Why does brown coolant sensor need to be machined?

[LagunengrunE36]

As the title states, it fits fine in my bro's car, so he's wondering why it needs to be machined?

Thanks!

[Danny]

What motor is your brother swapping in?

[LagunengrunE36]

M50... the sensor is from an M20 going on an M50.

[Danny]

OBD1 motors already have the correct size hole in the head. Only on OBD2 motors do you have to machine the sensor down, or tap the head larger or use an aftermarket coolant sensor adapter thing.

[LagunengrunE36]

Alright, thanks for the help.

[agustingig]

It goes in the front hole on the head right? the one that has a blue plug on the M50 wiring harness?

[7pilot]

There should be a second port after that one.
It may not matter which hole, but the factory may have had a good reason to put the Blue plug sensor in the front hole.

Even on older engines, BMW places the blue coolant temp sensor closer to the radiator or upstream of the temp gauge sender.


m

[Schwarz325]

It goes in the front hole on the head right? the one that has a blue plug on the M50 wiring harness?

no 2nd hole from the front, should be a black sensor. The blue one is for the ecu, make sure you leave that one in there.