Whats this hose?

[Cabriolet]

I was changing some hoses on my new to me M3 and I found this hose.
is it supposed to be there? and what does it do?

[reelizmpro]

That isn't supposed to be there. Those holes are supposed to be plugged up. Very strange.

[Cabriolet]

thx barry. the hose looks to have a small leak that needs to be addressed.

[reelizmpro]

I'm curious why the plugs were removed and there are fittings for the hose there in the first place.

[Todd Black 88]

Iirc, the early m3 cars had the two sensors found on the tstat on later cars, in the rad there.
My car actually still has the sensors in place, but the ones being used are in the tstat now

[reelizmpro]

Iirc, the early m3 cars had the two sensors found on the tstat on later cars, in the rad there.
My car actually still has the sensors in place, but the ones being used are in the tstat now

My silver car is an early car...produced 5/87. Never had sensors in the radiator, the wiring harness is on the passenger side too. Wouldn't make sense to have two pairs of sensors. Maybe you have a 318 radiator or a euro radiator?

[Todd Black 88]

http://realoem.com/bmw/showparts.do?model=1003&mospid=47312&btnr=17_0014&hg=17&fg=05

This is the realoem link for my car, and it shows a sensor on the drivers side. One of the holes is a plug and one is a sensor, according to realoem.

Not a definitive source, I know, but......

[reelizmpro]

Thanks for posting that. I have never seen an M3 with that setup and I've seen a lot over the years. RealOEM also shows the same sensor in the thermostat housing for the same car 1/87. It also shows that the late M3's had a sensor in the radiator. So no matter what year M3 you choose it shows two identical sensors 1 in the radiator and 1 in the thermostat. That just doesn't make sense as it only uses one dual temp sensor. I guess where ever your connector is determines the sensor location. I've only seen it in the thermostat housing though. I wonder if another 3 prong connector is tucked away in the harness on the drivers side somewhere.

[reelizmpro]

Just an update. There is indeed another 3 prong aux fan connector on the drivers side under the headlight bucket. I believe it is zip tied in place but it is there! I didn't realize it at the time but I wired up my puller fan to the low speed terminal from this connector as it runs through the relay. I changed headlights today and my fan stopped working. When I looked at the wiring I found this connector. I accidentally disconnected the wiring for the fan when I switched headlights.