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Still overheating but head gasket looks to be OK

 
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Old 22 Dec 2012, 04:34 pm
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Location: San Diego, CA
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Default Still overheating but head gasket looks to be OK

Hi all, looking for some thoughts on my continuing issues with my sonís 2001 PT Limited, with 155K. Itís been overheating and so far Iíve found a defective high speed fan (replaced), cracked radiator (replaced), new thermostat, new OEM rad cap, drained and refilled with HOAT and bled the system several times. It still overheats.
The car has been square wheeled in the garage for 2 weeks but yesterday , due to lack of other vehicles, my son had to drive it to his work 2 miles away. It was ok on the way there but he got the warning ding on his way home.
Once it was back in the garage this morning I removed the rad cap, there was a clearly audible release of pressure and it had only been driven 50 yds into the garage.
The other week I bought the gizmo and fluid to check for exhaust gases in the cooling system. Today was the first time I had a chance to use it and after warming the car up and running the test, the fluid did not change color. I tried it twice and it was still blue and did not even turn slightly green let alone yellow.
I noticed as the car was running that there were plenty of bubbles in the coolant tower and a constant flow of coolant from the top hose so it looked like the waterpump is doing its job but the amount of bubbles bother me.
I was certain that the head gasket was a goner but the test result says otherwise but it does look like Iím getting air sucked into the system somewhere and itís causing an airlock, thatís my theory and Iím sticking to it!! .
My son also reported that when he was driving it home last night that he could hear boiling from the overflow and that the windshield kept fogging up with hot damp air coming from the vents.
Are there any common fail points in the PTís cooling system that let air in and cause overheating? I did notice that there was no gasket on the coolant tower to the block when I swapped the thermostat but didnít realize that there was meant to be until afterwards, I donít see any HOAT leaking from there either. Also I checked the tower when it was off and didnít see any cracks.
Any thoughts or input gratefully received!!
Blair
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Old 22 Dec 2012, 05:26 pm
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Default Re: Still overheating but head gasket looks to be OK

I'd be willing to bet you've got an air bubble(s) in the system and it'll cause all kinds of freakish overheating issues. When you do a changeout of the rad, or even the hoses, it can cause an air bubble to hang in the system.
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Old 22 Dec 2012, 05:43 pm
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Default Re: Still overheating but head gasket looks to be OK

x2...the repair manual shows that there is a notch in the thermostat housing into which the air bleeder on the thermostat must fit. Also, make sure the thermostat was installed with the spring pointing down. Sounds like you left the gasket off so you have to go back in there again anyway. While you have the thermostat out it might be a good idea to test it.
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Old 22 Dec 2012, 06:28 pm
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Default Re: Still overheating but head gasket looks to be OK

The only notch I saw on the tower was for the Oring on the thermo itself so it fits into the tower. Is that the notch you're referring to?

I could see the thermo working today as the tower was full of coolant and then it would drain and I could see the thermo. And yes the spring is pointing downwards.

Looks like I'll have to take it off again anyway to fit a gasket underneath it regardless!
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Old 22 Dec 2012, 07:19 pm
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Default Re: Still overheating but head gasket looks to be OK

Quote:
Originally Posted by panjammer View Post
The only notch I saw on the tower was for the Oring on the thermo itself so it fits into the tower. Is that the notch you're referring to?
The repair manual refers to it as a locator notch...it looks like a little cutout in the circumference of where the thermostat o-ring seats...the air bleeder on the thermostat is supposed to align with it.
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Old 22 Dec 2012, 10:30 pm
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Default Re: Still overheating but head gasket looks to be OK

okay im gonna take you old school.

Before bleeder valves there was a different way to remove air.

This method is called burping.

Im going to tell you to do that WITH the normal bleeding. Bleeding the system will only remove air close to the thermostat, if there is any in the engine block, lower radiator or main hose that is trapped, it will cause massive issues.

step 1. Remove the radiator cap

step 2. Start the car. turn the heater on defrost and blast it at full and let it warm up.

step 3. once the car is warm grab the main radiator hose and squeeze it, the fluid should rise and almost spill every time you do this.

step 4. Watch for the thermostat to open and the engine to suck in fresh fluid. Then refill the radiator housing so its at full. after you should see the coolant bubbling, this is the trapped air escaping when the thermostat opens.

step 5. Turn off the engine and let the car cool.

