Hi everyone! First time poster and total car n00b here.
I’ve had some ongoing overheating problems with my 2001 Dodge Neon. Replaced radiator, thermostat, and many other components. The issue is that the car runs fine while it driving, but if I drive it for a while, then stop the engine, when I turn it back on shortly thereafter, the engine temp is VERY high. Usually I cannot drive it again without letting it cool for a few hours. For a while, once I stopped the car, the coolant would slowly heat up and start to boil. The boiling was fixed by replacing the radiator cap. But the car still overheats if it is driven, stopped, then driven again.
From what I can tell, the fan is working fine - but NOT when the car is off. If the engine is hot, the radiator fan SHOULD come on to cool the engine after turning it off, right? What would cause my radiator fan to stop coming on when the engine is turned off? I’ve put so much time and money into trying to fix this. Please help!
Hi everyone! First time poster and total car n00b here.
Some cars allow the fans to run with the ignition switch off, but most don’t. Many driver’s complaigned the fan running would run down the battery and/or why their car was still “running” without the key in it. I don’t know how the Neon is set up.
You can expect the car’s motor to generate some heat once it is shut off. Your problem with “boiling” is either the coolant is the wrong mixture (or type) and/or the radiator cap is not holding enough pressure in the system. Fluids that boil at zero pressure will not boil at 5, 10, or 15 lbs of pressure. Have your coolant checked to see if perhaps it is too diluted. Have you topped off the coolant with plain water? Also, check the pressure rating of the radiator cap. Perhaps the cap is defective or someone replaced the proper cap with one that is a lower pressure cap.
With the right coolant and proper cap your car shouldn’t boil over when you stop it. Then when you turn the key to restart the fan will come on, the running motor will have coolant circulated by the water pump and the indicator on the temp guage should move from being on the high side back to the middle or normal.
I just remembered another item to check is the thermostat. It needs to be the correct temp thermostat for your car and it needs to open and close properly. If the other items check out perhaps the thermostat needs to be looked at.
I concur with Uncle Turbo. Plus, in those cars that allow the fans to run with the ignition switch off, the purpose is to keep the accessories etc. under the hood from getting too hot, not the engine itself. I think the fan only removes heat from the block very slowly, considering there’s almost no coolant circulation.
My '88 Accord had the same symptom once, and it was a lack of coolant pressure.
Is the top radiator hose firm when it’s warmed up?
Make sure the surfaces on the radiator that mate with the rubber gaskets on the radiator cap have no crud or dents.
Thanks for the info/advice! So far I’ve replaced the radiator, water pump, thermostat (2x), timing belt, radiator cap, multiple flushes and refills of coolant, etc. At this point the problem is that the engine gets so hot after turning it off (if I’ve been driving at highway speeds for at least 30min), that I can’t drive it again till it cools off, which can take a long time. If I fire it back up within a few minutes of stopping (for instance, after getting gas), even if I let it cool off to normal temps, it’ll slowly start heating up after a few miles. Once it reaches about halfway up the gauge, it gets hot exponentially faster.
Still sound like a pressure issue? Or perhaps wrong mix/type of coolant? At this point I’m at my wit’s end and multiple mechanics have scratched their heads without a clue about it.
Thanks for the tidbit about keeping the accessories cool, and not the engine. That certainly does make sense, and tells me that maybe my fan isn’t supposed to come on. I know earlier Neons (mid-late 90s) DID have the fan come on with the ignition off, but that lead to widespread problems with drained batteries etc. So maybe they stopped it with the 2001 model? Anyway, thanks for chiming in with good info!
One follow up question: Would low coolant pressure cause the engine to not cool enough or as quickly once the engine is turned back on?
Other than the guage reading “hot”, exactly what is the problem. After turning off the car it won’t restart? Or, when it restarts the guage reads almost all the way to the top? Are hoses bursting?
After you stop for gas or an interstate rest stop; start the car put in gear and get it moving. All it takes is a little air moving by the radiator to cool it and then in turn cool the motor. You don’t need to wait to start the car and go. On some really hot days on long trips I’d open the hood when I stopped at a rest stop to allow more heat to escape the engine compartment. But when its time to go you close the hood fire it up and go. No need to wait until the motor cools down.
If you can’t live with this aspect of your current car, then perhaps you need to get a different car. They all do what you are describing, just some show it more than others.
First, Let me say that the radiator fan will have no appreciable effect on temperature if the engine is not running. It pulls air through the radiator when the car is running but not moving to remove heat from the circulating coolant (water/antifreeze mixture). Your symptoms are really screwy. I would check to see if your system has enough coolant and add as needed. If that is not the problem, I’d have the entire system checked for blockages and flushed, and replace the thermostat for good measure (they’re cheap).
If things are working right, you might see a slight rise in the temp. gauge after a fully warmed-up engine is shut down as the coolant (which is now not circulating) will absorb some heat from the metal, but it is really a net temperature loss. Once the engine is shut down, it stops generating heat.
The correct pressure in the system is important for the cooling system to transfer heat out of the motor to the radiator and into the air. I just can’t understand your symptoms. Are you just way to focused on the temperature guage? Or, is there a real problem?
After all this work could a hose be pinched and not be allowing good coolant flow? Has all the air been properly bled from the system. What is happening with the overflow coolant tank. Does the fluid in there expand so the there is more fluid in the tank and then does it go down to a lower level in the morning before you start the car for the day? The overflow tank should be about 1/3 full when the motor is cold, say 2" in the bottom of the tank. When the motor is hot is should be about 1/2 to 2/3 full but still have about 2" of air at the top.
If the tank is empty in the morning when the car is cold then add a 50/50 mix of coolant and water, but don’t fill it more than 1/2 way. Run the car and check it again the next morning. Add coolant mix again if it is empty. Keep adding day by day until the tank is stable when you check it cold in the morning at the 1/3 level. This will get rid of any air that may be trapped in your system. Air in the cooling system can cause some crazy symptoms and may contribute to some of the stuff you are seeing.
One thing that can prevent the cooling fan from coming on after the engine is shut off is, a burned fusible link dedicated for that circuit.
If you try to start the car when the temp is high, will it start? How quickly will the gauge go back to normal if you ignore the apparent overheat and start it? The temp sensor may be in a spot in the engine that gets pretty hot after the engine is shut off and there is no coolant flow. This may be normal behavior for this vehicle. I don’t think there are any Chrysler products built in the last 15 years or so that let the fans run with the key off.
I am havinbg the exact same issue with my Daughters 2000 Neon.
Did you come to any conclusions or find a fix?