Overheating while running A/C

[SGM330]

Hi Everyone,

I'm trying to diagnose an annoying problem I'm having, especially during the heat wave we're currently dealing with in Toronto. My car is starting to overheat if I'm idling or in slow traffic while using the A/C. I believe it may be my aux fan not engaging into the 'high' mode to keep the car cool. I've noticed that it seems to be running at a lower speed and I was able to catch it running on a higher speed once and at that very moment, the cars temp gauge did not move. Is the aux fan supposed to engage 'high' mode a soon as I turn on the A/C?

I've read it can be a number of things from the aux fan, fan clutch or possibly the coolant level sensor not telling the car to turn up the fan speed. I've also read it can be my thermostat or high speed fan relay (I have no leaks and no other overheating issues).

I just want a little bit of direction or tips on how to diagnose this problem before I start throwing parts at it.

Any insight is appreciated!

Thanks.

[ShaunG]

If your fan clutch has never been replaced there is a very good chance that is the issue.

[Ramps]

I run my car without the clutch fan, just the aux fan. It comes on when the temp goes over normal OR when i turn the AC on. I don’t know that there’s a hi and low speed, it sounds like it’s all the same speed to me but I could be wrong. How old is your cooling system? It could be sensors or fans or cooling fins that are clogged and letting enough airflow to cool the engine enough but the AC puts it over the top.

[NaM3]

I would start off by diagnosing with INPA and use that to see if you can turn on the fan manually. Once you have eliminated the aux fan then check to see if the cooling system is properly bled.

Personally, my problem was the fan clutch, I did all the testing via INPA and the aux fan came on as it should.

[eacmen]

The aux fan is easy to diagnose. Run the car at idle. Once up to temp either the fan comes on or it doesn't.

Debris can clog condensor and rad. Either clean or replace both of them.

Oil temp can influence coolant temp as well. Make sure oil cooler is clean.

[yhp2009]

The aux fan is easy to diagnose. Run the car at idle. Once up to temp either the fan comes on or it doesn't.

Debris can clog condensor and rad. Either clean or replace both of them.

Oil temp can influence coolant temp as well. Make sure oil cooler is clean.

Interesting point about the radiator and the condenser. Seems like we always hear about the fans or the thermometer and coolant. But after 15-20yrs i suppose its not a bad guess that the insides of the radiators are corroded and allows for less flow... As well as the obvious outer damages from debris and bent fins.

[beefaroni]

Can anyone who has tun the fan test in INPA comment on whether this is normal behavior?: On a non-M E46 INPA lets you enter a fan speed (%) and will tun the fan at that speed. With the M3 the fan test ramped the fan up to full speed then immediately ramped back down to zero. I am wondering if it is supposed to stay running at high speed until the fan test is terminated.

My coolant temperature increases with the AC on too (no mechanical fan, Spal puller only) and I wonder if the high speed fan relay is working properly.

[0-60motorsports]

I replaced fan clutch and new fan clutch fan with genuine bmw items and same crap. Temp gauge goes to 3/4 with AC on. Only things remaining to change are radiator and coolant temp sensor in block.
I’m also running performance pillows but never had this issue since I owned the car, 15 years.

I’m getting really annoyed as it can’t be the pulleys I’m sure. Even water pump is brand new with brand new thermostat. Car has 50000 miles approx. weather temps here are around 125f with high humidity.

[eacmen]

I replaced fan clutch and new fan clutch fan with genuine bmw items and same crap. Temp gauge goes to 3/4 with AC on. Only things remaining to change are radiator and coolant temp sensor in block.
I’m also running performance pillows but never had this issue since I owned the car, 15 years.

I’m getting really annoyed as it can’t be the pulleys I’m sure. Even water pump is brand new with brand new thermostat. Car has 50000 miles approx. weather temps here are around 125f with high humidity.

You still have the aux pusher fan installed?


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[0-60motorsports]

You still have the aux pusher fan installed?


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Yes it checked out perfectly fine as I installed a brand new one and it was the same. So installed the old one back. It’s 125f and high humidity here. No one can use this car here without a fan clutch and aux fan. We even tried electric fan in place of the clutch fan and it doesn’t work in this region because of the heat.

[eacmen]

Yes it checked out perfectly fine as I installed a brand new one and it was the same. So installed the old one back. It’s 125f and high humidity here. No one can use this car here without a fan clutch and aux fan. We even tried electric fan in place of the clutch fan and it doesn’t work in this region because of the heat.

Sorry should have read the whole thread. Seems like you already replaced the pump and tstat? Assuming there is no air in the system you have a few things to try:

- sensors (the cheapest thing to try first)
- clean rad and AC condensor inside and out, over time they get gunked up and air won't flow freely
- run a higher ratio of distilled water to coolant, in your climate you don't need as much antifreeze.
- replace rad and AC condensor

As long as you haven't removed the factory fan shroud the OEM fans should be fine.


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[0-60motorsports]

Sorry should have read the whole thread. Seems like you already replaced the pump and tstat? Assuming there is no air in the system you have a few things to try:

- sensors (the cheapest thing to try first)
- clean rad and AC condensor inside and out, over time they get gunked up and air won't flow freely
- run a higher ratio of distilled water to coolant, in your climate you don't need as much antifreeze.
- replace rad and AC condensor

As long as you haven't removed the factory fan shroud the OEM fans should be fine.


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I’ll be trying the sensors next And radiator has been cleaned and the condenser is brand new and clean too. Thank you and I’ll keep everyone updated.

[High.miles.big.smiles]

Having the same issue, let me know what the issue ends up being.

I have also done a fan clutch and the aux fan is pulling hard. Going to try and drain the coolant and run just DS water in the summer

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[0-60motorsports]

Having the same issue, let me know what the issue ends up being.

I have also done a fan clutch and the aux fan is pulling hard. Going to try and drain the coolant and run just DS water in the summer

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Well apparently it’s fixed. Returned to stock pulleys and all good. I’ll be testing it over the next few days at noon time when it is hottest and then will report back.


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[yhp2009]

Well apparently it’s fixed. Returned to stock pulleys and all good. I’ll be testing it over the next few days at noon time when it is hottest and then will report back.


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which pulley did you have on?