rocker cover gasket leak

[isisalar]

I have twice replaced the rocker cover gasket on my wife's car , a 106 1.4 diesel L reg,(lets call it a Saxo) and it's still leaking!
The original gasket had had silicone sealer applied previously, which I carefully removed, before fitting the new gasket, and applying some non silicone sealer, then tightening the bolts in the correct manner(as far as I know).
When it started leaking again, I figured that it was the original silicone residue stopping the sealer sticking, so used some motor factor bought silicone sealer, and fitted another new gasket.
STILL LEAKING!
Have I been misled by the original application of silicone, should it have any sealer at all?
Advice needed please.
Thanks.

[Peter.N.]

I don't think the proper gasket needs extra silicone but you can make a gasket from ordinary silicon sealant, throughly clean the surface of the rocker cover then apply a bead of sealant over the appropriate area and leave overnight to set, any areas with an excess will be squeezed out leaving a nicely fitting gasket.

Peter

[Gibbo2286]

I'm not familiar with the 106/Saxo engines but most PSA engines are designed to run with negative pressure in the crankcase, this is achieved by suction from the inlet manifold through the breather pipes and valve, if these are faulty, split or blocked pressure builds up and will blow oil out of the point of least resistance, usually the rocker cover gasket or camshaft crankshaft oil seals.

[isisalar]

Could I test for this pressure build up with my hand over the oil filling hole in the cover?

[Peter.N.]

Yes.

[Gibbo2286]

Failure of this valve or leaks, blockages in the pipes to it will cause the problem

[CitroJim]

It's also possible that some ham-fisted mechanic in the past has over-tightened the cam cover in the past and warped it. It's only a thin pressing and easy to do on a TU. Also, bizarrely, that rust and it may have a small pinhole or three in it...