The "Not-Just-Another-Flashing-Coolant-Light" Post

O.k., so its been hot lately here in Phoenix...really hot. So yesterday, for the first time since my coolant tank went over a year ago, I get the dreaded flashing coolant light (slow flashing). I know what this can mean, but I've still got some questions (that to the best of my knowledge have not yet been addressed in this forum). So here is the story: 1) 3 months ago: I bust a coolant hose in my driveway after the nightly communte and spew most of my coolant everywhere. I replace the hose, refill the coolant, and burp the system the best I can. Coolant level drops a bit over the next few days, and I chalk it up air working itself out of the system. 2) Two days ago: I check the coolant level in the morning before I go to work and notice that I still must have air in the system, since the level is slightly below the min. mark. Still nothing to be too concerned about as there is no visible oil in the tank or gunk in the oil filler neck, and the tank and cap are still relatively knew and show no signs of leakage or coolant smells. I bring the level back up to half-way between the min and max marks. 3) Later that night: I go for a spirited drive after I've let the car sit for about two hours after my long and hot stop-and-go freeway commute home. I noticed when I started it up that the engine was still very warm (needle a tad to the right of 12:00). My coolant light starts flashing within about 5 minutes, and I stop to inspect. Coolant level is fine, purge valve on coolant tank is open, but engine compartment fan is sucking in outside air so I figure my engine compartment temp just got too hot. Turned off the car, drove it around, and no more flashing light. 4) Today: I'm running errands around town at lunch, stop-and-go traffic, slow speeds, and just a tad under 110 outside. The light starts flashing again, and the egine lid fan is once again sucking. Coolant level is fine (above max, actually). So now the questions: if in fact my light is flashing because the engine compartment temperature is too hot (I guess it could still be air bubbles), shouldn't the fan come on before the temp gets to this point so that it never gets too hot? Is something wrong, or is this something I have to live with when I drive in town in the heat of the summer? Can this damage my car? Any advice would be great! (edit: forgot to mention, car never ran hot, as the needle never passed beyond the "0" in 180). Sorry for the long post, Scott.

Man this AZ weather doesnt like our babies. I remember there being two reasons the light comes on, low coolant and another. Check the manual. I might have to move for my cars sake.....

No kidding. I can tell that my car is markedly less peppy in this heat. You are right, low coolant is one reason the light will flash, the other is a hot engine compartment, which is what I am 99 % sure is tripping my warning light. I just need to know what that means exactly, and how to prevent it (without moving out of Arizona!)

What is the coolant temperature reading when the light is flashing?

1999Porsche911, I'm not sure of the actual coolant temperature, but when it was flashing today the needle was not quite to the right-hand edge of the "0" in "180." Rather, it was probably about 2/3's of the way to the edge. BTW, that is a fairly common temperature range for my car in the past, but never has it tripped a flashing light.

When you replaced the coolant tank, did you NOT connect the cable to the level sensor on the bottom of the tank tightly? There are only three causes of a flashing ight. 1) Fault in the engine compartment fan 2) coolant low and 3) coolant too hot. However, based on your description of the engine being hot 2 hours later and the engine fan running and the flashing light, your gauge reading is suspect and you might in fact be excessively overheated. If you have a scanner, use it to take the actual coolant temperature reading, although this may also show an incorrect reaing if the coolant sensor is bad.. Also, try unplugging and then reconnecting the coolant sensor cable on the inlet on the back of the engine, bottom, passenger side. It is a 4 pin connector. After a couple hours of sitting, does the system release vacuum when you remove the coolant cap?

