Overheating on Idle/AC on

[kkkk]

I am after some assistance chasing a problem that I have had for a number of years. Only now it is much worse.
The car had always overheated (gone to the 3/4 dot) when the AC was turned on, but as soon as I turned it off it would drop back to the middle.
I was doing the Rod bearings and then figured I may as well put in a CSF radiator to see if would help. Even on idle, the coolant temps reach the 3/4 mark now.. If I rev the car up to 3000, the temps drop, but start climbing as soon as the revs drop again.

Here is a timeline of what I have done
I have already changed the water pump and run it for a number of years with no issues.
23/3/19: Changed the clutch fan (BEHR) . First noticed oerheating on a hot day with AC on. With No AC, and ambient temp of 23C, Coolant temp is 91C.
8/4/19: Changed Aux fan and controller with a used one from a non M. Apparently they use the same part numbers but different shroud. Crusing with AC on 95-96C coolant temp.
With AC off, Coolant temps were at 89. (Ambient 15-20C)
17/2/22: New thermostat and CSF radiator. Ambient 30C. Idling hit 100C
Drove it home and the ambient temp dropped to 25.5C (but humid). Coolant temp was at 98C idling in the driveway.
18/2/22: Parked the car overnight outside and drove it in the AM. When I popped the bonnet in the morning the engine was warm. It had been sitting from 11pm - 6am in about 21deg ambient weather outside. . Ambient temp 20.5C. Coolant temp 95-97 idle. Crusing 92-93C idle .
18/2/22: Afternoon. Ambient temp 25. Idle gets up to 98C. AC turned on , temp gets up to 100C and Aux fan is loud. I turn the heater on and then it drops to 93C idle, then climbs to 95.

My mechanic seems to think that the sensors are out of spec. I fired a laser thermometer at the top radiator hose after the thermostat opened and it read:
Dash: 95,. Laser: 90 . (Idling)
Regardless, I still think 90C idling is still too hot for the coolant temp, seeing as a normal M3 would be at 86 deg while driving.

Notes:
1. If the temp sensors are out, why are there no codes? Is there a way to test if the sensors are out?
2. When I turn the car on and put on the AC the front aux fan does not scream like a jet, however when I turned the AC on at 98C, the front AC fan was very loud. Is there a way to test if its working properly?
3. Could I have a headgasket leak?
4. Should I just change to OEM radiator, aux fan+ controller, and AC condensor ?
5. Could my AC condenser be blocking the air flow?

[sapote]

1. If the temp sensors are out, why are there no codes? Is there a way to test if the sensors are out?
2. When I turn the car on and put on the AC the front aux fan does not scream like a jet, however when I turned the AC on at 98C, the front AC fan was very loud. Is there a way to test if its working properly?
3. Could I have a headgasket leak?
4. Should I just change to OEM radiator, aux fan+ controller, and AC condensor ?
5. Could my AC condenser be blocking the air flow?

1. The DME has no way to tell of the temp sensor is off by 5 or 10C. It has no reference to compare or check.
2. The fan speed depends on the lower hose temperature (from the sensor); 100% fast (loud) of it is hot, slower if less hot.
3. Squeeze the coolant hose to see if it is very hard for combustion gas leaked in.
5. Can you tell if the condensor blocked by debris or dust? Remove the radiator and spray water backward through the cooling fins to clean it and also clean the condenser.

Even on idle, the coolant temps reach the 3/4 mark now.. If I rev the car up to 3000, the temps drop, but start climbing as soon as the revs drop again.

Higher rpm generated more heat, so if temp dropped then it means it was due to more coolant flow through radiator and more air flow by the faster clutch fan.

On highway high speed, did this help to drop the temp?

[kkkk]

On highway speeds, I saw the temp actually climb a little because the revs arent "high" while I am cruising .

- Is the dash temp under hidden functions dependent on the lower hose temp sensor on the radiator or the one near the engine?
- If my CSF radiator wasnt bled properly, what other symptoms would I have? This morning when I checked the coolant at cold, it was above max. When I squeezed the top radiator hose, it was soft.

