258 Valve Cover, holes on top? - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 08-13-2001, 10:52 AM   #1 (permalink)
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Post 258 Valve Cover, holes on top?

Can the vent holes on top of the valve cover be sealed or closed? How necessary are they? They leak a lot of oil and I can't seem to get a good seal with the hoses. Anybody know any cool tricks that might help keep the engine clean?
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Old 08-13-2001, 10:57 AM   #2 (permalink)
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How old is the engine? Better yet, how old are all the gromets and rubber fittings that come out of the holes in the VC? If they're pretty old, you might try replacing them with newer ones...when I did, the leaking pretty much stopped. I had a bad leak from the oil fill cap that i remidied by replacing the gasket on it and then winding some twine between the new rubber gasket and the bottom of the top side of the cap (if that description doesn't make any sense and you want it to, tell me and I'll find a picture..). You can maybe try that, but I would say things like the PCV Valves are important (but don't know for sure)..
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Old 08-13-2001, 11:03 AM   #3 (permalink)
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DO NOT plug them off. You'll have even worse leaking in worse areas. The holes releave crank case pressure. Simply replace the rubber gromets and go.
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Old 08-13-2001, 12:08 PM   #4 (permalink)
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Mine are part of the AMC undercoating system.
This apparently was a dealer installed option on the 258's.
The tub is in fine shape under all that oil. <IMG SRC="smilies/biggrin.gif" border="0">

I'm assuming you have the plastic valve cover.
Instead of the hose at the rear you could get a filter that fits there (don't know who sells em)

I replaced those grommets, and the leaking was a lot less, but still a little, even at the new oil fill cap.
My motor seems to have a self oil leveling mechanism.
When I do an oil change, it lets any excess out form all those little areas, until it's at the right level. <IMG SRC="smilies/wink.gif" border="0">

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[ 08-13-2001: Message edited by: Maine Jeepah ]
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Old 08-13-2001, 12:31 PM   #5 (permalink)
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Quote:
Originally posted by Maine Jeepah:
<STRONG>Mine are part of the AMC undercoating system.
This apparently was a dealer installed option on the 258's.
The tub is in fine shape under all that oil. <IMG SRC="smilies/biggrin.gif" border="0">
</STRONG>
LOL! Hey, I have this same option on my Wrangler with the 258. Hardly a spot of rust on my frame--I highly recommend it. The good news is, you don't even have to go with the plastic valve cover to get it!

But seriously, don't plug them. --Or you'll be replacing your pan gasket and rear main seal before you know it.

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Old 08-13-2001, 02:04 PM   #6 (permalink)
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Speaking of leakers, I'm picking up my CJ from the shop after they agreed to just clean the oil off everything and then add a blacklight responsive dye to the oil and then check to see where the oil leak is coming from...Turns out (according to the blacklight and dye) the leak is coming from my rear main seal--what I thought 2 years and $1000 ago...Next step: New Exhaust. Anybody got a good header for the 258 they wanna part with? <IMG SRC="smilies/biggrin.gif" border="0">
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Old 08-13-2001, 04:58 PM   #7 (permalink)
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Thanks for all the info guys. It's an '85 with a plastic valve cover.

Maine Jeepah: LOL <IMG SRC="smilies/smile.gif" border="0"> I like the idea of an undercoat, but the water sealing by-product on my driveway is kind of unsightly.

1982 CJ-7: You're talking about the seal between the block and tranny?
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Old 08-13-2001, 08:18 PM   #8 (permalink)
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If you're getting excessive amounts of oil coming out of those holes, it's due to blow-by. It probably means it's time for a rebuild. I had the same problem, and after rebuilding it, it is completely fixed. The front hole closest to the oil fill hole is for the PCV valve. It has a tube that goes to the charcoal vacuum canister. The rear hole is the crank pressure relase hole, or whatever you want to call it. If a bunch of oil is coming out of this, you can put what is called an oil separator filter on it. It'll catch most of the oil coming out and let it fall back into the engine. This hole should lead to your air filter housing, where the noxious gasses are sucked back into the engine and re-burned until they are the right mixture to be spat out the exhaust. If your Jeep is running shitty, it probably because there's a ton of oil going back into your engine from this hole.

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Old 08-14-2001, 10:43 AM   #9 (permalink)
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patooyee: Could this also be causing blue smoke at start-up and sometimes at idle?

I do see a rebuild in the near future. After all, the poor girl has 120kmiles on her.
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Old 08-14-2001, 11:04 AM   #10 (permalink)
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Quote:
Originally posted by murrar1:
<STRONG>Could this also be causing blue smoke at start-up and sometimes at idle?
</STRONG>
Yeah! blue smoke means oil-burning
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Old 08-14-2001, 11:23 PM   #11 (permalink)
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Yeah. That blue smoke is oil burning. I'd say it's time for a rebuild. Sorry to be the bearer of bad news.

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Old 08-15-2001, 11:25 AM   #12 (permalink)
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Well hold up on that rebuild, here's another thought....If I'm thinking right, couldn't he just swap the 4.2L head out for a newer 4.0L HO head and kill two birds with one stone - solve the blow-by problem + increase HP and efficiency?? I may be wrong about that solving blow by, but I don't think so..Just trying to save time and $...My 258 has 150K+ miles on it and its still going strong, with minimal blow-by...I'd say if your compression is still good (even if its not great a 3-angle valve job is necessary when swapping in a new head and that'll increase your compression) and its just a blow by problem, then do the head.
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Old 08-15-2001, 10:16 PM   #13 (permalink)
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The problem isn't in the valves. It's most likely the rings. He could try the head swap, I'd be interrested to see if it worked. I doubt it would, though. Mine had the same head both before and after the rebuild.

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