M3 Running Cold w/ New Thermostat??

I just picked up my first M3 last Friday knowing that it was running cold. I assumed it needed a new thermostat, but after installing a new one it still runs cold. It's definitly an improvement over how it ran before, but the needle still isn't dead center. More often than not it favors the cold side. Is it possible I got a bad thermostat? Or could it be something else?

Originally Posted by 328ci906

I just picked up my first M3 last Friday knowing that it was running cold. I assumed it needed a new thermostat, but after installing a new one it still runs cold. It's definitly an improvement over how it ran before, but the needle still isn't dead center. More often than not it favors the cold side. Is it possible I got a bad thermostat? Or could it be something else?

Just out of curiosity, have you checked the actual temperature using the OBC function? It could be possible your gauge is reading wrong. Always look into the simple things first.

Yeah I was thinking that, but even my oil temp gauge never hits center, it always stays below 210 even when I beat on it.

It happened to me before, the new thermostat was bad, in my case I bought a cheap one on Ebay (around 30$), I returned it and bought another one from advanced auto (around 80$) and it worked fine.

Yeah, I guess it's possible. I bought this thermostat new from my local dealer. But I'm not convinced its bad, only because it is an improvement over the old one. So I'm thinking something else might be wrong.

A few things you need to know, not sure if you had a normal E46 before this M3?

The standard E46 temp gauge is buffered and it always sits dead center over a 50+F range. Only if it goes over center you should be very careful.

The M cars have much colder thermostats and the temp gauge is not buffered. Your car should have a 79C stat, which means a 175F.

Your temp gauge should stay about 11-11:30 position until the outside temp gets to 65-70F then it may start to hit the dead vertical position?

Not sure on the M3, but the oil temp usually is going to be about 10-20F above the coolant temp? Not sure the M3 has the oil-water-air heat exchanger like my M5, but I assume it has some sort of oil cooler?

Best to check the link below in my signature for the Hidden OBC menu, bring up the coolant temp and watch it. Should not drop below 78-79 once it warms up. If this is where your temps are with outside at or below 70F then you are probably normal.

The M is a very different car than the standard E46 in many ways, so you need to read up on it.

Originally Posted by jfoj

A few things you need to know, not sure if you had a normal E46 before this M3?

The standard E46 temp gauge is buffered and it always sits dead center over a 50+F range. Only if it goes over center you should be very careful.

The M cars have much colder thermostats and the temp gauge is not buffered. Your car should have a 79C stat, which means a 175F.

Your temp gauge should stay about 11-11:30 position until the outside temp gets to 65-70F then it may start to hit the dead vertical position?

Not sure on the M3, but the oil temp usually is going to be about 10-20F above the coolant temp? Not sure the M3 has the oil-water-air heat exchanger like my M5, but I assume it has some sort of oil cooler?

Best to check the link below in my signature for the Hidden OBC menu, bring up the coolant temp and watch it. Should not drop below 78-79 once it warms up. If this is where your temps are with outside at or below 70F then you are probably normal.

The M is a very different car than the standard E46 in many ways, so you need to read up on it.

Great information here!

As jfoj stated, the M3 needle is not buffered, and to run a little less than straight up is entirely normal (around 80C). The oil will usually stay right below the center 210f mark unless you beat on it (6k RPM plus multiple times). Tracking the car the oil temps can hit almost 300f if its really hot out and you are really beating it.

Thanks for all the info guys! I spent some more time searching the forums and have been reading exactly what you've said. People that DD their M3's in colder weather will show a slightly cold coolant temp on the gauge. It's been just about 45 degrees here for the past week or so, so it makes sense that my temp gauge wouldnt hit dead center. I feel alot better now that I know why my car has been running cold. I was afraid something else was broken...

Originally Posted by 328ci906

I just picked up my first M3 last Friday knowing that it was running cold. I assumed it needed a new thermostat, but after installing a new one it still runs cold. It's definitly an improvement over how it ran before, but the needle still isn't dead center. More often than not it favors the cold side. Is it possible I got a bad thermostat? Or could it be something else?

Completely normal. The M3's gauge isn't as buffered as the non-M. It's setup so that it's dead center from 83 to 85 degrees. It'll lean left below that and lean right above that. The m3's thermostat opens up at 80 degrees, so it will lean left for the most part. I confirmed this when I was studying the M and non-M eeproms; there is nearly no buffer in the M3 while the non-M buffer zone is gigantic. I'll see if I can dig up what temperatures the 1/4 and 3/4 dots represent.

Fwiw my oil temperature is around 180 in this weather. When it warns up, it's more like 190-200. I have to really beat on it to get it above 210

Originally Posted by TerraPhantm

Completely normal. The M3's gauge isn't as buffered as the non-M. It's setup so that it's dead center from 83 to 85 degrees. It'll lean left below that and lean right above that. The m3's thermostat opens up at 80 degrees, so it will lean left for the most part. I confirmed this when I was studying the M and non-M eeproms; there is nearly no buffer in the M3 while the non-M buffer zone is gigantic. I'll see if I can dig up what temperatures the 1/4 and 3/4 dots represent.

Fwiw my oil temperature is around 180 in this weather. When it warns up, it's more like 190-200. I have to really beat on it to get it above 210

Ok that makes me feel a lot better. That's exactly the kind of temps I am seeing with the new thermostat. Now I just have to rebuild my Diff seals to make it 100%. I was just waiting to place my order for diff seals until I had this cooling figured out. Thanks for the tips guys