My 03 is overheating, stumped

[glibbis]

I need some advice about my sister's 03 PT Cruiser. 2.4, DOHC, non-turbo.

About four years ago the car started overheating and I replaced the cooling fan. All was well.

Last year, my family took my sister's Cruiser on a 300 mile road trip from Tacoma, WA to Spokane, WA. This was in August and the trip involved going over one mountain pass and a lot of flat driving through hot arid country. About 200 miles into the trip the Cruiser started running hot, eventually overheating and boiling the radiator dry. I shut off the A/C, refilled the radiator with straight bottled water (all I had) and hit the road again. It boiled the water dry again and I limped along until i found a town with a Napa that had a thermostat in stock. Replaced the thermostat, filled up the radiator, went on my way only to have it overheat and boil dry again. Basically I ended up driving about 100 miles at highway speed on an overheated engine (I had to drive fast because the only way the engine would stay out of the danger zone on the temp gauge was if I kept the RPMs above 2700). Found a shop in Spokane who replaced the water pump. Flew back to Spokane, drove the car back home to Tacoma with no overheating problems.

Car ran fine for a few months, then started running hot and rough. I replaced the thermostat again, had the cooling system flushed by a dealer, and replaced the plugs and wires. Rough running is mostly gone but the motor still overheats, and it is getting worse. It now overheats in regular light driving, and if I put the A/C on it REALLY gets hot fast.

So, new thermostat, fan functioning has ben checked, cooling system has been flushed, high speed fan relay replaced, low speed fan relay replaced with the factory spare from the power distribution center. This morning with the engine cold I popped the radiator cap and started the car and watched down the throat of the radiator cap housing. Sure enough, I saw bubbles in the rad fluid as soon as the car started running. The bubbles continued as the car warmed up to the point that coolant began flowing. The bubbles slack off when the RPMs are increased, but come back as soon as the car returns to idle.

Given the bubbles and the checking of every other possible cause, do I have a blown head gasket or warped head? I known this little 2.4 has an aluminum head that could have been warped by driving it over 100 miles on an overheating motor.

Compression check results:

#1 = 155
#2 = 150
#3 = 150
#4 = 160

Those don't look like typical failed head gasket numbers....

The car isn't showing any trouble codes either.

Any ideas?

[glibbis]

OK- did some reading and have been told that it is likely the head warped and the head gasket failed in a way that exhaust gasses will leak into the cooling system but coolant will not leak anywhere else. Time to pull the head and take it to a shop.

[Hooligan]

We have to assume that each time you bled the system whenever you refilled it, right? You didn't mention that procedure at all.

[4x4safari]

I would recommended doing a cooling system pressure test and posting your findings.

[glibbis]

Sorry, been a while since I followed up on this. After replacing the thermostat again, and having a dealer flush the system, it turns out that the head was warped. I took it back to the dealer who confirmed the head was warped. So, $2k later the overheating is fixed and the Cruiser runs great. Can't say I am happy with how easy the head warps on this car, but otherwise it has been OK. I still don't know why the water pump failed with less than 70k on it.