Getting rid of burned oil smell

[TroutMD]

My '72 w108 280SE 4.5 runs great, but has this very pronounced "burnt oil" smell after it has been running for a while. The smell can be felt both inside and outside cabin. I think (?) the smell comes from a haphazard oil addition when oil was poured without funnel and some ended running down the engine block and further below.

I tried cleaning as best as I can, but there are areas I cannot access. Does anybody have any tip on how to get rid of this smell? Thanks in advance.

[Diseasel300]

If the oil is indeed from a sloppy fill, it should burn off with a few days' worth of driving. Get it out on the highway and get it good and hot and it'll burn off faster.

If the smell remains after a few days' driving, you probably have something leaking (most likely a valve cover).

[Mike D]

Spray bottle and some good degreaser. I believe the LA's Totally Awesome is the consensus choice. I find it at almost any "Dollar store" for about $2.00 a bottle. Give a good squirting, five minute soak and a GENTLE rinse. .

[97 SL320]

Be aware that older cars tend to have oil / fuel smells, modern cars are pretty sterile these days.

If using a " Simple Green " or similar cleaning product, don't use full strength / let soak long because the cleaner will attack / discolor soft metals like aluminum.

[rocky raccoon]

If the smell is persisting after several days/driving cycles my guess is a valve cover gasket leaking oil onto your exhaust manifold.

[Idle]

Originally Posted by rocky raccoon

If the smell is persisting after several days/driving cycles my guess is a valve cover gasket leaking oil onto your exhaust manifold.

The fix in the old days was to tighten down the valve cover to stop the leak. That was with American cars with cork gaskets.

But German cars used a different gasket material. It is far superior to the old cork, but when it starts to leak all the bolt tightening in the world will not stop an oil drip.

You might want to replace the gasket anyway, and I think this engine still requires a valve adjustment now and then? If so you might as well take care of that while you are in there.

The oil smell will still be there for a few days. It will just have to burn off the sides of the block where it has dripped onto. The exhaust manifolds get hot quick, but not so much the block.

[97 SL320]

Originally Posted by Idle

The fix in the old days was to tighten down the valve cover to stop the leak. That was with American cars with cork gaskets.

But German cars used a different gasket material. It is far superior to the old cork, but when it starts to leak all the bolt tightening in the world will not stop an oil drip.

To expand on this, the technology had made it's way to USA cars in the mid 80's on the Chevy 4.3 V6 / 5.0 5.7 V8 Vortech motors.

This type of technology relies on premeasured stops in the valve cover or a silicone seal in a rigid plastic carrier. The bolts can be tightened with a screw driver or just short of braking and the clamping force at the silicone seal will be the same.

[TroutMD]

Well, the burned oil smell persists so it must likely be a valve leak then. I don't see any dripping oil making it to the floor of my garage though.

I am not very mechanically inclined, how can I confirm it is a valve leak? And how difficult/costly would it be to fix? Thanks again.

[optimusprime]

New rocker box gaskets will cure it .Remove a spark plug and look on the metal part of it if it is wet with oil thats the problem , and also the plug hole it screws in to will be wet with oil .Just repaired my gasket as the oil was leaking down on to the hot engine to burn off ,= the smell

[Diseasel300]

Originally Posted by TroutMD

Well, the burned oil smell persists so it must likely be a valve leak then. I don't see any dripping oil making it to the floor of my garage though.

I am not very mechanically inclined, how can I confirm it is a valve leak? And how difficult/costly would it be to fix? Thanks again.

The valve covers are your most likely source of leaks. On the M117 they're right above the exhaust manifold, so if you have any oil weeping out, it's gonna drip down, burn and smell terrible.

The easiest way to look is to use a strong light and a mirror and look along the lower edge of the valve covers to look for evidence of oil. If you see oil, a "sweat" or a bunch of caked up dirt and grime, you've probably found your issue. If so, replacing the valve cover gaskets isn't difficult or expensive.

[Tony H]

My coupe had (has) old rock hard suspension grease 1/2" thick all down the underbody from years of overgreasing the suspension mixed with misc oil leaks thrown all the way from engine to the gas tank. It is a very smelly mixture with that "old car" smell. Removing it is very labor intensive and messy even with the engine and suspension removed.

[TroutMD]

Thanks for all your input.

I am planning to have the valve covers replaced at my next oil change. Any idea of reasonable cost/labor involved if I have a mechanic do this?

[Mike D]

Well, I'll say this much about you. You don't act on "spur of the moment" impulses!

[Tomguy]

It would take me - a non-mechanic - 15 minutes tops to do the both sides (4 bolts per side, you do need to unclip the plug wires, and the breathers on each cover). I'd imagine a mechanic would bill for no more than 0.5 hours. Plus parts markup unless you supply the gaskets - which on an older car like this may be advisable, as sources that most mechanics have won't get them in stock within a day or two.

[grbeiz]

From experience, old cars tend to leak from many places which eventually when driving could flow on the engine and burn off giving away that nasty smell.. I suffered from this until I washed thoroughly the engine and checked for leaks sources on a day by day basis and after every drive.. Ended changing the valve cover gasket as well as hydrolic fluid pipes from and to steering wheel pump that were also leaking .. the smell is gone for good