E30 Zone

the water pump went on my 318i m10 a few days ago so i replaced it with as brand new one and bled the system to remove all air locks but on a short test drive it went to three quaters on the temp gauge, i got home and looked under the bonnet to see that the hose going from the top oof the engine to the thermostat was double its size and rock hard was told it could be the thermostat so i got a new one and fitted that, bled the system again and it sat at half way no matter what until a test drive when again it hit three quaters but i put the heater on and it went down to half again. and once home looked under the bonnet and the same pipe from top to thermo was double its size again and rock solid looking like it was gonna pop ?????????

the hose on the bottom of the rad gets hot like the others too and the heater blows red hot

ive checked the search but havent found anything like this can anyone help

I think the first thing you need is a new top hose! The hoses are supposed to be 'rock hard' under operating conditions, but should not be swollen.
Check that the pressure cap isn't the original - it was recalled 13 years ago!
If you still get problems after all this, bleed the system from the top heater hose on the bulkhead.

i think the pressure cap is the original one as the car is completly original ive been bleeding the system from the top heater hose on the bulkhead from the start, ill try a new hose and pressure cap next , cheers

update.............

fitted new pipe and pressure cap today, temp sits between half and three quarters, sometimes edging more too the higher then it drops down to in between again, is this ok temp wise ????

Hmmm.. i wouldnt be happy with that ! although its in the normal temp zone, ive never seen one that goes over half way ! is your viscous working ?

i can move it easy by hand, and it seems to speed up ok with throttle ????

You need to do the newspaper test to see if it's locking when the engine is upto temp, get it warmed up so it's at half way or a bit over then stick a rolled up newspaper in the fan.

Fan stops = viscus knackered
Paper gets shreaded = viscus is ok

In traffic i can hear my fan when the engine revs rise and it's never been over half while running.

Could also be a blocked radiator... they have lots of little pipes in them so accumilated rubbish that will still let water pass on the garden hose test may well be blocked enough to allow overheating as described.

fitted new viscous coupling today that now works perfect but temp still hits near enough three quarters before dropping back down to half way ????????? i take it the rad can be the only thing left to replace now

its only a few degrees difference between halfway and the 3 quarter mark

is it not worth worrying about it then ???