Apparent Overheating E30?

["Gary Asmussen" <GARYA@xxxxxxxxxxxxxxxx>]

Could anybody offer assistance with an "apparent" overheating 
problem with my (E30) 89' model 318i (M40).
I have perfromed the following tasks and still have a higher than 
normal albeit erratic temp gauge reading.
1 Replace radiator with new one
2 Flush block and replace all hoses.
3 Thermostat is new and operates fine.
4 Installed new water pump and V-Belt.
5 Elevated front of vehicle and refilled coolant (40:60 Glycol/H2O), 
taking great  care to remove all trapped air. Including bleeding off 
thermostat drain screw etc.
Symptoms are car takes about 5-10 mins to reach 1/2 a needle 
width under half way on gauge- Normal. Then at random intervals will
climb to 3/4 or just under and then return to just above 1/2. If I tap the 
perspex cover it will sometimes click back to just under 1/2.
Since the Tachometer is reading OK, I am told it probably isn't the SI 
board lithium battery. Could it be the temp sender unit or the gauge 
itself? I need to know if the system IS overheating or not. There are 
no leaks of coolant anywhere and a compression test indicates all is 
OK with head gasket (Used cooland looks good too).  Brakes 
are also not binding. Any kindly advice greatly appreciated.
Gary Asmussen
Perplexed DIY Beamer Buff.
Brisbane, Australia 

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