99' M3 overheating at idle

[Bimmerbean99]

After owning my 99' M3 for a week, I left my car sitting at idle for about 10 minutes with the AC for the first time. Think that's the longest it's sat at idle since I've been driving. Anyways, when I came back into the car I saw the temp gauge at the 3/4 line. I turned on the heater to get some of the heat out and noticed that also noticed that no hot air was blowing. Nonetheless, the temp gauge started going down and when I started to drive the heat kicked in as well.

I've posted in other forums a video of my car when I turn on and off the AC (https://www.reddit.com/r/BmwTech/com..._system_noise/) . There's a noise that comes from the engine bay and I think it has something to do with the AC Compressor, one person said the bearing sounded like gravel haha. So I just want to know if changing out the alternator, along with the bands, would possibly help the overheating OR is this something to do with the aux fan or some type of fuse. Last owner told me the cooling system was completely redone and the radiator it has is a mishimoto. How should I go about diagnosing this issue?

Thanks

- - - Updated - - -

Might I also add that the air intake boot and the alternator air duct are completely toast, as in the rubber has started to crack (boot) or is completely destroyed (duct). Do these parts have something to do with my issue? I'm a newbie to mechanic, not sure if those parts I listed correlate completely with each other.

[shogun]

Moved from 1991 - 1999 (E36) E36 Common Problems and DIY Fixes forum to E36 M3 forum

[RRSperry]

Ok, first thing. Check that the Aux fan in front of the radiator is turning when you have the AC on... Start the car, turn on the AC, the fan should be running.

Work from there.

The temp gauge in the dash, shouldn't move at all at idle. Does the engine have the mechanical fan attached to the water pump?

The intake boot would be a drivability problem, If it's cracked, replace it. The alternator duct is no big deal.

[realjones]

Fan clutch and blade. Stick a newspaper in it while engine is running if it stops easily it needs replacement. The symptoms you are having (overheating at idle, drops while driving) suggest this...however...

Your auxiliary fan is also probably not working. Idle with AC on and no airflow = no bueno. Nothing to do with alternator.

[blckstrm]

To get really basic, your fans that blow air over the radiator are not working. These guys up above are telling you how to check the two fans.

The main fan is attached to the water pump. If the engine is running, the pump is turning and that fan should be turning. There is a clutch built into the base of that fan - it locks up when it gets hot. If you can roll up a newspaper and stop that fan, it's toast and needs to be replaced.

The auxiliary fan is backup, and also runs when the AC is on. If it doesn't, it's dead. It might just be a blown fuse, but if the fuse is blown, there's a reason it's blown.

If you're overheating while sitting, BOTH aren't working - either alone will keep you cool indefinitely.

Check those two things and come back if you still need help.

[UsernaM3]

A bubble in the cooling system could also cause the car to overheat, although it would usually be more than just at idle. Something to check

[Bimmerbean99]

Thank you, so the fan does not come on when I start up the car with the AC turn on so I'm assuming it's. Also, the engine does have a fan that is attached to the water pump.

So in order to replace this would I need the fan itself or the whole assembly? I'm searching on ECS Tuning for one and it comes with a shroud. Off brand is like $100 and the genuine bmw one is $500. One more thing, could this also be some type of fuse that has shorted out?

- - - Updated - - -

[GVR]

I had a problem with my aux fan not coming on and it ended up being a bad wire connection. It was the 3 pin connector at the bottom of the fan. It was dirty and corroded. Cleaned it up and everything worked as it should.

[RRSperry]

Dude, do not just throw parts at this. Learn how to troubleshoot things, unless you have very deep pockets.

yes, there are fuses, and relays that control the aux fan in front of the radiator.(high and low speed..)

buy a Bentley repair manual. Or find a set of the Electronic Troubleshooting Manuals / Technical Information Service DVD’s on eBay.

buy a digital multimeter DVM and learn how to use it.

ok, as far as the mechanical fan.

warm up the car

try to stop the fan with a rolled up newspaper. If you can stop it, you need to replace the Fan Clutch. The blades can be reused.

[Bimmerbean99]

Don't mean to come off as such a novice, I appreciate the information though and will take all of it into consideration. Thank you

[R.Thomas]

You can easily jump the radiator temperature switch that controls the auxiliary fan to test its function. The temperature switch is located on the passenger side of the radiator. Disconnect the plug connector at the switch and, with the key in the on position, use a small piece of wire to jump the ground to low contact. The aux fan should operate. Repeat same and jump the ground to high contact.

[realjones]

So in order to replace this would I need the fan itself or the whole assembly? I'm searching on ECS Tuning for one and it comes with a shroud. Off brand is like $100 and the genuine bmw one is $500. One more thing, could this also be some type of fuse that has shorted out?

The whole assembly...I've had the off brand $100 one on my car for years with no issues...this is definitely one part where I think you can pass on the genuine bmw one. You probably need a new fan clutch for the engine fan too.

[blckstrm]

You can easily jump the radiator temperature switch that controls the auxiliary fan to test its function. The temperature switch is located on the passenger side of the radiator. Disconnect the plug connector at the switch and, with the key in the on position, use a small piece of wire to jump the ground to low contact. The aux fan should operate. Repeat same and jump the ground to high contact.

... Or you can turn on the AC, which he did, and it didn't come on.

I'd check the fuse, and you could also check the plug - sometimes the pins are the wrong size and don't make good contact (I've had this happen).

But whether it's the fuse or not, you need a new auxiliary fan.

If you want you could double check its not a wiring problem if you get a multimeter, but it's almost certainly a dead fan.

Check out YouTube videos on E36 fan replacement - should give you an idea of what to look for.

[das borgen]

Does the fan get 12V at its connector when it should be? Check the relays for function too as well as the fuses as RRSPERRY says