Blowing Coolant Out!

[Ruf Racing]

I have the symptoms, of a blown head gasket. Six month old, three layer cometic. I had to change one out on a different head, same cylinder. It's not running hot, motor runs great. Besides the head gasket failing or the radiator cap, what else could be the cause? Could a closed thermostat, cause enough pressure to bypass the radiator cap? Thanks.

[eastside 400]

how much is blowing out? its normal for some to blow out in a moto. I dont fill my bottle past the low line and i still blow a little out, coolant expands alot when it gets hot. you would overheat the motor if the thermostat stuck closed, it would probably blow coolant out but you would also have a warped head if it got that hot. I would take the tstat out either way, you dont need it.

[Lquad71]

mine did the same exact thing. turned out our radiator cap was just worn out. replace it and you should be fine.