Is this normal? Temp to drop when going real fast in cold weather

[LunatiC]

So I was doing 160km/hr (100mph) tonight -- it's 3:42AM local time here and it was about 8 deg C (46 deg F) ambient temp according to the OBC, when I noticed that the temperature gauge on my dash board was actually dropping.

Usually the needle is a hair-width's away from the middle notch, but tonight it dropped a fair bit to the left, past the notch between stone cold and middle.

I found this quite odd, does this make sense to anyone at all?

[Ross]

T stat ought to keep the temp up. Sounds like a lazy one, cheap replacement if in doubt.

[632 Regal]

ditto, replace it with a BMW stat available at your favorite online sources.

T stat ought to keep the temp up. Sounds like a lazy one, cheap replacement if in doubt.

[mattyb]

i would consider this normal. i do this quite often and the needle ussually drops just a fraction at higher speeds. makes sence to me.

[LunatiC]

i would consider this normal. i do this quite often and the needle ussually drops just a fraction at higher speeds. makes sence to me.

OK well this has thrown a spanner in the works! (Haven't emailed Patrick yet). I noticed that my needle is fine now, it only did it at (really) high speed. It's not often that I drive so fast anyway.

If the replacement is cheap and easy to do, I might as well do it. How are you supposed to know what t-stat you need though, since there are so many? I had followed a little bit the "controversy" surrounding installing a different t-stat to what the factory put in your car and it does this and that for your engine which supposedly improves something, however I am not interested in this and just want to maybe replace the t-stat with the same spec as what was installed originally in the car.

[Dave M]

OK well this has thrown a spanner in the works! (Haven't emailed Patrick yet). I noticed that my needle is fine now, it only did it at (really) high speed. It's not often that I drive so fast anyway.

I wouldn't consider this normal. A small drop, maybe, but what you're experiencing, no way. I've driven in -40 at highway speed across Canada, with the temp pinned at 12:00. You definately have a lazy thermo. The only time you should see a decrease is if you're coasting (neutral) down a loooooong grade (mountains) where an idling engine cannot keep up with the cooling effect. I've seen this quite a few times, but we're talking 6-10 mile decents in neutral, fun

Dave

[Blitzkrieg Bob]

T stats come in several temps 90, 88, etc.

and local shop tried to sell me a 72 for my M50tu...eeeh Wrong!

[TC535i]

Bad t-stat, my 540i ran just above blue the whole way back from Oregon. Swapped a fresh one in, and it sits at the middle all day.

[Tiger]

Yep... bad thermostat...

[LunatiC]

OK thanks for your replies guys. Looks like I'll be writing an email to Patrick from BMA