Mysterious coolant leak

[aps1231]

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]

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]

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]

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

[aps1231]

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]

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.