Disappearing coolant leak?

[Rob175]

OK.....water pump has been replaced so the obvious leaks in front of the rear wheel on the passenger side are no longer........BUT......

I now have some very small coolant drops (at engine cool-down) appearing behind the rear passenger wheel with a few drops where the bumper cover screw is located (the one closest to the passenger rear tire). I pulled the truck lining up and the lining along with the truck floor is bone dry BUT THEN I realized that there is what looks like a "black masonite material" that creates a sub-floor which is raised up from the steel body. After removing the section of "sub-flooring closest to the coolant holding tank there is a very small amount of the newest bright yellow coolant that I soaked up with paper towels. I've NEVER had a leak under that portion of the car and there really wasn't very much....AND it was the yellow colored coolant my mechanic used to refill the system after he drained (the old coolant was more greenish)....so I know it's the new stuff used for the new water pump2 weeks ago.

I wiped the tank and the connecting hoses with paper towel and the towel was dry.....only the metal trunk floor had a little bit of coolant, which as I said, I dried up with paper towel.....

So here's my question, since I've never before had any sort of drops coming from the rear bumper cover area and know its the NEW yellow coolant added 2 weeks ago during the water pump install job (complete coolant flush and fill), and all sides of the tank and hoses are dry, could it just be a coincidence or could it somehow be related to the water pump install? (overfill, sloshing around in the tank, etc)......where does the tank overflow to?

Any thoughts?

Obviously, I plan on driving the car in the next day or two and then once again checking for any additional coolant in the trunk again.

[Starter986]

I'm guessing it burped... maybe some air in the system, or too much coolant.

We're you running it hot and hard before you shut it off/down? I believe the recommendation is to, after running the engine hard, is to let it idle for a couple of minutes in the driveway... then shut 'er down.

Wiser minds?

[Rob175]

I suppose....but IF it "burped" or it was overfilled I would assume it would flow out of the overflow tube (IF there is such a tube) and not deposit a little bit in the trunk.
As I wrote it just seems too coincidental to the water pump replacement 10 days earlier.

I guess I'll remove the trunk carpet and sub-floor after I drive it next and inspect it again.

[blue62]

Originally Posted by Rob175

I suppose....but IF it "burped" or it was overfilled I would assume it would flow out of the overflow tube (IF there is such a tube) and not deposit a little bit in the trunk.
As I wrote it just seems too coincidental to the water pump replacement 10 days earlier.

I guess I'll remove the trunk carpet and sub-floor after I drive it next and inspect it again.

If it was me I would leave the carpet and sub floor out for a number of drives and check it each time I drove it. Then I would know for sure. Also there is a wire loop on top the coolant tank it is a bleeder valve there is a gasket under it which can go bad and cause some coolant weeping. Or the service tech could have just spilled a little around the top of the tank and it found its way to the ground.

[Rob175]

Thanks for the suggestion.....I removed the carpet, drove it all day, stopping several times to check the trunk. It took about 3 trunk checks before the leak once again showed up. I drove it to my "indy" Porsche guys and sure enough the bottom far corner of the tank (seen with an inspection mirror) has what looks like stress cracks (btw, the plastic tank is very dark brownish/yellow). These cracks appear to be dripping coolant once the coolant gets hot and the system gets pressurized. It holds the coolant for awhile than just "spits" it out all at once, then pressure goes down a bit, the coolant stops leaking from the cracks, until the pressure builds up once again and it "spits" again.....and the process just keeps repeating. That's why it sometimes appears that the leak is gone in between clean-ups.

So.....it goes to the shop tomorrow for a "genuine" Porsche coolant tank replacement. Between the new water pump replacement 2 weeks ago and a coolant tank replacement this week i'm "tapped out". My 1998 Boxster has never cost me as much as it has in the last few weeks. Hopefully it won't need anything else for this driving season. I can't really complain because the car has barely cost me anything over the 15 years that I've owned it, except for the usual maintenance, tires, brakes, oil changes, battery, etc etc.

Before anyone suggests I perform the work myself, don't bother. I have no way to lift the car, nobody to assist and limited space and expertise to attack it so I "pay the piper"....LOL

[alynch]

Originally Posted by Rob175

OK.....water pump has been replaced so the obvious leaks in front of the rear wheel on the passenger side are no longer........BUT......

I now have some very small coolant drops (at engine cool-down) appearing behind the rear passenger wheel with a few drops where the bumper cover screw is located (the one closest to the passenger rear tire). I pulled the truck lining up and the lining along with the truck floor is bone dry BUT THEN I realized that there is what looks like a "black masonite material" that creates a sub-floor which is raised up from the steel body. After removing the section of "sub-flooring closest to the coolant holding tank there is a very small amount of the newest bright yellow coolant that I soaked up with paper towels. I've NEVER had a leak under that portion of the car and there really wasn't very much....AND it was the yellow colored coolant my mechanic used to refill the system after he drained (the old coolant was more greenish)....so I know it's the new stuff used for the new water pump2 weeks ago.

I wiped the tank and the connecting hoses with paper towel and the towel was dry.....only the metal trunk floor had a little bit of coolant, which as I said, I dried up with paper towel.....

So here's my question, since I've never before had any sort of drops coming from the rear bumper cover area and know its the NEW yellow coolant added 2 weeks ago during the water pump install job (complete coolant flush and fill), and all sides of the tank and hoses are dry, could it just be a coincidence or could it somehow be related to the water pump install? (overfill, sloshing around in the tank, etc)......where does the tank overflow to?

Any thoughts?

Obviously, I plan on driving the car in the next day or two and then once again checking for any additional coolant in the trunk again.

Check the dimple in the middle of the underside of the coolant tank. That was where mine had a crack and the coolant was seeping out into the trunk. The coolant was then leaking around the rubber plug in the trunk floor eventually ending up in the same location you described above.