Mysterious coolant leak - 986 Forum - The Community for Porsche Boxster & Cayman Owners

aps1231 · 04-14-2009, 03:57 PM

Just got my Boxster from the 60,000 miles service. It ran like a dream for a week, then I noticed the engine temperature going up abnormally. It was short one gallon of coolant. I filled it up, drove three miles to the shop, then the temperature started going up again. I stopped immediately and witnessed another gallon of coolant leaving the car, approximately next to the right rear wheel. I then got it towed to the shop.

They pressure tested it, let the engine run for ~45', no leak!! They say there's nothing wrong with it!?

Also, worth to mention, the Porsche dealer had to replace the overflow tank (cracked) and the cap one year ago. I know use a mechanic specialized in imports, after a few bad experiences with the dealer.

I noticed similar stories in the forum, but didn't have a good explanation. Does it sound like the overflow tank again (although pressure tested) or the water pump?

Thanks in advance for any tip you can give me.

aps

23109VC · 04-14-2009, 06:48 PM

water pump? it's located near the bottom of the motor somewhat on the right side more toward the rear than the front. i can't say it's at the "right rear wheel" but that's probably the wheel it's closest to.

mine is leaking off/on. i have occasionally seen a small puddle in that general area and mine is leaking, but only here/there.

just a thought.

releese78 · 04-14-2009, 07:49 PM

Check your coolant cap. It should end with a .02 or .03 if it's one of the updated models. If it was pressure tested, that should rule out the entire system including lines, hoses, radiators and pump. Generally a pressure test device screws on in place of your coolant cap, so this only leaves the cap to be a failure point.

Being that you lost almost a gallon in a few miles, I would imagine that you'd see some water in the trunk, or condensation in the lid, if not damp carpet in the trunk. If the cap leaks, it usually dissapates as steam leaving a bit of mist on your trunk lid rather than a full stream of leakage. Another tell-tale would be the odor of coolant when you open your trunk.

Should you need a new cap, check with Suncoast www.e-partssales.com they have pretty low prices on OEM parts. Good luck!

nola911 · 04-14-2009, 07:58 PM

I had a very similar situation. For whatever reason, the shop replaced the thermostat and it never did it again.

aps1231 · 04-14-2009, 08:36 PM

All,

Thanks for the suggestions. I don't think it's the pressure cap, as it was already replaced and the coolant was flowing from under the engine, in a matter of minutes, definitely not in the trunk. We'll check the thermostat, though, but I still suspect the plastic overflow tank and the hoses, or the water pump. Why it suddenly spills the coolant after driving a couple of miles, and does not when idling for 45' and while pressure tested remains to me a mystery.

aps1231 · 04-26-2009, 11:22 AM

Back to the drawing board. The mechanic says he pressured tested the coolant system, let the engine run for 45' and didn't find any leak. He then replaced the thermostat, pressure cap and bleeder valve, but the car is still loosing coolant. Today, I just drove two miles and left a trail of coolant (~ one gallon) on the road. The temperature was perfectly normal. The coolant drips profusely from the bottom, next to the rear right axle. I checked the overflow plastic bottle and connections. There's a little bit of coolant there, but there's no way one gallon would have gone thru the cap.

The mechanic suspects a head gasket leak. Is there any way for the coolant to escape in that area, other than the pressure cap?

Again, your experience and advice would be welcome.

aps1231 · 04-26-2009, 02:28 PM

Additional info. I started the engine with the expansion tank almost empty. In a couple of minutes, the level goes to the top and some coolant leaks thru the cap, while more coolant drips profusely from the bottom. Coolant temperature was about 185F.

nola911 · 04-26-2009, 08:32 PM

Could it be overfilled? Mine definitely did that before I had over-heating problems. Im not totally familiar with the coolant systems, but I thought it had an overflow, or that the cap relieved pressure and fluid. I know I had a problem with water vs. coolant

I wish I could be more helpful, I just really don't know enough. Let me also recommend the forum at renntech for technical stuff.

jjanari · 04-27-2009, 06:01 AM

also, I would check your oil level to make sure you're not getting coolant in the oil, though I doubt that's what's happening from you description since you seem to see where all the coolant is going (on your floor!). (I also question the suspect head gasket diagnosis by your mech, but I'm certainly no mechanic). if it were my car, I would try and pinpoint the leak by getting the car up on ramps the next time it happens to see exactly where the coolant is coming from.

aps1231 · 04-27-2009, 07:13 AM

Thank you for your replies.

1- The oil is clear like new (Just got the 60,000 miles service)
2- The coolant is definitely not overfilled. In fact, last night, I removed the cap, started the engine with a low coolant level (Bottom of the expansion tank), and then suddenly, the coolant went up and spilled profusely all over.

What's puzzling me is that it's intermittent. I drove the car 20 miles after replacing the thermostat, with no problems (Just lost two cups of collant). Then I got this problem again yesterday after driving two miles, and the temperature was a normal 185F. It looks like suddenly some gases escape into the coolant and push up the coolant out of the expansion tank.

stephen wilson · 04-27-2009, 07:51 AM

I hate to mention it, but, head gasket? You could try a compression or leak-down check. My Integra wouldn't "take water", and it ended up being the head gasket from being overheated.

machone · 07-13-2009, 05:59 AM

Any resolution to this? My '99 has the exact same symptoms, looking for any clues on what to try.

Thanks,
-Michael

Keith Newby · 07-13-2009, 07:51 AM

I just purchased another coolant cap and it's been updated once again with the number ending in 04. The dealer had both an 03 and 04 from which to choose. As a preventative measure I replaced the original cap ending in 00 with an 02 which, after 6-months, failed leaving a nice stream of coolant behind the right rear wheel. Let's see how the new cap fairs. The original cap never failed and I'm using it as a backup.

sb01box · 07-15-2009, 07:54 PM

Quote:

Originally Posted by Keith Newby

I just purchased another coolant cap and it's been updated once again with the number ending in 04. The dealer had both an 03 and 04 from which to choose. As a preventative measure I replaced the original cap ending in 00 with an 02 which, after 6-months, failed leaving a nice stream of coolant behind the right rear wheel. Let's see how the new cap fairs. The original cap never failed and I'm using it as a backup.

coolant leak started today on my 01. the level is right at the max limit after 15 miles of drive. coolant spots are just by the splash guard and pretty much center of the rear wheel over the half shaft. i did smell light coolant order when the car was in the garage two day ago, but no spots on the floor.
I've two question - hope I'm not highjacking this thread.
1) if the cap is bad, can the coolant be found under the plastic plate by the cap? and 2) what is the path of the coolant to the overflow hose
thanks in advance.