Hi everyone

I'm a total rookie-newb to boxsters and wrenching on any car ever.

when i returned home from a short trip in my 98 986, there was a puddle of green antifreeze in the driveway. i lifted the car and the plastic covers on the bottom of the car under the passenger side footwell were dripping green antifreeze.

i removed the covers and found this nipple kind of thing that runs between two pipes under the passenger side footwell that seems to be the source of the leak.

what is it and why is it leaking antifreeze?

and is it normal or is there a problem?

i searched for coolant/antifreeze leaks and nothing came up that was similar to what i am seeing. i looked in the bentley manual and the dempsey book and no mention of this nipple.

the coolant tank is very full when cool. the trunk carpet is dry although i did not look under the plywood.

i didn't notice the temp gauge so i don't know if it was reading high.

you have all been so helpful in the past please help me figure this out.

thank you

 

You say the coolant tank 'is very full when cool'. This may be your problem. The tank should be at the low mark or slightly above when cool and at the high mark or slightly below when hot. What is likely happening is your coolant is expanding when hot and the pressure release on the cap is letting out the overflow down the tube to the ground which it is designed to do. You say the cooolant is under the passenger footwell but it could make it there from anywhere because of the underbody panels. The overflow tube itself is under the coolant tank.

So, when cold remove as much coolant as necessary to get just above the low coolant mark using a turkey baster. Also, make sure you have the latest coolant cap installed (the P/N should end in .04). Older caps sometimes have a weak pressure release spring letting coolant out under low pressure. And this may sound simple but make sure the cap is not cross threaded and tightened properly. The one and only time my coolant burped out was when I anadvertantly cross threaded the cap.

If this doesn't solve your problem you may have a leaky coolant tank. This is very common considering these cars are getting on in years. The fix isn't cheap but necessary if the tank is indeed cracked. Cross your fingers that it is the coolant level or perhaps a $20.00 coolant cap.

 

The cap is $28 last time I looked. When I replaced mine, the coolant reservoir was about $60 from Amazon. Most of the fellers here don't recommend using an aftermarket tank, but mine has been okay. Green antifreeze is the wrong stuff for a Porsche, it should be the red stuff. The green stuff has phosphates, the red stuff is phosphate free--mix them and you will get jelling. When I flushed mine, I replaced the red stuff with orange Prestone, which is phosphate free and relatively cheap. Dexcool it's called. The fellers here don't like Dexcool, but if you flush the old stuff out and use the new coolant as directed (cut it with distilled water) it should be okay. Nice thing about the Prestone is it's relatively inexpensive and available almost everywhere. And distilled water is less than a buck a gallon. If you carry some in your trunk, you can also drink it if you get thirsty.

The local guy who owns the Indie shop gave me a cap, I gave him a 5 star rating on Google and Yelp. Indie guys a way more likely to give you a straight answer than the service writer at the Porsche dealership.

Btw, you mention "passengers footwell" do you mean the floorboard that's ahead of the passenger seat? If that's dripping, you may have a leaking heater core. There's a drain up there somewhere that lets condensation from the A/C escape.

A little coolant leak is okay, massive puddles aren't. If you can't get it resolved, ask your local Indie to diagnose the problem. There are no NEW Porsche problems and he or she have probably seen the cause of your leak many times before. Pay for expertise!

 

Coolant leaks are not normal and should be found and addressed. A leak lets pressure bleed away and it is pressure that keeps the hot (>212F) coolant from boiling. If it boils it creates steam pockets in the cooling passages which can work to insulate the hot surfaces from contact with the coolant leading to localized overheating. This can result in serious engine damage.

As for the coolant pipes under the car I would be surprised there is any nipple or valve in the piping but I am not familiar with the piping.

All I can offer is a coolant leak can be one place but the coolant can flow anywhere and everywhere and where you see coolant is not necessarily where the leak is.

The original radiator cap part number -00 ? is suspect. My advice is to get a new one just to be safe. I do not recall the newer cap part numbers. While in my experience the only thing the old cap let leak was water vapor if the cap can't maintain pressure as I covered above this can be a problem leading to steam pockets forming which can cause the system to be too full and force coolant out the cap or some other place.

There is also the coolant tank. The bottom seam can fail and under high temperature/high pressure conditions open up and let coolant leak. In the case of my car I observed hot coolant just gushing out the bottom of the tank. I let the car cool overnight then the next morning added about a gallon of distilled water to the coolant tank to bring the coolant level up to some acceptable level then started the engine and confirmed no leaks then drove the car a couple of miles to the dealer with no leaks. Of course in just that short distance the engine didn't get very warm at all. After the old tank was removed it was clear the tank had been leaking for some time, but just seeping.

A cold pressure test often fails to discover a leak.

A hot pressure test can help one discover a leak. You should use a garden hose to rinse off any residual anti-freeze/coolant. You can leave the under body panels off for this if you want.

Next top up the *cold* cooling system tank with distilled water to bring the level to at least the low mark but do *not* over fill the tank. Be sure the cap threads both the cap and tank threads are clean and the cap threads squarely onto the tank and you tighten the cap down properly. The cap can take more force to tighten than you might expect. But do not over tighten the cap you can damage it or the tank.

With the A/C off drive the car around town, just legal stop and go driving, until you hear the radiator fans come one. I used an OBD2 code reader plugging into the car's OBD2 port to monitor coolant temperature and the fans come on when the coolant reaches 212F. Head home. On your driveway raise RPMs to 1K or so and run the engine until your hear the fans come on. Shut off the engine.

The hot -- 212F or higher -- coolant will get hotter from the heat load of the engine and this will raise the pressure of the coolant. Because the system is hot if there is a leak it is more likely to leak and make itself known.

Be careful. When I did the above it didn't take any time before hot coolant was gushing from the coolant tank. This just behind the passenger side rear tire.

Check at the front of the car, the engine compartment -- which you should have exposed -- and under the car for any leak sign. Ideally the car should be in the air for a thorough check for leak sign can be made under the car -- but with extreme caution -- but in my case the leak was from the coolant tank and that was obvious.

After the car cools be sure you install the under body panels.

 

I think that rubber thing is just a semi-open/one-way drain plug for a hole in the floor. Check the interior (or trunk or wherever it is) above that thing and see if it's wet (possibly under the carpet or mat, etc.). That may help locate where the green stuff is coming from.

 

Wow thank you everyone for your help. This is so great to have such an amazing group of people.

So Trygve, Thank you for pointing out the not-quite nipple looking black rubber drain plug looking thing between the two coolant pipes. I failed to direct attention to this in the picture in my original post. The coolant is definitely coming from there.

I just drove it for about 20 minutes just now getting it up to temperature and the temp gauge was working fine AND only a single drip came from the black drain plug thing.

included are pictures of the coolant cap which looks to be original (ending in 00) and also of the area under the coolant tank which looks to be fine. There is a bit of moisture but it could be oil I’m not sure and certainly not enough to have leaked all the way down to that nipple thing.

So I guess the way forward is to replace the coolant cap at least as a start.