Last time I checked there was vacuum. Not if I let it sit overnight, but if it is just a few hours, there is definitely vacuum, but I'll check again in one hour. Also, just to clarify, I've never heard or seen the fan on my car stay on after the car was turned off. When I saw the fan spinning on the last two occassions (when the light was flashing), the fan turned off when I turned the car off. I'd be really surprised if the guague reading is off, because my car has pretty much acted the same with respect to the temp. needle since the day I got it over a year ago. The temperatures are still running and have always run in approximately the same range...the only difference is that the light has flashed on occassion in the last two days when it was really hot outside and I was doing a lot of stop and go driving. When I replaced my coolant tank in April 2006, I also replaced the coolant level sensor at the bottom of the tank (and the cap). I'll make sure the coolant sensor connection is tight. I'll also check the coolant sensor cable. When you say "back" of the engine, do you mean towards the front or the rear of the car? Thanks so much for your help.

I just double checked for a vaccum. car has been sitting for 2 hours and 20 minutes and the level is perfect and there was strong vacuum when I released the cap (purge valve was not sticking up). Also, where is that connector that I can disconnect to check the operation of the engine fan...I recall it is somewhere on the passenger side of the enginge near the intake manifold (after the first black plastic intake duct...is that it?)

If in fact the fan turns off when the ignition was shut off, there may be your problem. If the engine temperature is high enough when the engine is running to activate the fan, it should still run when the engine is shut off until the temperture drops. The operation of the fan should work like this: The engine compartment fan will turn on when the engine compartment temperature is greater than about 175F or the coolant temperature is greater than 215F. When the engine is turned off and the engine compartment temperature is more than 140F , the computer will continue to monitor for another 20 minutes. If the engine compartment temperature rises to about 185F , the fan will turn on for 20 seconds. If temperature is still greater than 185F after the 20 seconds, the fan will remain on for another 30 seconds. I would check the sensor connection above the intake tubes on bank 1. Unplug the cable and reconnect. I would also reboot the computer to eliminate any memory faults. Disconnect negative battery cable for a few minutes. You will need to reenter your raio code afterwards.

Awesome. You rock. I will try this tonight. This may be the culprit, as I don't believe I have ever heard the fans on my car continue after I have turned the car off, which is odd since I've already put this car through one Arizona summer, and drive it in some pretty horrific conditions (daily driver, 25 mile freeway commute everyday, often stop and go in the afternoon). This will give me an excuse to hang out in the garage when I get home tonight (it should be plenty toasty!).

Nice call 1999!

The sensor pulls straight out of the grommet and then you can test it with a hot hair dryer or put a can over the sensor and heat with a torch and see if it follows the rules I outlined above. Once the car is warmed up, disconnecting the cable from the sensor should start the fan immediately.

O.k., here is an update. the flashing occurred again on the way home just now. When I pulled into the garage the fan was blowing (as were the two radiator fans up front). It seemed to me that the flashing commenced more or less right about the point that the temp needle hit the very far right edge of the "0" in the "180." When I turned the car off the fan immediately stopped. I waited for twenty minutes, and the fan did not come back on, until I put the key in the ignition and turned it all the way to the "ready" position (just short of starting the car). The fan went back off when the key was pulled out. Before I left work I pulled the sensor from the gromet and disconnected the wire connector, and the fan did not go on. I will try starting the car in a while, and pulling th sensor to see what happens.

O.k. took the car for a quick drive tonight. Everything was normal, no lights flashing, and no engine fan. But, with the car running and the temps nice and low, when I pulled the temp sensor the fan went on, and then went off when I re-inserted it. I'm now paranoid, as I was hoping it was something as benign as the fan or some related relay or connector. If the fan is operating correctly and I'm not running hot (still my assumption as of now), and my coolant is the proper level, could it be that my recent stop and go driving in hot temps is causing air bubbles to escape that I never completely purged from the system when I had my blown hose, and that this is what is causing the light to trip?

99Porsche: Are you saying that when you pull into the garage and the front fans are running...and you shut off the engine...that the fans should continue running? Although I don't have the flashing lights like Scott does, when I turn off the engine...the forward fans stop immediately. (I've never even heard the fan in the engine compartment) My fans only come on in the hotter weather when the needle hits the right edge of the "0"....and the needle has never gone beyond that point. Does your fan(s) ever continue to run after you shut off the engine?

