2003 LS Sport Engine Coolant fill cap?

[drew212f]

I am having a problem burping my cooling system following the fill instructions. The Thermostat housing has what appears to be a relief hole on the side of the neck and coolant starts pouring out of it as soon as engine starts to heat up. The cap on the degas bottle and thermostat housing are exactly same, are they supposed to be the same? If I had to guess, the cap for the thermostat housing should be a spring pressure relief valve that would block the coolant from escaping unless pressure exceeded safe operating conditions.

 

[joegr]

V8 or V6?
Either way, the caps are very much different. You also likely need to replace the thermostat housing and related plumbing, as well as the degas bottle.

 

[drew212f]

Thanks, this is a V8 purchased used with blown head gasket that some else "tried" to repair. Lots of other problems that I'm tackling one at a time.