Water temp. gauge shot up but no overheating?

[bcbuilder]

Just had some work done on the BMW about 4 weeks ago. New radiator, hoses & thermostat. Last night I was driving in heavy traffic and the temp. gauge shot up all the way and the oil light came on too. Didn't notice any performance problems. Pulled over and let it cool down. Checked all fluids and nothing is low. I drove it home on the freeway and it stayed cool. When I got it home I let it idle for about 10 minutes to see if I could recreate the problem but everything checked out fine. Temp gauge stayed in the center as it usually does. Do you think the thermostat got stuck then unstuck itself? Maybe an instrumentation problem because the oil light came on? I'm taking it back to the guy who did the radiator work today but I would appreciate any expert advice. Thanks.

[keykey]

Originally Posted by bcbuilder

Just had some work done on the BMW about 4 weeks ago. New radiator, hoses & thermostat.

Likely caused by air in the cooling system. BMW's are a bitch to bleed the air out of the cooling system on. They can work fine a while but suddenly the temp gauge goes up or down because of not good enough circulation.

Did you change the water pump? They are a common failure point. (plastic impeller cracks, comes loose and at last explodes into a million plastic pieces)