It is possible that you have some air in the system, but normally thi air would work itself out withing a few days as evidenced by a drop in coolant level in the tank. You may try driving around with the purge valve open for a few days. To do this, simply move the metal clip on the valve to the upright position. It also helps encourage air to escape by parking the car with the nose facing down a hill after you have been driving it. I would still like to know if the gauge is actually giving you an accurate reading, What does the climate control coolant reading show? Have you looked at the coolant temperature with a scanner?

The front radiator fans will turn off when you shut down the engine. The above was referring to the engine fan only.

So today at lunch I drove around for half an hour in stop and go traffic, trying my best to keep the revs up, the speeds low (so as to keep wind cooling to a minimum), and the ac blasting. I managed to get the temp needle to almost the far edge of the "0," at which time the AC display diagnostics screen reported my coolant temp to be 107 c (or 224.6 f). The light did not blink, and the engine fan did not come on (although the radiator fans had been going for a while).

Looks like you fixed whatever the problem was.

We'll see if the light goes on after the communte tonight. Thanks so much for the help and advice!

Any updates, my car has been running much cooler. I took the car home and stayed there about 90 minutes. But I left and the light started flashing today for a brief 1 mile drive. I stopped for about 10 minutes to make the 1 mile drive back and no light. The engine fan shuts off when I turn the car off. but if put it back in and turn on the accessory the engine fan starts, I remove the key and it continues to run?????????? WTF!!!!!!!! My car hates this f in town.. This is a complete noob question but how do you check the coolant temp in diagnostics?

Use the climate control screen to look at the actual coolant temperature. To see it, do the following: Press and hold in the recirculate and the top (arrow up) buttons on the right side of the panel for a few seconds. The left screen will change. Using the + key below that screen, advance so the display reads 6c. Then press the center vent button once. The display will show you your coolant temp. To go back to normal, simply press AUTO.

Ok just checked car been cooling down for about 20-30 turned on accessory engine fan fired up, temp is 101c. Fan stayed on!!!

I've been using the LED readout to look at the various onboard temps....but I can only get the temps to show in Celcius....is there a way to make them readout in Farenheit? It may be that they only display in C....

No blinking on the way home tonight, even though I got the temp up to 108c (226.4). Fan was on when I got home, though it stopped again the instant I turned the car off (it went back on if I put the key to the ready position). 1999, you indicated that there are only three things that could be wrong if the light is flashing: low coolant (definitely not the problem), coolant that is too hot (I still don't think this is the problem), or a fault in the engine compartment. I've seen posts from Loren, however, indicating that the light can mean th engine compartment is too hot. Could it be as simple as this last condition? And if so, what should I do about it?

It does ease my mind a little bit that its not just my car..... A relief for a very stressful situation. The light did not come on during the commute this morning and the AC blew super cold. I will check the temp after work, as that is when most trouble occurs.....

Do you have a photo or can you describe the location of this sensor? Is it mounted to the plastic intake tubes between the first two on the passenger side? Thanks.

denishartigan, I don't have a picture, but what you describe is it. the sensor sits in a grove between the first and second intake tubes on the passenger-side bank.

I did a run to the Post office driving the long way to play around with 6c. I did a quick run to 148mph and got the temps to 106c after parked in the driveway. Also, the Speedometer is less that 3 mph off assuming that 19c or 20c is the KPH gauge. I cruised at 99mph with a reading of 155kph.

Do my fan mod and get those temps down below 200F and you'll love the new found power.

Where are the fan mod procedures, clearly I'm just twiddling my thumbs this morning. Never mind, I did a search in the 996 forum under "fan mod".

Radiator Fan and Engine Compartment Fan Switch Mod The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance. The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan. Radiator Fans Connect a wire to the ground of the 2 high speed fan relays located on the relay carrier located in the driver�s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. For those who have an air filter that draws air from within the engine compartment, the following mod will substantially reduce intake temperatures. (by as much as 30F - 40F+) Engine Compartment Fan Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver�s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver�s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment, such as the EVO SC. If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing, Jim