Plenum Gasket: What is it, where is it and what should I do about it? *INFO*

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dodge dude94

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*all credit goes to Merc225hp*
“Plenum Gasket, what is it, where is it and what should I do about it” applies to 3.9, 5.2, 5.9 magnum motors.

When Dodge made the intake for these motors they made it in two pieces, cast aluminum for the top and a stamped steel plate for the bottom, with of course a gasket between the two. Over time this gasket fails for whatever reason (there are many opinions on this as to why it fails this is not a thread to discuss that).

Signs that the gasket has failed/failing, oil consumption goes up, pinging from the motor, possible blue smoke from the tail pipe, a miss in the motor (most times cylinder 8), rough idle, fouled spark plugs, general lack of performance.

Is there a test to see if it’s leaking? Not a real good one: Just opening the TB and looking down in the intake to see if oil is in there is not enough. The PCV system puts oil in the intake no way around that fact so that test is out. The idea of looking for oil pooling inside the intake at the back to me is also not a good test as there are vortexes inside the intake that will pick up the PCV oil and drop it elsewhere inside the intake.

What a leaking Plenum gasket can do to your motor: If left for too long, you will foul spark plugs, foul the O2 sensors, plug the catalytic converter (if the cat plugs and you run it that way you up the chance of cracking the already weak heads).

Can you test to see if it has been fixed before? Yes and no you can use a telescopic magnet put down the TB and see if it has a steel plate or an aftermarket aluminum plate. If it does not stick to the bottom it has been changed to the aluminum plate so you might be okay. If it does stick to the plate just start getting ready to do the job.
*notes from DD94: there was a fella somewhere that attempted this and his magnet was filled up with sludge, so depending on how nasty your intake is, this may or may not work. You may have to Seafoam it before you do this*

Fixes for this, from Dodge and other wise:

Dodge did a couple of TSB’s to try and deal with this issue, one is the routing of the spark plug wires (TSB 18-48-98), next is the Death Flash (TSB 18-34-97). Both of these TSB’s are bogus cover ups for the real problem. And TSB 09-05-00 where the job is done in full.

Aftermarket fixes: There are aluminum replacement plate’s out there, one on eBay and the other is Hughes engines, I believe both are full kits. This is the route many take to solve this problem. The other two options are replacement intakes one is the Mopar M1, two is the Hughes F1, and neither are cheap and both should be used with other supporting mods.
*notes from DD94: the eBay is just an aluminum plate with the plenum bolts, Hughes offers both the pan with bolts, as well as a full kit. Going the eBay route and then sourcing your supporting parts else where has been proven to be cheaper in most cases...the Mopar M1 is also unfortunately no longer in production, making them harder to find and they're climbing in price*

Can I fix this myself?: I have read and helped many a greenhorn do this job, some take longer than others but most can do it in a day. The biggest mistake I see is the use of wrong torque setting for the intake bolts, the torque setting is in inch lbs not foot lbs, so make sure you have a torque wrench that reads in inch lbs. The other obstacle is broken intake bolts, it happens, no doubt about it, and most can be removed with a pair of vise grips, however, some may end up requiring the replacement of the heads.

A good shop should be able to do this work in about 4-6hrs, some shops will know nothing of this problem so expect to hear "what are you talking about?"

All part numbers listed are Mopar parts readily available from your Dodge dealer. The P denotes performance parts, in some cases these parts are cheaper than stock parts, the intake bolts are the exact same as the stock part just cheaper.


53030541 Throttle Body Mounting Gasket
05017208AA Gasket, Intake Manifold Plenum Pan
P4876049 Intake Manifold Gasket Set $33.25
P4876772 Intake Manifold Attaching Bolts $7.75 set.
P5249862 Roller Lifters $117.50

Opt parts

P5007709 Timing chain tensioner part $30.00
P5249267 Double roller chain and sprocket set $58.00
Water pump
Cap
Rotor
Oil psi sending unit

Fel Pro 5.2/5.9 Intake Manifold Gaskets with belly pan gasket MS95392-1
*notes from DD94: You're never going to get a better chance to easily replace the cap and rotor, so do it while you've got the intake off.*



I hope this helps someone. :)

Big thanks to Merc for taking the time to ponder and write all this up for everyone!
 

crazzywolfie

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can't you also test the plenum with a vacuum gauge? i know it would probably have to have a pretty bad leak for it to show vacuum in the crank case with the pcv disconnected but it is worth a try.

i think we might also need some pictures to go with this so that people understand what it is better
 
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dodge dude94

dodge dude94

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There was a vacuum procedure, but I don't remember what the outcome of it was.


