Hey guys,

I seem to have a coolant leak that overnight leaves a small mark in my parking spot behind the rear drivers side tire. It seems to be dripping off of the turbo reservoir drain plug but I cannot trace it up. It looks like I may have a little dampness up front but then the coolant reservoir tank doesnt seem to be low it seems to be level perfectly. Once I dried off the leak it isnt dripping anymore.

Any ideas on what this could be? I'll attach some photos of the mark on the ground, where I saw the drip from and anything else I can photograph later.

 

I would clean the drip off, like you did, then put a cardboard box under it to see if it comes back...

 

Are you still using the original reservoir? You can easily tell - is your reservoir yellow or white? If it's yellow - get it out of there as fast as you can. Eventually coolant will go right through the side.

 

My 996 Turbo coolant tank never leaked, but the one in my Boxster did, big time.

A hot cooling system pressure "test" can really make a small leak become big which makes identifying it easier.

What I did was to top up -- with distilled water -- the coolant tank then put the cap on nice and tight. It takes more force to tighten the cap than at least I expected.

Then with the A/C system off I drove the car around in town in stop and go driving until the radiator fans came on. Then I drove home and on my drive raised RPMs to just over 1K and held the RPMs at the level until the radiator fans came on. Then I shut off the engine.

The heat load of the engine raised coolant temperature -- already at 212F which is the temperature at which the radiator fans come on low speed -- and pressure. With everything hot if there is any leak watch out...

When I did this hot cooling system pressure test with my Boxster it wasn't long after I shut off the engine that the coolant tank was gushing hot coolant. Turns out the mold seam along the bottom of the tank had failed but most of the time the coolant wasn't hot enough to leak out or if it did only just a bit. That it had been leaking some was evident from the build up of coolant "crust". I let the engine cool down over night then topped up the tank with distilled water the next morning and started the engine. After a quick check to make there were no leaks I drove the car a couple of miles to the dealer and had a new tank installed.

So while my Turbo's tank never leaked in the OP's case as you mentioned it could very well be the source of the coolant leak. Might mention both of my cars required a new coolant tank cap. The old/bad cap would let water vapor leak out. There was never any anti-freeze but some water condensation under the rear trunk lid in the fluid service bay area.

With the Turbo and its "open" engine lid I don't recall seeing any condensation but I replaced the cap nevertheless when the cooling system was manifesting a slow drop in the coolant level.