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My mechanic says the alloy in my valve covers is becoming porous as a result of degradation (age & heat, I suppose). He says this is making the threads brittle and is the reason that a new seal kit didn't fix the oil leaks (he did that job successfully about 5 years ago, but the recent redo was an expensive disappointment). He thinks I should try to get some aftermarket replacements.

Is this a common problem? Are there any options out there?
 

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Older than old school
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Threads brittle? The 540's valve covers have no threads. They have cap nuts with washers and grommets sandwiched between their flange and the covers. The valve covers will degrade and bubble with time, making them look ugly, because they're made of highly reactive magnesium, but that doesn't make them leak. Where is the oil leaking from, i.e. front? back? both valve covers? around the cap bolts? New gaskets, properly installed and with sealant at the half-moons in back, should end any gasket leaks, and new grommets will take care of leaks around the caps

One concern, however--he may have over-torqued the cap nuts and stripped the threads in the camshaft bearing cap studs that the the nuts screw onto, making it impossible to compress the gaskets enough to be oil tight..
 

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Wingnut
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+1 to bobdmac post..he knows his stuff on the 540 engine
 

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Methinks the porosity allows the coating (paint, powder coating) to be lifted by oil seeping out over the years. I had to redo the powder coating after many years.

BTW, this is a good example of German overthinking. Aluminum (as in earlier BMW engines) would have been much more practical, but somewhat heavier.
 

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Make sure to torque the valve cover bolts...that sounds like overdoing it but most people do NOT know what 11 nm feels like...most overtorque and they end up leaking 6 months or so later instead of last 5-7 years


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I have new leaks coming down from sides and back from a high location i assume to be from the VCG's. But I've felt around the vcg"s and their dry. What other oil gaskets are below the VCG's. ?? The leaks appear to be above the upper oil pan gasket. The diaphragm on the back is dry too but see oil puddles next to the manifold
Any help would be greatly appreciated
 

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The alloy is porous, but not enough to leak oil. It is enough to lift any coating, including paint and powder coat.

The earlier six cylinder engines had similar alloy valve covers. They look bad with age, but on the plus side they don't slowly warp and crack as the plastic valve covers do. If you bake the oil out first you can get conventional paint to stick for 5 years or so. Just resign yourself to painting and changing the gasket twice a decade.

For any type of valve cover it's important to follow the recommended procedure and torque closely *every time*. The gasket will not seal otherwise. Screwing it up one time may bend or crack the cover, or strip threads, and you'll never get a gasket to seal well in the future.
 

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Also possible that a poorly-designed gasket set was last used. The set must contain new donuts for the studs. Victor sets are preferred.

The acorn nuts are designed to bottom out on the cylinder head surface, and do not need excessive torque.
 
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