MadaboutKitcars

Does anyone know what is the normal running temperature (ie when the thermostat opens) of the BMW engine? Also - what temperature should I set my electric fan to kick in at? At the moment if I set the fan thermostat to "normal" it seems to start far too low (indicated 80 on the temperaure gauge)

Kind regards

Robin

typically most engines have a thermostat that starts opening at around 75 deg, fully open by 80-85 deg. My fan kicks in at 95deg and off at 87-90, the idea of the fan is just to stop the engine overheating when stood still, generally it shouldn't run at all whilst driving. You will get more power running the engine cooler at 80-85deg and better emissions when running at 90-100deg (the coolant being pressurized so the boiling point is lifted higher than 100)

Thanks Chris

It's strange - but I have been "playing" with engines for years but never really thought about the operating temperature. I suppose it's 'cause most temperature gauges are only marked NORM and HOT.

I adjusted my fan so it now comes on at about 95. It quickly cools the engine and goes off again in a couple of minutes when the temp is just below 90. The first long run will be to the SVA next Tuesday - then I will find out if it really works!

Robin

My original thermostat was jammed shut so make sure you are getting hot water all the way down to the bottom radiator hose.
Although cylcing the way you describe sounds correct so I expect everything is working fine.
My temp gauge being american is in fahrenheit and my engine hovers around 180-185 degrees which is about 85 celsius.

Wow - sounds much hotter in Fahrenheit ;-). As I found out it is plenty hot enough to make you yelp if you touch the pipes feeding the heater with bare skin. I think I will have to put some (SVA compliant) insulation on them!

Did you try adjusting the tappets yet? I reckon you might also find some more power once they are correct...

Robin

Mine sit just over 80C most of the time, when standing it gets hotter before the fan kicks in.

Yes, I can hear the turn indicator clicking now

I've still got one ticking rocker, but in genearl the engine is transformed.
I'll have another go when the skin has grown back on my finger! I managed to notch it with my breaker bar, ouch!!

Ouch, what did you set your valve clearances too? I've been using 0.25mm but E30.de recommends 0.30mm. I might try that next time I have the rocker off.

well............ it's a rather embarassing story but i'll post it here in public so you can all have a good laugh ound:

It all started when I overhauled my engine before fitting it back in the Sportster. As the engine ran fine in the old BMW I decided not to do a full overhaul of the cylinder head but I did replace the camshaft, rockers and rocker shafts from another head I picked up on ebay.

When I set up the valve clearances, I looked up the manual and it said 0.25mm. I then picked up my feeler gauges and picked the one marked 025 and set up each valve in the spcified order. The engine has ran fine since but has always sounded a but noisey (which I think I may have mentioned on this forum?)

Anyway, it was only after listening to Robin's engine last week (his car is looking great and just about ready for SVA next week, good luck, Robin) that I realsed that there is something definately wrong with my engine. On the way back from Robin's place my mind was running wild with thoughts of worn bearings, knackered camshaft, burnt valves, etc when suddenly i had a thought... (yes, you've probaly guessed by now...)... supposing my feeler gauges were old imperial ones and 025 was actually 0.025". For those of you too young to know, we used to use feet and inches and feeler blades were in thousandths of an inch!
Well, 0.025" is in fact 0.635mm so my valve clearances were set to 0.635mm instead of 0.25mm

It just shows you how tolerant that M20 engine is in that it'll happily run with such large clearances!! No wonder it sounded like a bloody Singer sewing machine



OK, that's enough, you can all stop laughing now...........

At least you've figured out what's up now