overheating problem

[innes]

got a prob on my 525i 1991 uk J reg

sat in traffic for about 15 mins and the needle went up to the red and i got the 'coolant temp' message.

on driving away after being sat in traffic for approx 30 mins the needle went straight back down to half way.

Fan seems to be working and coolant is plentiful, whats the most likely method to cure this?

[colo525i]

Easiest thing to check is the cap on the rad, make sure the seals are in good shape, the cooling system needs to be under pressure. If the car has an electric fan, check that it is working as well. Mine was seized and would cause the car to heat up to the 3/4 mark if you sat in traffic for 10-15 mins. If these things check out, I'd say the water pump may be your culprit.

[DaveVoorhis]

If the fan coupling (aka fan clutch) has failed, it will spin but not pump enough air through the rad to keep temperatures down. See http://www.mwrench.com/Whitepapers/FanClutchtest.pdf for testing procedures.

[Waynegro]

Money says it's your fan clutch. I just had to replace mine. Get the Sach's one rather than the Behr. BMA still has the best price on it I believe.