As for pictures, pictures of what?
 

Merc225hp

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TSB 09-05-00 has the vac test in it as well as the plenum gasket replacement steps.

Here are some pix of the plenum, it's gasket, pcv oil spray pattern on the pan (normal).

The kegg intake.

Oct2011025_zps2c9dbb70.jpg

Bottom of the kegg, the steel plenum plate.

Oct2011026_zps8a9cafb6.jpg

Inside bottom of the steel plenum pan.

DSCN0662_zpsc3b51390.jpg

Broken plenum gasket. In most case's the gasket will be pushed out from between the two parts.

DSCN0663_zps67df56f7.jpg

Bottom of the kegg intake.

DSCN0668_zps8b14da9a.jpg

Pcv oil spray pattern on the plenum plate, (normal)

Oilpattern_zpsa45b32b2.jpg
 
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dodge dude94

dodge dude94

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Good thing you had the pictures sitting around, Merc.

This is gonna be good! :D
 

crazzywolfie

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here is a picture of how much the gasket can be pushed out on a rusted steel plenum pan. i pull the intake off a truck at the junkyard that had already been picked apart which is why the pan was so rusty.
IMAG0514.jpg
 

meistermash

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Thanks for the info. I checked out my 01 yesterday and it had burned 1 1/2 quarts of oil some how. Hasn't ever done that before and no8 spark plug was a royal pia to remove. So maybe I'm developing this issue. Plugs looked fine though they were worn to .45 or .46 from the factory .40. Found a vacuum leak in the form of the pvc hose. When these go is it like a big vacuum leak or is there no change in that respect?
 

crazzywolfie

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i don't think it is like a big vacuum leak but any vacuum leak can hurt how your engine runs. most people do not notice the leaking plenum gasket until it has clogged the cat and you loose a lot of power.
 

jsq789

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A couple of questions..
Can this leaking gasket cause a wind sucking noise under the hood ?
Where can I find this kit to fix it ?
 

crazzywolfie

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usually you only get the air sucking noise when you upgrade to a CAI or open element air filter that would suck its air from under the hood instead of behind the bumper. a leaking plenum gasket should not cause that noise.

here is the kit
Hughes Engines
now some people have issues with the gaskets supplied with the kit and would prefer to get what ever gaskets they choose and order just the pan off ebay. in the end it all adds up to about the same price after shipping.
Dodge Jeep Aluminum Plenum Plate Belly Pan 318 360 5 2 5 9 Manifold Repair Kit | eBay
 

lleno65

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Do the heads need to come off to do this repair??? thanks,Leo
 

Merc225hp

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No the heads do not need to come off for this work to be done.
 

lleno65

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thanks,I think my truck had this issue,I go thru about a qt. of oil every 250-300 miles,it just disappears, no external leaks....it a 99 ram 1500 w/3.9l magnum engine,124k miles....Seems to be lacking power....
 

crazzywolfie

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well i don't think the v6's had that much power to start with but i don't think a leaking plenum gasket would help it. you could try replacing the pcv valve first. sometimes when they are not working properly they can allow your engine to burn a bit more oil than it should and only cost about $12 at the dealer.
 
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dodge dude94

dodge dude94

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Try not to load this thread up, guys.

I wanna keep it clean-ish so that way we don't end up with something like what happened on DF...
 

Steedo

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Why are the roller lifters included in the parts list and not under opt parts?
 

Merc225hp

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Why are the roller lifters included in the parts list and not under opt parts?

Because thats how I feel about it. Many and I mean many a person has done this job only to have to take it all apart again to change the lifters because they will not load up. Dirt,carbon whatever will get into the oil port or in the lifter itself and will not pump up so best bet is to install new ones, as these are roller lifters the cam does not need to be changed with the lifters, thats old school.
 

jbmobbs

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A couple of questions..
Can this leaking gasket cause a wind sucking noise under the hood ?
Where can I find this kit to fix it ?

My dodge has the same noise.....it happened when I swapped throttle body's I'm fixing to find another tb and put all brand new sensors cause my throttle now sticks some times........just a heads up beware lol......my last dodge did it too.
 
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