2001 Chrysler PT Cruiser

  • 4 CYL
  • FWD
  • 202,832 MILES
My engine is sporadically overheating. The radiator was replaced about 3 months ago, I have just replace the water pump, thermostat and timing belt. The cooling fan works on both high speed and low speed. Today following the replacements I ran the car about 15 miles and let idle for over 20 minutes with no overheating at all. After the car cooled down I started it up to drive again and it began to overheat in less than 2 miles. When the car overheats and I turn the heater on it will not blow hot constantly (alternating hot/cold air coming out the vents). There is no water in the oil or oil in the coolant, also no white steam out the tailpipe. Some have suggested the head gasket, but there are really no symptoms to indicate a blown gasket.
Do you
have the same problem?
Saturday, March 6th, 2010 AT 7:22 PM

1 Reply

A blown head gasket won't always show symptoms as you described.

What happens is:

When your engine is under load, exhaust gas will blow through any leak in the head gasket, causing bubbles to enter the cooling system. These bubbles will begin to collect at the highest point in your system, which in your case is the heater core.

Once there's enough bubbles, it will block the circulation of your coolant. (Thus no heat) And once your coolant stops circulating, your engine will soon overheat.

You can usually drive around town at low speeds without overheating. But once you hit the highway, sustained high speed will quickly cause your engine to heat up.

To quickly check for a blown head gasket, remove the cap to your surge tank or radiator. (Engine cold) Start the engine and have someone rev the motor up and down to at least 1,500 r.P.M.S while you watch inside the coolant for bubbles. (NOT FOAM)

If you see bubbles everytime the engine revs, then this is exhaust gas.

Also, when you replaced the radiator, did you flush the system? Sometimes the heater core will get clogged up.

Remove the upper radiator hose and run a garden hose through the system. If water doesn't flow freely, then somethings clogged, and it's probably your heater core.

One last word, you should never, ever hunt down a problem by replacing parts until you hit the jackpot. This only waste your time and eats a hole in your wallet.

The proper way to diagnose any problem is to isolate the system at fault and thoroghly testing each component until the guilty part is found.
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Monday, March 8th, 2010 AT 10:06 AM

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