[roadkillrob]

Car is a 2008 garage queen, 18k miles owned since new, coolant changed last year.

No issues recently, nothing has been touched on the car in a year. Went for a ride today, 78 degrees on the highway, 5 miles from home, get the overheat light, yellow then red right away. Oil temp is 180, coolant is at 253!!!

Pulled over shut it off for a bit, got down to 210 degrees figured I would get off the highway as exit was close, started it up, got on the road and coolant temp drops to 180 almost instantly, then slowly heats up to 200 and just sits there for the drive home, no issues.

Checked codes with the BT cable, no codes, weird! Ran the pump tests from BT comes on and runs fine, sounds a little noisy to me, but never listed to it before with car off.

Also thought it was odd the rad fan was never load like most people experience, at 250 for coolant temp, I would think the cooling fan would be on high. It is almost like the car wasn't that hot and just reading high.

My commute is short so will see what it does tomorrow I guess, was totally expecting a code and to be ordering a pump, but now not sure?

[X_Drive]

Does your fan work at all? This sounds like your fan took a poop. See if it turns freely by hand, engine off of course!

[roadkillrob]

I will check but was on the highway at 80mph which would generate more airflow than the fan would so it should not have overheated unless coolant flow is an issue, but would expect a code for something not working!

[els_86]

Sounds like your radiator isn't cooling the coolant. Did you check out the radiator?

[X_Drive]

Originally Posted by roadkillrob

I will check but was on the highway at 80mph which would generate more airflow than the fan would so it should not have overheated unless coolant flow is an issue, but would expect a code for something not working!

Ah I see now! I dismissed this due to your post of the pump test. However I should have asked, if you confirmed that coolant flow was ok with the pump activated. Simply take off the expansion tank cap and activate the pump. You should see a stream of coolant spraying during the activation.

If you don't then you may be safe to say that the pump is done. It may sound like its moving, however there may be no or very little movement of coolant causing the overheating that you experienced.

If you do see coolant spraying, your pump may be still on it's way to the parts "round file." Or garbage can.

Keep us on the update.

[els_86]

You say the coolant itself is getting too hot, so you can eliminate water pump, t stat, air pockets, etc because those would cause just a general overheat to your engine. The problem is your coolant is passing through the engine and not getting cooled, which to me says there is a problem with the radiator. Anyone else agree?

[roadkillrob]

Originally Posted by els_86

You say the coolant itself is getting too hot, so you can eliminate water pump, t stat, air pockets, etc because those would cause just a general overheat to your engine. The problem is your coolant is passing through the engine and not getting cooled, which to me says there is a problem with the radiator. Anyone else agree?

I don't understand your reasoning on this, guess it depends where the coolant temp sensor is located, but I think it is in the head, so if the coolant isn't circulating then it would measure hot in the head.

I think the pump stopped or thermostat stayed closed and just kept circulating coolant in the engine without going through the rad as once I pulled over and let it cool down to 210, I started it up to get to the exit ramp and after about 15 seconds, the temp dropped to 175, which would indicate that the cold coolant in the radiator suddenly started to circulate into the engine to drop the temp so significantly and so quickly, otherwise it would have just stayed at 210 which is about normal temp for my coolant.

I also forgot to note, I have the electronic steering wheel, so it shows me cooland and oil temp both on the wheel.

Drove it to work today, 6 miles each way, warmed up to a normal 210 or so and stayed there fluctuating between 205 and 212 max - no issues.

Just can't help but feel it is an early warning sign, but wish it set a code, but may just replace the thermostat and pump since they are known to fail.

[NashvegasR]

My gut is water pump (electric water pump) is on the way out and intermittently not working... Did you pull codes as to why / what?

Unlike basically any other car I've ever had, the water pumps do this before they completely fail... might be worth checking.

[Miller335]

How many miles on your ride?

[thomas88162]

Electric waterpumps can and do fail intermittently. Let this instance be your warning.

[roadkillrob]

Originally Posted by NashvegasR

My gut is water pump (electric water pump) is on the way out and intermittently not working... Did you pull codes as to why / what?

Unlike basically any other car I've ever had, the water pumps do this before they completely fail... might be worth checking.

Absolutely no codes (actually was disappointed - was hoping to get a code for the pump and then would feel better spending the 500 bucks!)

[roadkillrob]

Originally Posted by Miller335

How many miles on your ride?

18,000 - just broken in (but 6 years old), a little early for a water pump, but have read of others as early as 9k miles.

[roadkillrob]

Originally Posted by thomas88162

Electric waterpumps can and do fail intermittently. Let this instance be your warning.

Yes - thinking it is a warning from the bmw gods and I should listen!

[bbstoke]

I know my fan isn't working, only do short runs in it, if I have to go further I use the wife's car... Fan cost was £400 so haven't bothered to get it done.
Does this affect the general running of the car?

Tick over is not perfect at the moment, not bad just not 100%.
Car has done 94000 miles.

Because the fan isn't working I was wondering is this affects the flow of the coolant?

[trapahh]

This is exactly whats happening to mine.

[elons335i]

I seem to be missing something. Can someone enlighten me how or where to display the coolant temperature?

[thomas88162]

Originally Posted by bbstoke

I know my fan isn't working, only do short runs in it, if I have to go further I use the wife's car... Fan cost was £400 so haven't bothered to get it done.
Does this affect the general running of the car?

Tick over is not perfect at the moment, not bad just not 100%.
Car has done 94000 miles.

Because the fan isn't working I was wondering is this affects the flow of the coolant?

Just don't use the A/C and don't stop/idle your engine. The fan has no affect on coolant flow, only radiator and condenser temperature.

[db2761]

I just went through this..

Replaced the 40a relay in the DME box, under the hood. 2008 335i coupe with 80k..

Was driving me nuts..

Dan

[elons335i]

Originally Posted by elons335i

I seem to be missing something. Can someone enlighten me how or where to display the coolant temperature?

?

[1QuikWS6]

Originally Posted by db2761

I just went through this..

Replaced the 40a relay in the DME box, under the hood. 2008 335i coupe with 80k..

Was driving me nuts..

Dan

You & I have the worst luck with relay's

If you remember, I had that finicky relay in my fuse box that was giving us trouble when installing the M3 Gages

[thomas88162]

Originally Posted by elons335i

?

INPA? that's how I do it. I don't know if you can call it up on the dash or not. I imagine that tunes will show it as well.

[1QuikWS6]

Coolant Temp info can be pulled off CanBus from OBD Connector under dash.

Both my P3Cars Vent Gage, & my New Dynavin N6 radio display Coolant Temp...