Results 1 to 3 of 3

Thread: Plenum Gasket Fix Writeup!!

  1. #1
    Registered Dr. Righteous's Avatar
    Join Date
    May 2004
    Location
    Knoxville TN
    Posts
    1,460

    Default Plenum Gasket Fix Writeup!!

    I did this fix on my '95 ZJ last year and documented as I went to hopefully help those out where are facing this themselves. I just now got off my lazy butt and put together this writeup.

    Dodge/Jeep Magnum engines all use the 'Barrel' intake manifold that has a bottom cover and a gasket. Over the years the gasket may fail causing the vacuum in the intake to suck oil from the lifter gallery area.
    Hate to say it but it is a pretty common problem if you have a 5.2L or a 5.9L Jeep or Dodge truck for that matter. The symptoms are most noticeably is pinging under acceleration (worse when hot), increased oil consumption, poor performance, mileage, and a poor idle. If you think your ZJ may be suffering from a bad plenum gasket according to these symptoms here is a couple checks.
    Remove the air bonnet from the throttle body and open the throttle plates. Peer down the throat of the throttle body with a flashlight and look for gummy grimy oil deposits. Also, sniff for a nasty oil smell. Good chance you need the plenum gasket fix done.
    You may ask: "Is this a HAVE TO fix?" The answer is YES if you expect your ZJ to live a long life. When you get oil in your air/fuel mixture the, the drastically lowers the octane rating of the mixture by making it more 'unstable'. That is the pinging/knocking when you accelerate. Prolonged detonation/pre-ignition/pinging/knocking, whatever name you call it will damage rod and main bearings. So one day you are driving down the road and your Jeep slings a rod. Not fun, it died of neglect.

    Lets get started. If you are going to attempt this you have to have a descent set of tools. Metric and SAE, your Jeep has both.
    Get your tools together and pull your Jeep into your work area.
    Open the hood and take a good look at what has to come off to get this job done. That's right, everything! The basics first. Disconnect the battery. Remove the fan, fan shroud, radiator and upper and lower hoses and accessory belt. With those out of the way we can eyeball the accessories and see how they mount.



    With the big aluminum bracket the accessories bolt to, they can all be removed together and set aside.


    Unbolt the dipstick. Be careful, it breaks pretty easy.


    You have to wrestle this tube a bit to get it out.


    Unbolt the power steering pump.



    This little trick makes the job go much quicker. You see what I did was lay a old floor mat over the battery, and used a bungee cord to keep the whole thing from flopping over. You AC hoses will allow you do this, but go easy, they can't be stressed too much.


    Now we can see the whole intake. Doesn't look too tough now does it?
    Take this time to familiarize yourself with tube routing, the wiring harness, and how things hook up in general. You may want to mark tube or wiring to keep the goofs down to a minimum.


    Take a look at this jewel. This hose is not leaking, but it doesn't look so hot. It is worn out and could fail any minute. I did have enough sense to buy a replacement because this is a time consuming tear down. Can't say the same for the water pump. I should have replaced that too even though it didn't have a problem. It was the factory piece, it was 10 years old and I ignored it. Yep, and it started leaking a week after I got everything all back together. Save yourself a lot of heartache and replace the old stuff while you have it apart and be DONE with it.


    Time to start removing hoses and wires. BE CAREFUL because the rubber/plastic parts are old and brittle. You may find like I did some parts just break off in your hand. Have some of the correct size ID tubing to replace the rotten stuff. Take your time here. The tube that broke on me has a 1 way valve in it. Keep things in order for reassembly. Take a few pictures if you have to for reference.


    You need a special tool here. Don't try to pry it, you will just get frustrated for no reason.


    Don't forget to release any pressure in the fuel system at the test fitting on the fuel rail.
    Slip the tool into the coupler and press HARD. You might have to move the coupler around a bit before you successfully get it off.

    Continued in second post!
    Turbocharge it!
    Then I am interested!

    95 ZJ limited V8 stock SOLD
    04 Durango Limited with Hemi New wife mobile
    94 ZJ Limited 4.0L Lifted and locked SOLD
    72 Satellite Sebring project MoPar
    '85 Dodge Ramcharger Cummins DIESEL BOUND!

  2. #2
    Registered Dr. Righteous's Avatar
    Join Date
    May 2004
    Location
    Knoxville TN
    Posts
    1,460

    Default Plenum Gasket Fix PART 2



    Here we are. Bolts out, wiring harness removed, tubes off. Take a break, go grab you a cold one because the hard part is next.



    At the rear of the intake is the EGR valve device and the exhaust tube. In my opinion this part is a bitch. You have to remove the EGR device before you can unbolt the tube. There are 2 bolts holding it on. You can just manage to get down to them with a skinny 1/4 ratchet with a long extender.
    Once you have it off you can get to the EGR exhaust tube. This sucker isn't easy to get off but it take some patience because you are crammed into the firewall while you are putting a wrench to it. You can see the oil pressure sender right beside it. Be careful, not to wack it, they break easy.
    Did this fix on my buddy's '95 Dakota 5.2L and there was gobs of room behind the intake. It was a breeze. On a ZJ it isn't.


