It seems that while I am driving my engine builds up oil pressure at the top of the valve cover and then leak out of the rubber grommets.

Is there a reason for this?
Something that I should look for?

 

You most likely have one of two things going on. Either your bolts just need to get snugged up or you need a new gasket.

 

What year is it? Also check the PCV valve at the rear of the VC. It has a metered orifice that draws fumes from the engine and into the intake manifold. Make sure it's not plugged up.

 

Those rubber grommets also tend to get hard, shrink and leak too. The dorman replacements are pretty cheap.

 

those grommets are a very poor design, a weak link. I have seen a modification that I may do, install a metal bard fitting in there place to securely and leak proofly attach the breather hoses.

 

You could improvise with bulkhead plumbing connectors. Just have to recreate the same sized orifice in the rear.

 

You just need to replace the rubber and the pcv, it's not sealed tight. This is a vacuum leak. I recommend doing this with the valve cover removed. Because they get brittle and most likely fall apart getting out. Might as well do the fresh air valve also and valve cover gasket.

 

Ok, very good info.
I will try to work on it this weekend.
88 Pioneer

 

Use a Felpro blue valve cover gasket. Replace the rearmost grommet and tube. Perform the mod below. CRUISER'S MOSTLY RENIX TIPS

CRUISER’S VALVE COVER MOD

NOVEMBER 17, 2015 SALAD 55 COMMENTSMost early and even later Renix 4.0s could be bothered by excessive oil in the air cleaner box.

A fix from my old days as Service Manager at a Jeep dealership follows. Information was provided to me from a buddy at JeepTech during those days. I don’t believe it ever came out in a Technical Service Bulletin.

Remove the valve cover and turn it over. Next, remove the fluted tubes that are now facing you by removing three screws on each.



Chop 1 inch off each of them. Then, drill a half inch hole as shown in the photo. The flat side of the flute that’s closest to the edge of the valve cover.



Clean and de-burr/sand all rough edges nicely, clean with solvent, and reinstall. Don’t be concerned about the chintzy gaskets that will probably crumble into oblivion when you remove the fluted tubes. They can go back together without gaskets.

Here’s a handy video from my friend Brendan showing more detail.



Revised 09-12-16


CRUISER'S MOSTLY RENIX TIPS

RENIX VACUUM HARNESSES

NOVEMBER 17, 2015 SALAD 29 COMMENTS



The vacuum harness that attaches to the front of the valve cover and includes the grommet/fitting, and is called the front harness, is Napa part number BK 715-1367 or is a Dorman 46003.



The vacuum harness that is closest to the air cleaner, EGR etc, and is called the rear harness, is Napa part number BK 715-1366 or is a Dorman 46004.



The tube from the rear of the valve cover to the intake manifold is part number BK 715-1365 or Dorman 46005 and comes with the valve cover grommet.

The Throttle Body to MAP hose is no longer available. Click HERE to access a fix for that.

 

The valve cover mod was one of the first things I did to my 90 4.0. My airbox was a mess prior to this mod.
Cruisers tips are right on the money!

 

To all users of CF:

PLEASE, before posting technical questions, take some time to help others out, by adding details in the user control panel. There's 2 ways to do this. First, in the upper left corner on the front page of the site, is a menu button labeled UserCP.




After you click on that you'll see this menu:





Please take the time to click on the highlighted sections and fill out the vehicle information for your vehicle. The signature link is also helpful for any additional information like mods done, links to your build or other vehicles owned.

This helps EVERYONE out by informing them immediately about your year, make, model, etc.

These details are necessary for responders to accurately answer your questions without guessing or having to ask what are the specifics of the vehicle you are referring to. You can add these details easily and permanently by creating a signature or adding your truck details to your existing signature.

5 minutes of your time doing this now will save a ton of time and effort later.



Thanks!!!

CF staff
__________________

 

Thank you Cruiser, I did the editing, I did not know about this feature.
Also thank you for the repair post, I will be going to my local NAPA this week.

 

Cruiser,
On second thought I may not be replacing the vacuum harness. I am a little dumber than the average bear an I can not locate these harness's on my engine.

 

Let's have a photo.