Coolant temp sensor

[SterlingMetE30]

Coolant temp sensor. Which oth the thermostat sensors is the cts I have looked online already. Nothing. Noob question I know.

[101]

Assuming this is an "I" car, on the thermostat housing are two sending units:

- The single wire one is for the temperature gauge on the dash.

- The one with two wires is for the car's engine computer (DME).

If its an eta there are 4 ...

http://www.r3vlimited.com/board/showthread.php?t=125869&highlight=temp+sender

[SterlingMetE30]

I was told it is an e engine. It has been replaced. But I only have two wires..?

[MR 325]

When in doubt, post a picture.

[SterlingMetE30]

Hope it loads

[ak-]

When in doubt, replace all of them

[SterlingMetE30]

Mine is the double wire sensor. Can't seem to find the part at the stealership or autozone cause they gave me the wrong one.

http://s36.photobucket.com/user/patricmhagarty/media/Mobile%20Uploads/image_zpsdb4b6212.jpg.html

[101]

It's unclear from your post exactly which of the four sensors you are thinking about replacing. Three of them have double wires. What are the symptoms you are trying to address?

http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=11_0759&hg=11&fg=35

This help at all?

[SterlingMetE30]

I am trying to address rough idle. Cold start and warm idle. And maybe 12 on the diagram.

[Chuck C]

Call or stop by a CARQUEST store with your BMW part numbers. CARQUEST is part of the Worldpac empire, and some things that are NLA from BMW are available from Worldpac.

[SterlingMetE30]

Sweet thanks! I will have to check it out.

[101]

I am trying to address rough idle. Cold start and warm idle. And maybe 12 on the diagram.

Got it.

There are tests for each of those sensors in the Bentley manual. Here's what I'd recommend:

1) If the temperature gauge on the dash looks to be reading correctly - I'd leave that single wire sensor alone. It does nothing but operate the gauge.

2) Test the "45'C" sensor (the one with the spade connectors. Its a simple on-off switch. If its cold, it should be an open circuit. If it's warm, it should have continuity across the terminals.

3) Use the Bentley manual to test the Thermo time switch. If this switch is bad the problem is usually more one of hard to start when cold or flooding when warm.

4) Replace the coolant temperature sensor. Its cheap enough.


For rough idle, the rest of the crew here will tell you to run a smoke test. These intake systems leak everywhere when the gaskets get old and the rubber hoses harden.

Full diagnostics at the ECU connector using the instructions in the Bentley manual is also a good idea. That was you can check all the sensors AND the wiring to the ECU at the same time.

On my eta, I changed the 45'C switch ($36) and the coolant temperature sensor ($17). I got them both at Bavarian Auto. Make sure you get the correct coolant temperature sensor as the one for the eta is different than the one for the "i" cars.

Good luck!