Wildly varying temps

[nickhills2002]

Just bought a 350i and love but am having heating problems. I have a manual overide on the fan, but the peoblem persists.
The temperature gauge can move 20 to 30 degrees in less than 30 seconds. Also, it seems to make little differrence if I put the fan on.
I suspect faulty sender or air lock. Any suggestions. Please keep it simple as I am machanicaly inept having ran company cars for 25years!

[danny hoffman]

Sounds like you are on the right track. Air locks are a common problem apparently (mine has never suffered). Have you check the water level at both caps?

[350matt]

I'd suspect the water temp sender as the change in temperature sounds a bit too rapid to be real. there are two senders on the engine, one for the gauge and one for the ECU. The gauge one is screwed into the manifold behind the alternator, also the gauge instruments are't damped very well and additional electrical load will cause them to move! Toggle the courtesy light switch with the ignition on and you'll see what I mean.
Any half decent Motor factors can get you the sender for about 8 quid, just ask for a 1986 Rover SD1 item.

Matt