Valve Cover Vent Options.

[skidoo_j]

In the process of replacing my valve cover on my 89 4.0 I'm locating and replacing the vacuum and vent rubbers and oil cap.

 

The piece I'm trying to replace is the rubber elbow that connects to the 1/2" line on the air filter box. It's sold at napa as 7151367 which is a vacuum harness that has all these extra lines that I've already eliminated.

 

What I've noticed though is all it is is a hollow rubber 90. I've read where people think there is some sort of valve flapper in the towers, well they're just baffles. in the 89/90 the "flapper" actually had a center support to prevent movement.

 

88 on left:

When looking at the 95's options for this rubber 90 it appears to be just another rigid plastic 90 with a grommet,

 

 

 

looking at the 99 same thing but they added an orifice that is restricting the vent size.

 

 

So my ?

Do either of these newer style add a check valve or are they just plastic 90 degree turn. I'm thinking i could replace them with a brass 90 (more readily available to me). Has anyone added a check valve in this location? All my other cars have PCV's.

[Keyav8r]

I believe the 90 with the orifice is for the vacuum line that goes to a fitting on the intake manifold. The purpose is to draw the oil vapors out of the rocker cover into the intake manifold where they will pass into the cylinders and be burned. The orifice limits the amount of vapors that will be pulled out.

The 90 without the orifice should be for the line from the rocker cover to the air filter box. This allows fresh air to be drawn into the rocker cover to replace the oil vapors that are drawn out by the other line and prevents creation of a vacuum in the rocker cover.

Neither 90 has a check valve.

I have just replaced the rocker cover on my 88 MJ with one from a 96 XJ that has the full length baffle. The fitting with the orifice is broken and so far I haven't been able to get it out - don't want to break it off completely as I don't know if new replacements are available. Heading for the parts store to see what fittings they have for a work around.

[Keyav8r]

Forgot to prefix the previous post with AFAIK. Others on here know a lot more about this.

[Eagle]

The 2.5L used a conventional PCV valve, and the 4.2L version of the I-6 used a PCV valve. I've always wondered how it would work to just use a PCV for one of the older AMC sixes.

[Jeep Driver]

 

 

 

No PCV in mine.

 

Elbow is sold at Advance.

 

I used a piece of 1/2" copper coupling inside the elbow to aid in providing internal pressure against the valve cover......tighter fit. I also used Ultra Black to seal the elbow. Months now and no seepage anywhere.

 

 

Do yourself a favor and get rid of the air box......for the 2.5 it is utterly a POS.

 

 

 

Edit:

 

 

The rear vacuum connection is 4.0......it's all they could order for me........should be the same for you......dealer part.

 

The front elbow is the same size also.........just different style.

[skidoo_j]

Ended up taking in the valve cover to napa and getting generic pieces for the vent. A grommet and a plastic 1/2" 90. Napa parts 6301047 and 6301070. I swapped the vacuum line and vent line so my hoses were shorter.

 

 

and cut my towers to a pseudo Cruiser mod. As mine already had a factory 1/2" hole compared to the '88 You can see the difference in height, I only removed 3/4" and maintained the same angle of the cut. You can see in the picture where the 89 had a factory drilled hole in the back vs the '88 sitting next to it for reference.

 

 

 

 

 

I decided after aligning the cork gasket that I'd rather not screw with the cork and have to replace it in two oil changes so i picked up the felpro one piece blue one.

 

[skidoo_j]

Had to change the vacuum hose I used. Originally I used a 1/4" hose, but the idle was too high to the point where the stepper motor couldn't recover it, so i changed it out with 1/8" the factory rigid is in between the two in diameter, but is alot longer and has three bends, so i figure 1/8" maybe smaller, but probably same amount of flow. Very happy with the seal of the fel pro blue.

 

 

The valve cover bolts are to be torqued to 55 in lbs, barely more then hand tight, although when removing the old cover it's very possible my leaking was cause by the back 3-4 bolts were so loose i could undo them with my fingers :( Hopeuflly My leak is resolved. I already have an o-ring for the oil adapter, rear man seal and oil pan gaskets sitting on the shelf waiting to go in.

 

 

 

 

Off topic, but will i need a timing gasket if i'm dropping the oil pan and rear main seal? I plan to do this with out removing the tranny. although i could wait as i'm pretty sure my clutch slave is leaking and just do all at once

[87mjdriver]

You shouldn't need a timing gasket, idid mine maybe 8 years ago and a vaguely remember the pan gasket being a couple pieces . I know I didn't touch the timing cover.

