(E46) Burning Rubber Smell From Engine Bay

[DeltamaxX]

Hello all,

Rambling Intro:

First of all, I'm a new guy here but I've had my 04 330ci for 1.5 years it's been doing pretty well starting out at 115,000 used. Until It was time to inspect it last summer and the guy at the shop wanted to rip me off majorly by racking up all these repairs and up charging for labor like many shops I've known in Pennsylvania. So I said screw all that noise and decided to learn how to work on my own beamer. I come from a family of mechanics and I've been working on computers and electronics for over 10 years so learning this car hasn't been as insanely hard as the general public likes to assume. I got my YouTube degree and $800 worth of common oil seals, tires, and a battery and it's finally ready for the road. (I can provide a list of repairs upon request)

Actual problem:

Before and after I replaced oil seals, and did general maintenance that was long overdue, I noticed a smell that came from the engine bay that was...like burning rubber but without any smoke. Think of it like you just got home from work on a hot summer day and you can smell the rubber from your tires but it's not a sharp odor to through off any alarms. The smell occurs after 2-3 minutes from a cold start and it's being blown from the mechanical fan. The serpentine belt is brand new (but again this suspicious smell existed before I put any work into the car at all.

I checked all moving parts to understand if there was a clearance issue and of course everything is fine. The only thing I haven't done was rip off all the pulleys on the motor to find a potential fault I can't see but I was hoping someone would have experienced this weird issue.

The motor hasn't exploded or caught on fire so it seems to be very minor. I still wanna try and figure it out before it turns into something expensive.


Thank you for your time

[Raddee]

Are you sure it's not oil? Since you've been poking around at the engine; check the rubber ring underneath the oil filler cap, if it's not seated properly oil will seep through and land on the exhaust manifold. If that's ok, check if the plastic panels covering the ignition coils are seated properly as they will cause the same thing.

[DeltamaxX]

Thank you for the reply. This is a very distinctive smell that I'm nearly certain isn't oil. I will check the vanity covers again. I just found it interesting the odor is behaving the same way before and after I worked on the motor. I'm familiar with the 20+ common problems of E46s and I know oil leaks ranks the highest since many beamer motors run hot.

[RobertDenali]

The only rubber smell would be belts unless you dropped something into the engine bay.

[MarcoZandrini]

The hint is the phrase “it’s being blown by the mechanical fan.” Obviously the source’s location is the front of the engine. I recommend that you get the engine hot, and then shout off the engine. Next, take a cardboard tube from a roll of paper towels. Place your probiscus (nose!!) in one end and then start placing the other end at/near the usual suspects. I’d start at the bottom of the engine - the harmonic balancer, aka pulley on the front of the crankshaft. Then work your way up.

[Comatose51]

I had a very, vert similar problem a while back. It turned out that when I changed my valve cover gaskets, I didn’t close the valve cover properly and the gasket was pinched in the back along with the wire from my O2 sensors. Check for oil on the back of the engine. It was a slow leak because the casing for my O2 sensor was enough to prevent most of the oil from coming out. But it did wick up some oil and some of it dripped down the back. Anyways, worth checking to make sure the back was closed properly and no wires were caught between the engineering, the gasket, and the cover.

[DeltamaxX]

MarcoZandrini I love the smell-o-scope idea. It's still freezing cold where I'm at and I'm waiting on a nice day to spend some time with it again.

[SiennaRotDrop]

Theres a control module on the frame of your electric fan, if your smelling an odd scent more like burning plastic it means yours is going to ignite soon and burn your car to the ground. Google "BMW catches fire" or BMW Owners Beware! | BMW Electrical Fires Happened just days after reading to my friends 325i because I was smelling the same every day while carpooling. Luckily when blue smoke started pouring out from under hood I was already aware and able to douse it with a bottled water and unplug the main fan harness to cut off electricity and save it before it set the car on fire. Replace your fan assembly ASAP! And purchase an aftermarket assembly, I think I found one for him for $161 made by Bosch or some other german brand that had a silvery metal control module on it not the plastic box with silicone seal you will see on yours, or buy the Mishimoto. Whatever you do ALWAYS unplug that harness at night and whenever parked until you replace the fan and keep water to douse it out if it happens to you. this was about 5-6 years ago to my friends and I still just bought my 325ci a few days ago, luckily it was already equipped with a Mishimoto fan along with dozens of other mods. Good luck, REPLACE THAT FAN!!!