questions about cooling system and repair...

[rsfeller]

We we did the PIA failed tubes under the intake manifold...I have to say this job was far more difficult then I imaged. For those doing it in 5-6 hours...good job. We had about 12 hours into but that had mostly to do with every single plastic tube breaking inside the engine cavity...but I digress...

Filled up system and took for test drive. Saw a bit antifreeze under the drive axle on both driver and pass side...taste test approved. Additionally, the cap had pressure the first few times I slowly opened it but doesn't seem to be holding much pressure now when opened (again slowly) hot. As you know with such a fix you smell antifreeze from the old leak for quite some time and we cannot see our fix area to see if all new seals are good. Wish I could have pressure tested then (didn't have parts). After more test drives I have not seen a leak under the car (like before) but again the pressure on the cap is low or non-existent.

Here are my questions:

1. is there another failure area such as the overflow tank that could be blame for any leaking and/or pressure concerns. (this wouldn't explain the puddle we say on the driver side).

2. Are the caps prone to failure and thus not a good seal?

3. Are Vw/Audi pressure testers going to work to test the Porsche system. It appears they have the same inner valve on the cap but the treads are noticeably different then my 96 Passat.

Water level dropped slightly after test drives (from max to min) but this may be expected due to air pockets filling up during high rpm and temp driving. The system took almost 2 gallons of 50/50 mix post fix and the pipe (small ones not large) did have a small crack as well as fluid in the manifold area...so there was a concern there.

I think my mechanic buddy thinks I'm being paranoid and i should just drive it home but I wanted it to sit for the night to see if any fluid leaked underneath and try to find a affordable pressure tester. It's not my $50K toy, so I'm understandably cautious.

Any useful comments would be appreciated for any other leak areas to consider or if the antifreeze I found on the ground (again new) was most likely hidding from the previous leak and simply dumped when the vehicle finally moved and/or warmed.

Edited September 15, 2010 by rsfeller

[NelsonMX]

To answer your questions....

Yes the catchment tank has been known to fail, that is, not hold pressure and leak....

The tank cap has an o ring seal that can get cut and allow pressure and coolant out the overflow hose...The cap is not expensive do if there is any doubt change it.

I'm not sure about the VW or Audi testers, but I used an Airlift 550000 which evacuates the system and thus uses the vacuum to fill the system. The idea is when you draw the vacuum it should hold the required setting, that is no leaks. This tester is fitted to the catchment tank cap so essentially you are testing the complete system for leaks....

Hope this is of some help...

Rgds,

Bob

[wvicary]

I have not come across any failures with the tanks but the water pumps have given problems.