Porschetech3

^^^^ this !! I expect you are actually NOT overheating. Do this procedure to get the ACCURATE engine temp. You are probably not getting hot enough to even turn on the high speed fans. You indication of 200C is not plausible, 200C =392F, assuming you posted a typo and meant 200F, 200F is NOT overheating, and is not enough to even turn on high speed fans. Please be more specific in presenting accurate indication of temp so help can be presented.

cjlanghorn

two corrections as to my initial info:

1. 200 F not C
2. LOW speed of fans not engaging


Additional info:

outside temperature = 68 degrees F

Mbren1979

Quote from the service manual :

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). Note: The electric fans for the radiators are only triggered when the engine is running!

Meaning.....low speed kicks on at 206F degrees and high kicks on at 216F degrees. I can attest that this is correct as i just changed to a low flow LN t-stat ans factory water pump with a complete flush of 6 gallons of coolant. Watching on the scanner (NOT THE DASH!) these are the exact temps my fans kicked in. This was all done with the A/C off.

If you car is running around 200F and the fan is not on.......nothing is wrong with it.

Also to note, none of this has anything to do with the under hood fan. That is controled by under hood temps only and not coolant temps.

If you are expecting you temps to be lower due to the Low Temp T-stat........please read my recent post on the issues https://rennlist.com/forums/996-forum/1130727-what-temp-to-expect-with-a-ln-low-temp-t-stat.html

Imo000

You ARE throwing parts at it and hoping something will work and in that process you've replaces almost everything with no results. You wouldn't have replaces all this if you didn't think you had an overheating issue, right?
You need an independent source to see if you actually have an overheating issue and this is where the infrared comes into play. The temp gauge isn't that accurate and if the issue only happens at idle than you need to look for why the coolant isn't cooling at idle. You need to do a systematic diagnosis or else you will keep chasing your tail. If the gauge hasn't gone into the red then your engine wasn't overheating. Let it idle and see if it goes that high and trips the warning light. Nothing will happen to the engine if it goes into the red during idle. Just don't let it keep going up.

Mike Murphy

The low speed fans on my car will also not come on until it "appears" as though it's too hot. However, if yours aren't coming on at all (even when you press the AC button on the dash), then something is broken. Please try the AC button and report if those low speed fans are still not coming on.

docmirror

Check: Radiator hose in left upper wheel well fairly cool.
Check: Verify engine overheating(use IR gun, contact thermometer, burn your hand, etc).

If both true, then you are not getting circulation. Two things generate circulation. Water pump impeller not turning(has happened before), or thermostat not opening. Easiest, is to remove t-stat and drop in a pan of water on the stove. Heat it up and watch what happens. Next, is to remove the water pump and verify impeller integrity to pulley. The last thing would be an obstruction in the circuit. Could happen but unlikely.

jllphan

808Bill

Was it over heating before you changed the T-stat? I have seen ((rare)) new T-stats not work.

Mbren1979

Several people (including myself) have already pointed out that this car may not even be overheating. The OP has said his car gets up to 200f and the fans dont operate. 200f is not overheating! Yes turning the ac on to verifiy fan operation will tell us some of the info like fan and wiring integrity. But regardless the car needs to be started cold with coolant at the correct level with the ac off. Watch the coolant temp with a scanner. Do not do anything other than watch. The car should get up to north of 210 degress which is normal. As previously posted the low speed fan does not operate untill 206f and the high speed until 216. The car is expected at an idle to get more than hot enough for the fans to turn on. You should expect to see the temp climb to over 210 and then drop due to the fan coming on. After a few minutes the temps will climb again until the fan turns on. This is completely normal and is exactly how the car was designed. Low temp tstats will allow the tstat to open earlier.....not run at a lower temp. At cruising speeds you can expect a consistant 180 to 190 temp due to constant air rushing thru the rads. At idle this will not happen. This is the entire purpose of ths fan. Before throwing more parts at it or assuming there is a problem - confirm there actually is a problem. When i got done with my water pump and tstat the temp climbed over 225 degrees the initial time. This was also using an airlift.

if your temps start climbing over 230 and the fans have not turnes on then we can start diag. But confirm it first.

NuttyProfessor

200F is not that bad. The low speed fan problem is more than likely faulty capacitors. If it's not the capacitors, then it is the relays. However, the capacitors are known to fail.

Mike Murphy

Do you mean resistors?

Mike Murphy

wyovino

You may or may not have an overheating problem but the maintenance you've done was not a complete waste. Except for the replacing the fans, those are all good things to do on a 20 year old 996 if you don't know when they were done last.

NuttyProfessor

Exactly! That's what I meant. Thanks for the correction. I had just changed out my capacitor on my home's HVAC compressor fan and it was still fresh in my mind. But I did have problems with the "resistors" on the 996. Seems like a common failure with these cars.

OP, another thing I would like to mention... Last year I had my coolant flushed from the system and when I first drove the car I noticed abnormal temp readings. The tech told me the car's ECU needed to "relearn" and in the meantime I would experience some temp faults. He was right, after several long drives, the car normalized and was reading the proper 180F mark.

Imo000

It was completely unnecessary. With that mindset you should replace everything in a 20 year old car. All the owner needs to do is inspect the coolant hose once a year or whenever the car is off the ground and if they show sign of aging THEN you replace those ones.