Overheating Bimmer

Long story short, my 2001 330Ci-5sp's temperature went up past the middle when I idled in traffic and it actually went down when I cruised in highway or did autocross run (seriously). I caught it in time so the temperature never reached the red zone.

My suspicion is dead electric fan since it didn't kick in when I turned the engine on (it's supposed to turn on momentarily when the engine is started) and when the temperature reached middle point it still didn't kick in. I checked the fuse and it's fine.

I posted these question on e46fanatics and my local chapter of BMW club and got two other potential alternative: bad thermostat or bad coolant temperature sensor (the one located in the lower radiator hose). Btw, mine doesn't have fan clutch.

What do you guys think? Is there anyway to test the electric fan directly to see if it's toast? If it's the electric fan it seems very easy to replace but quite pricey (around $300 - $350). Thanks guys.

If the cooling system is all original, it needs to be replaced.

It's an 80-100k mile wear item on BMWs.

New radiator/hoses/thermostat/water pump/thermostat housing.......

Unplug the coolant temp sensor and the fan should run after 30 seconds. Turn on the AC and the fan should run immediately.

All e36s and as far as I know e46s have notoriously bad cooling systems. On my '36 M3 track car I went aftermarket w/ a Zionsville aluminum radiator/ o'flow tank / shroud w/ a 16" SPAL 2-speed puller fan - Stewart water pump - AL thermostat housing - new hoses - BMW coolant +water wetter.

On street cars the general rule id the whole mess gets replace every 80k or so with OEM stuff - I figured I'm keeping the car forever so I'd just do it once.

pigeon wrote: Unplug the coolant temp sensor and the fan should run after 30 seconds. Turn on the AC and the fan should run immediately.

Thanks for the input on cooling system overhaul. I'd do it if I am planning to keep the car long-term but I am planning to sell it as soon as I sort this problem out. I suspect the fan because I also didn't see any leaks. Pigeon, when you said the coolant temp sensor you meant the one on the lower radiator hose right? When I turned on the AC the fan did not turn on. And we're talking about the fan that's between the radiator and the engine. Also when I started the car the fan also didn't turn on like it should be. It should turn on momentarily for diagnostic purpose when the car is turned on. Hence my suspicion that it's the fan. But before I spend $350 on new fan I just want to check if there's any other way to check if the fan is bad. Thanks all.

just out of curiosity.. have you checked your coolant level? The temp sensor for the radiator fan is at the top of the radiator.. if you sitting at idle or low RPMs and have low coolant.. no hot coolant is going to touch the sensor to set off the fan

pigeon wrote: Unplug the coolant temp sensor and the fan should run after 30 seconds. Turn on the AC and the fan should run immediately.

Do you happen to know if this test will work on an E36 also? I have been looking for a way to test mine. I don't think I have ever seen or heard it run.

Whoops, just reread your post, is the E36's fan supposed to run with the A/C on too? I think mine be broken, it spins freely but never seen it turn on, A/C or not.

I was thinking of adding in a relay so it is always on with the A/C compressor. The downside of the 92 is the A/C is set up for R12 and its only cool not cold when used with R134. I am not sure what would be involved in making the A/C work better.

mad_machine wrote: just out of curiosity.. have you checked your coolant level? The temp sensor for the radiator fan is at the top of the radiator.. if you sitting at idle or low RPMs and have low coolant.. no hot coolant is going to touch the sensor to set off the fan

Yes the coolant level is fine. Plus I thought the temp sensor is on the lower radiator hose (i.e. at the bottom of the radiator).

The electric fan is controlled via digital signal so the conventional test method (giving it 12v at the connector) will not work.

Wish I could tell you more but I have yet to see any issues with the electric fan equipped e46's. Please do post the outcome of your situation.

ansonivan wrote: Wish I could tell you more but I have yet to see any issues with the electric fan equipped e46's. Please do post the outcome of your situation.

It was indeed the electric fan. Got a new one, dropped it in and sure enough the new fan is now working and the temperature gauge stays in the middle again. At least I caught it in time so that I never actually overheated.

It would've taken only about 10 - 15 minutes if not for one broken push expansion rivet...why couldn't they put in a regular screws or at least expansion rivet with phillips head instead of stupid push expansion rivet...

glad to hear it all worked out.

I could be wrong on the coolant sensor. The Ti uses an electric fan only (no clutch fan) and it's sensor is in the upper part of the radiator by the passengerside headlight. Run low and on coolant and sitting at idle.. nothing touches it to turn the fan on

Mine turned out to be a heavily corroded fan plug, so bad that it was unsalvagable. I replaced the plug and I now have an auxiliary fan. I have no idea how it did not overheat already in the Florida heat without one.