Coolant overflow question - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Twice I have had a puddle of antifreeze under the rear right tire after driving in hot weather (hot in Minnesota means 90 and the drives were short hops to the grocery store).. Looks like it might have expanded after I shut it off. The reservoir is pretty full and the bottom of the cap was wet like it had expanded up to that level. Anyone know if the overflow hose runs out at the right rear tire area? I am wondering if this is just a matter of the dealer (non-Porsche) I bought from simply overfilling the reservoir (he typed hopefully wishing for confirmation from all of the experience drivers here. ). I have only owned the car a couple of months and summer came late so haven’t had much hot weather experience with this auto. Oh, the temp gauge has been fine…not running too hot temperature-wise. Related question. Should the cooling fan continue to run for a bit after you shut down in hot weather? Seems different from car to car. My old Accord fan would run for quite a while but my Miata and A4s never do. Neither does my '02 Boxster (at least mine).

Check the water pump, a likely culprit, I've had two go bad with your exact symptom. In addition, your tank might be cracked and leaking through the trunk, check for under the carpets. Make sure your coolant cap's product number ends in 01 or better. The fan will run if needed, even after the car is turned off.

The coolant overflow comes out right above the rear passenger wheel. I had my entire coolant tank drain out one day. After a month at the stealership (and a lot of trouble with them) they concluded there was no problem, and probably just an air bubble or to much coolant. Unless you get a light, I wouldn't bother with the hassle I had to go through.

I checked and the cap number ends in .01 When I just looked the coolant level is a bit low in the reservior now but it is not leaking into the trunk. I had heard about the leaking tanks and checked that.

Before you toss it to the dealer...... it sounds like water pump is fine b/c you aren't overheating while operating but rather it's leaking out after shut down (a true sign of air trapped, bad cap or possibly pump). If the tank and trunk aren't wet, that's a good sign there aren't any leaks. So couple of things to check before you give up and brace yourself for an expensive fix..... (in order BTW) First off, let the vehicle cool down completely (overnight suggested). Then, using a flashlight, carefully check the coolant level. The Porsche coolant (mixed w/ 50% distilled water) is extremely difficult to read accurately via the tank guage w/out a flashlight. If it's over full, use a turkey baster to suck some out. In total, the system holds 18 liters IIRC. Next, check the bleeder valve and o-rings. They are known to go bad. (info in archives on how to access which you'll need for step below anyhow). If lot's of residue around valve - that's most likely source of problem or could just need bled. Now make sure the system is air free by properly bleeding it. (directions are in the archives - takes about 30 min to do). Short cut method, but not 100% gtd effective, is to open the bleeder valve (and leave open) and drive around w/ some random accelerations, upto 5K RPM, for about 15min. close valve and test her out). This will be when you'll check to make sure both radiator fans are working as well, but again since no overheat issue while driving, sounds like you're ok there. Hopefully you've found the no cost (bleeder valve will cost though) problem. If not, these things will definitely cost $ to diagnose.... Take to indy for a quick pressure test on entire system (about 1hr). You need to find a shop that has the special adapter to fit the Porsche coolant tank. Yes, you have the updated cap but it could still be defective..... might be worth picking up a new one ~ $15-20 (even at dealer) If none of this helps then most likely you'll need to have someone check the water pump to make sure it's working. You didn't say, not that I saw at least, how many miles are on your '02. My guess is w/ under 75K water pump should be good so you hopefully will find your answer in one of the above no cost options. Good luck and let us know the results.

Thanks for the info. The car only has 26k on it and reservior level was down to the minimum tonight. Might try some of your suggestions this weekend if my auto buddy has time to open up his Man Cave (aka his four car garage) and help. Otherwise might take it to the small import guy who inspected my car before I bought it. He was a Porsche certified mechanic guy before he opened his own small import service shop.

Okay, I found the instructions/photos of the bleeder value and can do the easy "driving bleed" but couldn't find the 30 minute bleed instructions. Russ

With each pound of pressure, the boiling temp of water is increased 10 degrees. The Boxster's cooling system is pressurized to 19psi. So, use extreme caution when removing the coolant cap when engine is warm/hot. Cover the cap w/ a towel when loosening (you'll most likely need one anyhow since it will be H-O-T hot! Anyhow, from the Bentley manual.... - For tiptronic, remove fuse B1 in fuse panel to disable ATF cooler shut-off valve) - remove filler neck trim cover - open up bleeder valve locking clip - fill w/ coolant to bottom edge of filler neck - run engine at idle. Top off w/ coolant until no more can be added when engine idle is raised sharply - replace coolant cap and tighten. Warm up engine for about 10 min at approx 2500 rpm until coolant thermostat opens. To be sure engine is fully warmed up, check to see that radiator cooling fans in front wheel wells are on. - allow engine to run addl 5 minutes at 2500 rpm. Every 30 seconds briefly rev engine to 5000 rpm - open reservoir cap, relieving coolant pressure w/ extreme care. Top off coolant, close cap and repeat process of intermittently revving to 5000K rpm for 5 minutes - allow engine to idle until radiator cooling fans cycle on and off once. Shut off engine and open reservoir cap, relieving coolant pressure w/ care - top off coolant until level reaches max - flip down bleeder valve locking clip -replace filler neck trim cover and cap. - If tiptronic, replace fuse B1 Good luck NOTE: the cooling system has a capacity of 18 liters IIRC and mix is 50/50 coolant w/ distilled water. As such, unless you've added a bunch of water recently, you should be ok to just use distilled water for the top offs (anytime as well as those called for during the bleeding process.)

I am going to go do the driving around easy thing first. Assume at the end of that you: - Shut off engine and open reservoir cap, relieving coolant pressure w/ care - top off coolant until level reaches max - flip down bleeder valve locking clip -replace filler neck trim cover and cap. BTW, I took off the filler cover and there was coolant condensed under it and puddled ever so slightly on the top of the reservoir tank. Minute amount but it had to come from somewhere. I am wondering if this might be from a bad cap or maybe those o-rings on the bleeder value. I think I will do the drive-about air bleed thingy and buy a new cap. If those don't do it I will try the o-rings. Russ

with condensation under the filler cover..... it definitely sounds like the o-rings are bad. The entire valve could be bad but doubt it based on the valve's pressure thresholds (see pressure test below). When the entire valve is bad, the results are much like having a bad coolant cap and you end up w/ what's affectionately known as a peeing Boxster. When this occurs, it dumps almost the entire cooling system contents in one shot after engine shutdown. It'll be plainly obvious by either the rushing water sound you hear or the extremely large puddle in front of the right rear wheel Anyhow, some dealers may try and tell (thus sell) you the entire tank needs replaced....... but the o-rings and valve assembly are available separate [from the tank]. Sunset or Suncoast sells them in case you don't have luck locally. Here's a write up on how to replace the o-rings: Coolant Tank Bleeder Vavle O-Ring Replacement Incidentally, if you ever do a pressure test on the system, you are to pressurize it to normal operating levels - 19psi. The bleeder valve is designed to open at 20psi and close at 14psi. So at 19psi, you'll be below the threshold of it activating and can truly test the system for leaks. I wouldn't worry about having a test done unless your problem persists after you replace the o-rings. Good luck

I had the same thing happen to me I replaced the coolant cap evidently the ones ending in 00 are faulty I have an 02 Boxster S I replaced it with the newer caps ending with 02 ....problem fixed

I bought a new cap and did the drive around "easy bleed" and so far so good. The car has not gone wee wee on the floor or parkling lots and haven't had any condensation under the cover.