19psi

You got air in the system and it's belching it out. You're low on coolant now because you had air taking up its place.
Do what Mrmerlin told you up above and it should be fine.

super928

I removed the engine freeze plugs and little debris came out but it's still not circulating correctly. Any ideas guys ? (besides the water pump)

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linderpat

See my post above. I think you have a clog. Maybe run the hose through the block (with engine off) before re-installing the block plugs and flushing, but otherwise, flush it thoroughly.

FredR

What grounds do you have to believe the water pump is OK? If the system is full and bled correctly the only things that can stop coolant circulating that I can visualise are a failed closed thermostat [not likely in this case] or a water pump that has lost the impeller.

If the coolant is puking from the reservoir a sure sign that coolant is not circulating suggesting the WP has gone. Apologies if I am missing something here.

How old is the current water pump? I did not see anything suggesting this has been changed.

Rgds

Fred

Mrmerlin

if you follow the advice i posted your cooling system should be working as it should ,
UNLESS you have a failed water pump.

The stop leak will only fill in small occlusions in the cooling system ,
If you were to examine a head gasket,
you will find the holes are smaller to the front and get larger to rear of the head,
thus to make the cooling system work.

please report your findings after doing the filling and driving sequence I posted

SeanR

.... wrong post

super928

The water pump was replaced about six years ago. So it's probably time to replace it again. I'll flush it once again and if there's no improvement I'll replace it and the timing belt. Who makes the best water pump ?

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rcwkr

My first 928 was a badly neglected '79 euro. It's first and most pressing problem was nearly immediate overheating. I had the radiator professionally cleaned, actually ran a mixture of gasoline and water through the cooling system, because the radiator had developed a leak between the oil and water cooling "compartments" in the rad. None of this helped. I figured that the water pump wasn't circulating the coolant at all, and began the process of replacing it. Turns out that the pump was new, as was the timing belt driving it. It had just not been installed with enough tension to drive the pump.

super928

Thanks I'll check for belt tension also.

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Imo000

Pull the thermostat and put it in a pot of boiling water. Also see if the rear thermostat gasket is there and in good shape. I've got mixed feeling on changing water pumps because of age.

super928

Gentlemen Thanks for all your advice!!!
I flushed my coolant system two times today and removed the freeze plugs and I'm Happy to say that it's circulating Correctly !!!

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Ladybug83

Nice! Good job !

Imo000

What freeze plugs?

super928

Sorry ! Block drain plugs !

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