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Discussion Starter · #1 ·
Please read before replying. I am a bmw tech for years, i've rebuilt multiple S62s, I know these cars inside and out.
This is my personal car that i have rebuilt the engine on(stock rebuild). Everything was down to bare block. Driven the car for 4000kms now. The car pulls hard as [email protected], no noises no issues, runs smooth as it should. Everything on the car is brand new. There is no item that hasn't been replaced during the rebuild. Everything was put on genuine BMW parts, not worldpac. There are no codes.
I have taken the car apart recently to recheck the cooling system, i have removed oil pan and oil pump to check if all is good, no issues found anywhere.

WHY THE [email protected] is my coolant temp at 105 celcius and oil temp 2-3mm to the right of the middle under normal driving when its cold outside. 8deg celcius. On the highway everything goes back to normal, ones i am in abit of traffic or street driving it starts climbing. I've had so many of these cars before, they should not be running this hot unless it's +30 degrees out. The fan clutch comes on i can hear it. The electric fan does not. I tested it and its dead but i don't think it should even come on when its this cold out.

I have no idea what to do. I'm about to sell the car, this is driving me crazy. IF anyone has experienced something like this please let me know. THANKS. PIC of my car.
 

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Discussion Starter · #3 ·
Um. I think the answer is in your post.
The fan clutch doesn't do the main portion of the cooling. It's the electric aux fan that does the vast majority of the cooling when stationary.
When you are moving, it would be the air blowing to the radiator that cools the car.

Did you pull the codes? Any aux fan codes? Or just test if the aux fan functions by turning on the AC. AC fan should start within some time.
If it doesn't, your aux fan is dead.

Don't have access to ISTA right now, but at the temperature you are reporting right now, the aux fan should be working regardless of ambient temp.

Cheers,
Gabe

--- EDIT ---
Ok. No codes.. that's weird. But the test procedure should still be the same.
thanks, yeah the aux fan doesnt activate with ista. I got a new aux fan coming monday. Last resort.
 

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Discussion Starter · #9 ·
Oh I must have mistaken. Sorry for the wrong info.
105 rings a bell to me btw. The M62 thermostat is a 105 degree one. Maybe used the wrong thermostat?

- Gabe
M62 has nothing to do with S62. Two completely different engines. S62 runs a different cooling system lower temp thermostat. Read the everything please. Its a genuine bmw thermostat, very low chances of it being defective. Don't confuse people with your 540 stuff, its irrelevant here.
 

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Discussion Starter · #10 ·
That is so wrong! On the M5 the aux fan is the primary cooler and the mechanical fan is secondary. That is obvious if you just look at the activation temp and compare it to a 540. The M5 activation is a higher temp, and when you consider the operating temps of the two motors, one would say it is considerably higher. That is the OPs most likely problem short of some odd mistake on assembly.
yeah new aux fan coming monday. last chance
 

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Discussion Starter · #24 ·
I've had a similar issue this year, but my aux fan does work. I can confirm Shady/others are correct in that the aux fan does more. While trying to diagnose, I drove the car for an entire day this fall (mid 60's F) without the mechanical fan installed. I had pretty much the same operating temps in slower speed driving. It gets into the low 90's C. I'm sure it would go higher if I kept idling and moving too slow to move enough air across the radiator.

Turns out my issue is the radiator, which I was suspecting even though it's only 7-8 years old. Not enough flow at low speed and idle in traffic. I had already removed it and cleaned debris at the end of summer. It helped a bit but now I have the smoking gun - the radiator started to distort - it expanded the core. Internal clogging is my guess.

Since you're going to replace the fan, you'll have a chance to review the radiator condition. If you're hitting over 100C, you might suspect more than just the aux fan. As you know, best to replace one thing at a time though.
Hey, so the radiator is brand new. Less than a month. Its a behr which lately behr products have been sh1t not genuine bmw. I have installed a new electrical fan and it works, it did make quiet a big difference during traffic but car still runs at 95 deg celcius oil passes middle mark when cruising
 

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Discussion Starter · #25 ·
UPDATE!
APOLOGIES FOR NOT USING FAHRENHEIT numbers, i am in Canada, it takes to long to convert everytime.
OK SO, UPDATE. I replaced electric fan It does come on now in traffic, now the coolant temp goes up to 95 degrees Celsius (before used to go up to 110-112) so that takes care of one issue, that tells us that the electric fan does play a bigger role than the fan clutch in an S62 car.
2. I have drained the coolant from the block and the radiator. I have warrantied the already new thermostat and waterpump, i have removed the new radiator and connected a water hose to it to check if flows well, no issues there.

3. Everything back together, drove the car on the highway and streets, oil temp still tries to pass the middle mark sometimes, not always when cruising with or without traffic, and also coolant temp is still too high at 95 degrees, it is cold af outside, it should be 90 or below, i've had so many of those cars, i know this isn't right. The electric fan is on almost all the time now during street/traffic lights driving, shouldn't be happing when it's +5 celsius outside, in summer when it'll be +25 i feel the car will struggle to keep temps down.

CONCLUSION: The only thing left to do at this point is to replace the heat exchanger. When i rebuilt the engine i cleaned it properly with hot water, checked for flow or debris, none found. AFTER this i am clueless. Feels like a very minor restriction of flow somewhere. Anyone ever replace oil filter housing?
 

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Discussion Starter · #28 ·
UPDATE 2 CAR IS FIXED.
REPLACED HEATER VAVLE WITH AUX PUMP together, Aux pump was not turning on at all. I have no idea how the [email protected] this is related to car running too hot, because as far as i understand it's just for heater while the engine is at idle. But it did fix the main issue so I'm happy. Not a cheap part to replace.

Thanks to everyone for your inputs and trying to help.
 
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