Help re: intermittent overheating

[kkkk]

I had this problem and hunted it down for ages
Go into the secret menu and press 19/7 to get the temps up for the coolant engine temp sensor and let me know what they are with and without AC on (+ ambiemt temps)

I changed
2 water pumps
1 radiator
Engine coolant temp sensor
radiator temp sensor
Clutch fan

Its a little better but still gets up to 93C with the AC on. and 88C without. When I pull the lower radiator hose sensor, it gets to 86-87C. This leads me to think its the aux fan or the aux fan module playing up

[sapote]

After a decent testing period, I can say that the coolant temp starts to climb: (1) on hot days; (2) with the AC on; and (3) when the motor is being run harder—meaning, shifts at 5k+ or while under load (uphill). Another clue is that the coolant temp returns to the midpoint when turning the AC off. And yes, I can hear the aux fan doing its thing

A few thoughts.
1) If Elec fan was running which means the lower hose was hot. But this is possible only for a normal car, so double check by reach in and feel the lower hose to make sure it is indeed hot.
2) If the lower hose is hot, this means the Tstat opened properly and the WP works fine. Then the issue is the radiator doesn't exchange enough heat.

[EthanolTurbo]

Yeah if things are original, I would replace everything too at that mileage

Me too. I just assume any E46 M3 that has 100-200k miles on it needs almost everything replaced that's a wear item unless noted otherwise.

[heinzboehmer]

Mileage = 138k

Yeah if things are original, I would replace everything too at that mileage

[LSB4Me]

And there you have it folks. The use of logic and shame in equal measure by our friend T-Bone has landed me at full overhaul.

Good to know that a radiator would have likely solved my problem(s). Half measures be damned, as they say.

[Tbonem3]

I, personally, would replace everything at that mileage, esp an lsb of a pcar owner

[LSB4Me]

Don't buy mishimoto anything.

You never mentioned the mileage.

Crossing Mishimoto off the list of good guys. Mileage = 138k . . . hence the urge to fully refresh/baseline.

Based on the advice here, I’m planning to with the radiator, hoses, clutch fan and fan blade. That seems like the front half.

[jet_dogg]

Hah! T-Bone will enjoy the irony there.

I will give some thought to cleaning the radiator but at $300ish, it’s probably best to start fresh as the cooling system is one of the last mechanical components to be baselined. I’ve been through everything else in the last 3 months. Good times.

Copy that. Genuine radiator it is.

Question 1: Does the fan clutch make a noise (a rattle, perhaps) when it’s on the way out?

Question 2: I will replace the hoses with the radiator. Silicone (Mishimoto?) or stock here again?

Don't buy mishimoto anything.

You never mentioned the mileage.

[heinzboehmer]

Rein makes good stuff. Their hoses are totally fine. Might even be OE for the BMW stuff. It's just the o rings that aren't good enough.

Job would take me 1-2 hours. Probably closer to 2 after I spill a bunch of coolant on the floor and waste a bunch of time cleaning it up. Someone who actually knows what they're doing can probably get it closer to 1.

[Tbonem3]

ECS is charging shipping on that? Look at FCPeuro too.

[LSB4Me]

Roger that, guys. I had the o-ring guy’s post bookmarked for a later day . . . which seems to be today. I will get those for sure.

Regarding Rein, I’ve used their parts on a prior P-car (as they were the OE supplier and I was in a pinch). I’ll see what the Genuine hoses run and will likely go that route as retracing steps due to inferior parts is a pet peeve of mine. Do it once . . .

ECS has the genuine radiator at $280ish. After LA tax and shipping, it’s $340. Seems reasonable to me.

What’s the time requirement on this job for a seasoned pro?

[Tbonem3]

[heinzboehmer]

3. Get this o-ring kit. This dude is a forum member.

Also recommend doing this.

You can get the rein hoses to save a bit of money over the genuine BMW ones. On the now-dead M3forum, there were reports of people having issues with the rein o-rings (the hoses are fine), but if you replace them with the ones from WOLFN8TR, it won't be an issue. That's what I did on my car.

Edit: ah damn tbone beat me to it

[Tbonem3]

Stock for everything. Factory bmw radiator (Modine build) is surprisingly cheap right now still at $3xx. For hoses, genuine again, but to save $ you could get the cheap OEM REIN, but then replace the junk o-rings with quality ones sold by fellow member here @wofln8tor.
Fan clutch goes bad when the viscous element fails. I believe they work by centrifugal force. So not a noise or bearing thing, just won't have much force to spin. You can roll up a newspaper and stick in there and see if the fan stops.

I would delete the fan simply to avoid it grenading the hoses and hood.

[oceansize]

Hah! T-Bone will enjoy the irony there.

I will give some thought to cleaning the radiator but at $300ish, it’s probably best to start fresh as the cooling system is one of the last mechanical components to be baselined. I’ve been through everything else in the last 3 months. Good times.

Copy that. Genuine radiator it is.

Question 1: Does the fan clutch make a noise (a rattle, perhaps) when it’s on the way out?

Question 2: I will replace the hoses with the radiator. Silicone (Mishimoto?) or stock here again.

1. Not in my experience. This should be replaced at 100k in my opinion as a wear item.
2. Stock is fine, no need for silicone unless you want to.

3. Get this o-ring kit. This dude is a forum member.