[lowrydr310]

I need a few new injectors on my 335, and I'm wondering if I should replace the valve cover while I have the injectors and hard fuel lines off, one of those 'while you're in there' jobs.

There are no symptoms of a cracked valve cover or leaky gasket. When I bought the car over a year ago there was some oily grime built up around the metal tray/ledge above the exhaust manifolds that looked like a leaky VCG but I wiped it clean and it's stayed clean ever since. I think that was spillage from an oil top off by the previous owner.

There aren't really any signs of excessive oil consumption or a malfunctioning PCV system. I have to add a quart after 4000 miles (mostly city driving and lots of aggressive acceleration) which seems normal.

I'm just unsure of replacing or not since there are no leaks. Cover appears original to the car from 2007, with 170K miles on it.

[Mgh024]

I would imagine it’s had at least one head cover gasket replacement since 2007…

Do you have any history of the car?

If it’s original, I would probably suggest changing it. That said, they tend to develop a slow leak, and over time grows bigger, giving you ample time to replace it before things get bad.

If you don’t have the history, it could need a change in 1000 miles, or 75000 miles…

[whyzee125]

IMO if it’s not leaking, leave it alone. I agree, it’s almost certainly been done once before (the gasket) but it’s a way bigger pain than injectors and the two can both be done independently so I say just leave it.

FWIW, my previous 07 was still on the OG gasket and cover at 166k so it is possible though this was almost 10 years ago. I bought the full cover but ended up just using the gasket and selling the cover as mine looked perfect. Never cracked or anything.

[E93Dude]

Nah, I’d go ahead and replace the gasket. Maybe it has been replaced already. Maybe it hasnt. You just dont know. Mine failed at 91,000, while others have gone north of 150,000 with nary an errant drop of oil. If you are already taking off the fuel lines and injectors, replacing the gasket requires very little extra work, and also gives you a chance to see how clean the motor is on the inside (and by extension whether or not it had regular oil changes). That might be informative for you to know.

I’m not really in favor of pre-emptively replacing functioning expensive things just because they have a lot of miles or years, but the gasket is cheap, easy to get at if you are already in there, and it will fail at some point.

[StradaRedlands]

If you decide to do it, I believe Rock Auto carrying Elring to be the best non BMW option out there. At least for the N52 VC.

[lowrydr310]

I had the cowl tray off to replace my AC expansion valve and inspected the rear of the valve cover. It's slightly damp with oil and grime but nothing major. I'm not sure if it's leaking a bit or if that's still leftover residue from spillage during an oil top off by the previous owner.

I think I'll just go ahead and replace the valve cover gasket when I replace injectors. Thanks for all the insight!

[Brandoch]

Originally Posted by lowrydr310

I had the cowl tray off to replace my AC expansion valve and inspected the rear of the valve cover. It's slightly damp with oil and grime but nothing major. I'm not sure if it's leaking a bit or if that's still leftover residue from spillage during an oil top off by the previous owner.

I think I'll just go ahead and replace the valve cover gasket when I replace injectors. Thanks for all the insight!

Inspect the VC, they are known to crack. I did the gasket just to find out that I didn't inspect good enough. Had to do it again with a new VC.

[lowrydr310]

Originally Posted by Brandoch

Inspect the VC, they are known to crack. I did the gasket just to find out that I didn't inspect good enough. Had to do it again with a new VC.

That's what I'm thinking. Wondering if I should just order a new VC at the same time. Where do they usually crack?

[Brandoch]

Originally Posted by lowrydr310

That's what I'm thinking. Wondering if I should just order a new VC at the same time. Where do they usually crack?

Mine was here

[StradaRedlands]

That plastic is getting old... plus who knows when the PCV will let go.

[Bims328i]

I went ahead and replaced the whole VC and gasket with genuine kit 9-30-22 at 90488 because it needed a new gasket while nearing 100k mark. Didn't want to do the gasket only to have the damn iNtEgRaTeD PCV/oil separator fail later.

I'm at 115k currently and no leaks.

[Cloverdale]

Majority of injector failures on the N54 are due to oil leaks including VC.

[Brandoch]

Originally Posted by Cloverdale

Majority of injector failures on the N54 are due to oil leaks including VC.

Huh? Injector failure is the piezoelectric nature of the injector and contamination in the fuel.

[lowrydr310]

Originally Posted by Brandoch

Huh? Injector failure is the piezoelectric nature of the injector and contamination in the fuel.

Exactly.

N4 injectors don't fail because of oil contamination, it's the design of the injector. Gasoline direct injection was relatively new technology for BMW when these N54s first came out, and it took 11 injector design revisions to finally get it reasonably reliable.

[whyzee125]

Originally Posted by Cloverdale

Majority of injector failures on the N54 are due to oil leaks including VC.

What?! lol how’d you come to that conclusion?

[krhodes1]

Originally Posted by StradaRedlands

That plastic is getting old... plus who knows when the PCV will let go.

This! I don't know early N54s well enough to know if they have the PCV integrated into the valve cover like my N52s do, but if they do, for sure it's ready to let go at that age and mileage. Do it while it's all apart and don't worry about it for another 15 years.

[Mgh024]

Originally Posted by lowrydr310

Exactly.

N4 injectors don't fail because of oil contamination, it's the design of the injector. Gasoline direct injection was relatively new technology for BMW when these N54s first came out, and it took 11 injector design revisions to finally get it reasonably reliable.

Heyyy now

184000 miles on my 08 335xi with index 8 injectors and original turbos + wastegates.

Engine running as smooth as ever, no misfires, etc.

That said, I don’t disagree with you. I’m stock, and don’t really push the car.

[lowrydr310]

Originally Posted by Mgh024

Heyyy now

184000 miles on my 08 335xi with index 8 injectors and original turbos + wastegates.

Engine running as smooth as ever, no misfires, etc.

That said, I don’t disagree with you. I’m stock, and don’t really push the car.

Three of mine are original 2007 Index 1 with 170K miles on them! :-)

But reading around the forums, we are the exception rather than the norm.

My engine runs well, no misfires and no wet plugs the next morning after shutdown, but there's some excessive ticking when cold, a rich exhaust smell on cold starts, and some pretty big (10, sometimes close to 20%) discrepancies between bank 1 and bank 2 fuel trims.

[Cloverdale]

More precisely I should've stated that every one of my several personal injector failures have indeed been the result of oil leakage into the very cylinder with the injector damage, involving a number of different indexes. All remedied with used injector replacement and repair of the leak source. In one of my modified N54's (2007) I'm still running a majority of Index 1's with nothing beyond an Index 9.

[lowrydr310]

Originally Posted by Cloverdale

More precisely I should've stated that every one of my several personal injector failures have indeed been the result of oil leakage into the very cylinder with the injector damage, involving a number of different indexes. All remedied with used injector replacement and repair of the leak source. In one of my modified N54's (2007) I'm still running a majority of Index 1's with nothing beyond an Index 9.

How did you get oil in the cylinder? Do bad valve cover leaks (or leaks from spilling while adding oil) pool up outside the injector and leak past the seal?