Coolant Warning Light

Hi all, The coolant warning light in my '99 996 comes on frequently. All it takes is a strong acceleration somewhere above 5,000 RPMs and she starts blinkin'. Meanwhile, the engine temp never hits 250. This is a new purchase for me and so I don't know how "normal" this is or when it started. Per recommendation, I have repeatedly checked and topped off my coolant level. Cap is on correctly -- properly threaded & no leaks. When I restart the engine, it goes away and stays away. ...that is, until the car -- not me, but the car -- starts feeling "spirited" again. I was once told to ignore it, so long as engine temp stays low, but this seems to be asking for trouble, as I become increasingly complacent towards this ever-blinking warning light. One day, somethin's gonna 'splode. Any ideas? Any advice is greatly appreciated. Dave

Could it be that everything is OK but you have a bad sending unit or a lose wire that is tripping the light incorrectly? I have had this several times on other cars and generally, if it was really overheating, I knew it. Steam, gurgling sound of coolant in system, etc. If the car seems to be operating normally, I would have the sending unit checked out. Unfortunately, I am not mechanically inclined enough with the flat 6 to tell you where the unit is located. Good luck.

The blinking light signals that your coolant is low. If you are able to top it up this verifies it is loosing coolant. I think what is likely happening is that you have a leak in the expansion tank so after you drive it the tank fills with coolant which is allowed to leak out before cooling and being sucked back into the system. You might not even see it but if it's leaking it will occur directly over teh drivers side exhaust tip (actually leaking onto the tip in most cases). This is a guess but you will probably need to replace the expansion tank, it should take an hour or two. There are instructions on renntech.com or maybe someone else can link it. I think it's a couple hundred bucks at the dealer. I had the same symptoms as you and this fixed it for me. As long as the light isn't solid red and the needle stays within range you shouldn't have a problem that you need to fix immediately but keep in mind you are very likely loosing coolant and need to get it fixed at some (unless it's a sensor which is not very common and you can't diagnose anyway). -Keith

If you have a 99 or 00 then it is not the sensor or that it is probably not full, but the tank design itself. I just replaced mine with the new style which has a special float deal so that this doesn't happen. Also the older tanks are prone to cracking and I was told mine was but when I removed it I didn't really notice any residue under it. No matter for about 150 bucks new cap and tank the fact that it's done and that light will never blink again is nice.

I had this happen on my 01 C4. Turned out to be a leak in the coolant tank. Took it back to the dealer 3 times before they found the hairline crack in the tank but since then not a single problem. Rob

Here is the long explanation from the service manual on the flashing coolant light. "Four functions of the coolant warning light: 1. Engine coolant level too low -- light flashes slowly (0.5 Hz) 2. Engine compartment temperature too high -- light flashes slowly (0.5 Hz) (engine compartment blower might be faulty) 3. Engine coolant temperature too high -- light is lit; pointer on the right 4. Temperature sensor at water outlet faulty -- light flashes rapidly (1 Hz) ; pointer on the right Note: The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously."