Engine Temp

[lixmas]

Hey Guys,

I had the thermostat and a radiator changed on my 1999 996 carrera. It ran at 80 degrees for about 3 months, and now when in traffic it has started creeping up to around 93 degrees. The dealer assures me that this is normal as some cars run hotter than others. When i asked why it didn't run at this temp as soon as the thermostat was changed, they couldn't answer me. I fear there may be some other issue here. What is the normal temp for these cars to run at? I believe the temps on my gauge are in celsius. Thanks so much.

[dammad]

There are a bunch of threads on here related to fans not running at high/low speed that cause some cars to go up to the mid-to-high 100's celcius. Might want to check if your fans are running.

My 1999 996 rans around 94C normal, but has recently edged up to 100+C, so I'm investigating the same issue myself.

[1999Porsche911]

First of all, your engine never ran at 80C. If it had, your thermostat would have remained closed. The high speed radiator fans do not come on just because the A/c is on. I have heard otherwise on this board but on the more than 35 996's I have tested, NONE of them come on high just because the A/C is on. High speed fan operation is determined by pressure in the A/C and/or coolant temperature.

The targeted coolant temperature for the 996 is 90C and in reality, it will run slightly above that at highway speeds. Slower, around town driving may raise the temperature to as high as 105 -110C unless your fans are running on high.

[JeTexas]

Nine times out of ten, if the car is overheating while sitting in traffic, it's due to the fans not running.

[dammad]

First of all, your engine never ran at 80C. If it had, your thermostat would have remained closed. The high speed radiator fans do not come on just because the A/c is on. I have heard otherwise on this board but on the more than 35 996's I have tested, NONE of them come on high just because the A/C is on. High speed fan operation is determined by pressure in the A/C and/or coolant temperature.

The targeted coolant temperature for the 996 is 90C and in reality, it will run slightly above that at highway speeds. Slower, around town driving may raise the temperature to as high as 105 -110C unless your fans are running on high.

Apart from something broken or jammed, why won't the fans run on high with the car above 105C? What temperature are the fans supposed to switch to high speed?

[Loren]

First of all, your engine never ran at 80C. If it had, your thermostat would have remained closed. The high speed radiator fans do not come on just because the A/c is on. I have heard otherwise on this board but on the more than 35 996's I have tested, NONE of them come on high just because the A/C is on. High speed fan operation is determined by pressure in the A/C and/or coolant temperature.

The targeted coolant temperature for the 996 is 90C and in reality, it will run slightly above that at highway speeds. Slower, around town driving may raise the temperature to as high as 105 -110C unless your fans are running on high.

Apart from something broken or jammed, why won't the fans run on high with the car above 105C? What temperature are the fans supposed to switch to high speed?

I know I have posted this before...

From the 1999 Porsche Carrera Service Information Book:

"There are two radiator modules installed in the front of the vehicle (on the left- and right-hand side). These radiators are each fitted with an electric fan. They can be operated at two speeds and are activated by the DME control unit whenever the following conditions apply:

Electric fan, speed 1

(Ground to DME control unit, terminal 35)

Coolant temperature higher than 96.75°C or air conditioning switched on.

Electric fan, speed 2

(Ground to DME control unit, terminal 36)

Coolant temperature > 102°C or air-conditioning fluid pressure switch closed (coolant pressure > 16 bar)."

[BruceP]

First of all, your engine never ran at 80C. If it had, your thermostat would have remained closed. The high speed radiator fans do not come on just because the A/c is on. I have heard otherwise on this board but on the more than 35 996's I have tested, NONE of them come on high just because the A/C is on. High speed fan operation is determined by pressure in the A/C and/or coolant temperature.

The targeted coolant temperature for the 996 is 90C and in reality, it will run slightly above that at highway speeds. Slower, around town driving may raise the temperature to as high as 105 -110C unless your fans are running on high.

Apart from something broken or jammed, why won't the fans run on high with the car above 105C? What temperature are the fans supposed to switch to high speed?

