My CJ keeps blowing valve covers...

T

Tombredone

New member
I have a '82 CJ 5, 6 cycl with a weber carb. Even before I put the new carb on, I keep blowing the seal under the valve cover. Two shops have resealed it, with and without gaskets. The most recent type at the shop to do this, it held for a day then started leaking on the drivers side. As I was checking out the leaking, I noticed 4 small hair line cracks in the valve cover itself, about midway up, and they were space across the length of the cover. This is a brand new valve cover. I have replace the pvc about a month ago. What is happening and how do I fix it,, To much compression? Pull the pvc and put a filter cap? HHHeeelllpppp

Thanks
thomas
 

9/11

Does it have a plastic valve cover on it? You might want to try an aluminum cover as it might help keep the cover from cracking. As for blowing the gasket, I'll let someone else take that one. I've been told, those engines are prone to leak under the valve cover.... I'm not saying it's right, I've just heard it's not unusual.
 
If it has a excessive amount of pressure in the crankacase, it has to go somewhere. There has to be someway, to release the pressure, with the throttle both open (scavenger) and with the throttle closed (PVC).
One test, that works for me, is to take the oil cap off, hold my palm over the hole (warm not hot motor) and blip the throttle, if it blows my hand off the hole, it´s either excessive blowby or something is plugged up.
Seriously clean both sides, of the sealing surface (with solvent/brake cleaner), use a rubber gasket, put it down with gasket cement (special contact glue). Don´t over tighten the hardware. If you have to remove it again, it´s gonna be a pain, to clean it up, just about got to scratch and scrape the left over cement off.
Cracks in the valve cover can be repaired, with Loctite, two part epoxy metal mender. Never known it to fail, if the material to be glued, was cleaned with solvent (brake cleaner), and roughed up some (sanding/steelwool).
When one or the other of my crankcase ventilators, gets plugged up, oil often comes out the crankshaft seals.
 
I have noticed that after installing valve covers, even when you torque to the specs. It still took a drive around the neighborhood and getting the engine up to opertating temp to see problems. Every time I just re-torque and i have never had a problem. In terms of gaskets. I had a ton of trouble with $15 rubber gaskets. I went back to the $5 cork ones from NAPA and was set.
 

Most of the trouble with the rubber ones, is they slip. In most normal applications, I´ll throw away the rubber and use the cork. If I´m gonna glue it down, I use the rubber, because you can cut it with a box knife, even when it gets older, to help remove whatever piece you glued together (somewhat easier to get back apart again). Cork, gets pretty darned hard.
In most cases I prefer the cork also (without glue).
 
I've had a lot of Jeeps over the years with the in-line 6 in them... they all leaked at the valve cover...

Actually if ya retorque all the bolts after it warms up you should be good to go. Use a loc-tite too if ya want but only blue not red (hard enough to loosen the blue stuff, the red is damn near permanant).

Only thing about your solvent cleaning... that stuff is a might touchy around heat and sparks. So start with a cool engine (obviously) and give the stuff a chance to evaporate/dry/wipe it off before ya go for a ride when you're done.

A buddy of mine torched a Bronco (ah well, no great loss it was a Ford) that way. I've never had any problems though by letting the stuff dry and such.

Good luck,

Greywolf
 
I usually clean the block and cover, sealing surfaces, with an old T-shirt and slovent, a little solvent a little rubbing, a little solvent etc. Some cork gaskets have coatings that help with the seal. When the T-shirt comes up clean, you´re probably clean enough. Paper towels also work, but sometimes come apart.
Retorqueing is a good idea, but don´t be a muscle brain, like I´ve done in the past. Over tightening and crush, break the gasket nad/or push it out the side.
 

Are you using a crankcase breather/hose(the hole in your valve cover closest to the fire wall)? If not pressure will build up and cause problems/leaks.
 
New issue with the valve cover. I removed it yesterday and looked in the inside where the cracks were on the outside, and noticed rub marks all the way down from one end to the other. The lifters are apparently rubbing on that side, creating the cracks and problay lifting that side up a tad and breaking or loosing any weak spot seals... this is the first I have notice this,, what can I do about it if anything...
thanks
thomas
 

?????????????? are your rocker arms too big?? did someone possibly put aftermarket arms on there that don't belong? is your valve cover even the right cover?
 
The engine is not the orginial one. It is a '82 on paper but the valve cover that fits it, or so I thought fit it, is from a '79. Someone told me that the engine was a ford engine, how do I tell or find out?
 
ford engine? i know that ford did make a straight 6... but it was a 300 ci.. not a 258... is it possible that the cover design was changed during those years?
 

great day in ARKANSAS

I don't even know if it is a 258 or a 300 how do I tell?
 
if your distributor is on the driver side, it is the 300 (4.9L)... if it is on the passenger side, you have the 258 (4.2L)
 

This is a very good post for me as my 79 gasket is leaking as well. I was going to go in there and replace it but I think I will wait till you get yours fixed befor I even try. Please keep me posted as you fix it. tug
 
i'd say to get that gasket replaced... but when you do it, make sure you replace ALL pcv fittings and lines... and it is important to clean the valve cover as well... one thing you might want to check are your oil return holes... when the cover is off... pour some oil over the rockers and see if it drains down through the head... if not, you might have some plugged holes, and that can cause pressure to back up... if the holes are clogged, run a pipe cleaner down them really good... then treat your engine with some Sea Foam
 
Wacky Wipers!?!

Ok,,, Several days later but here is what I found. I took the head number to a shop, and they said "oh, this is the one you need" refering to valve covers. It looked just like the old ones. Took it home, put it on and my valve springs still rubbed on the side of the cover pulling it slightly loose from the seal. So I took a ballpeen hammer and from the inside of the valve cover, hammered out all the places that I could see rub marks on the valve cover from the springs hitting, glued the cover back on and no more leaks... what a deal.. if you cant find the right one, make the one you have work...
 

I had the exact same problem with the valve cover rubbing the rocker gear. I bought one of those aftermarket chrome ones for about 40 bucks because mine was leaking and bent up from who knows what. The chrome was the cheapest I found and it might even look good. The darn thing wouldn't even seat all the way around, much less rub. My engine is a reman '79 258. What was suggested to me at the time was that I had non-stock rocker gear in there that was too big for the aftermarket cover but fit under the stock one for some reason. I was told that the reman shops mix and match parts sometimes as long as it works. I thought about bending it like you did, but I just returned it. The guy I bought it from said he had sold alot of them and never heard of an issue. I found an old used one that was in good shape and put it on. Worked just fine, and my rubber gasket hasn't leaked yet.
 
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