car has high miles, having the radiator cleaned out after a head gasket job is a very good idea.
  • mkeownmkeown Posts: 1
    Does it blow out soon as you crank it with the engine cold? If so-head gasket.
  • The head came off pretty easy Joe (except most of the 13 mil. bolts had rusted to 12's!!). It was warped a fair bit (.012 - 0.014") in the middle. The valves looked pretty good, and unfortunately, so did the head gasket. Regardless, I'm going to get it skinned down about tomorrow, and I picked up new ex. manifold studs, valve guide seals, head bolts (per my German parts guy???), and of course a head gasket. Sure hope this fixes the coolant blowout and skyrocketing temperature after 15 minutes of operation . . . The block seems perfectly flat on top. I checked with three different straight edges. Hey Joe >> do you believe in lapping the VW valve seats a little bit?? They don't looked burnt, but they are discoloured. Thanks for your help with this.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Oh so the head was bent, sounds like. I guess I'd just wire brush the valve seats maybe, but hand-lapping really doesn't work on a modern engine if that's what you meant. If you mean having the machine shop clean up the heads, yeah sure, I'd do that.

    I think you have the problem licked. Such fast and violent overheating really has to come from combustion leaks seems to me.
  • Just finished test driving the rebuilt head. The machine shop took off about .015", replaced the guides and seals and ground the valves and seats. The engine is purring like a kitten. Thanks Joe!!
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Well done! :D
  • kjaxxkjaxx Posts: 2
    I have a 1966 Pontiac Tempest. It had an original straight six in it when we got it, which we later changed out to a 389.

    My problem is the radiator likes to overheat on warm days especially after a medium drive (30-40 mins)at 60-70 mph. The inside thermostat light will come on and if you slow down to 45-50 mph for awhile (when stopping isn't an option) it will cool down and the light will go off. Later, once it has been parked and completely cooled off and checked, the radiator will be extremely low AND the cap on the overflow container will be off (even though it was secure before the drive).

    We've tried changing out the thermostat and it didn't make a difference. Asside from the overflow container cap blowing and spewing coolant when it gets too hot, I'm fairly sure there are no leaks.

    I never drove it extensively enough with the original straight six in it to know if it always did this or just since having the 389 in it. The radiator is original and was not changed out when we switched engines.

    Is it possible that with the larger engine the original radiator just isn't enough to keep it cool? Does it sound like a newer radiator would take care of it, or might there be another problem?
  • kiawahkiawah Posts: 3,666
    I think you should do a cylinder pressure test, to check for a blown headgasket.
  • burdawgburdawg Posts: 1,524
    To run a 389 in this car I'm fairly sure you'll need a larger heavy duty radiator. It also wouldn't hurt to convert it to electric fans. Did you mean the radiator is original, or just the original size? Hard to believe that a '66 would have an "original" radiator.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Yep, you probably need a larger radiator and a different radiator shroud. If they took the shroud off during the engine conversion (to make it fit), that's a no-no right there.

    If you have high speed overheat that's a circulation issue; if you have low speed overheat that's a cooling fan issue); if you have an immediate rapid overheat from cold to warm in 5 mintues, that's usually a head gasket issue or a thermostat issue.

    So it sounds like you have a circulation issue, which suggests a) a bigger radiator, b) correct shroud and c) probably a coolant overflow tank attachment.
  • kjaxxkjaxx Posts: 2
    Sounds like I really need to look into getting a bigger radiator. Thanks for the advice.
  • dave8697dave8697 Posts: 1,498
    '96 Riviera with 3.8 and SC with 156k mi. It runs great and gets better than EPA hwy rating. My cooling fans started coming on as soon as I start car over 1 yr ago. With dual fans running full speed, I suspect that can overcool engine in winter and it can wear out fans that previously hardly ever came on. I checked the fuse and swapped out both the relays in the fuse panel that have 5 prongs on them. There are two of them. I recently pulled one out because that at least limits one of the two fans to a much slower speed. I swapped out the coolant temp sensor. I bled the air from the coolant. I keep a couple inches of coolant in the overflow tank. None of these have helped. I think there is a radiator low level sensor mounted on the radiator. Could that be the problem? Is there a coolant pressure sensor that detects a tiny leak in the intake manifold and turns on both fans just in case? If there is another relay thing somewhere else under the hood, where? Could the thermostat which has at least 90k mi. and 5 yrs on it be a cause? It could even be original. Car was so much quieter without the fans running.
  • kiawahkiawah Posts: 3,666
    You're going to need to get a copy of the schematics for your vehicle, or find a person who happens to have your specific vehicle and that model year service manuals. I suspect you have another component in that electrical circuit that may be defective and is the problem.

