420A Recurring Valve Cover Gasket Leaks

[BLACK'98DSM]

I've replaced the valve cover gasket 7 times, the cylinder head 2 times, and the valve cover 2 times. New grommets and tube seals each time. I follow the 2gnt guide sometimes, and sometimes I just try to think logically about what might make it seal up.

My point is, my valve cover gasket has never sealed for more than a week at a time. Everytime I think it seals up it just blows out again. I've tried so many things and I'm so tired of it. It especially sucks now that it's dumping oil all over my new engine.

For now the car will stay parked until I figure out how to seal the damn thing up. That way I only have 1 large pool of oil instead of a bunch of small ones.

Yes I have verified that the valve cover gasket is the source of the leak, it is the only leak.

At this point any recommendations or suggestions are fine by me. Let's hear what you guys do or think I should do. Thanks

 

[luv2rallye]

Could your pcv valve be clogged/stuck letting pressure to get too high?

 

[DSMPT]

Agree with @luv2rallye Sounds like you have a bad PCV valve or excessive crankcase pressure that is more than your PCV system capacity for some reason.

 

[DogWhistle]

As @luv2rallye points out, something’s amiss. A non-turbo engine can produced crankcase pressure.

On our 4G64 NA, we kept blowing the dipstick out on hard acceleration, and we were finding oil in the spark plug tubes. Even though the pvc valve was replaced a couple times within 5k miles, it never seemed to improve.

We ordered the vented oil filler cap from @Boosted Fabrication, and the problem went away.

 

[motomattx]

We just ran into this issue on a 420a, changing the bolts out to regular 6mm bolts with no step on them fixed the problem, I can see a lot of your gasket in your pictures which to me says that your cover isn't getting tight enough most likely.

 

[BLACK'98DSM]

I'm torqueing the VC bolts in three steps, ending with 8.9 foot pounds (106 inch pounds).

I replaced the PCV valve once, and I didn't really notice anything different with the car when I did.

@DogWhistle Would that not cause a vacuum leak? The vented cap I mean. Unless it's designed like a pcv to only let pressure out but not in, then it would pull air into the intake manifold.

 

[VelocitàPaola]

@DogWhistle Would that not cause a vacuum leak? The vented cap I mean. Unless it's designed like a pcv to only let pressure out but not in, then it would pull air into the intake manifold.

I'm not necessarily convinced a vented cap wold fix your problem, but it wouldn't cause any more of a leak than that little red breather filter you have. The crankcase isn't sealed, otherwise the PCV system wouldn't work.

 

[DogWhistle]

No vacuum leak. The 4G64 already has a second vent hose connected from the valve cover, into the intake snorkel.

Under average throttle driving, the vented cap essentially changes our NA PCV (Positive Crankcase Ventilation) to an open type, so if anything, the vented cap, which has a filter installed, may be allowing air IN to the crankcase to help the PCV system evacuate pressure better.

In high acceleration situations, our crankcase pressure was apparently overwhelming the PCV's capability, and blowing the oil dipstick out of its socket. So under this circumstance, the vented cap is allowing excess crankcase pressure OUT of the engine. Turbo guys would plumb the vented cap hose to a catch can.

We didn't over analyze it. We installed it, and the problem was solved.

 

[BLACK'98DSM]

I'm considering using a layer of rtv around the entire perimeter. It sounds horrible and won't look good either. But at this point I just need it to seal.

 

[1990TSIAWDTALON]

Does it puff any smoke out of the oil fill cap if you remove it when it is running?

 

[XC92]

Isn't it also important to only use an OEM PCV, as aftermarket ones supposedly fail?

 

[BLACK'98DSM]

Does it puff any smoke out of the oil fill cap if you remove it when it is running?

It absolutely does. I was actually about to come on this thread an point that out as I saw it yesterday.

 

[BLACK'98DSM]

The issue is finding a vented oil cap that is threaded for the 420a. Does anybody know who sells one? Or is that something that needs to be custom ordered?

I'm considering modifying my existing cap. I might even make an article about doing so if I succeed.

 

[1990TSIAWDTALON]

The issue here, and I am sure you realize it, is the positive pressure in the motor. SOME is always there and the PCV valve handles it but when it becomes excessive, the system is overwhelmed and can't keep up with the extra positive pressure. Somewhere, the motor is loosing pressure from the combustion chamber into the crankcase. Usual causes are rings and/or valves seals but more likely rings.
You could always run a "snot tube" and let it get rid of the excess pressure or run a catch can.
Just trying to be helpful in diagnosis!
Marty

 

[dustyboner]

I would either reinstall the line to intake pipe or install a bigger fitting for the breather filter. Minimum 10AN (1/2").


The intake manifold has a high vacuum at idle and the intake pipe has a low vacuum. so it sucks vapors from the valve cover thru the pcv valve and fresh air is sucked from the intake pipe..
at WOT the intake manifold has low vacuum but the intake pipe has a high vacuum. That means that for it to operate properly, you need the line going from the valve cover to the intake pipe connected. (a sealed catch can between the VC and the intake pipe keep your intake track doesn't get as dirty).
There isn't enough flow thru the smaller VC fitting with just a breather filter. The negative pressure in the intake pipe will cause increased flow thru the fitting if the line is connected.

 

[BLACK'98DSM]

I got a vented oil cap and the issues stopped.

 

[vmu9999]

I got a vented oil cap and the issues stopped.

Can you link to what oil cap you ended up getting? I'm having the same issues you are describing.

 

[BLACK'98DSM]

Can you link to what oil cap you ended up getting? I'm having the same issues you are describing.

Made my own. It's best to run one through a catch can.

Another thing I ended up doing was swapping over to full thread bolts. The stock ones bottom out too early and that helped a ton.

 

[vmu9999]

Made my own. It's best to run one through a catch can.

Another thing I ended up doing was swapping over to full thread bolts. The stock ones bottom out too early and that helped a ton.

That's a good idea. Thanks for the quick reply on an old thread.

 

[BLACK'98DSM]

Another thing I'd like to point out is that the Chrysler 2.4 valve covers have significantly larger breather ports than the 420a valve cover. I also swapped over to one of those.

 

[vmu9999]

Another thing I'd like to point out is that the Chrysler 2.4 valve covers have significantly larger breather ports than the 420a valve cover. I also swapped over to one of those.

I'll keep that in mind. Thanks for the advice.