E30 1990 model 320i overheating

[AtletheHun]

10 years ago my E30 overheated in slow moving traffic resulting in a top end rebuild (skimmed head, new camshaft etc). All was well until about 2 years ago (yes I don't use the car much - does about 600 miles per year -I used to work overseas) when I noticed that the car was losing coolant. It never leaks on the garage floor and I've never found the expansion tank to overflow but after about 150 miles I need to add about half to one litre of coolant. I can see no leaks from the water pump nor from any of the hoses or anywhere else and there's no evidence of water in the oil. According to the gauge it's running hotter than it used to, the temperature rises to the halfway mark (12 o'clock position) then continues alarmingly to the 3/4 or 2 o' clock position before falling back to the mid point (12 o'clock). I'm sure that in the old days the temperature was steady between 1/4 and 1/2 (about 11 o'clock on the dial). I think that the higher running temperature is increasing the pressure in the system and causing coolant loss somewhere even though I don't know where but I do know it's not out of the expansion tank cap. The fan is the mechanical viscous clutch type and seems to be working OK -do these things need any maintenance?? My next move is to remove and back-flush the radiator and flush the fins and also to replace the thermostat. Anybody got any other suggestions I could try please?

[German-Whips]

Have you checked the oil to see if there is any white mayo under the cap?

[AtletheHun]

Have you checked the oil to see if there is any white mayo under the cap?

Yes there's none

[Brianmoooore]

The first thing to do is to remove the instrument cluster, and tighten the small brass nut on the back of the case that holds the temperature gauge in place. Only when that is done, will you know whether the car is overheating and losing coolant, or just losing coolant.

[AtletheHun]

Thanks for the reply but can you tell me why tightening the securing nut on the temperature gauge should produce that result? The needle is pretty well damped so I don't think it's vibration

[Brianmoooore]

The nut provides the 'earth' connection for the gauge, and when it works loose and a poor connection occurs, the gauge reads higher than it should. Very common fault.
(Tighten the fuel gauge one as well, while you're there.)

[AtletheHun]

OK thanks I'll give it a go!

[AtletheHun]

Problem sorted.
It wasn't the earth nut on the temperature gauge (but thanks for the tip) , it was good and tight. I took off the radiator , flushed the fins and back-flushed the radiator (not much junk came out). I then replaced the thermostat. Pleased to say it's now running at "normal temperature" ie just above the first notch on the gauge so I reckon it must have been the thermostat. I've still to check the operation of the old 'stat but I'm pleased with the results of today!