joon

Hello, I recently read a thread about unplugging the switch behind the passenger side lamp to get the oil cooler fan going at all times. Here in Arizona, I thought it was a good idea, so I did that.

When I sent my car to the shop, I was told that I should not do that, because the oil need to get up to temperature to boil out the moisture and contaminants. I was told that I should let the thermo sensors do the job and operate the fan as designed. So I assume if everything was working properly, then even in stop-go traffic, I should not see elevated temperatures.

Now, this is a reputable shop, and it makes sense about moisture in the oil that needs to get boiled out. If the fan constantly runs, then the oil does not reach temperature to acheive that.

Please offer comments.

97Targa

Seems like the over ride switch discussed here and shown on Robin's website www.p-car.com would be the better way to go. Then after the oil gets up to temp. and /or when you anticipate extreme conditions you can turn the high speed fan on.

mborkow

i have been trying to decide if i should do the override switch or not. i have been thinking about it because i do drive around in the south bay quite a bit where the temps can get hot (90s last weekend) and there is plenty of stop-and-go traffic (which heats these cars up fAst). however, last weekend i decided not to do it and here is why. my girlfriend and i decided to go to the garlic fest, at around noon (big mistake). we got to within a few miles of the exit on HW 101 and then ran into traffic that simply wasn't moving at all. it was already in the 90s and i was pretty nervous about just sitting there in traffic with a/c on, but sit is all we did for the better part of an hour (me moved just a few feet every few minutes). i had my eye on the oil temp and was pretty worried (and really began wondering why i had not installed the override switch), but the needle never got higher than half-way between 9 and 10 on the guage (and this was with a/c on max). as soon as we got out of the traffic (we bailed on the garlic fest) and started moving again the oil temp fell down beneath 8 again. in this case, the oil coolers seemed to have worked as designed and since it seems to work on its own, i am going to leave mine for now.

EThec

mborkow,
you could have kept those temps between 8-9 the whole time if you had the switch. just flip it on in anticipation of the traffic when you see it ahead. when the switch is off the system operates normally. there's really nothing to lose putting it in IMO.

vjd3

I disagree with the shop's assessment ... the thermostat for the oil cooler itself does not open until the oil reaches a temperature Porsche feels is too high without the cooler ... about 200 degrees on my gauge. The cooler is there to keep the oil temperature below that temperature; it must reach that temperature for the cooler to open in the first place.

Vic
95 C4

deltawedge

Although I like the Garlic Festival, I hate traffic. I went to the San Jose Grand Prix instead. Had a great time.

mborkow

you know, we debated going to that as well...like i said, we made the wrong decision. the good news was that everyone in gilroy was at the garlic festival so there was no one at the discount outlets there...i have never seen the line at in & out so short there!

chris walrod

The trouble with waiting for fans to run is the coolers (and entire system) are heat soaked by the time the CCU gives the command. I unplug the sensor only for track events, and this works great. Believe me, the oil still gets hot enough to burn-off any moisture

But I do see where your mechanic is coming from..

kary993

I agree, that is rather sstrange to say because the oil is plenty hot. I have a switch so when I am tracking I just turn it on when it is hot outside. If cool or running on the street I only turn it on when the oil starts getting hot. Though I do have two coolers and when I run the air conditioning it also fans the oil cooler on the drivers side.

Get the switch, it works well and is easier than the behind the headlight trick.

mborkow

"you could have kept those temps between 8-9 the whole time if you had the switch"
but from what i understand as long as it is under 10 (and i was even in those pretty bad conditions) then you are ok.

vjd3

Well, 10 o'clock (at the mark) is 248 degrees ... Bruce Anderson's rule of thumb for a 911 is "230 F is warm, 240 F is hot, and 250 F is too damn hot." He feels 180-200 is ideal temperature, that's the first mark off the bottom of the dial (8 o'clock) -- 194 degrees. The 993's I've owned tend to run about a needle's width below the first mark, which I'd say is about 180 or so, in "normal" conditions, i.e., not very hot outside, running on the freeway @ 60 mph, and so forth. That seems to be where Porsche wants the temperatures on a regular basis, and what they want the oil cooler to accomplish, which is why the thermostat to it opens at 194 degrees.

I think the factory mentality after that is under dire conditions (temperatures in the 90s, high humidty, stalled in traffic, AC on) not to let it get "too damn hot" by using the oil cooler fan on the high setting. But it seems more prudent to not let it get there at all, which is where the fan switch comes in.

We have it pretty good on the 993 ... I've owned 911SC's with the "trombone" cooler which is fairly useless, 3.2 Carreras with the radiator cooler with the emergency fan, which is better, but not a lot better, and an 87 930, which gets hot as hell real fast and stays that way in summer caught in traffic. The 993 cooler is remarkable in comparison, especially since the earlier cars had an engine-mounted oil cooler as well as the front fender cooler. People would notch the front fender to improve the airflow to the cooler, add aftermarket coolers (the Turbatrol was a popular choice for the 911SC), add an extra cooler ... and that was just for regular traffic!

Vic
95 C4

dhicks

How do you test that both speeds of the fan are working? I suppose that I could start the car in the garage and let it sit and warm up and listen for the fans switching on??? Any better ways???

Arrwin

How long after you got out of traffic did the temp needle fall to 8? I'm asking b/c it usually takes me some time before it reaches to 8 again. It seemed a lot quicker before this summer however. I am thinking of taking the bumper off and clean off the leaves and dirt that has accumulated in the oil cooler. Maybe that will help a little.

vjd3

Good info here:

http://p-car.com/diy/fan

On my car, both fans were working as far as I know ... what I didn't like was on a humid night caught in traffic for 20 minutes, went up to the 9 o'clock position and didn't come back down even after driving 60 mph on the highway for 20 minutes. I pulled the connector in the passenger side headlight bucket to let the fan run on high all the time and now haven't passed 8 o'clock, even in daytime traffic idling with the AC on for 30 minutes. I plan to do the switch, but for the summer I'm leaving it disconnected for now.

Vic
95 C4

Arrwin

This is my exact situation, so maybe there's nothing wrong with my car. It definitely has been extremely humid this summer.

Maybe I will think of the override switch as well....is it good to have the fan on while driving or only when it is stationary in traffic? Should the fan be turned off as the traffic picks up? I only ask this, b/c i'm not sure if the fan comes on while in motion as I only hear after it's idling for 2 min. or so.