Overheating due to dead electric fan...I think

[ea-sport]

My car is a 2001 330Ci - 5 speed with about 90Kmiles. On Saturday while waiting for my autocross run in Bowie the temperature indicator all of a sudden went up beyond the middle and kept going until I turned the engine down. I then turned my car on right before my run and during my run the temperature actually went down and got back to the middle. After my run I pulled over and it seemed that my electric fan didn't turn on as it should've been so instead of waiting in line for my next run I just waited on the side and shut down the engine. I only turned the engine on right before my run and sure enough during my run the temperature actually went down because of the air flowing from the front of the car. On my way home after the event I was lucky there was no traffic so I cruised home and with the air flowing from the front of the car I was able to get home safely. I checked the fuse and it was ok, I was told to also check the relay for the electric fan but I couldn't find where it was.

Yesterday, I drove the car for a little bit and let the car idle for a while and somehow the electric fan kicked in. I don't drive the car daily anymore so today after work I drove the car for a little bit and let the car idle for a while again just to make sure and sure enough the electric fan didn't kick in and the temperature kept going up past the middle until I shut the engine down.

In short, my electric fan sometime working sometime dead.
- Is it a sign of a bad electric fan or just bad relay? Where can I find this relay and how do I test it?
- Should I try to replace the coolant temperature sensor in the lower radiator hose first before changing the electric fan?
- If it's the electric fan from what people told me and looking at the Bentley Manual it should be very easy for E46 non-M with stick shift, is this accurate?

Thanks for the info guys.

[SamB325es]

Hey, Emir right? glad you got your runs in even with the overheating. I am more of an e30 guy but I would try the temp sensor first. It seems like the fan works so maybe the sensor is malfunctioning. You might try the e46fanatics board, that's all I got, good luck!

[ea-sport]

Hey, Emir right? glad you got your runs in even with the overheating. I am more of an e30 guy but I would try the temp sensor first. It seems like the fan works so maybe the sensor is malfunctioning. You might try the e46fanatics board, that's all I got, good luck!

Yeah Sam, it was me who asked you about my overheating car. Glad I caught the temperature going up and shut it down before it got to the red line. Anyway, running it on the course actually lower the temperature. I also posted on e46fanatics board, I figured the more resources I check the better.

[mcoupemindy]

My car is a 2001 330Ci - 5 speed with about 90Kmiles. On Saturday while waiting for my autocross run in Bowie the temperature indicator all of a sudden went up beyond the middle and kept going until I turned the engine down. I then turned my car on right before my run and during my run the temperature actually went down and got back to the middle. After my run I pulled over and it seemed that my electric fan didn't turn on as it should've been so instead of waiting in line for my next run I just waited on the side and shut down the engine. I only turned the engine on right before my run and sure enough during my run the temperature actually went down because of the air flowing from the front of the car. On my way home after the event I was lucky there was no traffic so I cruised home and with the air flowing from the front of the car I was able to get home safely. I checked the fuse and it was ok, I was told to also check the relay for the electric fan but I couldn't find where it was.

Yesterday, I drove the car for a little bit and let the car idle for a while and somehow the electric fan kicked in. I don't drive the car daily anymore so today after work I drove the car for a little bit and let the car idle for a while again just to make sure and sure enough the electric fan didn't kick in and the temperature kept going up past the middle until I shut the engine down.

In short, my electric fan sometime working sometime dead.
- Is it a sign of a bad electric fan or just bad relay? Where can I find this relay and how do I test it?
- Should I try to replace the coolant temperature sensor in the lower radiator hose first before changing the electric fan?
- If it's the electric fan from what people told me and looking at the Bentley Manual it should be very easy for E46 non-M with stick shift, is this accurate?

Thanks for the info guys.

If it were my guess, I'd say that it was the electric aux fan switch. If it's like the e36, it's cake to replace.

Additionally, it could be a bad thermostat in the car too. Reasoning being that it's opening late, only after the block is too hot to be innondated with really cold radiator coolant. This would also cause the fan not to come on properly as the coolant is below the threshold temp in the radiator.

A typical autocross run should put more heat in your system, not less, during the run. It's really too slow of movement to handle the extra heat generated by slow speeds at high throttle.

