Cooling leak 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

[steely]

You might have better luck in the Porsche 996/997/991 Forum - Pelican Parts Technical BBS.

This one is mostly air cooled.
But check back just in case.

HTH

[pessemist]

Thanks I'll repost it over there.