sons car, dumps coolant 10 mins after shutdown

New Here and need help on my Son's '99 G.P. with the 3.1 and 115,000 miles. The car runs and drives great but has a coolant issue.

The car runs normal temps. It is still warm here in Mesa during the day, last night it was about 70, we drove down the highway and the car ran about 180, he said on a warm day in traffic the car can get as high as 200 so that all seems normal

He will drive long enought to warm it up and the after he parks it will leak coolant inside and behind the pass. front tire, assumedly from the overflow, BUT it does not do it right away, it takes 5 to 10 minutes to start and it will leak out a small puddle.

We used to bleed the cooling system in the race cars with them not running and the front raised by opening the bleed screw on the t-stat housing and filling the radiator till it leaked from the bleed screw, then tighten the screw and finish filling the radiator and cap it, we did this to his car last night and then drove for about ten minutes and parked at home. There was no leaking when we got out and looked underneath but we came back out after about 15 minutes and there was a puddle (about the size of a Large dog pee spot!!!)

I have been searching for ideas and that is how I ended up here and I read that you should have the car warmed and running to bleed the system. Could this still be part of the problem, could it be that it is sucking air some place as it cools down.....I am not sure what to check next!!!

There is no antifreeze in the oil or vice-versa and the car does not smoke at all, as I said above, the car runs great, smooth and good power.


Any help would be appreciated!

I think your issue may be with the water pump. When it is running the pressure remains constant and the pump works fine. When you shut the car off the pressure increases and forces the water to leak out of one of the seals or the gaskets around the pump. I would remove and replace pump and see what happens. Based on your description this would be the easiest area to work on. Otherwise you may have a cracked head or block that is causing this issue.

Cracked head or block would have other problems also and we do not have any of that, also, it does not seem to be leaking by the water pump or around the pump seals


I will look tho

What condition is the radiator cap in? The pressure even with engine off would have to exceed 15 psi to get overflow to the reservoir.

In a worse case scenario you may (hope not) have the classic lower intake manifold gasket problem common on the 3100 VINs "M" and "J".

Also, try bleeding after the engine warms up to operating temperature to make sure no air is in the cooling system. Good luck.

OK, will try a warm bleed next and this time will stay by the car to verify exactly where is is leaking in case it is the pump a stated

If it is leaking on the inside, it sounds like the heater core.

If it is leaking on the inside, it sounds like the heater core.

No, sorry, it is under the car, inside and a little behind the front pass tire.


I will see hime tonight so I am going to try the warm bleed as above

Thanks

Possible crack in the overflow tank.... just above the "full when hot" line? Or maybe if the lower intake is leaking to the outside on the back of the engine onto the exhaust, you would only see fluid on the ground when the exhaust cooled. not much else on that side to leak from.