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Unread 04-13-2008, 06:06 PM   #1
kaz1961
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4.2 valve cover leak opinions needed

I search the topic and read through dozens of threads regarding a leaky 4.2 valve cover. My gasket was replaced at a shop by the PO (they charged him $249)! It started leaking a couple of months later and he brought it back to the shop that installed it and they redid it. Well, sure enough it is leaking again. They used a cork gasket with some kind of RTV sealant which some threads say is a no-no and I'm betting they overtightened it to make sure it didnt leak again. At this point I am not sure if I should just try a new gasket (maybe a felpro) or if I should replace the valve cover with a new one. What do you guys think? Is it likely that the cover is warped since it has gone through 3 gaskets in less than a year?

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Unread 04-13-2008, 06:28 PM   #2
sam.b.
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my gasket leaked like that at the back of hte engine so i had to put some washers on the bolts to make them shorter so i could tighten down a bit more and i havent had the need for any silicone
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Unread 04-13-2008, 09:35 PM   #3
pat8942
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I replaced mine about 4 months ago with a Felpro and torqued it to specs and not a hint of a leak.
You have to torque the bolts a few times in sequence as the gasket compresses but if you do it right it won't leak.
You don't need any RTV Either.
Don't over tighten as that will either crack or warp the cover.
Quote:
Originally Posted by kaz1961 View Post
I search the topic and read through dozens of threads regarding a leaky 4.2 valve cover. My gasket was replaced at a shop by the PO (they charged him $249)! It started leaking a couple of months later and he brought it back to the shop that installed it and they redid it. Well, sure enough it is leaking again. They used a cork gasket with some kind of RTV sealant which some threads say is a no-no and I'm betting they overtightened it to make sure it didnt leak again. At this point I am not sure if I should just try a new gasket (maybe a felpro) or if I should replace the valve cover with a new one. What do you guys think? Is it likely that the cover is warped since it has gone through 3 gaskets in less than a year?
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Unread 04-13-2008, 09:46 PM   #4
Douglas S.
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If you do end up taking it off, check it on a flat surface to be sure it isn't warped, then reinstall it.
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Unread 04-13-2008, 11:11 PM   #5
goatboy
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One of the old fashioned way of sealing valve cover/oil pan/timing cover/diff etc gaskets is to use yellow death (3M yellow weatherstrip adhesive) on the cover side of the gasket, and #2 Permatex non-hardening on the other side...I still use this method and rarely, if ever, have a leak...I NEVER use RTV or any other silicone with the exception of where it's recommended in the corners...
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Unread 04-14-2008, 12:13 AM   #6
xxxflhrci
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IMO, RTV or silicone is nothing but a mess later on down the road when you need to do it again.

I always use a cork gasket with Permatex Form-A-Gasket 2 on both sides and never have problems getting a good seal.

http://www.shopwiki.com/detail/d=per...pToFirst=true/
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Unread 04-14-2008, 05:21 AM   #7
levergun
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Just remember- if ya fix one leak it's just gonna leak somewhere else. It's a Jeep.
On my 89 YJ I have replaced every single gasket and seal on the engine- and it still oozes out. The joy of having worn rings. The first thing I would do is check the PCV system. It is often the cause of most new gaskets leaking. If it allows pressure to build up it will force oil out everywhere. On my jeep the vacuum line itself- not the valve- was clogged. Pull the valve off with the engine running. It should die almost instantly. If not that means the lines clogged and it needs to be replaced. I personally prefer the Rubber gaskets over cork but that's just personal preference.
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Unread 04-14-2008, 12:51 PM   #8
goatboy
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Quote:
Originally Posted by xxxflhrci View Post
IMO, RTV or silicone is nothing but a mess later on down the road when you need to do it again.

