2003 montana coolant boiling?

[jimmywalters]

Have a 2003 montana. When I shut the car off, it sounds like the coolant is boiling for probably 5 minutes after the car is totally off.

So, I turn the car off, and usually within 30 seconds or a minute I will hear a boiling sound that seems to be coming from the radiator. It will continue for about 5 minutes and then slowly die out. This is with the key out, I'm totally outside the car and the doors are locked. Car is 100% off.

My car doesn't seem to be overheating at all. I thought maybe the coolant level was low but it seems exactly right in the reservoir and so I checked on a cold engine and took the fill cap off, and coolant starting coming out the fill cap so I know there's enough coolant in the system. Not sure why it was so full, full enough for coolant to spill out when cold, but even losing the amount that I lost when checking that hasn't seemed to help the problem. So at this point I'm convinced that it probably has the right amount or possibly slightly over the right amount of coolant.

Is this normal for these cars, or any cars i guess? I've never noticed any of m other cars sounding like the coolant is boiling but maybe I just never noticed before.

If this is abnormal, what could be causing this?

Thanks!!

 

[melsg5]

when you shut off any engine the cooling system stops also but the heat in the block is still there. The result is you get a spike in coolant temperature. How long since you replaced the coolant?

 

[gregd]

The overflow tank is higher than the radiator. When you pull the cap off the radiator, coolant in the overflow tank will siphon off and end up on the floor. A real pain in the ass. I usually pinch the overflow hose when pulling the radiator cap.
Not sure if you know but there is a valve to get all the air out of the coolant system where the upper radiator hose attaches to the engine.
When my head gasket was blown I was getting the bubbles blowing into the overflow. Not saying that's your problem , even a real weak antifreeze mixture can cause boiling. But head gasket problems on this van are common.

 

[jimmywalters]

Hi, thanks for the replies. I don't think I'm having head gasket issues, the boiling sound is the only problem I'm having.... everything else seems to be fine.

I'll change the coolant and see what's what. thanks again!

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[Zimgxp]

How about a bad coolant tank cap. Not allowing pressure to build up?