thread sealant on valve cover studs?

[weaselberry]

Hey all,

I'm about to throw on some lower turbo valve covers on my "new to me" '71 911T. The original valve covers are on the engine with silicone gaskets and just about every cover stud is leaking. I'm assuming the PO slapped these big old floppy gaskets on thinking they would cure his every little leak. I have silicone bead gaskets to put on with the turbo covers this time around. I've been looking through the archives and see that quite a few people have their cover studs leaking oil. I was curious to see what people thought about putting thread sealant on these studs? I come from a "classic" motorcycle background and I use this stuff on quite a few threads that might otherwise leak oil or fuel. I've never had any issues and I don't know why it wouldn't work on these studs. Yes, I do also have new hardware to go along with the new covers and gaskets.

And yes, I'll try to post some pictures soon. Thanks all.

-wb

[defcon65]

A lot of Pelicans put a gob of RTV silicone sealant on the studs where they come through the covers before they put the nuts on to prevent these from leaking.

[David]

There's usually aluminum washers on the valve covers that should seal them.

[ChrisBennet]

If you must put some sealant on them please use something non-hardening like Dow Corning 111 or Curil-T. RTV has no place on those valve covers IMO. (Just spent a half hour last week scraping that crap off the lower valve cover studs of a Turbo that someone had put old magnesium valve covers on.)
-Chris

[azasadny]

I've used the silicone impregnated gaskets with new washers and Nylock nuts and they seal right up, no leaks!

[vash]

the gasket goes around the stud. i dont understand how a properly installed and torqued fastener will allow oil to drop down the threads of a the stud. i agree with the above. why apply something that will make it more difficult to change out the next time? cleaning gasket off of mating surfaces is on the list of "not fun".

[john walker's workshop]

just don't. what vash says.

[sammyg2]

I've asked this question before (and didn't get a direct answer) but I'll throw it out again:
If the gasket is sealing properly around the studs, how can oil get to the studs? Why do we need aluminum sealing washers unless the gasket is leaking? is it a case of the oil leaking down the threads of the stud from inside, or are the threaded holes blind holes?

BTW I do not use sealant of any kind in this area, I use the red silicon gaskets, i re-use the nylock nuts and washers and I don't have any leaks from the valve covers.

[sand_man]

I've had the valve covers off of my Turbo about 4-times now in the past two months and I've re-used the hardware including the washers with no problems (no leaks). I'm using the red silicone gaskets.

[MotoSook]

Take some 800 or 600 grit sand paper and clean the surface of the mating surfaces (on the cam housing and covers), then apply the gaskets dry with nothing on the studs/nuts. I've use just the paper and the paper with silicone bead without any leaking.

I think some of you guys are just not cleaning the surface well enough. I've worked on a lot of cars that have crud on the mating surfaces. So the owners out there or their wrenches are not taking the time and care when workign with the valve covers.

Remember, the valve cover nuts only see about 8 ft-lbs of torque. No way would I rely on them to seal with or without aluminum crush washers. I've reused washers and nuts in a pinch and it's not a problem.

One wouldn't expect to get a good seal on poor surfaces...right?

[Early_S_Man]

wb,

Are the silicone gaskets red? If so they are WeltmeisterŪ Valve Cover Gaskets or Real Gaskets, Corp. silicone from their inventors ... then the gaskets are reusable, unless damaged!

One reason for these cases where multiple studs are leaking ... is that the Nyloc nuts and aluminum sealing washers were reused in an attempt to save money! A new sealing washer and Nyloc nut very, very seldom leaks! The 'freshness' of the Nylon ring inset on the nut, i.e., how many times it has been run down the stud and torqued -- is directly related to its sealing capability in this application!

I have seen Nyloc nuts which were leaking that could be removed with fingers after the initial loosening torque was applied with a wrench! That condition was clearly a case where the 'loc' function of the Nyloc nut had been lost due to multiple reuses, and the sealing function of the Nylon insert was gone as well! The damage to the Nylon insert is also related to the amount of rust on the few threads of the stud that are exposed to the elements after the Nyloc nut is torqued in place! My suggestion is to wire brush the exposed threads before loosening the nuts, and again after removing the valve covers. Degrease ther studs with Brakleen before using heavy-duty rubbing compound on the studs to polish the threads -- use Naval Jelly if wire-brushing didn't remove all rust. If any studs have nicks or mal-formed threads that cause resistance when running a conventional hex nut up and down ... replace the stud!

If you ALWAYS use new nuts and washers on all 22 clean, shiny studs for the exhaust valve covers ... you are much less likely to encounter leaks in the future!

Another cause for the leaks is as Souk points out -- lack of thorough cleaning of the mating surfaces, or warped valve covers. Wet sanding the valve covers on a thick plate glass surface can return them to flat.

The Porsche spec for the latest graphited gaskets is 8 Nm or ~6 lb-ft [96 lb-in] and the Real Gaskets, Corp. spec is 48 lb-in. It takes a 1/4" drive torque wrench to accurately measure these values! You can use the four-finger weak hand technique on a 13 mm combination wrench to approximate the 6 lb-in value and not be in danger of over-torquing the nuts.