I always use a cork gasket with Permatex Form-A-Gasket 2 on both sides and never have problems getting a good seal.
Exactly so...the reason for the yellow death on one side is that theoretically, you can pull the cover off and reuse the gasket...can't say that I ever have to do that much, normally, in my experience, once I've replaced that gasket, I personally never have to worry about it again...either it seals like it should, or the vehicle goes down the road before I have to think about replacing it.
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Unread 04-14-2008, 01:35 PM   #9
pat8942
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I guess I'm doing something wrong because mine doesn't leak anywhere and I never use RTV,Permatex or Gorilla Snot (Yellow Death).
It can sit for a week and no oil under it.
I guess if yours leaks the it's a Jeep excuse is as good as any.
I have a 74 VW and no leaks on that either.
Quote:
Originally Posted by levergun View Post
Just remember- if ya fix one leak it's just gonna leak somewhere else. It's a Jeep.
On my 89 YJ I have replaced every single gasket and seal on the engine- and it still oozes out. The joy of having worn rings. The first thing I would do is check the PCV system. It is often the cause of most new gaskets leaking. If it allows pressure to build up it will force oil out everywhere. On my jeep the vacuum line itself- not the valve- was clogged. Pull the valve off with the engine running. It should die almost instantly. If not that means the lines clogged and it needs to be replaced. I personally prefer the Rubber gaskets over cork but that's just personal preference.
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Unread 04-14-2008, 05:06 PM   #10
ctm
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also you can get a really good gasket at NAPA that has a metal strip sandwiched by cork, sorry I don't have the part number handy.
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Unread 04-14-2008, 05:10 PM   #11
levergun
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Quote:
Originally Posted by pat8942 View Post
I guess I'm doing something wrong because mine doesn't leak anywhere and I never use RTV,Permatex or Gorilla Snot (Yellow Death).
It can sit for a week and no oil under it.
I guess if yours leaks the it's a Jeep excuse is as good as any.
I have a 74 VW and no leaks on that either.
If you read the whole post.... Mine doesn't leak any more now that I fixed the PCV valve. The first comment was a joke.
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Unread 04-14-2008, 06:45 PM   #12
pat8942
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Sorry about that, but I read the whole post and you never said you fixed it.
Anyway glad you're leak free
Quote:
Originally Posted by levergun View Post
If you read the whole post.... Mine doesn't leak any more now that I fixed the PCV valve. The first comment was a joke.
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Unread 04-14-2008, 06:54 PM   #13
goatboy
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Quote:
Originally Posted by pat8942 View Post
I guess I'm doing something wrong because mine doesn't leak anywhere and I never use RTV,Permatex or Gorilla Snot (Yellow Death).
It can sit for a week and no oil under it.
I guess if yours leaks the it's a Jeep excuse is as good as any.
I have a 74 VW and no leaks on that either.
Excellent! There's a lot to be said about meticulous surface cleaning and preparation...
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Unread 05-31-2013, 07:31 AM   #14
kbucket
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Fel-pro tech note mentions 4.2L specifically and developed a gasket just for that

http://aftermarket.federalmogul.com/...et%20Facts.pdf

Look just below tech tip. It is the worst leaker ever and AMC tried foru time to fix it and failed. Fel=pro developed Sponge Lam just for this engine.

I'm giving it a shot. The Sponge-lam trademark was released several years ago and this gasket is not on their website. I did find one at NAPA and their computer has it listed as Sponge-Lam type. The Perma-Dry Plus is not offered for the 4.2 which originally came with Plastic Valve Cover (Vin J) but is offered for VIN C, which has several more stud holes.

The Sponge lam gasket I got look like it had been on the shelf for a while and had some curling, so we did permatec 2 non-drying on the bottom and 3m yellow weather strip adhesive on top.

Hope it works, noting has so far, including, cork, rubber, RTV, right stuff. One issue I see is the engine tilt front to rear has oil pooling up on the rear of the cover, basically an oil dam.

We have been meticulous cleaners on each attempt. As Fel-pro say, this engines "defies" solution.
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