Someone explain the coolant temp sensor to me

[equate975]

Ive gotten all confused about what to do with the coolant sensor. I did an OBDI conversion which required me to either tap another hole for a 2nd coolant sensor, or splice wires from the stock one on the s52. I opted to splice wires since theres less of a chance I can mess things up :)

Anyways, my temp sensor does not work. Now I am told I have to tap a hole and thread an e30 sensor in to make the temp sensor in the cluster work, is this right? Also if so, where would I hook it up? Im not seeing a spare connector anywhere.

[325Projectz]

Read this carefully

[equate975]

I did read that but I never saw anything about doing that in an e30.

[325Projectz]

Same thing, its on the engine harness, not the body side.

[equate975]

Well in that case, thats what I have done and the temp sensor on the cluster does not work.. Maybe a wire came loose

[Jason89i]

Read this carefully

are you sure? do you have hands on experience? i only ask because there is a lot of "hear say" information out there that may be correct, but not 100% correct. i dont want to sound like a jerk, but i hate to see misinformation passed around.

were you able to use the e36 obd1 temp sender for the m50 conversion? the obd2 vs obd1 temp gauge has the same resistance for the e36.....but different for the e30.

that page you linked is e36 specific. double check resistance at the dual temp sender vs. the e30 resistance.........i found them to be different. hence, the e36 obd2 (or e36 obd1 for that matter) will not tell the cluster the correct reading for temperature.

cheers, jason

[Addissimo]

no question the e30 and e36 gauge temp senders are different.

You'll probably have to go about this route, and using a multi meter and a pot of water figure out the voltage difference between the e30 sensor, and the obd-2 e36 sensor, then put a correct resistor into the wire going to the temp sensor. (hopefully it supplys too much voltage)

-Addis

[conrod]

no question the e30 and e36 gauge temp senders are different.

You'll probably have to go about this route, and using a multi meter and a pot of water figure out the voltage difference between the e30 sensor, and the obd-2 e36 sensor, then put a correct resistor into the wire going to the temp sensor. (hopefully it supplys too much voltage)

-Addis

That won't work accurately. First test the gauge and wiring, ignition on, disconnect plug from temp sender.Short the gauge wires together. Should give full scale deflection of needle. (disconnected may read "cold", shorted may read "hot" or could be the other way around, I don't remember which way these ones work, but that is not important, as long as you get opposite readings) If this does not work, then fault is in wiring/gauge. if this works okay, fault is in temp. sender. Sender must be same as original (in your case E30) as resistance table will be different to E36 one, and fitting a resistor inline will give an inaccurate reading.Don't confuse ECU temp sender(blue) with temp. gauge sender.(black)

[equate975]

Awesome thanks for the help. Do people with m50/s50 just thread a e30 temp sensor in? Or whats the "normal" way to do this? Just out of curiosity...

[equate975]

I was thinking, if I put a resistor on, wouldnt this change what the ECU is reading for a temp? Or does this sensor only send info to the gauge? Does the ECU need to know the temp for any reason?

If not, then why not just put a s14 sensor in? Make it a lot easier

EDIT:

Oh I get it now, with the OBDI conversion... I split the wires from the sensor, which means one set goes to the ECU, the other set goes to the gauge. I will just have to add a resisor on the set that goes to my gauge. Unless the voltages are to small, in which case I might get stuck tapping my head.

New thought:

I wonder if I can just use an e36 temp gauge?

[FredK]

One solution I've seen is to tap the thermostat housing for the temperature sensor, on the output side of the housing, to ensure the temperature measurements aren't affected by the thermostat. If the t-stat were to get stuck closed and you put it on the other end of the housing, you might be in for some unpleasant times indeed.

I'd like to know which sensor is which; are we talking about the M14 Engine Coolant Temp Sensor or the M12 Temperature Sensor?

I'm planning the swap in a 318is. The temp sensor is the same, and the engine coolant temp sensor is different from the E36 version (1 pole vs. two pole), but have the same threads (M14x1.5). I'm hoping I don't have to monkey around with this stuff.

Also, I believe early production S/M52s came with an extra M14 hole that was plugged with a bolt, because they were just using the same leftover castings until they ran out. Depending on which sensor you're talking about, there might still be some hope for us!

[Jason89i]

One solution I've seen is to tap the thermostat housing for the temperature sensor

yea, that is how mine is currently. i dont like the idea of getting water temp housing reading versus head temp reading. reading the water temp off the housing leaves a lot of room for error......bad thermostat, water pump failure, water loss......

cheers, jason

[Jordan]

Why is everyone so afraid of tapping the head? Its not hard, I've done it at least 3 times....

[Jason89i]

Why is everyone so afraid of tapping the head? Its not hard, I've done it at least 3 times....

did you pull the head off?

[equate975]

Ill tap it if I have to, I would rather just not, and not have to shell out for an extra sensor and more work, if I can just add a resistor it would be a lot easier for the same result.