I had this issue a couple of summers ago. I ruled out the relays first (there are different relays for each fan speed, each side of the car). It turned out to be a ballast (I think?) at the fan motor itself. Anyway, same symptom. The fan would run on low but not on high. Fix was a new fan. FWIW.

[bmohr]

okay, been having temp issues myself. I replaced the resistors last summer because the low speed fans were not coming on. Tested today with ac on the fans blow hard. But when driving on highway the temp hack get as high as 103c. Around town with ac on and thus high speed fans the temps got to 105 and probably would have gone higher if i was driving around longer in town. So at this point i'm wondering if maybe it's time to blow out the radiator fins. Thoughts?

[perryinva]

Clean the rads, but you HAVE to take the bumper cover off to do it right. Blowing them out or vacuuming through the inlet is only maybe 50% efficient. Aslo check for corrosion if a year round driver in area that uses salt. Funny, but on the 3 996's (all 2002s) I've looked at, the fans start immediately when the AC button is pressed, regardless of temp.

[1999Porsche911]

okay, been having temp issues myself. I replaced the resistors last summer because the low speed fans were not coming on. Tested today with ac on the fans blow hard. But when driving on highway the temp hack get as high as 103c. Around town with ac on and thus high speed fans the temps got to 105 and probably would have gone higher if i was driving around longer in town. So at this point i'm wondering if maybe it's time to blow out the radiator fins. Thoughts?

Your high speed fans ARE NOT on just because the A/C is on. The high speed will only kick on if the pressure switch senses too high a pressure or the coolant temperature reaches 215F.

[RFM]

Let the warm engine after a run idling with the A/C OFF, that allows you to have a much easier and less confusing control about the fans working cycle.

[bmohr]

i know you are sure of that 1999porsche911, but what can i tell you, the fans are on low speed or off on intial check, then i get back into my car and press the ac button, come back out and the fans run high...so whatever that proves is really meaningless to me at this point. What i mean is i care about is if the fans are working, both high and low..and they are. So if my temps are still running high i have to figure out why and correct it. Sorry if this pushes a hot button for you.

[1999Porsche911]

i know you are sure of that 1999porsche911, but what can i tell you, the fans are on low speed or off on intial check, then i get back into my car and press the ac button, come back out and the fans run high...so whatever that proves is really meaningless to me at this point. What i mean is i care about is if the fans are working, both high and low..and they are. So if my temps are still running high i have to figure out why and correct it. Sorry if this pushes a hot button for you.

If your high speed fans are turning on when the coolant temperature is below 215F, then, assuming the system is functioning as designed, your A/C fluid temperature is too hot which is the result of too much pressure which makes the air being sucked past the radiators from the condenser hotter than it should be which reduces the cooling capacity of the radiators.

I would suggest grounding the high speed fan relays and driving that way for awhile and see the difference in coolant temperatures. If you still see high temperatures, have the high pressure of the A/C checked. Running the engine compartment fan also helps reduce coolant tempertures.

[bmohr]

okay, i see. Thank you for the run down. I appreciate it. I will follow your advice and see whats up. Plus I'm going to try and set up the rad and engine compartment fan mod that you posted.

[BruceP]

Clean the rads, but you HAVE to take the bumper cover off to do it right. Blowing them out or vacuuming through the inlet is only maybe 50% efficient. Aslo check for corrosion if a year round driver in area that uses salt. Funny, but on the 3 996's (all 2002s) I've looked at, the fans start immediately when the AC button is pressed, regardless of temp.

Yes, and separate the AC condensers and rads and clean each, and then between them.

My car's cooling issues have been persistent since I bought it. It turned out not to be any mysterious Porsche dysfunctional hydrophenomic ronky booboo valve or other such 996 failed engineering mystery. It turned out to be the PO's failure to keep this area clean, and the eventual corrosion caused by damp, salt soaked mung between the AC condenser and rad.

AC condensers were salvaged and hot tanked to clean them thoroughly. Both rads were replaced with new ones. Now, finally, the car cools properly. That simple.