over heat??

[mjkacz]

this is my first time posting here, so bear with me. My car is a 1998 328I.
Yesterday idling home in Friday afternoon, boston traffic, with my AC on, I noticed my temperature gauge quickly went up to almost overheating, I immediately tried to work my way to the side of the road, The needle went into the red and I turned off the AC and turned on the heat....

About the same time traffic started to move a little and it seemed as quickly as it the needle went up, it came back down, and it didn't seem to do it again afterwards... even after I put the AC back on.

So when I got home I opened up my book and tried to test the Aux Fan bu shorting out the temp switch. I could never get the Aux to turn. I checked the Fuse 16 and it is good, and pin 1 on the temp switch is 12v.

So my question is... Do you think it is the fan? how hard is it to replace the fan, it looks like everything I read says you have to remove the front bumper?? is it an expensive thing to have the dealer do? Stupid question.... Oh yeah, I had the car in the shop in April for a 100K service and they replaced the radiator, and the water pump. So I think the coolant system is OK.

Thanks (in advance) for any help
Mike

[colin93 325is]

the fan will only turn on if it needs to. i wonder if you noticed a drop in oil pres., this could be reason for engine temp to rise. check to see if you have enough coolant, although your car would probably tell you just like mine. my only other thought is that one of your belts was worn and broke. that seems like the most likely scenario being that when you started moving the eng. temp came back down.

[mjkacz]

Yeah, I thought about the belts also, but they were replaced recently as well, and are still intact. I tried forcing the fan by jumpering the temp switch.

I am working on the aux fan now.

thanks again