4.0 ohv valve covers...

[racsan]

my '93 4.0 has the leaking valve cover issue once again, about 7 years ago i put on new gaskets when i changed out a bad fuel-rail gasket, noticed the drivers side valve cover was a little bad with rust then, now that its leaking again im sure the valve cover itself needs replaced. is there a aftermarket or factory alloy cover available? sure its a 20-year old truck, with 160,000 miles, but it still runs good, just leaking worse and id like to cure this issue for good.

 

[RonD]

Sure, there are quite a few replacement valve covers for the 4.0l, fancy and plain, but stock are fine if flat and not rusted,
You do have the coil bracket to deal with but it can be raised.

Valve cover oil leaks are gravity leaks, but can be started by blow-by pressure.
Blow-by is the pressure pushed into the crankcase/valve cover area each time a cylinder fires, this is normal on all engines, but as the miles go up the rings wear down and blow-by increases.
There are two things on the engine that vent blow-by pressure, the PCV Valve and the Vent hose, both need to be clean and working to keep pressure in valve cover area low to prevent leaks from starting.

Valve covers and gaskets:
Stamped steel valve covers(like the stock ones) seal best with cork gaskets, the cork absorbs some oil and swells to seal better, down side is that over the years the cork near the exhaust manifold(the side that leaks) will dry out and harden, so seal can fail after a few years, thicker cork gaskets last longer, but longer bolts are usually needed.

If using after market cast valve covers rubber or silicone gaskets are better to use, these are often used because valve covers can be remove and reinstalled without new gaskets needed, cork can break if valve covers are removed often, so the cast covers and rubber gaskets are the choice for people that like to adjust valves....alot, lol.
The cast covers also look very nice on an engine.


With either choice obviously both the head and valve cover need to be clean and flat, warped valve covers will not seal well.
Follow the pattern for tightening and do NOT over tighten, too much torque can warp and bulge gaskets.

 

[4.0B2]

I've had A LOT better luck with the Permatex rubber gaskets... with metal inserts in the hole. I'll never buy cork again for those.

 

[RonD]

Yup, some don't like cork, I have never had an issue that was cork related so still use it on stamped metal valve covers.
But there is certainly merit in using non-cork gaskets.
All things being equal they will certainly last longer than thin cork gaskets.

 

[4.0B2]

my 2.9 and 4.0 hates the cork ones...

 

[RonD]

My current 4.0l is cork and no leaks, my past 2.9l leaked "like a Ranger" when I got it.
I replaced the valve cover gaskets, with cork, and no issue for the years I had it.

I don't use any sealer, just put some oil around the head where gasket will sit, so hopefully if I need to remove the valve cover it will come off intact.
Just been lucky I guess.

 

[4.0B2]

Some folks are lucky lol
I don't use sealant on dry gaskets either, just they always leaked for me

 

[racsan]

the gaskets i used the last time i had the valve covers off were the rubber/neoprene ones with the metal inserts where the bolts go through, awesome design! i really only notice the leak when the engine is shut off, then i smell the oil and see the oil vapor "smoke" coming out of the seam between the hood/ right front fender. i was under the truck the other night and the left side of the block was pretty wet with oil, its not that its leaking a great deal, but it is noticeable. seems to just be the drivers side cover thats leaking...weird!

 

[bonedoc]

I just did these on my '93 4.0L. While I was at it I did the upper & lower intake and fuel rail gasket. I used the Felpro gasket kit. I also replaced my valve covers with new ones as my originals were rusted and leaked like a sieve. I bought them off of Ebay, spent about $100.00 for both valve covers and about $80.00 for the complete gasket kit. Just had to buy the fuel injector O-rings.
The felpro valve cover gasket is a rubber and plastic design and it has a built in "step" to accommodate the slight lip where the lower intake meets the cylinder heads at the front and back of the motor.
Worked perfect and no more leaks.