    With the EGR exhaust tube off the intake is free. Crack it loose with a big flat blade screwdriver and slide it forward a bit, checking for wiring or something you missed.


    Here is a rule to live by: NEVER LIFT A MANIFOLD BY THE FUEL RAILS!!
    If you accidently bend the fuel rails your injectors won't seat correctly and you will have a fuel leak. The position of the fuel rails is critical, be careful!
    Set 'er on the bench and have a look. Its ugly isn't it? I toyed with the idea of totally stripping it and having it bead blasted and then shooting a coat of clear on it. That would make it purdy. I did take a wire wheel to the top. The scale comes off pretty easy.


    Take the throttle body off and turn it over. There is the plenum cover plate. Unbolt the plate and remove it, now for the heart of the matter.


    An oily grimy mess. If you have a pressure washer you are way ahead. Momma won't let me buy one so I had to douse it with degreaser and water hose it several times to get it clean enough to reinstall. Do the same with the gasket cover plate, it is nasty too.


    To clean the mating surfaces I used a wire wheel on a die grinder. Works really well but make sure the wire wheel you use is rated for a die grinder. Otherwise you will be picking peices of wire out of your forehead.
    Put a thin layer of RTV on both surfaces, then put the gasket on. Put the bottom cover on and install all the bolts torquing them to spec.


    Time to turn our attention to engine. All mating surfaces have to be clean and ready for fresh gaskets to be installed. Scraping with a putty or gasket tool is really the only way to get the surfaces ready. Get to work!


    A good trick to get the crap out of your lifter gallery is use a shop vac. Remove any coolant that spilled, along with all that you can get to. Even if you try to lay a towel or something down to keep it clean, you always end up cleaning it out anyway.



    Much better. It is time to start reassembly.
    Just do everything in reverse order! BYE!
    Just kidding.
    Part three coming up!
    Turbocharge it!
    Then I am interested!

    95 ZJ limited V8 stock SOLD
    04 Durango Limited with Hemi New wife mobile
    94 ZJ Limited 4.0L Lifted and locked SOLD
    72 Satellite Sebring project MoPar
    '85 Dodge Ramcharger Cummins DIESEL BOUND!

  3. #3
    Registered Dr. Righteous's Avatar
    Join Date
    May 2004
    Location
    Knoxville TN
    Posts
    1,460

    Default Plenum Gasket Fix Part 3!



    Set your intake gaskets in place. I use a dab of RTV on the head side of the intake gasket to make sure they don't slip when installing the intake. Use plenty of RTV on the cork to insure they seal. Carefully position your intake on WHILE you make sure your EGR tube goes in the right place and can be threaded back in. Start the intake bolts in a few turns to make sure the intake doesn't move on you. Now start threading in the EGR exhaust tube fitting. Give it a shot of penetrating oil so it screws in smoothly.


    The manifold bolts as well as the cover plate bolts are 'torque to yield' and they recommend you replace them on reinstall. I have done 3 of these fixes so far and I reuse the bolts. So far there has been no problems. Just follow the tightening sequence and torque to spec. (please use a quality torque wrench) Now it is time to start reconnecting everything. First the EGR valve assembly, then the fuel line. Pull the wiring harness back into position as well as the plastic and rubber tubing. Get all that in place before you reinstall the throttle body. Reinstall the throttle linkage and bracket after all the wiring and tubes are installed


    The connectors on the harness tend to 'fall' into the correct position so figuring out where they went isn't hard. The fuel injector connectors are identical so I did number them.


    Some of the wiring I scratched my head over until I realized they connected to the AC system.


    Now it is reinstall the accessories. Start with the heater hose tube, then the PS pump. Now you are ready for the accessories. You should have just kept all the bolts in the holes in the bracket. Just drop it in place and tighten the bolts. Reconnect the dip stick tube.

    Remember to check wear item like belts, hoses, etc. Replace them while you have the thing apart.

    Now the brackets for the AC compressor on top. Now the radiator, shroud and fan.
    CHANGE THE OIL. It has water in it from pulling the intake. Reconnect your battery and crank her up.


    Check for leaks, blah, blah, blah, blah.
    Good work. Now you are a plenum gasket duty expert. Congratulations.
    Turbocharge it!
    Then I am interested!

    95 ZJ limited V8 stock SOLD
    04 Durango Limited with Hemi New wife mobile
    94 ZJ Limited 4.0L Lifted and locked SOLD
    72 Satellite Sebring project MoPar
    '85 Dodge Ramcharger Cummins DIESEL BOUND!

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Jeep Parts | Jeep Accessories | Trektop NX | Jeep Seat Covers | Jeep Wrangler | Jeep Wrangler Parts | Jeep Wrangler Accessories | Bestop | Jeep Tires | Jeep Stuff | Jeep Wrangler Tires | Jeep Wheels