M20 Coolant Temp Sensor (Blue plug) replacement help!

[doogie]

OK.... much swearing at lunch time trying to change my temp sensor (blue plug) on my M20 engine..... In theory I should

disconnect battery
disconnect blue plug
unbolt temp sensor
bolt in new one
reconnect blue plug
reconnect battery

which would be easy peasy... if I could get a spanner in to unbolt the current temp sensor! I tried a normal open end spanner (19mm, the right size) and a socket, and I could not for the life of me get in to get the nut and turn it. I tried disconnecting some hoses, and even started unbolting the whole housing that all the hoses go into (could only find two nuts though and I don't have a new gasket for that so that would kind of suck) - do I need to remove that, or do I need to remove the fuel lines etc to get into it? Or am I just missing something ridiculously obvious ????

Thanks guys!

[JonE]

I would also be interested in finding out how this is done. Seems very cramped near that sensor.

[doogie]

I've looked at a shorter socket but the blue plug fouls that; I'm going to buy a 19mm ring spanner on the way home and see if that will do the trick. someone else suggested cutting it open, but that's just asking for trouble!

[doogie]

Right, got a 19mm ring spanner, took out the sender with the brown plug and then managed to unbolt the blue one and replace it - hopefully i've bolted it in tight enough (yeah, Bentley tells me the torque rating, LOL! :p ) - I'll find out tomorrow!

[JonE]

Aha, take the brown one out first, then the blue one. Good thinking. Let us know if any leakage.

[moots]

I'm curious as to the reason you need to change the temp sensor.What's the defect associated with it that you are having?tks

[doogie]

I'm changing the temp sensor as an independent BMW mech told me part of my rough idling and engine starting problems are due to "the ECU thinking the engine is freezing cold all the time" and an AA roadside mechanic telling me "the reason it's not starting is probably due to overfueling because it thinks the engine is colder than it is"

So hopefully it'll solve my problems and not have any leakage :)

[JonE]

I think there is a test procedure for that sensor, measuring the ohms resistance at least a couple of different temperatures. I can see using the ambient temperature, but always wondered how/where to measure at other temps. I know the procedure is in my E30 Bentley, don't know about the E34 Bentley.

[doogie]

Yeah, my Bentley suggests using a thermometer and a water bath to check the resistance at different temperatures.... I might do that when I've got spare time.

[doogie]

Hmmmm.... it's not particularly running better with the warm start problem I was having, but it does seem to be running better while accelerating etc.... Will need to look at Bentleys again and maybe look at something else to fix the problem. :(