I have a fully built ls/vtec motor turbo'd with a GSR thermostat and as of today, after doing a few pulls and cruising around the coolant overflow keeps getting full. I emptied half of it and after driving around for another 20 min it was getting full again. The car is not overheating, no leaks, motor runs strong. So what gives?

Compression is fine, no smoking nothing. Motor is solid. Upper and lower radiator hoses are hot but since day 1 that thermostat is suspect. I just have this gut feeling, but still, it wasnt doing this until today.

 

sounds like the head is lifting and pushing coolant into the overflow.

do you have headstuds? it might be time to pull the head and have it checked for warpage or just have it machined. use a new gasket and headstuds.

 

Do a leakdown test. My car was doing the same thing when i had a cometic headgasket in there. I would get on it a little bit and my overflow would be FILLED. Did a leakdown test and coolant started to push right out of my radiator. New oem headgasket and re-torqued the headstuds and she's all good to go now. Leakdown is a very good way to confirm.

 

The headgasket is most likely your issue. It wont always show the signs under a leakdown test. The gasket could have a slight burn to it and it will only show under load. You have to remember that cylinder pressures are way higher then any leakdown test. Its not the cometic gaskets fault. They work fine.

Pull the head and check the gasket.

 

Didn't say it was...but i do believe a leakdown test should be done to confirm if it's the headgasket. Even if the test does nothing like what you said it's still worth doing.

 

Odd. I have ARP studs, and already retorqued them after 10-12 heat cycles. The motor only has about 300 miles on it maybe. It is a Cometic head gasket. So rather than just jumping to conclusion that its the headgasket that needs to be replaced, and doing a leakdown test, is there anything else that could cause this? Lets start with the simple problems.

Would torqing the head again help anything? I doubt it. Its already torqued at 75 ft lbs.

Lets try to replace the radiator cap first. I dont wanna jump to the headgasket with only 300 miles on the motor, headstuds tq'd properly and the motor running strong.

 

I have the same **** going on and its bugging me. Not overheating, good compression, passes leakdown test. I did find that my radiator cap was broke though. Replaced it and no issues yet. Let me know what you find out, im curious.

 

Yeah you're tellin me bro. Im not gonna buy for one second that my head is lifting or its the head gasket after only 300 miles and with ARP studs tq'd to 75 lbs. whatever.

 

Is it so hard to believe that your head/block may be slightly uneven? There is too much pressure in your radiator, either you have a bad cap, or there is an external source pushing the pressure in. The only other high pressure source is a hole in the water jacket.

 

Well i just replaced the radiator cap and its still doing it. I know 100% for a fact that the block and head surfaces are perfect. The machine shop that did my block did all the checks and said it was good to go and the shop in Florida that did my head stated the same.

Maybe the cometic head gasket is to blame. So i guess getting it tuned for any more power is out of the question haha. Just more damage is presume.

 

had the same problem. i threw the cometic gasket out replaced it with a copper sprayed golden eagle and the problem is solved. a leak down will tell u if its the gasket

 

If you have the cometic "fuzion" gasket that may be your problem, however the normal cometic head gaskets work great, i have on 340whp no problems, and i have seen them on countless 500+whp evo's...

 

Its funny how multiple people on the forum have had the same issue and it was with a Cometic headgasket. As far as using copper spray... i dunno bout that. I used to, but then was told by many that its not necessary and sometimes a bad thing.

 

I was never pushing anything over 250whp, but both my deck and head were flat and I used an OEM headgasket with ARP studs and torqued them down. I never retorqued them after any heat cycles.

I drove my car everyday for 17K+ miles, including the summer, and never once had an overlfow problem. The car has been NA since I took the turbo off and it's been another 16K w/o any issues.

 

Like miller said replace your head gasket.

 

before you do anything have you checked to make sure the radiator cap holds pressure? they're easy to check if you have a coolant pressure tester, or they're less than 10$ to just replace.

 

Havent done a test, only replaced the cap.

 

i didn't read everything but it is possible you are just running hot...

 

I agree.
My problem hid from me and I didn't notice it untill one hot day. Pulled the head to discover my valve reliefs were missing from my pistons.

Pull the head now that you know there is a issue. It can save you alot down the rode.

I'm glad I didn't just retorque the ARPs like I was going to do. Haha.

 

Did you change the gasket yet?

 

Not yet, i dont have time for this project yet. I dont drive the car anyway so she'll just sit in the garage until i get the headgasket in. Well at least once the new headgasket is in, ill be satisfied that its OEM and not cometic. I didnt want cometic to begin with but thats all i could get a hold of.