So, when I bought my 97 s420 the first thing I did was check/replace all the cam oilers. Which means removing the valve covers. I replaced with new ones, and torqued to the appropriate torque. But now they leak, I've since then replaced them twice, being sure to install properly, and even "upgrading" to name brand gaskets (I've used the Reinz ones most recently). Still leaking. So, anyone have any thoughts? should I use some gasket seal?

My car is a W123 diesel but ....

I too have also had problems sealing my vc gasket when using aftermarket gaskets including Victor Reinz. Last valve adjustment, I splurged for an MB OE gasket. Leak easily gone and I'm not looking back from now on. Cost is about twice that of a Reinz but still at around $20 it is a bargain to keep your engine clean.

I used to use a coating of assembly grease to hold the gasket in place while refitting the cover. The MB OE gasket fits tightly on the cover thus not needing any sort of assembly aid. I have never used a gasket sealing compound and don't believe in them. The surfaces, particularly on a Benz should be machined well enough to not need any help.

I guess you know to not overtorque the hold-down fasteners?

Yeah, I'm pretty careful with the torque, since everything is aluminum on this engine. I'll give the OE gaskets a chance...I avoid them because I hate spending extra $ on a name (and the Reinz ones should be fine.

Please let us know if this works. Feedback is important.

Sorry I've been MIA

I actually discovered that the non-Mercedes brand oil fill cap was part of the problem. I replaced that and the breather hose (from the passenger side valve cover to the throttle body - which was also non-mercedes brand) and it seems to have cleared up most of the oil. I'm still not convinced I have it all solved - it will take some driving around and observation - but I think that did it. I probably will still replace the valve cover gaskets - just because I have them. But - lesson learned. Mercedes branded is superior ( in this case at least).

Adam

Well, for those of you keeping score.
The new valve cover gasket is on (MB genuine) we will see if that makes a difference.

It likely won't, I found a divot under one of the valve cover bolts, it MIGHT be small enough to be sealed by the copper washer - but I don't think so. Probably needs a new VCover.

But that would explain why this has been an ongoing issue.