Why did Porsche not want my electric oil cooler fan to come on until 244 deg?

Maxhouse97 · 06-08-2008, 01:38 PM

I was sitting in traffic on Friday (summer has arrived in VA) with the a/c on and the oil temp got real close to the second white hash mark (around 248 deg). I never heard the fan come on. So I came back and looked up what temp the fan is supposed to come on - at found out that its 244 deg F. Even though the red part of the gauge doesn't start until 302 deg F, people here say you should get over 250.

My question is why would the factory set the thermoswitch temp so hi? They must have had a reason.

I have read about swapping the thermoswitch for a BMW part that opens at 230. Others have wired a manual switch. I am thinking about the former.

Thing is that Porsche engineers usually have good reasons for what they do - any ides?

old man neri · 06-08-2008, 01:57 PM

I think it is just a simple wire slice to have it run all the time with the engine on. That is one option to look at.

Steve@Rennsport · 06-08-2008, 02:04 PM

Tony,

Porsche allowed these engines to run that hot for emissions compliance.

They are not as concerned about engine longevity and durability.

GH85Carrera · GH85Carrera's Garage

I have heard that the fan is not a real long lasting unit. If you run it all the time it will fail soon. My 85 Carrera did not come with a fan. I added a fan and just put in a toggle switch. If the temp is over 200, on goes the fan. I figure it is a human interface temperature switch. I never need it in the winter months.

Maxhouse97 · 06-08-2008, 07:04 PM

I was thinking of installing the bmw 99 deg C (210 F) thermoswitch - I like the idea of an automatic switch rather than a manual just in case my wife is driving the car.

That still seems so hot - emissions or not.

CrossT · 06-08-2008, 07:16 PM

I've heard about that lower temp switch. But, what BMW switch is that specifically?

thx
todd
89 targa

fintstone · fintstone's Garage

Quote:

Originally Posted by Maxhouse97

I was thinking of installing the bmw 99 deg C (210 F) thermoswitch - I like the idea of an automatic switch rather than a manual just in case my wife is driving the car.

That still seems so hot - emissions or not.

Most folks install both. You can switch on the fan anytime you want...but if you forget, it will come on when the temp exceeds 210F.

wolf · 06-09-2008, 12:53 AM

I understood the fan only delivers adequate cooling when the oilcooler is really hot.

Barrpete · 06-09-2008, 06:14 AM

I installed the fan kit from Elephant Racing. It comes with an adjustable thermostat. IIRC The range is something like about 170 to 280 F.

rfn026 · 06-09-2008, 06:20 AM

I would think you should see at least 212- degrees to get any moisture out of the engine. You can run too cool. There's an optimum temperature. To cold is as bad as too hot.

You engine makes it's best power running a little on the hot side. In fact most engine show peak horsepower just before they blow up - but that's another story.

Richard

Maxhouse97 · 06-10-2008, 03:18 AM

Richard,

That goes back to th original question - maybe its no so bad to run around at 250 degrees if the factory didn't have the fan come on until 244 and the red line is placed at 300. I know I get nervous when the needle gets there, but maybe I shouldn't.

I have to check the owner's manual to see if it says anything...

GH85Carrera · GH85Carrera's Garage

Quote:

Originally Posted by rfn026

I would think you should see at least 212- degrees to get any moisture out of the engine. You can run too cool. There's an optimum temperature. To cold is as bad as too hot.

You engine makes it's best power running a little on the hot side. In fact most engine show peak horsepower just before they blow up - but that's another story.

Richard

Drop some water on the pavement on a 100 degree day and watch how fast it evaporates. It does not have to get to boiling temp to purge the moisture. In the winter time the engine temp simply will not go above 185 on my 911. I don't worry about it. That is plenty hot enough to purge any water. The thermostat controls the oil going to the front cooler. Until it send oil up front the fan is useless. The front cooler is never going to make the engine temp get to cold. Your engine will last a lot longer at 225 instead of 250. 260 is flat out to damn hot.