GEN 2 DOHC 3.5 Intake Plenum fix

PT52590

New member
I am stripping down and going through a 95 SR to make sure it is overland worthy and wont leave me stranded and I have realized that the lower intake plenum is the older part number that notoriously has issues. I looked at the bushings between cylinders that typically are the first to go, and it appears that a few are starting to crack a little. After doing some research I have found three main options to fixing this:

1. Purchase the 'updated' part for close to $500 (OUCH!)

2. Remove the butterfly valve assembly and seal up the plenum to prevent a vacuum leak

3. Figure out a way to replace bearing/bushings on the current plenum to prevent issues from occurring

These options bring me to a few questions:

1. Has anyone who has purchased the updated part had any similar issues with the new part or is it simply a one time fix?

2. How big of a difference in mileage & low end torque has anyone noticed that has removed the butterfly valve assembly?

3. Has anyone tried taking the old plenum to a machine shop (or doing this themselves) to get the bearing/bushings drilled out and replaced, and possibly get the butterfly valve discs welded to stem so they dont break off as easily?

Any ideas or advice is much appreciated.

-PT
 

coffeegoat

Adventurer
There is a fix for the bearings/bushings running around. I forget who found it, but apparently it's some russian guys that are making new bushings.

Let me look around for it, maybe ADD can import a bunch of them....
 

PT52590

New member
Thanks coffeegoat, it isn't Siberianbushing.com is it? I looked on their website but it looks like they only make suspension bushings.
 

coffeegoat

Adventurer
No, it's some no name group, I looked and couldn't find it, I'll keep poking around...

They're just these little plastic bushings, but I seem to recall them being a funny shape.
 

PT52590

New member
Thanks for the info, the bushings and everything look to be pretty similar, maybe even the same? I guess it doesnt really matter if you can't buy only the bushings. Pretty interesting how the kit that the person got in Russia has an actual mitsubishi label on it and says "for internal use only"....

Does anyone have any experience with the similar issue that 2003-2004 Kia Sorrento's had? Kia started a recall campaign to fix them and the intake plenum looks very similar, not to mention it is for a 3.5L v6. After watching a little bit of this video https://www.youtube.com/watch?v=PJ7kkdiSrq8 , alot of the parts look very similar. Since they had a recall, they offer the middle plenum for much cheaper than normal and the new part number is 29222-39800QQK. I just called the local kia dealership and they have it in stock for about $70. I'm going to stop by on my way home this afternoon to take a look. It would be pretty awesome if it would bold directly on, but after looking at pictures it doesn't appear that it will. I'm hoping to at least be able to pull all of the bushings, maybe even the entire stem. Even if I can just use the bushings/seals for the plenum I would still chalk it up as a win, $70 is less than the guy on adventuredrivendesign.com was wanting to charge for the bushings from Russia and it is a heck of a lot cheaper than the $500+ mitusbishi wants for the new plenum.

My next step would be to see if a 3D printing place could help me out, but I might just remove the valve, plug the holes in the plenum and call it good if I have to do that.
 
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PT52590

New member
So I stopped by the kia dealership yesterday and the sorrento plenum looked pretty much identical to the mitsu with the exception of the bolt pattern for the upper plenum so I bought it for $70. I took it apart when I got home to make verify that it will work, and sure enough the shaft, bushings, butterfly valve flaps, etc are all the correct size. The cam on the end of the shaft that connects to the vacuum actuator is even the same, so all you need to do is remove the butterfly flaps and shafts from both plenums, and the shaft with bushings and the cam from the kia can be installed directly into the mitsu plenum without any modifications. Since the butterfly flaps are the same size, you can install the shiny new flaps from the kia as well. The process is pretty straightforward; all you have to do is remove the flaps, then remove the two screws on the end that hold the little metal gasket/spacer in place that holds the shaft in the plenum and the shaft will slide out. I did learn a few things in the process, so here are a few pointers:

-Use channel locks to break the screws free that attach the butterfly flaps to the shaft, then use a phillips head to remove them the rest of the way. I learned the hard way with the mitsu plenum that those little screws are made of very soft metal and stripped just about every one of them during removal. The screws on the kia plenum seem to be stronger/harder, but they had some blue loctite on them so I used this process to avoid stripping them and it worked.

-Be careful when sliding the shaft out of the plenum, the small rubber gaskets that are on the shaft between the chambers have some sort of adhesive holding them in place on the shaft. I'm not sure how strong the adhesive is, but I'm sure if someone tried to force the shaft out they could rip them off.


I haven't completed the reassembly as I am going to clean up the old plenum first, however I did install the shaft to make sure everything fit correctly and it fit perfectly. The revised kia part number for the plenum after the recall is 29222-39800QQK and it can be had online for about $60. The main differences between the old and new appear to be the material the two thin plastic sleeves around a couple of the the rubber bushings are made out of, and the bushing on the end of the shaft. The bushing on the new one is one piece, it looks and feels much stronger than the old one and it is fixed in place with a pin rather than having a small spring/clip holding it in place. All in all I feel pretty accomplished for fixing the plenum issue for only $70 because I really didn't want to just remove the valves and $500 for a new plenum is a tough pill to swallow.
 

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Swift_45a

Observer
Nice one! Thanks for that, I'll have to save this when i tear into the DOHC when I get time to work on the Valve Stem seals. Do you know if that model KIA uses the same Valve stem seals?

Have things gotten to the point where we have to 3d print stuff? Wow, Mistubishi NA really left us by the wayside, I remember a few years ago, when Nissan was exploring taking over Mitsubishi NA, that parts were not able to be sourced and someone mentioned looking to Kia.

Those Koreans have a real affinity for these trucks, too, they are refurb'ing them like what ICON does for Landcruisers.
 

PT52590

New member
I don't know about the valve stem seals, however I looked at rockauto and it looks like all the aftermarket manufacturers have different part numbers for the two vehicles so my guess would be that they aren't the same.
 

PT52590

New member
I don't believe the valve stem seals are the same, judging from the aftermarket manufacturer product numbers that are different I feel like it is pretty safe to say that they aren't the same.

I finally got the time to clean everything up with some degreaser and get the plenum put back together last night, so I just wanted to add a few other pointers:

- When reassembling the plenum, make sure that you use the original black spacer/retainer that holds the shaft in the plenum. The one that comes on the kia plenum is slightly thinner than the mitsu one, and its just thin enough to make the butterfly flaps rub a little when they close, to the point where it almost feels like it gets stuck closed.

- I ended up cleaning and reusing the original butterfly flaps after all. Although the new ones didn't need to be cleaned, the old ones seem to have been worn in with the cylinders a little bit so the fit was better. The new ones seemed to rub, causing some resistance when opening/closing.

-make sure to use loctite on the screws that attach the butterfly flaps

-I lost a screw at some point during the process, so stopped by Fastenal and was able to get new screws and lock washers that worked perfectly. I don't remember the exact size but if anyone needs it I can find it out.

-Last but not least - I used ZEP fast 505 industrial degreaser and cleaner to clean off the plenum and this stuff works wonders. It's safe to use on basically any unpainted surface and worked better than any of the foaming degreasers I have tried.
 
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kalieracer

Observer
You guys are making it harder than it has to be.. I posted a fix for this a while back on the Montero Facebook group. You get the lower kia part, weldup and extend one tab on the stop upper portion of the mits unit and put a new seal in and you are done.
 

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