Temperature Switch for Front Oil Cooler

[spiderem]

Hello, looks like my temperature switch for the front oil cooler is no longer working on my 87' carrera.
When i put the ignition on, the fan start turning, even when the car is cold.
My questions are :
- how can i be sure it comes from the temp switch? (i have already checked the relay)
- to replace the temp switch i must remove the cooler and fan, does the oil needs to be drained for that? Or only little seepage is expected from the 2 oil lines at the connection above the front wheel, and no need to drain the oil.
Thanks.
PS: should i avoid driving with the fan turned on all the time, or actually it doesn't really matter? other than the noise and maybe the risk to "burn" the fan

[Lyle O]

If you checked the relay already, it pretty much must be the temp switch. I would have to check DME circuit diagram, as that could be the only other possibility I think.

To change the switch, you don't need to drain the oil, but you will have some spillage and will need to keep the lines "up" after disconnecting. Also, remember not to tip the cooler too much.

You can avoid the whole disconnection if you think it easier to remove the front bumper. Then you can access it from the front while the cooler is "in situ". Just another option.

Running with the fan on all the time won't hurt anything except cause more wear on a 34 year old fan motor. Mine wore out years ago, so you may already be on borrowed time on that front. If you are in Canada or somewhere north where the heat is not as big an issue, you might consider disconnecting it. Otherwise, you can let it go until convenient to replace. Also, consider going to a fan switch which comes on at a lower temp. I did this and feel better about the fan coming on earlier when needed. There are several threads about it if you do a search.
Good luck.

[chrismorse]

Juat did this on the 74. I had to use some pipe on a pair of wrenches to loosen the flex lines to the brass body lines, but first, put a trash bag over the brake assembly. You are ging to lose some oil. My sump tank was already, but i don't think it is necessary to drain the tank or engine. I plugged the dripping brass lines with wadded up paper towels, un did the fan wiring the top bolt and two bottom bolts and out it came.
Hopefully, someone will post the specs for the Nason/BMW 180 degree switch.
chris

[spiderem]

Thanks for the quick reply and useful info.
I will investigate the method by removing the front bumper.
Car is in France now and can be pretty hot in the summer!
With regards to the fan switch at lower temperature, do you mean a sensor with a lower trigger temp, or an actual manual switch? I've seen the mutiple thread about people installing switch in cokpit to activate or not the fan, but i haven't seen (and doesn't seem to be available on Pelican) a sensor with a lower trigger temp. Where did you get yours if this is what you mean?
Thanks.

[darrin]

Spiderem -- since your fan's always on, the easy option would be to install a switch in the cockpit that lets you manually control the fan. That way, you can turn it on whenever you see temps climbing and turn it off whenever you don't want it on. This would avoid (or delay) the need to tear into your car to replace the sensor.

Here's a recent thread on other oil temp sender options with lower temperature triggers http://forums.pelicanparts.com/porsche-911-technical-forum/1039954-lower-temp-switch-3-2-oil-cooler-fan.html --

[JRSIII]

Do a search on the hosts parts catalog for Part 61311364273. This is a BMW switch that activates at 210F rather then 245F as the stock switch does. There are two pretty inexpensive aftermarket options, in addition to the genuine BMW. Note that if you use this switch, you have to make some minor wiring revisions. The factory switch is single prong for power, and ground is connected to the lug on the other side of the top of the cooler. The BMW switch is two pronged, so you need to revise to connect the ground to the top of the switch. It's easy to do, especially with the cooler out.

[86 911 Targa]

https://www.google.com/search?sourceid=navclient&aq=&oq=nasson+switch&ie=UTF-8&rlz=1T4GUEA_enUS570US570&q=nason+switches&gs_l=hp..0.0i22i10i30l2.0.0.0.18327...........0.sD
^^^^^
Here is what I did as per the link on this post.

pm me for details.

Best,

Gerry

ps: We have been to Annecy on several of our trips to France.
Great chocolate................

[mo-mon]

Or, you can put a manual override switch. That's what I did. Enjoy the summer & tackle it in the winter. Search this forum for the relevant thread. I lost my bookmarks or I would've linked it.

To answer your question re fan on all the time- you can drive all you want but it'll take longer to warm up & yes, you might eventually risk burning the fan. Test the wires for the oil cooler fan in the right lower part of the frunk, then put a manual switch.

[spiderem]

Thanks all for your feedback. I will do more reading before undertaking repairs, and drive like this for now (maybe disconect the sensor when weather is not really warm and always keep an eye on the temp gauge).

[GH85Carrera]

Be sure the clean things up in the fender well and the oil cooler area first. Cover the brakes and hub with plastic, and I would suggest you order two new rubber hoses if they are original to the car. They often have seep of oil and are getting pretty old.

With new hoses threading them to the pipes was easy for me, but I really fought with getting the super fine threads to engage properly onto the cooler itself as they come in at an angle. It is real easy to cross thread them. An old stiff hose would be a real challenge to get on square and not cross thread.

For me to get them back tight enough to seal and have zero leakage required the two wrenches to be hooked to the lines at just the right angle to where just squeezing with your hands makes them scissor together. Using both hands squeeze the handles of the two wrenches together and tighten until you can't get them tighter. Clean up any oily drips with brakeclean and go for a drive until the engine is full temp for more than 15 minutes. Then inspect for any leaks.

I ended up using several zip ties to put a layer of paper towels around the connections, drove for 30 minutes, come back and inspect the paper towels for new leaks. Once I was sure they were leak free, I removed the paper towels. After 14 years and many miles they are still leak free.

My 85 came with the Carrera cooler, but no fan so I adapted a fan to it. I only need the fan when it is blazing hot outside and on long drives.

[chrismorse]

I found the access a bit better by using two wrenches, (Harbor Fright service wrenches) to disassemble the connection at the hard line to flex line - more room to get the wrenches in there and less likely to fug up the cooler threads.

One nice thing about the cheapo service wrenches is that you can slip a cheater on each one to counterhold/loosen the pipe to hose connection. You still need to loosen the brackets holding the lines to the RF wheel well for wiggle room to get the cooler with hoses out.

Glenn, good idea about tiewrapping paper towels :-)
chris

[darrin]

thinking out loud, how does the temp sensor operate (what values should it show when cold (fan off) and hot (fan on)? -- could a disconnected wire between the sensor and the relay mimic "hot" and cause the fan to run all the time? Seems like a lot of work to get to and replace the sensor and would be unfortunate if the OP found no change to his problem after sensor replacement.

[GH85Carrera]

Since my 85 came with no fan, I put in the fan, and just have a toggle switch. To get a cooler with the bung for the temp switch was insane expensive, and I end up with a cooler as a keepsake.

[spiderem]

Originally Posted by darrin

thinking out loud, how does the temp sensor operate (what values should it show when cold (fan off) and hot (fan on)? -- could a disconnected wire between the sensor and the relay mimic "hot" and cause the fan to run all the time? Seems like a lot of work to get to and replace the sensor and would be unfortunate if the OP found no change to his problem after sensor replacement.

Yes i would like to avoid doing all this work to find out it doesn't come from the sensor. I did disconnect the sensor via the connection that is in the trunk close to the sensor, which stopped the fan. But i don't know if it means anything and i am far from an electrical wizard... if anyone has an idea to ensure that it is a faulty sensor, i gladly would like to learn. Thanks as always to all contributors.