Do this 2-3 times in a row. Then replace the radiator cap, warm up the car and bleed it through the bleeder valve to remove air under the thermostat.

The reason i say to do this is the coolant only moves through the engine when its running, and when its warm. Otherwise it just sits there. Burping it like this forces excess air out of the block, into the radiator and up past the thermostat through the housing and the main hose :-)

Try that out and see if it works.

If not , check your water pump weep hole to see if its leaking, the car could just not be circulating the coolant fully :-)
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Old 23 Dec 2012, 01:13 am
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Default Re: Still overheating but head gasket looks to be OK

Guys, thanks for the suggestions. I'll pick up a gasket tomorrow and fit that and check the alignment, then I'll try the "old school" burping and see if that works.

One question, I know the water pump is driven from the timing belt and there is a cover but where do I look to see the water pump's weephole?

thanks
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Old 23 Dec 2012, 04:41 am
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Default Re: Still overheating but head gasket looks to be OK

You probably noticed it, but just to be sure...there is a bleeder on the housing just below the thermostat (not to be confused with the previously mentioned bleed valve on the thermostat itself) ...it looks like a brake bleeder. This bleeder must be left open when you are filling the radiator until a air bubble-free stream of coolant flows out.

Last edited by Carl48; 23 Dec 2012 at 04:45 am.
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Old 23 Dec 2012, 03:28 pm
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Default Re: Still overheating but head gasket looks to be OK

Quote:
Originally Posted by panjammer View Post
Guys, thanks for the suggestions. I'll pick up a gasket tomorrow and fit that and check the alignment, then I'll try the "old school" burping and see if that works.

One question, I know the water pump is driven from the timing belt and there is a cover but where do I look to see the water pump's weephole?

thanks
two ways, you can remove the splashguard inside the passenger front wheelwell. and gain access there behind the accessory belt.

OR *easy way* put the car on a lift or ramps, and crawl under the front passenger side under the passenger headlight. and look straight up, youll see the lower end of the water pump with the timing belt. Have someone start the car and see if you see coolant leaking out of the pump anywhere :-)
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Old 23 Dec 2012, 04:12 pm
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Default Re: Still overheating but head gasket looks to be OK

Quote:
Originally Posted by pluminator View Post
okay im gonna take you old school.

Before bleeder valves there was a different way to remove air.

This method is called burping.

Im going to tell you to do that WITH the normal bleeding. Bleeding the system will only remove air close to the thermostat, if there is any in the engine block, lower radiator or main hose that is trapped, it will cause massive issues.

step 1. Remove the radiator cap

step 2. Start the car. turn the heater on defrost and blast it at full and let it warm up.

step 3. once the car is warm grab the main radiator hose and squeeze it, the fluid should rise and almost spill every time you do this.

step 4. Watch for the thermostat to open and the engine to suck in fresh fluid. Then refill the radiator housing so its at full. after you should see the coolant bubbling, this is the trapped air escaping when the thermostat opens.

step 5. Turn off the engine and let the car cool.

Do this 2-3 times in a row. Then replace the radiator cap, warm up the car and bleed it through the bleeder valve to remove air under the thermostat.

The reason i say to do this is the coolant only moves through the engine when its running, and when its warm. Otherwise it just sits there. Burping it like this forces excess air out of the block, into the radiator and up past the thermostat through the housing and the main hose :-)

Try that out and see if it works.

If not , check your water pump weep hole to see if its leaking, the car could just not be circulating the coolant fully :-)

This great stuff

Step #2 does not apply to most vehicle anymore as the water is constantly circulating and the controls only effect vacuum or electrically control air duct doors.

Also if I may add that the vehicle doing this type of procedure be on level ground.
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