[cruiser54]

You shouldn't need a timing gasket, idid mine maybe 8 years ago and a vaguely remember the pan gasket being a couple pieces . I know I didn't touch the timing cover.

 

Don't need a timing cover gasket. Do yourself a favor and get the one-piece oil pan gasket.

[skidoo_j]

Don't need a timing cover gasket. Do yourself a favor and get the one-piece oil pan gasket.

 

Got a one piece pan gasket and a two piece dual lip rear main seal. I also got the o-ring for the oil flange, but read that there's also a smaller one too, so I'm going to try and source it before i pull the flange.

[Keyav8r]

Skidoo j - I took my filter adapter to NAPA and matched the small o-ring to it. Haven't put it back on yet so I'll measure it tonight and post the size for you.

[Keyav8r]

BTW - That oil filter adapter bolt is a bugger to get off. Cruiser54 recommended a longer cheater and that worked. I had to use a combination open end/box end wrench because there's not enough room to get a socket and pull handle on the bolt (motor mount bolt and frame in the way).

[skidoo_j]

Pulled the adapter today. Thank you Keyav8r for the PM for the info on the second o-ring next to the flange, but i found there are actually 3 orings. There is one that all the parts houses list, then the one under the large washer, but there's a third that is on the bolt. The 3rd one is what seals the oil to go through the filter.

 

Anyone else do yourself a favor and order them from a dealership or a vendor that sells crown auto parts. They're actually metric o-rings and standard sizes will not work for the one on the shaft. I went to every auto parts place in my town and no one had anything that would work on the shaft. I lucked out and a hardware store carried metric o-rings and i got a 20mm-id 26mm-od 3mm width that will work for the shaft and a standard size from napa that will work under the flange. These are the other two oring factory part numbers for a 89 era 4.0l. They're like $0.70 each from my dealer, but they're closed and unsure if they have them on hand at time of realization there was a third o-ring.

 

 

3300 2970 1 .80" O-RING .799X.103

3300 2971 1 1.30" O-RING 1.296I.D.X.1

[skidoo_j]

OH and the oring set that both schucks and autozone list is a generic set of orings and none of them are even close to either of the other two o-rings.

[Keyav8r]

I didn't notice that third ring on the bolt. Might have found it when I cleaned the bolt before I re- installed it, but maybe not.

Thanks for the info. I'll check the dealer and NAPA for the smallest one.

[skidoo_j]

I didn't notice that third ring on the bolt. Might have found it when I cleaned the bolt before I re- installed it, but maybe not.

Thanks for the info. I'll check the dealer and NAPA for the smallest one.

 

the problem i ran into with my napa was they had ones that were 1/16" and 1/8" in thickness, the 1/8" ones were to thick for the the bolt to go through the flange. The 1/16" ones may have worked, but they were so thin in the groove that they were able to shift alot. There was enough movement i was afraid of the longevity of the thin oring.

[Keyav8r]

Called my local NAPA and they do not carry metric o-rings. Guess I'll try the dealer with your PN's.

[Keyav8r]

Skidoo-j, that $0.70 o-ring at the dealer? It's more like $5.00! Yes, I bought it.

[skidoo_j]

Damn your local dealer puts the screws to you. Unless they didnt have it in stock and charged you for shipping. Looking it up by part number through my local dealers parts site lists them at $0.70 each. Sorry, but hey it will save you alot of headache vs trying to drive around to various other stores to find one.

[Keyav8r]

Yep, definitely had that burning sensation as I left. Same dealership quoted $50 for the shifter boot that bolts to the floor. May just find an inner tube and make one!

[skidoo_j]

Yep, definitely had that burning sensation as I left. Same dealership quoted $50 for the shifter boot that bolts to the floor. May just find an inner tube and make one!

 

I purchased this one from quadratec. It matched up with the OEM holes. fit my 89 with ax15. It's the one that screws to the tunnel.

http://www.quadratec.com/products/52106_03.htm

[Keyav8r]

I got the OEM boot for the 88 MJ for about $35. Same dealer, just ordered it through our company service department. Haven't installed it yet, had to pull the dash to change the heater core - found antifreeze on my newly sealed and primered passenger side floor. I've come to the realization that if it ain't broke, just wait and it will. Jeep Empty Every Pocket!

[A-man930]

BOTH very pretty valve covers btw. had to say it. Jeep Driver; what application is that?