Radiator pressurizing under full boost???

[RUNMYTA]

Just got back from doing some tuning and finally got it real close with street tuning. The last WOT run was in 3rd gear and went from about 70 to 120. Well when I let off of the throttle to coast back down, coolant sprayed up the passenger side of the car and the temp went up. I shut her down and pulled to the side of the road and popped the hood. All the hoses where intack and the coolant seemed to come from out of the overflow jug!! Well the first thought was a stuck thermostat, so we opened the bleeder valves and let off the pressure before opening the cap. Well the raditor was only about 1 quart low. So I pulled the thermostat out and it was open, but had no coolant. I added about 2.5 gallons of coolant and drove the car 80 miles home on the freeway with no issues. Temp was normal etc... Right before I get home, I went WOT through 2nd gear and stopped in my driveway. Only to find that I had blew out more coolant!!

Do you think I am lifting the heads at higher boost? I am making 13psi with a D1SC. The car idles and runs fine. No water in the oil or bubbles with the radiator cap off..

Also I noticed that I am pushing alot of oil out of the drivers valve cover. I will check to see if the gasket is bad or pinched, but should the valves covers see that much pressure?http://www.camaroz28.com/forums/images/smilies/frown.gif

[T/A KID]

Hmm, What head gasket you running and are you using studs or bolts?

[Fire67]

Is this a stock bottom end?
If so, that could explain the excessive blow by.

You didn't mention how much boost you're running?

[RUNMYTA]

This is on a fully forged (Compstar) 383 with Dart Pro 180 heads using headstuds and cometic MLS gaskets. I am making 13 psi of boost. Motor is new and has less than a 1K on the clock.

[Fire67]

At this point it would be wise to perform compression and leakdown tests. That way you can identify wich cylinder(s) is leaking and were from.

[Twisted Z]

you have a blown head gasket from the sounds of it. Back when I had mine going it never did that even at 14 PSI ;)


A leak down may or may not help at this point. Time to tear into it

[Fire67]

you have a blown head gasket from the sounds of it. Back when I had mine going it never did that even at 14 PSI ;)


A leak down may or may not help at this point. Time to tear into it

He's right, I dont know what the hell I was thinking... A leakdown is gonna show you that either its sealed fine without much cylinder pressure (heads lifting under boost), or that the gasket is completely shot and leaking no matter what. Either way, you'll need to tear it down so its almost a moot point to do a leakdown.

[RUNMYTA]

I am leaning toward a blown headgasket, but I drove the car 80miles without any issues after the first incident with pushing the coolant out and had no issues, until I got deep into boost again.:confused:

[uncool]

Cometics are a VERY touchy gasket. The surface finish is the key to getting cometics to seal. If you drove 80 miles with no problems, then got into it and blew coolant, I would say you have a gasket that is leaking. We use these in the diesels, but if the head and block finish is off, no chance of sealing. If the surface finish is good, they will hold 90 PSI on a diesel.

Good luck,

Marc


The gasket surfaces need to be almost polished to a mirror finish. After a few times of removal, I noticed that mine didn't seal as well. So this time around I'm going with a good ol Felpro...