Can a cracked echaust housing cause overheating only under boost?

[back2dsm]

I just bought this car from a guy who couldn't figure out this overheating problem. The car will idle for days without overheating, but as soon as it sees boost, starts pushing water out of the overflow.

The engine:
.is rebuilt
.passes a leakdown test at 100psi just fine
.passes a cooling system pressure test at 20psi
.has no thermostat
.cooling fans cycle on and off normally
.has an exhaust leak at the manifold

The turbo:
.s a 16g
.has bent fins on the intake
.has visible cracks on the inside of the exhaust housing

I've seen this exact overheating situation brought up recently by a couple other people, but nothing was resolved. Any ideas?

Thanks guys -- mike

 

[pj91gsx]

im not sure, but I would say fix the cracks anyway. leakes before the turbo and before the o2 sensor are not good. did you get the head shaved and make sure the surfaces of the head and block and headgasket are cleaned with carb cleaner or asatone. how long has it been since you rebuild.

 

[Maranello993]

This situation has come up many times. I too have this problem and would like to find a solution. My t25 is getting replaced but I don't think it has any cracks. The lack of airflow caused by the FMIC and condenser seems to be the only thing I can find on my car.

 

[back2dsm]

I bought the car with the engine already rebuilt, so I don't know what kind of work was done. But I've done plenty of leakage tests and I'm pretty confident the engine is sealed ok. I'm definitely gonna replace the turbo and fix the leak, just saving up money for that... I just don't want to have the same problem after I buy the turbo!

Yeah I don't even have a fmic... So airflow shouldn't be an issue.

 

[Gs Dewd]

Mine did the same thing about 2 yrs. ago. I also had a cracked exhaust manifold. My problem was the head gasket. I replaced it with a felpro oem style gasket and all was good. I was able to let the car sit all day at idle and it would not overheat just when I went down the road it heated up and pushed the coolant into the overflow and out on the ground. I had no water in the oil or oil in the water. What was happening was the gasket blew between the cyl. and a water passage and under boost it was pushing the combustion gases into the water passage hence the water being pushed out of the engine into the overflow.