    For instance, it may take a combination of inputs to determine if the fans should be ON (one or both fans), and at what speed (off, slow, fast). Inputs could be temperature of the coolant fluid (the need to cool it), whether the air conditioner was on or not (provided extra cooling load, and the need to have high air flow for the airconditioner cooling), speed (perhaps the fans are turned off it is known to have enough air flow on it's own), etc.

    If you get a set of schematics, you can usually figure out what is supposed to happen. Alternatively if someone has the service manuals for your specific model, that would tell you definitely what to fix.

    Good luck.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    What makes you think you aren't running too hot, or hotter than normal? You'd best get a mechanic's thermometer in the radiator or an analog heat gauge and see what's what.
  • dave8697dave8697 Posts: 1,498
    I have the factory service manuals and I will look for the schematics. I thought I looked before and couldn't figure it out.

    The dash temp gage says about one notch below 200 degrees usually. When I put in a new coolant temp sensor last Aug., the temp sat right on the notch below 200. When I was chasing the idle problem, I put the old 3-wire CTS back in and it warms up to a little above the notch before 200. Sometimes gets more than half way to the 200 notch. Since they read differently, I assumed they also read the temp for the gage as well as gave ECM info. I thought about the new sensor may have kept the car running cooler by a few degrees but it lets a bunch of coolant out to swap back again. Based on that, I had two gages telling me roughly the same temp for the coolant, so I thought the temp gage is accurate. With either sensor in, the fans still always ran.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    I think some systems have two turns the fan on and another turns it off. Also on some cars turning the AC on over-rides one or more sensors.
  • kiawahkiawah Posts: 3,666
    If you have the manuals in softcopy, or could scan it and create a gif/jpeg file and post it to your carspace, I'll take a look at it and see if I can help you.
  • dave8697dave8697 Posts: 1,498
    I have it scanned as a word doc. I looked on my car space and can't see how to load it.
  • kiawahkiawah Posts: 3,666
    Okay, let's try this with a word doc. Pls send it as an attachment to my edmunds email address.... [email protected]

