[n54335i02121997]

N54 335i

So, I am trying to pin point a couple things here regarding an oil smell.

To preface, I replaced the VCG at 165k, OFHG Kit around 170k, and I ALSO had a bad oil fill cap that was leaking oil into that little ravine by the injectors. I just replaced that maybe 1,000 miles ago (191k).

Car ALWAYS has driven strong, and performed quite well. Installed MHD on it and replaced the water pump in late December. Stage 1. Nothing crazy. That created an issue where under higher boost, the cold side charge pipe would come out of the intercooler a little bit, and cause mild boost oscillation, it'll pull, you'll hear some hissing as in the boost leaking (I did the ghetto diverter valve blowoff rig). Replaced the O-Ring and clip and that seemed to help. Before replacing them, it was quite bad.

Under stock map, HEAVY throttle, seems to hold boost just fine. But going from MHD to stock just feels insanely slow now, I used a JB+ pretty much a month after I bought the car so I've never really driven it bone stock.

So I am thinking, well hoping, it is not turbo related. I am not getting any smoking from the engine bay, no burnt oil in the exhaust, no turbo whine, and like I said, the car pulled completely fine up until I did the water pump and had the intercooler off..

I am about to take it to a performance shop that I deliver to, going to call em up tomorrow, so hopefully they will help me out on getting it to stay in and hold boost properly!

Turbos replaced at 80k under warranty, I've owned the car since 90k, and it's at 190k right now. It is almost all highway miles. Like seriously. Very long trips that just racked em up super fast. 100k miles over 2.5 years. It killed me to see it go up so fast, but I had to do it. My beater car was out of commission for a year and a half. But very calm driving, 75mph on cruise, extremely well maintained car and I rarely ever beat on it/floor it. So the turbos have had it easy compared to some kid trying to race everything he sees with hard burbles at 1500RPM set to 2 seconds. This is my first and only turbo car, but just assuming that a constant speed cruising pretty much does nothing to wear out turbos.

Anyway....

I wanted to preface with that.

I usually have to keep my air on recirculate, due to just smelling the burnt oil in the cabin. Like I said, NO SMOKE. Getting heavier on the throttle, the smell is a little more prominent as I noticed today, ALTHOUGH it could have just been another car, as I don't drive this one much let alone get heavy on it. It's kind of embarrassing if I have passengers.

There seemed to be a bunch of residual oil in the gully where the spark plugs are. I JUST replaced that oil cap which was definitely leaking. That may be the source.


December 2020, My VCG was leaking VERY bad and was constantly smoking. After replacing that, the smoking went away, so I'm guessing I installed it correctly.

There WAS oil on my spark plugs though when I replaced them immediately after doing the oil cap.

So, perhaps it's just the residual oil burning off slowlyyyy and giving it a constant burnt smell.


So lastly, does anyone have any experience or input? And besides the two main culprit gaskets, and the oil fill cap, are there any other things that I should be worried about? Even turbo related, which I am absolutely terrified for.

Thank you so much. And I just want to repeat, NO SMOKING from engine bay, OR from exhaust besides normal condensation. Does not smell like oil

There could damn well be a crack in the valve cover, but I haven't noticed anything.

[itsskywalker]

The only thing I can think of that wouldn’t be turbos would be valve cover or head gasket on the exhaust side of the engine. See if you can get it warm and see some smoke

[lookalikehuuh]

Go buy yourself a few bottles of brake clean and clean up all old/crusty oil from the engine block. If you had a really large amount of oil leaking from the valve cover you could just have tons of old oil burning off and causing that burning smell. Focus especially on the passenger side of the engine near the turbo manifolds.

[Serf27]

All that excess oil would have burned off a long time ago if you replaced the VCG 25k miles ago.
With the vanity/engine cover off, look at the rear bottom corner of the VC where it meets the head.
Is there any oil pooling there?
Small pools of oil will give off the smell but not necessarily clouds of smoke.

The turbo seals could also be bad.
If you have stock down pipes or stock secondary cats, those catch a lot of the smoke, but still leave the smell of oil.

[n54335i02121997]

Originally Posted by Serf27

All that excess oil would have burned off a long time ago if you replaced the VCG 25k miles ago.
With the vanity/engine cover off, look at the rear bottom corner of the VC where it meets the head.
Is there any oil pooling there?
Small pools of oil will give off the smell but not necessarily clouds of smoke.

The turbo seals could also be bad.
If you have stock down pipes or stock secondary cats, those catch a lot of the smoke, but still leave the smell of oil.

Well, turns out the oil fill cap (on top of valve cover), was leaking bad. I believe that was leaking into that valley. I'm going to check it out tomorrow and see how it's looking, cause I haven't checked in a while. It's been maybe 1-1.5k miles since that was replaced. There was oil pooling in that valley. If I run out to my car tonight I will check.

No smoke at all, BUT after a 700 mile road trip it.. seems? to not be as bad? I'll report back tomorrow.

I am praying there is no problems with the turbo seals, they are not OEM turbos, but it has been about 8 years/100k miles since they were replaced.

I'm not really losing excessive oil.

Will turbo seals cause any real issues if that ends up being it? I do plan on replacing them when the time comes... DIY'ing it, but they're pulling and spooling good!

[n54335i02121997]

Originally Posted by itsskywalker

The only thing I can think of that wouldn’t be turbos would be valve cover or head gasket on the exhaust side of the engine. See if you can get it warm and see some smoke

No smoke at all, but before I replaced the oil fill cap, there was a pool of oil in the valley with spark plugs, AND oil leaking onto the spark plugs but not too bad.

I haven't checked since I replaced that cap and it's been about a month, BUT I've only put maybe 1.5k on the car on two long road trips. It's not my daily driver.

I had a bunch of smoke before replacing the VCG.

[90c4]

What's the update on this? I was ready to buy a new valve cover after recently doing my OFHG and noticed oil around the fill cap also and I suspect that's the cause of the occasional oil smell. Flipped the gasket within the cap upside down and cleaned it, and will likely buy a new square gasket for under the engine cover and a new filler cap, and so far it doesn't seem to smell but it was a temperamental issue anyway so I'll need to give it a week or so.

[kkasson]

Not the OP and I have the N52 not the N54 but I've replaced the fill cap on two cars for this same problem. Thought it was the Valvetronic gasket or VCG but it ended up just being the fill cap. Flipping the gasket didn't help in my case but replacing the cap did. I suspect the little metal spring tabs got weak and it wasn't pulling it tight enough, so replacing the gasket didn't help but a new cap did.