TheAvenger

Hi guys

I was driving yesterday with my M5 (bought a week ago) and got a very strange indication by the engine coolant temperature gauge.

At first I noticed that the temperature stayed around 75-78C (167-172F) which is below the middle of 90C (194F). This was surprising for me because I expected the needle to stay in the middle and not move.

Several minutes later (during that time only one acceleration that reved up to 6500 rpm) I saw the needle staying at the far right of the gauge, above the red sector. I had no indication of the problem from the computer and the oil temperature was about 82-86C (180-187F).

I stopped, left the engine running and opened the bonnet. Everything looked fine, no signs of high temperature. I wanted to enable the tests on the car (had a guy with me who knew how to do it) so I stopped the engine and enabled them. I started the engine again and the coolant temperature was again displayed as about 75-78C (167-172F). I checked the temperature on the computer display (test 07 if I remember correctly) and it showed 78C (172F).

The whole procedure did not take more than 5 minutes so even with 3C (37F) temperature outside I don't think the engine can cool off so quickly.

I drove further now looking at both the gauge and the test info. The temperature remained between 78-86C (172-187F) even when I went down to third with 100 km/h or second with 80 km/h.

My questions are:

- Is it normal that the temperature does not reach 90C (194F) which is the middle of the gauge? Is it normal that the temperature changes with 2-5 degrees during the ride?

- What is the problem with the needle going above the red sector? Is it that the engine was overheated (not probable when the oil temperature remained OK and there was no indication from the board computer), is it the gauge or is there a problem with the cooling system (e.g. termostat)?

Thanks.

TheAvenger

gtobynj

That the gauge does not hit the middle and pretty much stay there seems to be within the realm of normality. My E46 M3 was straight up for 2 years and after that a bit limp only getting just to the right of the first white dot under regular driving and inching up to the vertical position when sitting in traffic or hitting a much slower road after a high speed highway run. Since I got the M5 the temp gauge behavior has been exactly the seem. I had both cars checked a couple of times and the dealer always says that the system is fine, yet most BMW owners have the vertical behavior. I don't know if it is a function of an ageing sensor which usually sends some error correcting data to the cluster that keeps it at the straight up while the engine operates within the normal temp range and that ability degrades over time, but it is not something that causes any errors that will have a dealer replace anything.

As for shooting to the red, I can't help as it has never happened to me but from your message there may be a gauge problem.

BTW, I just picked the car up from having the instrument cluster replace because of the pixel issue and the behavior of the temp gauge is still the same, so the cause is not there I am guessing.

m5foya

My car did that once and I ended up replacing the T-Stat. Aslo keep in mine the needle in these cars never stays in the middle for long its just the nature of the beast.

TheAvenger

Any idea how to try to reproduce the behavior again so that I can show it to the dealer and request a change (I have a warranty)?