[karter16]

Have you replaced the temp sensor in the lower radiator hose?


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[GolanM3]

You may want to read the post in the link below, good chance it's related to your CSF radiator

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/69074-help-diagnosing-high-water-temps-at-track-resolved/page7

[Chanman1029]

Ive heard csf radiators are a hit or miss with bleeding, thats why I went with a koyo, much better imo.

[Estoril]

"CSF"

[oceansize]

If I've learned one thing from this forum, it is use an OE radiator.

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/69074-help-diagnosing-high-water-temps-at-track-resolved?p=151507#post151507

[sapote]

1. On highway speeds, I saw the temp actually climb a little because the revs arent "high" while I am cruising .

2. - Is the dash temp under hidden functions dependent on the lower hose temp sensor on the radiator or the one near the engine?
3. - If my CSF radiator wasnt bled properly, what other symptoms would I have? This morning when I checked the coolant at cold, it was above max. When I squeezed the top radiator hose, it was soft.

1. This confirms fan or air supply is not the cause.
2. Dash displays the engine temp sensor, not the lower hose.
3. I don't think the radiator has air in it, as it is lower than the reservoir tank. No need to bleed air out of radiator.
Squeeze the hose when it is hot; in cold morning pressure is much lower so the test is not useful. On a normal engine, at operating temp the hose is not hard as rock unless combustion gas leaked in the coolant.

"This morning when I checked the coolant at cold, it was above max." this is not normal unless coolant was added above Max.

When coolant got to higher than 90C, grab the lower hose in your hand and see if you can hold it for 30 sec without pain. If you can then the cause is not enough coolant flow for some reasons.

[kkkk]

Update to this:
I changed a new water pump, thermostat and OE radiatior. Now the OBC idle temps are around 90C . I still think this is a bit hot given the thermostat opens at 80C.
Iv seen the temp go up to 96C but it drops down as soon as I drive.

The front aux fan DOES not do a test spin when I start the car up. I thought it was supposed to do this?
I will see if I can put the fan at max speed to see if it will drop the temp in INPA

[kkkk]

Had another look at this today to try and diagnose
1. Diagnostics say that the engine temp is 86C (engine coolant temp ) but the bottom radiator outlet is 45C.
is a 40 degree drop in radiator temp too much ???

2. when I unplug the temp sensor for the bottom radiator outlet the fan spins at 50-60 percent duty cycle . Shouldn’t it spin at 100 percent as a fail safe ?

[Arith2]

I don't think it failsafes to 100%. 60% sounds about right. There are two more sensors the DME has. Oil temp and block temp. A 40 degree drop across a radiator is where it should be. The temp will bounce around 80-90 degrees in winter and summer. Are your oil temps ok?

[kkkk]

Back at this.
Iv been driving around for the last 2 years and the coolant temp goes from around 90-92C. If it push it it may go to 94, but does come back down. I never see it below 89C unless the engine is still cold.
If I turn on the AC it may go up to 96C (and climb)

The oil temp is straight vertical (about 100C)

Im out of ideas, but Iv pushed the car and its never given up on me

[Anri]

ChapterM3


The following upcoming failure.
How you have been driving for those times.

kkkk

You need to fix this asap, or head out..


Regards,
Anri

[Stilt]

Back at this.
Iv been driving around for the last 2 years and the coolant temp goes from around 90-92C. If it push it it may go to 94, but does come back down. I never see it below 89C unless the engine is still cold.
If I turn on the AC it may go up to 96C (and climb)

The oil temp is straight vertical (about 100C)

Im out of ideas, but Iv pushed the car and its never given up on me

Still having issues?

I had over heating issues when I was running a clutch fan, and it was brand new. Mind you not I had done a full cooling system overhaul.

Recently I decided to redo the water pump gasket, the 2 gaskets that go between the heater core pipe and thermostat housing and pretty much every other gasket, using the Wolfn8tr gaskets. I also put in an e fan from a manual 330i ($60 bucks, so I couldn't resist).

I am no longer having over heating issues.

—
Side note, I was so fixated on the idea that I had a blown head gasket, tested and I was good.


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