Mild Overheating 316i/M40

[greg124]

For years my temperature gauge has sat spot on the centre tick once the car has warmed up. However in the recent warm weather the gauge now moves up the next tick, but hasn't (yet) reached the red zone.

So here is what I have checked so far:
1) I'm not losing coolant
2) The fan is cutting in
3) I've fitted a new thermostat
4) I've flushed the cooling system with Holts 2 part heavy duty Rad Flush - which cleared out a lot of muck - refilled and bled the system
5) Removed dead bugs and other detritus that may have been impeding air flow through the radiator

Has anyone any ideas what is most likely to be causing this?

Could it be:
1) Fan clutch is tired
2) Needs a new radiator
3) Water pump tired
4) Something else

thanks in advance

[Brianmoooore]

First thing to check is the nut on the back of the instrument cluster. A loose one usually results in the needle jumping around, but if for some reason contact has been lost totally, it will make the gauge read high by about the amount you describe.

[greg124]

Thanks Brian, but the gauge only reads high when climbing hills or sitting in slow moving/stationary traffic rather than all of the time. ie. when the engine is under greater load or there is less cooling through 'ram effect'.
I will check the nut though, as I seem to remember the gauge jumping randomly once or twice last year.
Cheers

[greg124]

Managed to wiggle the binnacle part way out.
Is this the nut nearly in line with the centre of the temperature gauge and above the oil warning light? This is tight.
Or is there another nut that I should be looking for?
And how do you remove the top moulding from over the steering column? The rear of the moulding is blocked in by the ignition key barrel.

[Brianmoooore]

The above isn't quite what you said in the OP! The nut in question is directly behind the temp. gauge, and holds it in place, as well as providing an earth connection for it.
Your problem is likely to be the fan clutch, and the radiator is suspect as well.
Removal of the upper cover of the steering column is not only restricted by the key barrel, but also has a considerable upstand at the rear which holds it in place. Doesn't need to be removed to remove the cluster though.
I usually remove the silly sheared head security bolts that hold the steering column to the cross member (drill the heads right off, and the remains will screw out by hand) and replace them with ordinary M8 bolts. A bit of an effort, but once it's done it's easy the next time.
On my own E30s, I also refix the column with a small (10mm) spacer between the column and its mount, since I find the standard wheel position a little high.

[Stubabalu]

Have you done anything to the cooling system such as drained and refill? There is definitely a knack to bleeding which if not done properly will cause high temperatures. As Brian said first thing to check is the fan with a rolled up news paper, if she stops easily it's knackered. If it requires replacement don't buy a cheap one, I did and it was permanently engaged!

[greg124]

Thanks guys. Will get a new fan clutch ordered.
...but will not bother removing the upper cover from steering column

[greg124]

Just replaced the fan clutch. Fairly straightforward job once you find a way to stop the water pump rotating - and providing you remember it's a left hand thread.

Just need a warm day now to make sure it's fixed the problem