Valve/Cam/Rocker Cover Gasket.... Or Not?

T

tiglon

Senior member
 South West
As briefly as possible... car going fine, I do MHD stage 1, all good for a couple of days, then misfire cylinder 3 during wide open throttle at high speed. Limp home.

Oil in spark plug 2 & 3 wells, but only a little in 2. Oil also in dips in engine casing either side of spark plug 3 (photo to illustrate).

Mop up all oil, change all 6 spark plugs to new NGK one step colder, replace coil 3. Misfire gone. Take it to stealer, they check visually and diagnose valve/cam/rocker cover gasket and oil filler cap both leaking. Oil level as per iDrive readout is still max.

This was all before Christmas.

Diagnosis makes sense, it's what I expected, so tomorrow it is in to have the work done (due to Christmas I couldn't get it in anywhere sooner). £500, not unreasonable.

However! Went for a drive on 28th for 1.25 hours, dual carriageway, just to keep the battery going. Gentle driving, no excessive speed or heavy right foot. Afterwards, I check under the engine cover out of curiosity - no oil anywhere, not in spark plug well 3, not around it, not around oil filler cap.

Today I do same, but B roads, plenty of traffic so fairly slow, but one wide open throttle pull, for a few seconds. Get home, check for signs of oil leak in same places. Still nothing.

So....

1) is it possible for oil to get into a spark plug well if spilt when filling? Spark plug 3 is directly below oil filler cap. Seems unlikely.

2) could it be just a very slow leak built up over time until there's enough oil in spark plug well to blow the coil and be noticed? I hadn't checked the spark plugs previously.

3) could it be that the leak only occurs under the very high pressures of wide open throttle at high speed?

4) oil filler cap does feel ever so slightly loose, could it be that under those conditions oil leaked from here and made its way into spark plug well?

Regardless, the gasket and cap will be replaced, but it really grates away at me when I don't understand something! Any comments appreciated!
 

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Both the gasket and cam box itself are prone to leaks (along with many other 4/6 cylinder BMW engines)..

However what seems to make the N54 worse is that everything seems to run so much hotter in the engine bay.

So the heat / cold cycles are more severe, so ageing of the plastic cam box and it’s associated gasket are accelerated.

It could well be that the crack / leak opens up when the engine has been really hot for some time…and / or the oil leak may have accumulated over a much longer period of time. So a short run may not reveal it?

FWIW if the car is a keeper I would ask them to very carefully inspect the cam box itself…they as did discussed can heat / age crack.
 
If your cam cover is leaking or cracked you will smell burning oil as vapour will escape.
A leaking cover will also affect the engines internal crankcase pressure
Just pop the plastic decoration cover off, go around and check all the cover bolts are evenly tight, dont overtighten them if you find a loose one.
If it was leaking you would certainly get something after your post leak discovery driving sessions.
I dont know if your car is an N54 or N52? but if you lose positive crankcase pressure you will get other problems as well.....
 
Clean it up and monitor it weekly. If no oil returns after a month then just forget about it. It could quite easily just be spilled oil, it doesn't evaporate so it will just sit there until cleaned up.

No point getting work done just for the sake of it. Just more opportunities for mechanics to break things.

You should have a really good look at the front of the engine around the serpentine belt, that's where the OFHG leak often shows up. That can foul the belt and pulleys and cause engine damage if it breaks.

The serpentine belt and pulleys are maintenance items. Suggested at 100k or after having oil contamination.
 
Thank you, appreciate all the replies.

When the misfire happened it was on a fairly short run, the oil was up to temp but had not been there for long - perhaps it needs even longer before pushing that hard. Even though the oil was hot, perhaps other parts were not quite there, will definitely be more cautious in future.

There's no smell of burning oil.

I've asked them to have a good look at the cover while they change the gasket, and asked them to give me the old gasket back when it's removed (not sure I'll learn much from that but might be interesting). Already in the garage so too late to pull out!

I'm just not convinced that spilled oil could find it's way into the spark plug wells themselves - on the engine case as per in the photo, sure, but the plug wells themselves seems unlikely. Am I wrong?

I think the lesson learnt here is to look at my engine more often - at the very least after every oil change, but probably on a monthly basis. I'll check out the front around the belt when I get it back on Wednesday.

Thanks again, really helpful comments :thumbsup:
 
When spilled in that area oil will make its way down the spark plugs and also into the injector. It's the same as if the valve cover is leaking as that also usually happens between 3 and 4.

It'll seep all the way down the threads eventually.

You should be checking log data with MHD. That gives you a much better idea of how the car is performing and where the weaknesses are.
You can post the logs here or just PM and I'll tell you if anything is suspect.
 
R.E92 said:
When spilled in that area oil will make its way down the spark plugs and also into the injector. It's the same as if the valve cover is leaking as that also usually happens between 3 and 4.

It'll seep all the way down the threads eventually.

You should be checking log data with MHD. That gives you a much better idea of how the car is performing and where the weaknesses are.
You can post the logs here or just PM and I'll tell you if anything is suspect.
Click to expand...

Will do some data logging when I get it back.

So it's very possible that I am paying the Stealer £500 for them spilling some oil. :?

Is it worth checking the injectors for oil as well?
 
You can't really check the injectors as you'd have to remove them from the head to do so.

I don't think the oil will harm, the teflon injector seals hold it from going any further. It'll just leak down into the cylinder whenever they are next removed.
 
So I got the car back, drove a good few hundred miles to Cornwall and back, all seems good now. I've taken a few logs but not much to see due to not pushing it very hard yet. AFRs seem to be pretty constant.

As requested, the dealer left the old cam cover gasket in the boot for me - it looks brand new in my not-very-expert opinion, so it does seem more likely that it was a spill rather than a leak. Although, in fairness, I have topped up the oil once myself so it could have been my spillage rather than theirs!

Unfortunately after picking the car up, the headlights are now pointing directly at the floor and the windscreen washer jets aren't working. :? Hopefully I can figure those out without having to take it back in!
 
tiglon said:
So I got the car back, drove a good few hundred miles to Cornwall and back, all seems good now. I've taken a few logs but not much to see due to not pushing it very hard yet. AFRs seem to be pretty constant.

As requested, the dealer left the old cam cover gasket in the boot for me - it looks brand new in my not-very-expert opinion, so it does seem more likely that it was a spill rather than a leak. Although, in fairness, I have topped up the oil once myself so it could have been my spillage rather than theirs!

Unfortunately after picking the car up, the headlights are now pointing directly at the floor and the windscreen washer jets aren't working. :? Hopefully I can figure those out without having to take it back in!
Click to expand...
The gasket flexibility is the issue, if you bend it is should flex and not crack/crumble. I wouldnt take it back to the same garage though if you have additional snags when you get it back....
 
Yeah the gasket is still very flexible, you can scrunch it up into a ball and still doesn't crack.

Might just be a coincidence that the other bits have come up now, the headlights seem to be a fairly common occurrence.
 
Looks like it was not the gasket, trouble is, as you discovered it’s not easy to see where the leaks are coming from. Good news is that it’s one more thing ticked off.
 
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