This car has been overheating, and bubbling out of reservoir. I changed the thermostat today and same problem remains. I also noted the fan will not run. Having hard time finding out why it won't run. To get back to bubbling overflow tank temp gauge will read normal and hot. Doesn't seem to matter what gauge says it still will do it. The fan fuse in car I changed it was blown still no fan, check fuse under hood it was fine. Help.

  • Dies it overheat when the car is moving?
    – Zaid
    Commented Sep 10, 2017 at 2:36
  • Call it a hunch, but check the water pump, it's pulley, and serpentine belt. Commented Oct 10, 2017 at 4:41

2 Answers 2


Assuming the A/C is off the radiator fan on these doesn't start until coolant temp exceeds 92.7C (199F) or even higher if the car is traveling above 44mph! You can check the basic functionality of the fan itself by turning the A/C on since the fan should then run constantly or by directly connecting the fan to a suitable power supply. I would be starting here as it's entirely possible that whatever caused the fan's fuse to fail also resulted in a dead fan and regardless we need to make sure that the fan works.

Once you've established that the fan itself actually works we need to work out why it's not running when you'd expect it to and what's going on with the contradictory symptoms.

The key, I think is to determine why the temp gauge says one thing and the boiling coolant in the overflow says another.

Option 1 - The temp gauge is a lying liar that lies

Or more likely the coolant temp sensor is.. these things do die every now and again and if it's died in such a way that it is blithely reporting a value to the ECU that suggests all is well that could easily explain why the temp guage reads normal and why the fan doesn't kick in and potentionally even the overheating.

Option 2 - Something is preventing the coolant from circulating correctly

This would explain the temp gauge not showing an overheating temp level despite the clear evidence of the coolant boiling in the overflow tank and also possibly the radiator fan not kicking in because different parts of the cooling system would be much hotter/colder than other parts, you could have stone cold coolant at one end and boiling at the other! My memory of the engine bay on the PT Crusier isn't great to be honest other than it being a pain for accessing things but if you let the car "warm up" and try touching all the different coolant hoses you can reach (be very careful - hot ones can be really hot) and see if you are finding huge discrepancies. If some are red hot and others are stone cold then that might indicate a lack of circulation.

There's various reasons why coolant flow might be impaired:

  1. Failed water pump - if the water pump, or the belt that drives it has failed then it's obviously not pumping the coolant around!

  2. Air lock - a sufficiently large bubble of air in the coolant system could prevent or impair flow, just like in a central heating system in a house where you sometimes have to "bleed" the radiators. You should be able to bleed the coolant system in the car by running the engine from cold with the radiator cap removed. Any air in the system should bubble up out through the coolant and escape through the open radiator cap and after about 10-15 mins the bubbling should stop. If it doesn't stop then there's air/exhaust gases getting into the coolant system somewhere, which could indicate a failed head gasket or similar.

  3. Partial/complete blockage - if someone has put a load of RadWeld-type sealant into the system at some point for example then this could have formed a blockage somewhere in the system (inside the radiator is a likely candidate) and this could be impeding coolant flow.

  • Agreed. This case looks to suffer from a lack of air flow across the radiator or a lack of coolant flow through the radiator
    – Zaid
    Commented Jan 8, 2018 at 16:59

It sounds like you have a blown head gasket, and it is probably due to your fan not working because the temp sensor to the fan is defunkt!

  • 1
    How did you reach the conclusion that the head gasket is blown? Could you explain your reasoning?
    – Zaid
    Commented Sep 10, 2017 at 2:43

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