Need Help Determining Root Cause of Temperature Needle in Red - SOLVED

[Slideways]

The gauge is controlled by the temp sensor under the intake manifold and they do go bad every once in a while. Fairly cheap and not a messy to replace as the thermostat or the lower radiator sensor.

[0-60motorsports]

The gauge is controlled by the temp sensor under the intake manifold and they do go bad every once in a while. Fairly cheap and not a messy to replace as the thermostat or the lower radiator sensor.

Glad I replaced that one.

[bimmerfan08]

Have you compared the needle position (red) to the digitally displayed temp?

Why I ask: I’m confused looking at your picture. The oil temp is bottomed out (cold) and the engine is not running per the RPM gauge, so I haven’t sorted out if the ignition is on.

(the temp gauge in the cluster can fail)

I had the engine turned on per my original post, then shut it off when the coolant needle moved to red. The oil never reached operating temp hence the cooler oil temp. My next step is to perform to check the digital display when I get some time this week.

[bimmerfan08]

The gauge is controlled by the temp sensor under the intake manifold and they do go bad every once in a while. Fairly cheap and not a messy to replace as the thermostat or the lower radiator sensor.

How difficult is it to reach? I've read similar posts that do fail over time, but it's uncommon.

[eacmen]

How difficult is it to reach? I've read similar posts that do fail over time, but it's uncommon.

I think you need to remove the intake manifold

[Slideways]

How difficult is it to reach? I've read similar posts that do fail over time, but it's uncommon.

Intake manifold has to come off and it is easy to access after that. Genuine BMW one failed after 30k miles and 6 years. Temp gauge would randomly fall to cold when at operating temp.

[eacmen]

This is easy to diag. Get inpa or similar. Log coolant inlet and outlet temps. If they are wildly different its a sensor issue.

[bimmerfan08]

Thanks for the quick replies back - much appreciated. I have some more investigating to do to determine the root cause.

[Obioban]

Grinding noise means it's not just a sensor.

I'd put money on the water pump being the issue-- I'd put it and inspect.

[heinzboehmer]

Just taking the belt off and spinning the water pump by hand might give you enough information about it's state. Should have basically no play and should not make any grinding noises.

[Slideways]

Yeah, rereading your post OP, it sounds more like the bearings in the pump are failing. I thought you might have checked that given all it takes is removing the belt check for play in the pump.

[bimmerfan08]

Grinding noise means it's not just a sensor.

I'd put money on the water pump being the issue-- I'd put it and inspect.

What I'm currently leaning towards.

Didn't have time to pull it apart last week before leaving for a trip. Will pull the belt and check for play later this week.

When my original water pump failed back in 2012, there was quite a bit of coolant leaking from the shaft and slinging off the fan. Much drier experience this time around.

[Obioban]

What I'm currently leaning towards.

Didn't have time to pull it apart last week before leaving for a trip. Will pull the belt and check for play later this week.

When my original water pump failed back in 2012, there was quite a bit of coolant leaking from the shaft and slinging off the fan. Much drier experience this time around.

They don't always leak when they fail for sure.

[bigjae46]

Thanks for the picture. Is the impeller composite or metal in this picture?

Can you share more context on the OE BMW water pump limited lifetime warranty? I'm not privy to this.

I think the impeller was composite, its been awhile. I know the OE pump I have on how is composite.

Geniune BMW water pumps have a 2 year unlimited mile warranty - covers the part and if installed at a BMW center also covers the labor. After the 2 years, there is a lifetime limited warranty on the part. So if you bring a failed BMW water pump to a BMW dealer, service will need to verify that the pump is failed and then they will warranty the pump at no cost. You will need the receipt with the original purchase where the part was paid for. No warranty on a BMW part replaced under warranty unless there is a warranty extension on that part (many N-series engine'd cars have warranty extensions on the water pump).

The 2 year warranty applies to 99% of BMW parts. The limited lifetime warranty has a limited list - I think its alternators, starters, AC compressors, shocks, struts, and power steering pumps. Because dealers are stupid not all will be aware of this so it might not be an easy/smooth process. The bulletin for this warranty is in BMW DCSNet. Or contact BMW North America.

[bimmerfan08]

Update. I finally had a chance to get back to diagnosing things. Last week I turned the cover, let it run for a few minutes, and saw the coolant gauge needle climb into the red zone again. The upper coolant hose warmed up, while the lower coolant hose stayed cool to the touch, but I didn't let the car run long enough to get it up to temp due to the needle position.

I haven't turned the car over in a week. The needle is still pegging outside the red zone (see pic).

I decided to pull the thermostat and the water pump since I needed to perform a coolant flush. I checked the thermostat via the boiling water method, and it opened. I spun the water shaft and checked for play. There's practically no play, and it has resistance similar to new. This leads me to believe the hardware (at least the parts I've checked) are fine.