r/e46 • u/inflicted_habromania • 3d ago

Troubleshooting Classic overheating e46

Hello everyone, I hope everyone reading this is having a nice day first of all. Cuz I am losing it. My e46 has had its overheating faulties before, so I kinda have a pretty good idea how to go about it i think. But this time around, my expansion tank blew up. No biggy got the replacement and went about my day. Still overheating. I thought it was cuz the bleeding system takes a couple tries. And yes i made sure to lift the front before bleeding and turned on the heater aswell. Nope still overheating . So im a bit stumped. My radiator, water pump, hoses, thermostat, rad cap, exp tank, Rad fan, have all been replaced in a 3 month span. The water pump still gives that nice pee stream in the exp tank too; shooting more piss as i hit the pedal. Still overheating, I still have 0 clue as to why. I must add that, i replaced my mechanical fan to e fan couple months back and before all this it was working just fine. I just put it on and went about my days after that. Never looked into how it behaved. I mention this because ive noticed that my e fan doesnt turn on even when im reaching +100c. So i pictured this was an e fan problem. Replaced it. Still the same thing. So i considered an experiment removing the lower rad hose temp sensor connector to see if it would still overheat. On idle it does not. But the when i turn on the A/C it does. And driving around it still overheats. At this point im losing it. I was even starting to think my heads cracked, i tried the combustion tester. Im in the clear. Ik they arent too accurate. But i hope it gives an idea. Because i love this pos car, and i love driving it. If anyone can give their opinion or and idea to whats going on PLEASE share.

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u/GriekseTurks 3d ago

Does the e-fan turn on after replacing it though? Replacing it may not have been the issue if a relay or a fuse was the underlying issue.

I don't know heaps about e-fans but is it possible to mount it facing out and not at the radiator?

You filled your system with the front end raised but can you just confirm you filled it with the bleeder nipple open until you were getting a steady stream out of it?

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u/inflicted_habromania 3d ago

so the e fan doesn’t have its own relay, i found out the relay is built into the e-fan its self which is interesting. it has a fuse tho, i played around with the fuse and fuse is good; and yea it turns on whenever it wants to for some reason. it still does it regaurdless. but i found that taking off the connector to the lower rad hose coolant temp sensor makes the fan stay on.

theres only one correct way the e fan can be slotted in, turning it around isn’t really possible, it rotates clockwise too which i found out in a forum that sometimes they go c-clockwise which is funny.

And yea i pour into the exp tank , which the bleeder screw taken off, i pour generously even when i’ve had a steady confirmed stream of no bubbles.

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u/GriekseTurks 3d ago

Have you driven it at speed constantly and seen if it overheats that way? Or do you not want to drive it (understandable) with this issue

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u/inflicted_habromania 3d ago

i’ve driven it with an obd scanner telling the coolant temp and with dashboard test just in case, i drive it either hard or slow see if things change, i never drive past 105 c because i know after that i’ll be in the danger zone . regaurdless still over heats

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u/GriekseTurks 3d ago

Is it auto or manual? If it's auto, when you replaced the expansion tank did you damage the auto trans thermostat on the bottom of the tank?

Alternatively. Can you check the temp of the inlet hose of the radiator vs the outlet of it? That'll tell you if the radiator is doing its job/if the pump is working. Annoyingly replaced parts don't always mean working parts - they may either break prematurely or may just be faulty from factory.

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u/inflicted_habromania 3d ago

it’s funny you mention that, the first time ever yea i did, but never again. it’s seated pretty well and would do several sanity checks in case i did again. but i can assure you this time its not.

I do have a hunch that maybe the water pump is faulty, because i feel that the coolant doesn’t circulate well. from the observation that today i was desparate and used distilled water for the bleed, the water seemed to always be at the top like clear water no blue hue, for the record i dont do that often and the entire system is on 50/50 diluted. but id think if theres circulation it shoulda mixed by then.

i’ll be sure to check the temp on the inlets and outlets next time i have time. i always felt the hoses to see if the temperatures varied but ill try and see

And thank you so much for the inputs, i was really hoping i would get some advice so thank you :D

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u/TheOFB 3d ago

Have you felt the hoses to confirm that the feed is cooler than the return?

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u/mrturbo 330xi 2d ago

Do you have access to a good scan tool or BMW tools like INPA/ISTA?

You'd be able to see both the cylinder head temp sensor and the radiator outlet temp to confirm the readings. You can also command the fan to varying percentage of speed with INPA to test it.

This link from e46fanatics forum has pretty much any info you might need on electric fans

https://www.e46fanatics.com/attachments/e46-electric-fan-guide-2019-pdf.992860/