Coolant leak (again!)

[trauh]

Last year I replaced the coolant resorvoir tank and the cap (yes, with the latest versions). I noticed that the coolant level managed to find its way back below the Min level several times after the repair. No signs of leakage around the cap or tank. This spring I had the system flushed and replaced the fluid. Three weeks later it is back below Min (and no sign of leak, no drips on the floor, no antifreeze in the oil).

Any suggestion about what to check before I head to the dealer?

[1999Porsche911]

Last year I replaced the coolant resorvoir tank and the cap (yes, with the latest versions). I noticed that the coolant level managed to find its way back below the Min level several times after the repair. No signs of leakage around the cap or tank. This spring I had the system flushed and replaced the fluid. Three weeks later it is back below Min (and no sign of leak, no drips on the floor, no antifreeze in the oil).

Any suggestion about what to check before I head to the dealer?

Most likely coolant replacing air that was in the system. Top is off and see what happens.

[Izzy]

Is this your 2001? What mileage on it? Is the engine oil looking thin or "frothy" when you change it? If the above doesn't work (getting the air out), may be a different problem.

[wdonovan]

(Aside from the above which are both possibilities)

If you don't have white smoke and you can't smell antifreeze after running it hard, you probably don't have a leak.

[trauh]

Its my 2001 C2 cab. Original fill was done properly with bleeding. I topped off the reservoir and drove 10 miles. It was back down. No sign of oil mixing with antifreeze. I'm taking the car to the dealer on Monday. Sigh...

[Loren]

IMHO 10 miles is not enough. When I added my third radiator I bleed the system and topped up the coolant tank daily for over 1 week. Then it stabilized and I haven't added anything since.

[trauh]

I just filled the reservoir up again, opened the bleeder value, and took a 15 mile drive. The level did not seem to drop, but when I got home I noticed that the bleeder spring had fallen back over into the deactivated position but the black plastic valve stem was still popped up. E.g., there was something forcing it up (if I pressed down on the black plastic post, it would move down a bit). Is that normal, or could that be a problem?

[Loren]

Normal, it opens and closes all the time.

[trauh]

Here is an update. I've added almost 1/2 gallon of distilled water, and it now seems to be holding at the same level. I'll keep an eye on it. I had used a local, independent Porsche shop to change the coolant and test for a leak during spring tuneup, but they must not done as thorough a job bleeding it as they indicated. Sad, as it was an expensive coolant flush. Lesson learned (I hope). Thanks again Loren and company...

[Chuck Jones]

I got the same advice from Loren when I replaced the coolant tank. I was sure that I had a major problem going...I'd go and look and see that it was down since I last put in distilled water. This went on for quite some time....is would drop down a bit, I'd put more distilled water in, then check it in a couple days and find it down. Loren said to keep adding and checking the coolant and oil periodically just to be safe. Finally it must have gotten to the point where it's levelled off. I initially was a bit concerned about an intermix issue, but all seems quiet on the Western Front.

How come I never have to worry about this stuff with my Dodge diesel truck?