crankcase vapors causing valve cover leak?

If there is a lot of blowby or the PCV system isn't working properly, it's possible there could be a buildup of pressure behind the VC gasket... check the PCV it is easy to do, might be your issue...

nate

If you are not getting oil up into your air cleaner then blowby is not the problem there. If it's like my 83" the heads are not machined at the VC seal area. They are rough cast. Sealing is a constant problem on the low side. The covers must be straight so when you have them off you need to check and correct them. Also, I made extra wide spreaders to go under the bolts so as to spread the force over a greater area of the cover and prevent deformation. Less wide after market spreaders are sold everywhere. Although I change my oil constantly and the inside of the covers and head have no buildup, I ran a wire down the oil return holes to be sure they were open. I believe the rear ones on mine were not completely open when I cleaned them out. Clean returns cause less oil to buildup in the cover. Don't over tighten. Leave some room to come back and snug up later.

Thanks for both replies so far.

I'd better mention now that the crankcase breather filter inside the air cleaner is rather well-soaked with oil. Also I am getting some smoke in the exhaust.

You just need to put the gasket on differently. Our Jeeps are notorious for cover leaks. Mine only has two small nuts in the center holding a plastic valve cover on, no rim bolts at all and I have no leaks.

The trick is to have the surface spotlessly clean, a fingerprint will cause a leak and then put a skim of RTV on both sides with a cork gasket between them. Then you have to wait the 24 hours needed (read the directions for the time) for the RTV to properly cure.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Matt wrote:

I've read that if pressure is building up under the valve cover you should be able to feel it by removing the PCV valve or oil filler cap while the engine is idling and pressing a hand over it. It would also increase with idle speed.

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What helps when the cork gasket is prone to leaking? Hylomar or Permatex II? Soaking the gasket overnight so engine heat will turn the moisture into steam and expand the gasket?

Then how do you do it?

Okay, maybe I just did a poor job of sealing the valve covers. I used cork gaskets and silicone sealer on both sides of the gaskets. I am using those wider-than-stock clamps. The sealing surfaces on the heads are pretty rough. It could be that the lips of the rocker covers are a little deformed. I'm wondering whether I can expect success if I redo it using different techniques or materials. I'm thinking I should use synthetic gaskets. Please advise.

One thing that I've seen is that the drain holes in the top of the head get sludged up, which can leave deep oil under the rocker arm cover. That was on the old straight-6, but I imagine the same would apply on a V.

George

I had an oil leak at the valve cover due to a leaky mechanical gas pump. I figure the gas disolved something; replaced the gas pump but the oil leak remained. Eventually replaced the valve cover gasket.

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My plastic cover hasn't leaked a drop since it was installed in 2000.

It must be clean or it won't work.

Mike

Bob wrote:

Those synthetic gaskets are total crap. I tried one of them and followed the directions. It didn't last a half hour.

The 'clean' cover and head edge job I did on my plastic cover in 2000 hasn't leaked a drop.

The big trick is to have the surfaces perfectly clean and to let the RTV cure. One fingerprint or oil drip and it won't hold. I recommend acetone or brake cleaner spray and you must wait for it to cure like the directions say.

I had one shop say 'naw, you don't have to wait for the RTV to cure on a differential cover, we are 'professionals', we know better'.

Well, that diff cover is the only damn leak on my Jeep!

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Cork gaskets generally leak because either they are old and brittle, they have slipped out of place or they have split. Since RTV is so slippery until it sets up it often causes the gasket to slip or split on installation. Cork gaskets are outdated and I can't hardly remember the last time I installed one, but copper coat, high tack or something similar was used on one side and the other was clean and dry. Bob

No wonder you have troubles sealing up gaskets!

You obviously don't have the proper tools to do inch pound or very light foot pound torque settings if you are splitting gaskets and bending valve covers like you mentioned here and in another post.

RTV has also evolved over the years and today's 'sensor safe' product is actually quite tacky. Totally unlike the old smelly silicone sealer that used to be used.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

I'll second what George said. The old Ford Y block V8s were notorious for this. When you pull the valve cover, check the drain holes. FWIW YMMV

Did you read the part where I said "once upon a time"? I went through a learning curve just like everyone else. I've made a good living for over 20 years doing auto repair and have had my own shop for the last 9.

I never said anything about bending valve covers, but now that you mention it I've seen plenty of cases where some tard like you goobered a gasket up with RTV, tightened it down until the cover was bent, the gasket squeezed out and then they can't figure out why it leaks worse then ever.

Gee Mikey, thanks for the tip.... Now don't you have a loose ground strap to tighten?

Glad I don't have to drive junk like that..... Bob