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View Full Version : Is my thermostad stuck open?



napuli
10-31-2009, 12:25 AM
Can you tell me how long it takes fot a 540i to reach normal running temp? Mine seems to take forever 10 min or more with city driving.

russiankid
10-31-2009, 12:26 AM
Depends on the ambient temperature. If its cold outside, should be up to 8 minutes. If its warm out or hot, about 5 minutes.

h2oyo
10-31-2009, 12:58 AM
I agree with the above, it doesnt take long during the summer but during the colder months it could take 7 to 10 minutes.

garethashenden
10-31-2009, 07:55 AM
mine was taking 20 last year, a new thermostat make it take 10

napuli
10-31-2009, 11:57 AM
Thanks, good to know.

Lax7
11-03-2009, 10:19 AM
id wish my thermostat was always open..wont the car be cool all the time then?

bblazen
11-03-2009, 10:21 AM
id wish my thermostat was always open..wont the car be cool all the time then?
Not good for the engine to go high rpms with cool internals.

moroza
11-03-2009, 02:25 PM
Not good for the engine to go any rpms with cool internals.

Fixed. That's a big part of why lots of short trips over a car's lifespan is so much worse than a small number of long ones. That's why "highway miles" is a selling point. You can't eliminate all cold running (obviously), but it's best to minimize it.

Thermostats are cheap and easy to replace. The waterpump doesn't need to come out.

Lax7
12-21-2009, 02:19 PM
Wow, going back over this post, when i recently did my cooling system after the head gasket, turns out my car have been running without a thermostat for years now. Any effects on the engine? Like unstable RPM's or etc?

zubbie
12-21-2009, 02:23 PM
Wow, going back over this post, when i recently did my cooling system after the head gasket, turns out my car have been running without a thermostat for years now. Any effects on the engine? Like unstable RPM's or etc?

Given your climate, I wouldn't be too concerned. As long as the temp needle was at or near the middle your engine would do just fine. I little bit cooler than normal is not necessarily a bad thing as manufacturers like a hotter running engine than required for emissions reasons.

misswin
12-21-2009, 03:45 PM
I was wondering why when I'd go 60mph or more my temp needle was going to cold. Maybe it's stuck open. How will I know if it's busted?

russiankid
12-21-2009, 03:53 PM
I was wondering why when I'd go 60mph or more my temp needle was going to cold. Maybe it's stuck open. How will I know if it's busted?

You won't know until you take it out and look at it. If your needle goes down when you get onto the highway, most likely the thermostat is either stuck open or it is lazy which means it is not functioning correctly. I would replace it.

M Quick
12-22-2009, 05:30 AM
id wish my thermostat was always open..wont the car be cool all the time then?

Sure. but then there is no reason for a thermostat in any engine.

1. you would do more damage to the engine if it is running cold all the time.
2. it would run much less MPG when cold (runs richer when cold).
3. you don't wanna drive the car hard when it's cold.
4. won't get any heat in the car

ArnZ
12-22-2009, 06:19 AM
my 535i warms up pretty quick. In about 2km my temp gauge is already reading at half way.