E39 M5 after repair knowledge needed

[fatmansv8]

Hi everyone I just had my car back after repairs. I had the thermostat and coolant temperature sensor switch replaced. The symptoms were temperature needle on the gauge never reached half way it ran 1/8th of a inch above the blue. On motorway journeys however the needle would shoot off the scale past the red but the car was not overheating there was no smell of overheating nor steam coming out in fact the car would run normally ,but when I switched the engine off and back on again the needle would read normal just over the blue again.So I put the problem to you guy's on this forum and it was advised I changed the thermostat and coolant temperature sensor switch. So did that yesterday along with the diff seals and rocker cover gaskets. But after I picked the car up the temperature needle is still just above the blue I took it back to the garage and was told it may be a gauge calibration issues and they could recalibrate the gauge. They did notice that the when the engine is turned onto accessories mode the needle shot over to the red and then back to just over the blue. Do I have a gauge problem or is there something else.
Sorry for the length of post but replacement of all the diff seals and rocker cover gaskets and thermostat and coolant sensor switch cost me £881. I need to know do I send the car back or get the gauge replaced.
Thanks for reading through FatmansV8

[TheAngryDog]

Did you have both temp sensors replaced?

When you see the needle go all the way to the red, have you ever checked the OBC menu option? (option 6 or 7, KTemp).

If not, it would be worth checking as that will help you work out if one of the sensors is playing up (I cannot remember which I am afraid). Temp should read at least 79 degrees C when warmed up.

[fatmansv8]

Hi 😡angrydog where are the 2 sensors located I can ask which one they replaced at the moment all I know is they replaced a coolant temperature sensor. He did say the old thermostat was jammed shut and definitely needed replacing. You know I've never used the obc ever so do I press the button on the end of the stalk 6 or seven times until the temperature reading appears. I'm sorry I'm bit of a caveman about car's angrydog.
Thanks Fatmansv8

[E30M3SE]

Fats' here's a video of how to unlock the hidden obc menu.
http://www.youtube.com/watch?v=TWjomuQQ0

[Depthhoar]

Strange symptoms but don't give up hope.

AngryDog is right, you need to access the 'secret menu' and check out the KTMP - actual coolant temp not just what the needle on the gauge shows. Simple instructions about how to do this here (check out the pdf file):

http://www.m5board.com/vbulletin/e39-m5-e52-z8-dis...

The accuracy of the KTMP test will be contingent on both the coolant temp sensors working correctly, replacing both sensors is a fairly simple DIY and not expensive but if you're not the DIY-type this work can be done by your spannerman at little cost.

Also, when in the secret menu carry out an 'instrument check' by using Test No.2, this will cycle all the instrument displays on the dash. Afterwards do Test No.21 to reset the dash otherwise you'll get an annoying somewhat mysterious icon appear on the dash at engine start up.

Also, try removing the electrical connector to each temp sensor and check for corrosion/dirt on the terminals.

Are you experiencing any running problems, higher fuel consumption, down on power etc. Running cold will almost certainly induce over-fuelling of the engine & very sooty tail pipes.

A long shot, but did your spannerman replace the metal/rubber gasket ring? (No.7 in the diagram below)

http://www.realoem.com/bmw/showparts.do?model=DE92...

Quite a few on the M5board think there can be issues if the gasket ring is not replaced when the thermostat is changed (the thermostat won't seat properly in the housing allowing coolant to circulate even when cold). Removing and replacing the the gasket ring is a royal PITA so many don't bother. Best practice would be to change it when the thermostat is swapped.

[fatmansv8]

If did notice soot in the exhaust tips where there was non before I handed the car in Hmmm.

[fatmansv8]

I did notice soot in the exhaust tips where there was non before. Hmm

[fatmansv8]

Hi everyone a quick update for you guy's. I took the car out after cleaning the exhaust tips off all the soot. A few things I noticed the warm up indicators went off alot quicker within a couple of miles whereas before they began switching off after 20 miles or so. So I guess that's good news. The problem with the gauge needle going off the scale on the motorway didn't happen over a 45 mile round trip, so I guess that's good news to. The needle did reach half way for a while then reverted back to the dot between blue and halfway.There is no soot in the exhaust tips also good news. I reported back to the garage as suggested by you guys I had the other sensor replaced at cost of the part only no labour. They then plugged into the ecu and left engine running their computer was showing engine running at 81 C to 83 C which is normal right? even though the needle was inbetween the dot above the blue and centre. So a big thank you for all your advice you have been a massive help and a big thank you to pistonheads for this forum.
Yours greatfully Fatmansv8

[plenty]

The standard 'stat opens at 79C which on the temp gauge is between blue and centre.

Some owners have chosen to use a Stant 82C unit which is straight swap and on the gauge shows a consistent 12 o'clock position on the needle.

[fatmansv8]

Hi guy's as you know I have just replaced the thermostat and both coolant sensor's. The warm up lights 🚥 go out alot quicker now but the the gauge is still reading between the blue and 1st dot on the gauge. I took the car back and had a diagnosis done via the OBC it showed it running at between 81°C & 83° C. Do I need to change the gauge guy's or is further work required. Thanks
Fatmansv8

[Depthhoar]

Use the 'secret menu' (mentioned in an earlier post) to check the temp you're running at. If it checks out with what your garage guy was reading via the OBD then all is good.

The gauge on the dash display is pretty coarsely calibrated, is less of a concern and only gives a general idea of temperature (there's something on M5board about this).

Call up the KTMP via the secret menu and monitor it whilst driving, the live data will be really useful and might put your mind at ease.

[fatmansv8]

Hi thanks Depthoar will give it a bash will try out the live data.thanks Fatmansv8