Diagnosis of a cooling issue

[lmarkie74]

I'm very new to this forum. Just bought a 2001 PT Cruiser a couple of weeks ago. The previous owner said his mechanic told him it had a blown head gasket. I didn't think so, it runs too good. He told me the radiator had just been replaced. I had him follow me to my house about 10 miles. As soon as we got there it start steaming up on the inside. I suspect heat core went. No biggie for right now. Summer is getting near. I'll deal with that later. I did a block test with the chemical and no HC's were present. Kinda hard to do it though. Bubbling and spitting through filler neck.

I have bypassed the heater core, replaced the thermostat, replaced the cap, and have replace the filler neck just in case it has a crack in it that I can't see. $13 at Advanced Auto. Cheap! Fan works. Comes on when it's suppose to.

Here is my biggest problem. Once the temperature gauge gets to half way, coolant/water pushes out from under the new cap.

What is this a sign off?

[soyomb]

don't know, but it's a sealed system and nothing should push out underneath the radiator cap. did you bleed the air completely out?

[NitroPT]

To answer your question about "your biggest problem".
The plastic thermostats housing seem to have a quality control issue with sealing under pressure between the radiator cap and the housing? I changed a few last year with this same issues. So now I carefully examine them prior the installation and pressure check the system before starting the engine after I service one.

[lmarkie74]

Originally Posted by soyomb

don't know, but it's a sealed system and nothing should push out underneath the radiator cap. did you bleed the air completely out?

I topped the filler neck off with coolant and ran the engine until there were no more bubbles. I let it overflow to get all of the air out. I place the brand new cap on the filler neck and opened the bleeder screw to get all the air out of the now closed system. I think the caps are rated at 15 psi. Am I getting more than 15 psi of pressure in system causing the spring on the cap to contract or is the housing not sealing properly?

Next step is to probably rent a pressure checker and see if it will hold pressure.

[lmarkie74]

Originally Posted by NitroPT

To answer your question about "your biggest problem".
The plastic thermostats housing seem to have a quality control issue with sealing under pressure between the radiator cap and the housing? I changed a few last year with this same issues. So now I carefully examine them prior the installation and pressure check the system before starting the engine after I service one.

I'll try pressure testing the system. Maybe it will tell me something about the new filler neck. The filler neck I replaced was with a Dorman, Advanced Auto, filler neck. Not a genuine Chrysler part.

[NitroPT]

Originally Posted by lmarkie74

I'll try pressure testing the system. Maybe it will tell me something about the new filler neck. The filler neck I replaced was with a Dorman, Advanced Auto, filler neck. Not a genuine Chrysler part.

The manufacture has nothing to do with it. It is just a poor design for good sealing. I started with replacing with Chrysler BTW. The Doorman was the ones that seem to work better in most cases, not always.
Even in the best scenario you can wiggle the cap when the cooling system is hot and the cap will bleed off. The less this happens the better for the system naturally because the because the cooling system depends on pressure to work.

[lmarkie74]

Originally Posted by NitroPT

The manufacture has nothing to do with it. It is just a poor design for good sealing. I started with replacing with Chrysler BTW. The Doorman was the ones that seem to work better in most cases, not always.
Even in the best scenario you can wiggle the cap when the cooling system is hot and the cap will bleed off. The less this happens the better for the system naturally because the because the cooling system depends on pressure to work.

I did notice last night that my new cap was quite a bit loose as I turned it on the new filler neck. What did you do when you had this problem? Return filler neck and get a new one?

[NitroPT]

Originally Posted by lmarkie74

I did notice last night that my new cap was quite a bit loose as I turned it on the new filler neck. What did you do when you had this problem? Return filler neck and get a new one?

I took a new STANT radiator cap with me to test fit. This at least in part insured that it may seal?

[Handy_Cruiser]

I test drove several PT's before I bought mine. And two with blow head gaskets acted exactly like this.

The head doesn't leak until the engine heats up. Then it blows the coolant out before the coolant get really hot. Often the coolant will not even burn you when first blowing out. And pressure testing and such may be inconclusive on this condition.

I good way to test this is to remove other variables. First assure your radiator is in fact new. Then remove the thermostat all together. Fill the car with water assuring there are no air pockets and then start the engine with no radiator cap. If the head gasket is good, some water may come out of the open radiator with no cap, but it should level out and circulate normally. Also the fan should operate normally. After running for a while, the engine should approach normal operating temperature unless it's really cold where you are. And there should be no or very little water coming out of the radiator.

But, if the PT runs for five to ten minutes and then belches out practically all the water, then you can just about bet it is the head gasket. Again, this appears to be a very common issue with early PT's.

[NitroPT]

Originally Posted by lmarkie74

I'm very new to this forum. Just bought a 2001 PT Cruiser a couple of weeks ago. The previous owner said his mechanic told him it had a blown head gasket. I didn't think so, it runs too good. He told me the radiator had just been replaced. I had him follow me to my house about 10 miles. As soon as we got there it start steaming up on the inside. I suspect heat core went. No biggie for right now. Summer is getting near. I'll deal with that later. I did a block test with the chemical and no HC's were present. Kinda hard to do it though. Bubbling and spitting through filler neck.

I have bypassed the heater core, replaced the thermostat, replaced the cap, and have replace the filler neck just in case it has a crack in it that I can't see. $13 at Advanced Auto. Cheap! Fan works. Comes on when it's suppose to.

Here is my biggest problem. Once the temperature gauge gets to half way, coolant/water pushes out from under the new cap.

What is this a sign off?

Originally Posted by Handy_Cruiser

I test drove several PT's before I bought mine. And two with blow head gaskets acted exactly like this.

The head doesn't leak until the engine heats up. Then it blows the coolant out before the coolant get really hot. Often the coolant will not even burn you when first blowing out. And pressure testing and such may be inconclusive on this condition.

I good way to test this is to remove other variables. First assure your radiator is in fact new. Then remove the thermostat all together. Fill the car with water assuring there are no air pockets and then start the engine with no radiator cap. If the head gasket is good, some water may come out of the open radiator with no cap, but it should level out and circulate normally. Also the fan should operate normally. After running for a while, the engine should approach normal operating temperature unless it's really cold where you are. And there should be no or very little water coming out of the radiator.

But, if the PT runs for five to ten minutes and then belches out practically all the water, then you can just about bet it is the head gasket. Again, this appears to be a very common issue with early PT's.

Handy aka MR T., I reposed your quote because generally it is ok information but did you read what I highlighted in RED? A blown head gasket or cracked head can't hide form this!