[gkrea1]

Your fan clutch may also be bad. If you are running hot at idle but then cool down when running hard, it could be that the viscous coupling is no longer working. Your motor is making the least amount of heat at idle so the main fan should be sufficient when the AC is off. (Was the AC on during all this? I bet not.) When the fan clutch dies, now your aux fan has to do all the work and you've discovered another weakness. The aux fan should turn on automatically to the low speed when the AC is turned on. That's a good way to check if the fan works or not. If it passed that check, then move on to the aux fan switch (thermostatically controlled switch, not mechanical) installed into the side of your radiator.

Do you have the Bentley Publisher's E46 manual? Get it. You'll save a lot of time, money (and stress) with these probelms.

Good luck, and post back with your progress.

[glindsay]

Your fan clutch may also be bad. ...

Good thought, but no fan clutch in a E46 330Ci. It does have 2 electrical fans; one behind the radiator for engine colling and one in front of the condensor for AC. As Jonathan wrote though, I too would focus on the thermostat.

[Zcruizer]

I thought the m54 regardless of displacement had a main cooling fan connected to the water pump w/ a coupling/clutch, and an electric fan in front of the radiator for a/c and transmission.
I have an '01 m54 2.5l and it's set up that way. I'm no genius though.

In either case, I'd have to assume if one of the sensors has gone bad a fault code is stored. Although no dummy light may be lit, a decent scanner will pick it up.

Could it be as simple as air in the system? Or should the air escape to the expansion tank and show low coolant?

I like the toasted fan clutch theory.
Just my 2 cents .

[ea-sport]

Thanks for all the input guys. As far as the fan clutch, my car does not have a fan clutch.

Before I change the thermostat, is there any way to check if it's bad? Reading the Bentley manual it says that if the thermostat is faulty there should be a fault code in the DME, so far I don't get any check engine light yet but should my Peake Reader be able to pick this up? Is there any other way to check bad thermostat?

For the electric fan, Bentley manual also says "When the vehicle is first started, the ECM activates the electric fan briefly at 20% of its maximum speed, then switches off. This is for diagnostic monitoring.". When I turned the engine on just now the electric fan didn't turn on. Does it mean that most likely it's bad electric fan?

Again, thanks for the input guys.

[JC5]

From what I understand the SES will only set off for an emission related fault. Defiantly think there's an intermittent fault in the control circuit ( relay, switch. sensor..) Could just be time for a good ol' fashion cooling system overhaul.

Be careful running the aluminum M54 block too hot. It could cause the aluminum to loose temper, and go soft. He a few buddies overheat. Later when having head work or gasket issues the head bolts stripped out.

[Zcruizer]

Don't know about the Peake reader but I use the Auto Enginuity software and can bring up specific sensors and watch them in real time. What's nice is I can monitor a dozen sensors at once and compare what's going on. Before you start turning screws I'd take it to someone that can do this, could save at lot of unnecessary replacements.

[gkrea1]

No fan clutch? Sorry about that. Bentley has you on the right track. Try to power the fan directly as one last check.

I hadn't thought about Al blocks getting soft when over heated, JC5. Yeouch. And, yes, you do want a 535is. Consider an E24, too. You can find the latter with the high compression M90 motor -- same motor that's in the M535 from the early 80's. That combination makes for arguably the ultimate E28 and E24.

[agreatham]

Don't know about the Peake reader but I use the Auto Enginuity software and can bring up specific sensors and watch them in real time. What's nice is I can monitor a dozen sensors at once and compare what's going on. Before you start turning screws I'd take it to someone that can do this, could save at lot of unnecessary replacements.

James, does what you have capture and log throttle and brake input? I need to work on those for autocross.

[ea-sport]

Just want to give a quick update. It was indeed the electric fan. Got a new one from Fairfax BMW (with member discount), dropped it in and now the temperature gauge is back to normal (in the middle). Glad I caught it in time so that I never actually overheated. Anyway, it would've taken only 10 - 15 minutes had it not been for a broken push expansion rivet (the one holding the fan to the radiator). Wish they used a regular screws or at least expansion rivet with phillips head..oh well..

[Zcruizer]

Great to hear it's fixed. You know it can never go perfectly.

Mike, the program can record the throttle inputs but I'm not sure it can keep up with the fast action in the foot. It's just not that fast. It's geared primarily for engine management and diagnostics. As far as the brakes, I'm not too sure (never tried). I think it'll just tell you what suffered a fault. At that point it can get confusing, with the traction control and anti-lock systems being an integral part of engine management it can get complex (for me). A bit more money spent should get software that is capable of monitoring what you need.