Oil leak at valve cover/timing cover

dang

dang

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My M30B35 (3.5L out of a '92 5-series) has a new or re-manufactured head (DOT-R) on it and I'm getting an oil leak between where the head and upper timing cover meet (under the valve cover). They're slightly different in height with the timing cover being lower than the head, so I was wondering what others have done to seal up this gap. The bottom of the timing cover uses the gasket that's part of the head gasket so whatever I do has to be done at the top. RTV? Something else? It's a fairly substantial leak.

Dan
 
The right stuff...

85224_1.jpg
 
Dirko or Hylomar per the manual. Usually in the corners where the cover meets the gasket and head
 
This is a tough one to seal. Sounds like the head was milled and the timing cover was not. Like Steve said, try it.
 
m5bb said:
This is a tough one to seal. Sounds like the head was milled and the timing cover was not. Like Steve said, try it.
Click to expand...
It's actually the opposite. New head so it's taller than the cover, but same issue in the end. It's not that bad but still leaks. I always try to avoid using sealer on valve covers but I'll try it and see how it goes.
 
I missed the part about it being the valve cover side, I guess still try the sealant and see if it works
 
Hi Dan, is the height difference at the bottom of the upper timing cover, i.e. by the chain tensioner, or at the top, by the valve cover?
If the height difference is at the bottom, I'd try cutting an additional gasket from gasket paper, to sit on top of the cyl head gasket, to fill the gap. It's recommended to use a dab of gasket sealant (hylomar or similar) where the head meets the block meets the upper and lower timing covers. I had an oil leak by the tensioner but fixed it by loosening the bolts on the lower timing cover, smearing a bit of hylomar in the area (using a feeler gauge to get it in between the lower cover and the block) and then buttoning up the lower and upper covers. Remove the oil from the tensioner oil reservoir pocket whilst doing this, but remember to refill it again once the upper cover is fitted.
For a height difference at the top of the upper timing cover, you could skim the top of the head perhaps? Or just use a thickness of auto silicon sealant
 
I don't believe Hylomar is a good one to seal a gap like this. As Mike suggested, The Right Stuff, or my fave, Loctite 598 in the pressurized can. 598 is a very tough RTV, spec'd to fill up to a .5mm gap. The Right Stuff is incredibly tough but a royal b***h to remove. That's how good it is, it tenaciously adheres. I once used it on an oil pan and needed tremendous effort with crow bars to remove it.
 
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