Over cooling ?

When I drive a car during the day, my temperature gauge points the middle. However when I drive the car in highway at night, the temperature is low like in the attached picture. What could cause this low temperature at night ? Outdoor temperature is 60 at day and about 30 at night.

Watch out for black ice if you are driving on the highway during freezing conditions at night! I think your gauge pointing left of center during these conditions is normal.

running between the arbitary 1/4 and 3/4 mark is, to a point, normal, though always running cold or always hot does indicate a problem.
In fact, if you sit in the drivers seat of an E46 they do not have the 1/2 mark at all, I'm not sure about other later BMWs.

Just keep an eye on it for now, but at the moment, i wouldnt be too bothered.

if it is indeed running cold, it is likely to be the thermostat, or could just be a faulty gauge sender.

Faulty thermostat? Maybe nit closing 100%?

Sent from Joe's Galaxy Tab 2 via BimmerApp

After I started a car, I touched the hose that is connected to a radiator. Although temperature is lower than 1/4 mark, the hose was already warm. Maybe thermostat is always open ? It was cold when I start a car.

Originally Posted by jhkim

After I started a car, I touched the hose that is connected to a radiator. Although temperature is lower than 1/4 mark, the hose was already warm. Maybe thermostat is always open ? It was cold when I start a car.

I had the same symptoms in 4 months, replaced the thermostat with OEM, and voila now it's fine, it was stuck open. My upper hose was also hot even though the thermostat was open all the time.

Originally Posted by Mamij

I had the same symptoms in 4 months, replaced the thermostat with OEM, and voila now it's fine, it was stuck open. My upper hose was also hot even though the thermostat was open all the time.

The reason for that is that the hot coolant from the heating engine are flowing through the hose even though its not at op temp yet. E28 does it too.

Agree thta the t-stat is likely the problem and should be replaced.

+1 on t'stat

Yay! Another DIY project. Do you guys think this is not too bad to keep driving? I'm planing to replace tstat when I replace coolant. It might be after a few thousand miles more. I wonder if how bad this is. I see that it takes a while until temperature bar is at the middle.

No it wont hurt anything. The stat is designed to get and keep the engine at a certain temperture so it heats up faster. This also effects your heater. If you are driving on the highway you may not have heat. I would change as soon as possible. ...you only have to worry when they are stuck closed

So, in post #2 I said this is normal while driving in freezing conditions. I'd like to retract that statement. Since then I've learned that thermostats open and close while the engine is running. For some reason I was always under the impression that a thermostat opened and stayed open once the engine reached normal operating temperature. But this is not true. A thermostat closes once the temperature starts dropping. Here is a cool youtube video showing this.


Now I fully agree that the OP has a bad (stuck open) thermostat.

To add to this, please read this thread (especially post #11) http://forums.bimmerforums.com/forum...d.php?t=292135 I don't know how true this is. But it is concerning.

Originally Posted by germx

To add to this, please read this thread (especially post #11) http://forums.bimmerforums.com/forum...d.php?t=292135 I don't know how true this is. But it is concerning.

Concerning and 100% correct.

That's a really cool video. I can't stop thinking about a slowly closing and opening tstat while driving after watching this vidoe. Thanks !

Education is a wonderful thing. A little knowledge is dangerous......

My temp gauge reaches the center mark, or maybe just a needle width to the left during highway driving at -25C, not getting up to temp at 30F is not normal. Although i think it would take a long time to get to the center mark/warm whem highway driving at 60F with a stuck open thermostat, no? I wonder what the actual coolant temp difference is between being 1/4 and 1/2 on the temp gauge is.
Replacing thermostat is not too big a job, replace the thermostat cover with an aluminum one while you are at it though. You might also consider replacing pump as well while you are in there, depending on miles and service history of course.

Keeping the oil cool is bad. It needs to up at normal operating temp.

Originally Posted by BMR_LVR

Concerning and 100% correct.

Yes, running too cool will cause problems. However, I suspect that by the time the needle moves off the cold section (blue) you are well out of the fuel enrichment cycle. This acts as a choke did on carburated cars. It doesn't take a long time for it to come off.

You should be fine for a short time. As simple as the stat is to change though, I would just do it. You wont lose much coolant, no real point in waiting.

Originally Posted by snowsled7

As simple as the stat is to change though, I would just do it. You wont lose much coolant, no real point in waiting.

+1

Change it. It's cheap, easy and if I can do it, anyone can. Hell my wife could do it...but then my wife's pretty damn smart...just don't over tighten the bolts?

Thanks for the advices ! I ordered the parts and waiting for them. Found a pretty good blog about it.

http://almostgonesblog.blogspot.com/...placement.html

I'm not changing a water pump so I'm wondering if I don't need to remove the fan. I will update the ticket after replacing the tstat if it fixes the problem or not.

Seems like I did have trouble with access to the bottom bolt...maybe I did take the fan off to do it properly...can't remember now. But the fan was easy to take off from what I recall...

It wasn't that easy project because taking out a fan wasn't easy. However I found a good tip which you can borrow a wrench that holds the fan.


http://www.autozone.com/autozone/acc..._&target=shelf

Part Number: 27018
Alternate Part Number: AZ188

With this tool, it was pretty easy to taking out a fan. You guys are all right. It was a tstat problem. A surprising fact is that the tstat has very small gap. It wasn't that big but it caused big temperature difference. After replacing it, the temperature is on solid middle. I drove about 60 miles and it did not change at all. Also heater works well. Yay! Thanks for the advices.

P.S. Does anyone know what the arrow means on tstat ? I put the tstat the way that the original one is but I don't know whether the arrow means something.

it indicates proper positioning of the thermostat; quoted from the Bentley "Install the thermostat so that either the arrow or hole are at the top." so it can bleed properly I assume...