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Author Topic: Oil cap leak  (Read 3599 times)

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Xpress

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Oil cap leak
« on: December 06, 2011, 03:44:53 PM »
My oil cap is leaking. Pretty badly now, before it barely seeped anything over a whole month, now i'm up to 2 quarts of oil in 60 highway miles.



got a brand new cap with grommet thinking it would solve the issue. Nope. I also noticed there is a bit of oil seeping into the air box. Just a little bit though, that wasn't there before. 89 TBI.
« Last Edit: December 06, 2011, 03:50:32 PM by Xpress »
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Offline sharpxmen

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Re: Oil cap leak
« Reply #1 on: December 06, 2011, 03:57:53 PM »
how much pressure is coming out of the large pcv hose? if all that is from the oil cap and not due to something else i suspect a lot of blowby, you can try and make sure the smaller vent is not plugged (i think the TBI has that as well, but not sure) but by the looks of it you're dumping a lot of compression.
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Offline Jeffy

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Re: Oil cap leak
« Reply #2 on: December 06, 2011, 05:37:38 PM »
That's gotta be blow by or else some other restriction that's causing the crank case pressure to rise then blow out.  Isn't the oil cap on the front of the valve cover?  Looks like it's blowing out the rear (EGR?).
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Offline chardrc

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Re: Oil cap leak
« Reply #3 on: December 06, 2011, 05:41:07 PM »
looks like lots o blow by as sharp said. (and i though my jeep was bad) anyways I would check the pcv valve and line to make sure its not clogged (can possibly pull off the line to the pcv and make sure the line has vacuum and air should be blowing out of the pcv). thats the valve and line coming out of the front of the valve cover (near the fan) ideally fresh air is supposed to come from the air box through the big black thing near the back of the valve cover (has a series of filters in it that are probably really dirty by now) and then back out the pcv valve and sucked into the manifold.

edit: the egr is driver side of the tbi and don't see how that would spew oil. but cap is in front.
« Last Edit: December 06, 2011, 05:42:03 PM by chardrc »
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Re: Oil cap leak
« Reply #4 on: December 06, 2011, 05:53:37 PM »
PCV valve is pretty new, when I put my thumb over the end of it while the Jeep is running it sucks pretty hard. I ran an old bike cable through the PCV lines and nothing is in the way, did the same for the crank breather.

I tried spraying the crank breather out with WD-40 and letting it sit for a while, seemed to clean it out, but when I re-assembled everything, nothing changed. It's definitely coming out of the oil cap, I've watched it. Nothing comes out of the crank breather or PCV.

It's almost to the point where i'm considering just gluing the oil cap shut and using the PCV hole to fill with oil.
« Last Edit: December 06, 2011, 05:54:16 PM by Xpress »
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Offline grumpygy

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Re: Oil cap leak
« Reply #5 on: December 06, 2011, 08:06:13 PM »
Still have your Cat on.  If so check it may be plugged.  That looks a lot like what my under hood looked like.  Also check the vent hose on valve cover, Pull that elbow out.  Is it open or does it have a restrictor in it
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Re: Oil cap leak
« Reply #6 on: December 06, 2011, 09:21:42 PM »
I highly doubt the cat is plugged (nor part of the problem), it was replaced not more than a few years ago. Rev the engine and a hurricane of air comes screaming out of the exhaust like any typical 4 cylinder would.

As far as elbows go... Which are you talking about? The CCV and PCV are all clear as can be.
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Offline sharpxmen

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Re: Oil cap leak
« Reply #7 on: December 06, 2011, 11:04:57 PM »
can it be that it is plastic cover and it's crooked or cracked there? I still say blocked breathers or blowby or both if the cover is good.

try adding another rubber gasket under the cap if you can (seen that done before on another vehicle but it had stamped steel cover).
« Last Edit: December 06, 2011, 11:14:07 PM by sharpxmen »
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Offline Jeffy

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Re: Oil cap leak
« Reply #8 on: December 06, 2011, 11:16:32 PM »
How's the seal look on the oil cap?
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Re: Oil cap leak
« Reply #9 on: December 07, 2011, 12:11:55 AM »
Brand new oil cap, it's all good and rubbery (not hard like the old one).

I have read that the aftermarket oil caps don't fit correctly, and only the dealer part fits tight enough to seal properly.
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Re: Oil cap leak
« Reply #10 on: December 08, 2011, 10:11:52 AM »
Well going to grab some parts from the stealership, hopefully they fix the issue. Going to replace the new PCV, CCV, oil cap, and I've got vacuum tubing to replace the old stuff. figured as long as i'm at the dealer, might as well buy all dealer parts.
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Offline grumpygy

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Re: Oil cap leak
« Reply #11 on: December 08, 2011, 05:22:04 PM »
Howis it running, Done a compression check.  Lastly is the PCV valve blowing any air.

  Check the Valve cover on the inside the place where the PCV valve is at on the inside may be blocked.
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Re: Oil cap leak
« Reply #12 on: December 08, 2011, 07:15:25 PM »
Nothing below the PCV hole but valves and rocker arms, and a metal plate. no blockage. PCV sucks hard when I put my thumb over it. Haven't done a compression check, haven't had time to borrow the tool.
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Offline sharpxmen

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Re: Oil cap leak
« Reply #13 on: December 08, 2011, 09:12:46 PM »
compression check sounds like a good idea

you could also take the cover off and do a leak test on the cap (flip it over and pour some oil in the cap cavity and leave it there - check later to see if it leaked).
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

Offline grumpygy

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Re: Oil cap leak
« Reply #14 on: December 10, 2011, 06:41:28 PM »
This one keeps bugging me.  Part of the reason is if the engine is right (No Bad rings or Cat) you could leave the cap off and not get that much oil.
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