over heating

[chief]

help please guys
my 325i is overheating i think. the guage goes to 3/4 on first cycle, then goes to the desired 1/2 then randomly between 1/2 & 3/4
tried the bleed and no air at all.
oils ok
no sign of mayonnaise in oil filler cap
no sign of oil in water tank
head should be ok at the mo i think because she's quick as should all through
i've had the radiator off and that flows good
maybe i missed a simple thing
any suggestions would be most appreciated
thanks

[Brianmoooore]

First point is, the E30 temp gauge is not linear. The centre section only covers a few degrees, so, as long as the needle is out of the blue and not into the red, it is fine.
Second point is, the temp gauge is tied up with the service indicator lights computer (SI board), and problems with this can cause the needle to jerk around.
Having said all this, and reading your post again, you could have a sticking thermostat, so, considering how intolerant M20 heads are to overheating, I think I would change it.

[Martinaston]

By watching my temperature guage i can tell when the thermostat is open and closed br the movement

[chief]

thanks guys , appreciate the feedback
reckon you're on the money there
been down the stealers today and a helpful chappie there suggested the thermostat could cause overheating as well as cold running which i was not knowledgeable. seems to figure the way he explained.
reckon the housing should be replaced whilst i do this as its in a bit of a mess. Ԛ£9 including washers & bolts , bleed screw & O-Ring
seems like fair money to get the job done well
will post the result after the job is done Saturday morning , maybe someone else is experiencing the same problem

[gareth320]

I had a similar problem with a 525i I had a few years ago and it turned out to be the water pump. The stock items have a plastic impeller(blades) on a steel shaft and over time the plastic can weaken and the shaft can slip. Aftermarket items are all steel. For a few quid it may be no harm to replace it. Also what condition is your fan viscous clutch? Leave the car idle and warm up to just above normal and try VERY CAREFULLY to stop the fan with a rolled up newspaper. If you can stop it then the fan cluch is shot. Also what condition is the drive belt in? Could it be slipping?
Best of luck.

[chief]

fitted a new thermostat today and my car now runs perfect . the temp guage is between 1/4 and 1/2