Will coolant bubble over with the cap off? [Archive] - GrandAmGT.com Forum

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manofmany
11-07-2010, 12:39 PM
Or SHOULD it?

Still diagnosing whether I have an air bubble in the system and need to use an airlift vacuum bleeder or if it's something more.

Basically, when the cap is off and my thermostat opens, the coolant rises drastically and will start bubbling and small amounts go out the overflow tube. I've never heard or seen it bubble with the cap on, nor do I experience loss of coolant. Block tester came back negative up until 195 but I couldn't use it after because the coolant level was too high.

Pauljp
11-07-2010, 01:33 PM
As I've read in other posts, the coolant system needs to be pressurized or it will boil and spill out the overflow hose. Your cap maintains this pressure.
A good indication of a worn or loose cap is bubbles and overflow.
So the answer to your question is "yes".

AaronGTR
11-07-2010, 04:30 PM
Yes, the coolant expands when it gets hot, and needs pressure to raise the boiling point. With the cap off, it will overflow out of the expansion tank.

[ChaosweaveR]
11-07-2010, 05:37 PM
You could, but this is unnecessary and messy.

The proper way to bleed it is by the small bypass metal line that goes across the front valve cover. On the right side, there's a nut. Crack that lose ONLY enough to let a small amount of coolant seep through. If there's air in the system, you'll see it burp out all the air bubbles.

Use a socket to loosen it, and a pair of pliers works great for keeping the nut in place, and not being pushed out by the flowing coolant.

manofmany
11-07-2010, 06:18 PM
;1141572']You could, but this is unnecessary and messy.

The proper way to bleed it is by the small bypass metal line that goes across the front valve cover. On the right side, there's a nut. Crack that lose ONLY enough to let a small amount of coolant seep through. If there's air in the system, you'll see it burp out all the air bubbles.

Use a socket to loosen it, and a pair of pliers works great for keeping the nut in place, and not being pushed out by the flowing coolant.

Thanks guys. Tried it many times. Just doesn't seem to be getting all the air out of the system.

Think I'm going to pickup an Airlift system and be done with it. It's like I can get 99% of the air out but every once in a great while at a stoplight the air will get cool until I take off. Doesn't happen often but it's still there.