Severe overheating

[slideordie]

Was out last night in my mates iS when he noticed the temp gauge was waaay up near the red so we pulled over and switched her off.

I cranked the heaters on to get the temp down but no heat at all came out, it was stone cold. Popped the bonnet and the expansion tank at the side of the rad was very hot to the touch. Took about ten minutes for the temp to go back down to normal operating position and about 5 mins later we eased the rad cap off to check coolant level, which was spot on.

Any ideas whats up? Possibly a blockage in the rad?

Thanks chaps

[kam-325i]

When i had the same problem, it turned out to be a air lock in the heater matrix.

Got the air out and also found that the pipe from the top of the red to the header tank was blocked.

[E30BeemerLad]

no hot air sounds like the usual symptom of there being no water in the matrix, either due to a blockage or air lock. Anything done to the coolant system recently. Maybe also worth checking the thermostat

[slideordie]

Got sorted, was an air lock.

Thanks guys