Porsche 1999' cooling system Gremlin

[pessemist]

Hello guys.

Kinda at my wits end here. Looked through forum but my issue still eludes me.

I have a 1999' 911 Standard Porsche coupe.

After about 30 minutes of driving the low coolant light comes on. I find it about a quart low.

1. The oil is pristine so the coolant isn't going there.

2. No bubbles in the coolant while watching it with the engine warm and the coolant cap off. So no head gasket suspected. (yet)

3. The car is pristine with 99K miles on it. never kept out overnight.

4. The overflow coolant bottle is not old and yellow looking. In fact it looks bright white, like brand new.

Some history. After driving the car about 200 miles the low coolant light came on. I was on the expressway and it was a pouring thunderstorm so I brought it home. The actual temperature gauge never rose past the '0' in the 180 mark.

As I pulled into the garage steam started pouring out of the back end. The cooling cap had vented a lot of antifreeze over the muffler (quite a scare). After it cooled it took about a gallon and a half to re-fill the reservoir.

Now I drive about 20-30 minutes and the low cooling level light comes on and I am down about a quart.

I ran the car at idle in the driveway for well past warm up. I can detect no leaks of any kind, anywhere. I even put large trays under the car in various spots to see if I was missing anything.

I inspected all around the overflow bottle but not so much as a drop was detected with the engine warmed up!

My neck step is to fork out $100 for a cooling system pressure tester. Just my luck that O'Reily auto doesn't have the correct adapter for Porsche in their loaner kit.

Any suggestions or tests you guys can recommend? Wouldn't the leak be detectable with the car running hot just as well as with a cooling system pressurizer?

The engine purrs flawlessly otherwise.

Thanks in advance for any suggestions.

Doug

[pessemist]

well, wherever the coolant is going I can't find the leak. Just ordered a new Coolant Tank cap on the premise that maybe the cap is weak and letting a little steam off when the car is run. If there is a drip somewhere it only happens when the car is driven around and not when idling for 35 minutes in garage.

I hate Gremlins......

[tonythetarga]

That's a good start. The cap you want should have the -04 part number. My guess is the original cap was the problem as there was an update to get rid of those and replace with the -04 cap. Review the coolant flush procedure. As I recall, there is a second cap with a wire (triangle looking thing) on top and it needs to be in the correct position. One position for bleeding, one position for normal running.

[wayne robson]

Hi Doug when you lost coolant at the first, then added more at home or later,
what can happen ,the system then requires primed or and vented,
you should run from cold with heater on hot side, while warming up
add coolant, this opens up the heater valves, at get rid of any air in
the system, also on your car i think there is a vent or similiar item near top or
inside radiator cap, open this when it is nearly hot, then top up as required
This should fix your problem.---- except for worn belts,hoses,old coolant , etc.
regards

[pessemist]

I got the new coolant cap -04 and meticulously followed the bleeding procedure. I'll let you guys know if it works! Thanks!

[pessemist]

Originally Posted by pessemist

I got the new coolant cap -04 and meticulously followed the bleeding procedure. I'll let you guys know if it works! Thanks!

The bleeding of the cooling system & replacement of the original cooling cap seems to have fixed the problem.

I never noticed the engine compartment fan coming on--even driving in stop & go with A/C blasting. I unplugged sensor and fan turned on so I thought the sensor might be bad and replaced it.

One note: A guy posted that the key merely has to be in the accessory position to test the fan by disconnecting the ambient temperature sensor. I found that the test only works if the engine is actually running.

I did use a heat gun to test the old sensor. It took a LOT of heat but the switch eventually opened. (shrugs) New one in anyways.

[looneybin]

glad you got it sorted, burping the system is a PITA
My engine compartment fan has only come on 1 time that i know of (it's loud), and it gets up to 110+ here