sealing a rocker cover - silicon, hylomar or something esle?

andrewj

Member
Hi Everyone,

Wonder if I could get some advice...I have overhead cam engine that is leaking profusely from the rocker covers (not a citroen - hope that's ok ;))

The oil appears to be coming from the joint along the rocker cover where the two gaskets meet (or probably don't quite meet). The photo below shows the top of the rocker cover, and naturally, the leak is on the opposite side underneath.

rocker cover s.jpg


So what to do? The gaskets seems in good order, so likely a waste of time and money sourcing new ones (which are not cheap!) So do I try a skim of silicon, or pehaps hylomar? And do I need to worry about being able to remove what ever I use from the head at a later date if necessary?

Cheers,
Andrew
 

N5GTi6

1000+ Posts
I'm intrigued - why the white ?

Ive been thinking of using Threebond No 1 on the Megane rocker cover bolts as the grey would hide amongst the alloy.

Cheers

Justin
 

schlitzaugen

1000+ Posts
You've got to be really anal when installing gaskets that meet in corners or things like that. Renaults are full of them and most of the time leak because of poor installation. Usually you get some installation guide with the gaskets if that is the case (meeting other gaskets, corners, bumps, etc). Sometimes you have to stretch the gasket by following a certain bolt tightening sequence to "squeeze" it along into the corner and make sure it seals. Rocker covers like yours are probably not that rigid and no matter how much you torque the bolts the cover might distort and lift at the corners. You might actually do more harm if you tighten too much. There's also situations when two or more cast parts meet and if they're not machined together and pinned (located somehow) they aren't flush and the result is an oily mess if you don't know how to install them.

Threebond is my choice as well, but make sure everything else is in good order (mating faces, distortion, etc) and don't overtighten the bolts.
 

andrewj

Member
You've got to be really anal when installing gaskets that meet in corners or things like that. Renaults are full of them and most of the time leak because of poor installation. Usually you get some installation guide with the gaskets if that is the case (meeting other gaskets, corners, bumps, etc). Sometimes you have to stretch the gasket by following a certain bolt tightening sequence to "squeeze" it along into the corner and make sure it seals. Rocker covers like yours are probably not that rigid and no matter how much you torque the bolts the cover might distort and lift at the corners. You might actually do more harm if you tighten too much. There's also situations when two or more cast parts meet and if they're not machined together and pinned (located somehow) they aren't flush and the result is an oily mess if you don't know how to install them.

Threebond is my choice as well, but make sure everything else is in good order (mating faces, distortion, etc) and don't overtighten the bolts.
Hi Schlitzaugen,

Really appreciate the advice. This my first experience with a complex aluminum engine, so I am going very slowly and carefully - prior to this I was only playing with cx/gs/2cv - all very basic. So this is super helpful.

When I check the rocker covers for straightness, would you think an engineers ruler and a feeler guage be sufficiently accurate, or should I find a more precise method?

Cheers,
Andrew
 

schlitzaugen

1000+ Posts
If possible at all to see all the way around the mating contact I would just place (no fixings) the cover where it goes (without gasket) and look around the join. Does it look like it has gaps? How does it fit at difficult points? Can you rock it around if you press gently at various points? This might hint you what to do, how to approach this. If you gently press on it at the points where the fixings go, what changes? Does it still have gaps?

No point in making sure it is flat as a surface plate if the mating face isn't. If the test above reveals some problem you can think about it then.

I did make this mistake once and straightened the mating faces of a cast Aluminium sump only to discover the block it was going on wasn't straight at all.

Looking at the picture above, can you bias the cover fixings to push the cover against that edge when bolted down?
 
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andrewj

Member
Hi Schlitzaugen,

Will try all this when some new gaskets arrive (coming from uk). I should be able to see the bottom side with a mirror and torch - hopefully I can get in there without removing the carbies.

Good point regarding the fixing on the front cover plate - most of the oil is coming from the bottom front corner, So while I am waiting for the new gasket, will try backing these off and retightening with some gentle pressure on the bottom side of the rocker cover.

Cheers,
Andrew
 
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