NineFiveWon

Hello!
I am new to my 944 and am I also a new poster (long time reader) of this forum. Parked my car went out an hour later and coolant was all over the ground.
I hobbled the car into my lift and pressure tested it, NO leaks. None. I tested it at 20psi and got nothing. Topped it off. Started the car go to drive it, pulling out of my shop, whats there... COOLANT! Cooled the car down, tested it again... nothing! Car held 20psi.

I checked all coolant hoses I could see for leaks, water pump, thermostat... nothing.

What am I missing?

Thanks for all help in advance, this is one has me scratching my head!

MAGK944

Heater control valve maybe? Thinking the coolant system will pressure test ok if the valve is not activated but might fail as soon as it has vacuum and opens.

StoogeMoe

When's the last time you changed your water pump? Sometimes they only leak when spinning.

NineFiveWon

Heater Control valve... I will check on that.

Water pump is dry. Had it on the lift revving it waiting for anything... one drop!

NineFiveWon

One question though I can get cold air out of my vents, wouldn't this mean the HCV is working properly?

John_AZ

Do you have the correct coolant/radiator cap on the reservoir?

The early cars took a 110KPA/16 pound cap
The later cars took a 150KPA/21 pound cap.

I have tested often with the radiator pressure tester.
Common areas for leaks:
WP pin hole leaks in the gasket.
Heater control valve as mentioned
Coolant overflow hose nipple on the radiator
Radiator fan relay/switch gasket

I only use 10-12 pounds of pressure when testing. 20 pounds of pressure will cause a leak between the plastic and metal on the radiator. The rubber seal will leak with that much pressure on the tester.

The leak you mention should be very obvious.

John

Yarf

Maybe the expansion cap is bad, allowing the fluid to escape.

John_AZ

More,
Have you seen Bruce Arnns info?

http://arnnworx.com/h2o-pump.htm

NineFiveWon

Tested it again at 12lbs and I was only able to get a tiny leak around the hose going to the thermostat. It took about 20minutes for it to leak a drop. I'll patch it up and see how it goes from there. Heater control valve was completely dry...

Thanks for all the info so far guys. This is a great forum.

I was curious about the auxilary water system. I am having a hard time finding any info. Does it use a separate pump? It popped into my mind just thinking about how when it initially leaked it was after I turned the car off...

Cheers!

bonus12

interesting because the auxiliary water pump cools the turbo after the engine is shut down.

Sentinelist

I had a small leak awhile back on my aux. pump for the turbo- definitely check the two connections there. If not there, it's probably one of the two hoses coming off the reservoir. Check the return line running above the exhaust manifold on the other side of the bay as well, as well as the firewall connection. The one leading up to the HCF can easily leak if not tightened down enough. Gotta find out where under the engine bay the leaking is coming from.

NineFiveWon

I hate to post idiot questions but the aux water system is still a bit unclear to me.
Does it use the same water from the cooling system?

KevinGross

If the radiator fan switch is not working, the engine can heat soak when parked, boil coolant, push it out the overflow. BTDT.

Kevin
Catellus Engineering

NineFiveWon

Installed a new lower radiator hose (cobra shaped goes to thermostat/water pump) and it has been idling happily for 45 minutes.

I still suspect the leak at the hose is not the issue I initially had, but I will let you know.

John/Kevin thank you guys for all your help. I am very happy to be apart of front engine porsche club now.

Cheers!

aleko951

check the hose behind your intake manifold they tend to crack.