coolant bottle blows up like a balloon

[olymon]

While riding my pieced together ultra, the coolant bottle swells up like a balloon and builds a lot of pressure. Any idea on how to stop it from swelling so much, it actually starts to effect how the brake works because the tank to brake caliper clearance gets reduced to nothing and the caliper can't move enough to grip the pads well.

 

[Jay]

Maybe replace your pressure cap, it's either not working or is the wrong one.

 

[olymon]

yeah, I didn't really think that the cap might cause the problem but maybe. I've got another one off of the same style tank that I can swap out and see what it does.

 

[slash]

YOU HAVE A BAD HEAD GASKET OR O-RING AND THE COMBUSTION PRESSURE IS GETTIN IN THE BOTTLE

 

[cascadesnowjunky]

^^^^^ What slash said, you have a bad head o-ring and cylinder pressure is pressurizing your coolant system.

 

[Jay]

I didn't think of that. Please let us know what you find, I'm curious now.

 

[olymon]

Yeah, never even thought about the o ring being bad. Coolant seemed really warn compared to the snow conditions. Makes sense! Do you think the bad cylinder would show up on a compression test?