i read about opening the rad cap while engine is idling to free up any air in the cooling system.

i was wondering if it's normal for the coolant to bubble when you take the rad cap off after a 30min drive? mine bubbles like crazy then the water will subside a bit while bubbling continues and rise again while still bubbling. is this normal?

or should i start the engine cold without a rad cap and wait for it to warm up and make sure there's no bubbles anymore?

thanks.

 

u shouldnt open it up while its hot, its a pressurized system.

The reason why they presurize it is because its harder to get something to boil when its under pressure, hence when u take it off it starts to bubble.

There is a bleeder screw on the water neck, follow helms manual to correctly bleed cooling system, though if u just drive around, it will suck water out of the overflow on its own and bleed itself out.

 

if you take the cap off, and it keeps bubbling while the engine is running, then that is possible sign of a bad head gasket. The air is leaking from the cylinders through the bad parts on the head gasket into the coolant causing the bubbling.

if your just popping off the rad cap after a drive, (which is not recommended) and it bubbles its just relieving pressure, which is normal.

 

it should bubble no matter what but if it keeps doing that then there might be something else.when u turn the cap u should here some bubbles then close the cap.