How to test Oil Temp Sensor?

Por_sha911 · Por_sha911's Garage

The oil temp gauge (No numbers) never reads above the first line above the white block at the bottom even on a long drive. I believe its either the temp sensor (on the right side of the block) or the thermostat. Does anyone know how to test the temp sensor? If I have to, I'll replace it first since the sensor is about $25 and the thermostat is going to be a bunch more money. My car has the cooler in the front right fender so I believe the thermostat to replace is the one in front of the right rear wheel. Pelican shows a bunch of valves a springs. How tough would it be to rebuild the thermostat?
BTW, if there is something else I can check, let me know but please speak slowly since I'm rusty on the wrench side of repair.

masraum · 02-19-2004, 06:01 PM

Joe, so, on your gauge there is the bottom of the scale, a mark, a second mark, and then the top of the scale, and your car runs at the first mark up from the bottom of the scale, is that right?

That is about 200* which is the temp at which the external thermostat opens. Most of our cars run around that temp most of the time. It's normal. You can check that thermostat by feeling the oil lines in the front fender by the cooler, if they are warm/hot then that thermostat is openning.

Por_sha911 · Por_sha911's Garage

There's a white bar at the bottom of the gauge and a red bar at the top of the guage. In the middle are two lines. The needle barely gets up to the first line after the white bar (it usually sits just barely above the white bar at the bottom).
Great idea about feeling the lines running to the front cooler. Duh, why didn't I think of that? I do that with a water pumper to see if the thermostat is opening.

vash · vash's Garage

porsha911, i did the same thing. i just installed a used system and my personality is paranoid by nature. i wasnt sure if my external tstat was working (the one by the rear pass wheel). i got some good weather today so i took it for a drive, about 10 miles. my gauge has numbers, it got to about 210-220 on my dial. i then used a infrared point and shoot thermometer and measured the temp at the tstat, i got 180. i felt up the lines and they were barely warm, barely. i didnt know if the tstat was working, so i took my front wheel off and cracked the oil line above the wheel. i got oil dripping out, so i can assume my system is working. ithink the temp sensor in the block, tells the gauge on your dash how hot it is. how accurate is the mystery.

cliff

Por_sha911 · Por_sha911's Garage

Is there any way to check ohms or volts from the temp sensor?

1980 911 sc · 02-19-2004, 07:54 PM

I have the same thing, I just bought a replacement..... If it still reads low after the swap, I will obviously have to drive it harder.......

Por_sha911 · Por_sha911's Garage

Quote:

Originally posted by 1980 911 sc
I have the same thing, I just bought a replacement..... If it still reads low after the swap, I will obviously have to drive it harder.......

I've read that driving it hard with cold oil is a BAD thing. If cold oil is running through the cooler it will clog up and there can be motor damage.

surflvr911sc · surflvr911sc's Garage

First off, I wouldn’t worry about the thermostat in the wheel well. If you have a problem, and I doubt it, it would probably be indication and not mechanical.

An easy way to check both your temp and thermostat it to feel the oil lines up in the front wheel well at the cooler. Have the car fully warmed up and feel the lines. If they are warm/hot your thermostat is fine and the car is getting up to temp. Also where you are saying your indication is should be about right for the thermostat to be fully opened.

W/ the cooler temps of this time of year it’s not unusual for the oil temps to barely reach operating temps. I think that everything is fine and you should feel comfortable driving it as hard as you like as long as the above check is good.

Por_sha911 · Por_sha911's Garage

Thanks for the info Doc.
I'm a little (maybe a lot) obsessive/compulsive about my car and was concerned that the thermostat was open all the time and hence the car not getting up to proper temp. If the thermostat didn't close, the front fender oil lines would be warm. Since this is my first 911, I wouldn't know whether warm is warm enough...