    You should be able to send from your own [email protected]
  • kiawahkiawah Posts: 3,666
    Based on the schematic you provided here's how your cooling circuitry is 'supposed' to work.
    - You have two fuses that power all of this. The top box on the left is the main fuse (60A) that carries the high current that drives the fans themselves. The second fuse shown as the box top center (I think it's 10A), is the power for the control circuitry of the relays.
    - The fans will be in one of three states. They will either both be OFF, they will both be ON running at low speed, or both be ON running at high speed.
    - The way they make the fans run at low speed, is that they string them in series....let me explain. These fans are 12V fans, and when they are given 12V they will run at high speed. 12V on one lead of the fan and ground on the other lead of the fan, will give the fan motor 12V and it will run fast. If however you wired the fans differently, in that you put 12V on the lead of one fan, took the output of that fan and connected it to the input of the 2nd fan, and then took the output of the 2nd fan and connected to ground.....each fan would only get 6V of power. Hence with only 6V of power, a 12V fan will run at low speed. This changing of the circuitry as to whether the fan is given 12V or 6V, is achieved with switching provided by the 3 relays depicted in the middle of the schematic.
    - Relay understanding#1. I don't know if you understand how a relay works, so a brief tutorial. A relay has two sides to it, a primary (or control) side....and a secondary side. The primary side is comprised of a relay coil, which when power is supplied to the coil it becomes energized and magnetically pulls a lever down. If you look in the center of the schematic on the left, there is a relay called Cooling Fan Relay #1. The leftmost circuit from B5 to B6 (a resistor and a coil symbol) show that primary circuit. S116 (which is fed from the 10A fuse at P107 top of page) provides the 12V power to the primary side of the relay at B5. When B6 is pulled to ground by the PCM (Powertrain control module) at the bottom of the page, that relay would then be energized. One common failure of relays on the primary side, is that the wire in the winding becomes burnt and breaks, and if this occurs then the relay won't energize anymore and the secondary will fail to connect.
    - Relay understanding #2. The second part of the relay is the secondary side, which is nothing more than a set of higher current contact points. These contact points have a resting position (when the primary isn't energized), and a triggered position (when the primary IS energized). The drawing is always the resting (un-energized) position. Back to your schematic and looking at the Cooling Fan Relay#1, it shows that when the relay is at rest, the points are open and 30 does NOT connect to 87. The 12V comes down from the fuse and connects to 30, and IF the relay is energized, then 30 will connect to 87 and the 12 V will pass on thru and connect to the LH Cooling Fan Motor. Common relay failures on the secondary side are that the contact points become pitted or burnt, and will either never close together, or will stay welded together and never part when the relay is at rest.
    - The two controls for all of this are the two connections at the bottom of the page from the PCM. There is a low speed Control, and a high speed control.
    - When the low speed control goes to ground, Cooling fan relay#1 primary gets energized, connecting the secondary contacts which gives 12v to the LH Cooling Fan Motor as described before. If you follow the output of that fan motor lead, it goes up thru the secondary points non-energized) of the Series/Parallel Cooling Fan, and then over to the RH Cooling Fan Motor, and then the other side of the RH motor is at Ground. Both Fans would run at low speed since they would each only have 6 V on them.
    - When the high speed control goes to ground, this energizes two relays simultaneously....The Series/Parallel Relay , and the High Speed Cooling Fan Relay . If you look at the secondary contacts of the Series/Parallel Relay you will see that the LH Cooling Fan motor lead will now be connected to Ground, which will result in the LH motor running at high speed since it has all 12V across it's leads. If you look at the secondary points on the High Speed Cooling Fan Relay, you will see that it will provide 12V to the RH Cooling Fan Motor, so that fan will run at full speed.

    So now that we understand how your system is supposed to work, we can understand your symptoms and try to determine what might be causing the problem.As I understand your symptoms, you say that both fans are running at full speed....which is a pretty important clue. In order for your fans to both run at full speed, then all three relays have to be energized. Cooling Fan Relay#1 would have to be triggered and energized, because that is where LH Cooling Fan gets it's 12V from. Since you say the LH Cooling Fan is running highspeed, then you also know that the Series/Parallel Cooling Fan Relay must be energized, because that is what turns the LH fan from running half speed to full speed. Since the RH Motor is spinning full speed and it get's it's full speed 12v power from the High Speed Cooling Fan relay, that relay must be energized as well.

    So what could be wrong? It is unlikely that you would have 3 relays all fail at the same time (like contact points were welded shut). It's possible, but highly unlikely. Therefore, the PowerTrain Control Module PCM must be sending the signals to energize the relays. Again, it does that by grounding the DK GRN wire on the left (thereby energizing the Cooling Fan Relay1), as well as the DK BLU wire on the right (thereby energizing the other two relays). You can verify this if you are somehow able to unplug these two wires, and see if your fans stop.

    In order to troubleshoot why the PCM is calling for high speed fans, unless you have a scan tool that can send the commands they're going to need to take it somewhere to fix it. If you possibly have the logic for the PCM, we might be able to take this diagnostics a little further.

    A couple things I would suggest looking at. First thing you should look at is whether an error code (Diagnostic Trouble Code) has been set. There's a little blurb that indicates that the PCM will enable engine cooling fans when certain DTC's are set. If you have an OBD reader, you can read the error codes and reset them. Some autoparts stores are reported to do that for you (free or nominal charge), and I have seen a reader outside Jiffy Lube for $15. I have my own personal one, so you might also be able to find someone who owns one themselves. Second thing I would check, is to see how is it that the Airconditioning circuit enables the cooling fans. It may be that there is a relay in the A/C circuitry that is bad, perhaps continually sending info to the PCM that the A/C is on when it's not.
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