My truck pushs coolent into the reservoir and out the overflow line at wot, it never overheats and don't get any air bubbles in the coolent even if I brake boost 3psi or so. Once the coolent level gets low enough it stops but it gets low enough that it gets air in the engine. I have a Corvette coolent tank witch sets quite a bit lower then the stock one, could this be the problem? it seems like its getting to much pressure for some reason.

 

Id say your problem is not the corvette tank itself, but that its lower than the stock tank.

 

I had the same problem once. It took me for ever to find. I had a small crack in a head and it pushed the cooling system full of air and would push it out the over fill. Then to coolant cap went bad and it wouldn't let it push out the over fill tube and popped my heater core 3 times. I check the coolant for exhaust gases 5 times and nothing. only way I found out what it was as when I changed to new heads and it stopped so i took the old ones and had them checked for fun, but it would only do it when the engine was hot and under throttle. was a pain to find ( by luck). Not saying yours is doing the same but I know mine did. Hope its not for you and something simple.

 

That's interesting, I guess it could be anything at this point. Seems odd it works so well just driving around

 

Try lowering the boost and see if it still does it. The radiator cap should be 15psi. If it continues at lower boost then replace cap and try again. After that if it continues I would do a coolant system pressure test, a cylinder compression test and a leakdown test. If those all come back good then you will need to pull the heads for inspection.

 

I had a coolant pushing issue back with my old stock 4.8. Too much boost with too much timing on E85 and seemed to have cracked the seal on the head gasket. Anything over 10 psi and would push coolant out the over flow. Under 10 psi and it was fine. Drove it for 2k miles like that before I built the new motor.

 

Will do. I will note that it was overheated to 235-240 once when my stock coolent tank topped from the heat of the turbo being to close, didn't think it was hot enough to hurt anything but could of cracked a head maybe Idk. It does have mls gaskets and arp head studs so it shouldn't be lifting a head.

 

head gasket

 

similar issue on the camaro on 14psi. dropped to 10 psi. no problems. then on 12 psi and e85 it lifted the heads. whoops. HG issue is the best guess. then have the heads pressure tested to be sure.

 

18psi on 18 degrees timing. It did start when I turned it up to 18, might be a head gasket then.