Coolant warning light. Coolant tank issue? How to diagnose?

Hi all, Driving in to work this morning, I got a flashing coolant warning light (near the coolant temperature gauge.) The temperature was running a normal 180�. I pulled over to check it out, and there was a *tiny* bit of coolant around the edge of the coolant expansion tank. No coolant leaks could be detected under the car, nor could I identify coolant coming from anywhere around the tank. There was a bit of residue on top of the tank, however. I assume the warning light was for coolant level. The car has been cooling for about an hour, but I need to wait for it to cool completely and get a coolant level check. Still no signs of leakage under the car. Other relevant facts: New water pump, hoses, and coolant tank cap in November of last year. I know the coolant tanks are known to fail. As far as I know, my tank is original to my 1999 C2. How do I diagnose a tank leak? It's always something! Thanks in advance for any guidance.

Flashing light = low coolant level. Not a huge problem. Refill with 50/50 mix of Porsche Antifreeze and distilled water. Make sure to reseat cap completely (looks like you have the latest cap). Drive it and check the coolant level visually more often. Same goes for your oil level (pull the dipstick and check it). If coolant level drops have the system pressure tested. That will show you where the leak is occurring. They can be hard to track down sometimes, but keeping your coolant level full is a basic requirement.

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Thanks for the reply. The coolant level is, in fact, low. I understand the need to add coolant (50/50). I was looking for more specifics on how to do a DIY diagnosis (i.e. pressure test), or where to look for common leak points around the coolant tank.

Search these forums for Coolant Tank and Coolant system pressure testing...many posters have had a wide variety of problems and have posted solutions. It probably was not clear - My suggestion was to refill the tank and closely watch for any leaks anywhere, including area's around and underneath the coolant tank, particularly when at operating temperature. Some leaks don't show until hot and can be very tiny. Wiping your hand underneath the coolant tank and feeling for any moisture might help pinpoint a leak. Other trouble spots: loose hose fittings, water pump shaft seal, AOS, leaking/weeping at radiator connectors and so on.....you have to have patience finding a slow, small leak, whereas a full blown coolant leak on the garage floor is usually pretty obvious.

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You need to get the car in the air and exam it from underneath looking for a leak sign. There will dried anti-freeze residue or maybe even wet coolant somewhere and where this is will clue you in where the leak is. The tank leaks from a split seam at the bottom of the tank. The hoses and their connections are at the engine. Check the front of the car the connections up there can be bad -- the lower portion of the radiator is at risk of damage from hitting road debris that impacts that area and busts the connection but doesn't really leave much if any sign that something was hit. There is also the possibility of corrosion from trash that has collected in/around the radiator/AC condensers. The AOS is another possible coolant leak source and do not overlook the *new* water pump. They can fail at any time. If you can't find the leak then a poor man's pressure test is to with the coolant tank topped up with distilled water and the cap on securely with the A/C off start the engine and drive the car around town until the engine is fully warmed up. Give this a half an hour or so. Drive it until you hear/feel the radiator fans come on at least once. Back home -- or even at the local dealer's service entrance apron -- raise the rpms to 1500 and hold until you hear/feel the radiator fans come on. Then shut off the engine. The heat load the engine has will raise the coolant temperature and its pressure and if there is a leak you'll see it. Be careful to not be too close to any cooling system hoses, tanks, caps, etc. as the tank -- my experience -- can gush coolant (hot BTW!) if there is where the leak is. But a hose can split, a cap leak, or something can possible spray out hot coolant and you will get a scalding you will remember for a long time.

Clean the top of the tank, and anywhere else that there is residue, with white vinegar to get rid of the residue. Then monitor it closely for new signs. See if you can get a mirror under the tank for a close inspection of that problem area.

Save yourself future headaches, and replace the tank now. Afterall that plastic container has held up for some 13 years, which is almost unheard of. I replaced my replacement not too long ago due to a manufacturing defect. It's really a simple DIY if you feel comfortable supporting the engine on a hydraulic table, loosening the two motor mounts, and lowering the engine enough to wrangle the tank out of the holder. Its the outrageous cost of a replacement tank that will cause you to shed a tear. The Gen 1 tank is almost double the cost of the gen 2 996. I agree with other posters too, that you need to rule out a leak from somewhere else too.

Thanks for the tips. This will be a project for this weekend.