I had some spare time today so I swapped out the spark plugs and changed out the valve cover gaskets on my 2003 Mitsubishi Montero (odo: 80K). This was no easy task. I started about 1000 this morning and wrapped up around 4:30. In order to replace the spark plugs you have to pull the intake plenum and throttle body. I was able to disconnect the EGR pipe from the exhaust manifold so I didn't have to buy the EGR pipe gasket. I also learned after the fact that you only have to remove the 7 inner bolts (two short, three medium and 2 long bolts) to remove the two pieces of the intake plenum as an assembly (after disconnecting the wiring harness and all of the vacuum hoses). I took some pictures before I began, but really didn't need them to hook everything back up. Parts list:


6 denso iridium spark plugs
intake plenum gasket set (3 gaskets)
Valve cover gaskets


I found that the spark plug cylinders on the driver side were a quarter full of oil due to failure of the seal at the top. I mopped most of it up with paper towels but wasn't able to get it all, the oil ended up running into the cylinder after I pulled the plug and I had a great smoke screen when I started her up. The old plugs were worn but looked pretty good, I would have changed them sooner if it wasn't so hard! Next task will be the timing belt

 

While working on the valve cover gaskets, by any chance did you replace the spark plug seals? You said your driver side spark plug wells were full of oil. That means the seals are going bad. Some valve cover gasket kits come with spark plug seals. It is a good idea to replace them if you are down that far anyway.

You are right - changing spark plugs on gen 3 Montero engine is a pain in the rear. However, you do not need to do it very often. If you use standard plugs, the book calls for replacement every 30k. If you go with the Iridium tip plugs, then you don't have to bother with them until 60k. I've been using Iridium tip plugs and have with 170k+ on the engine, I've only changed plugs 3 times. I love this Makes my friend with a Jeep mad too that i can go this far between needing to do this service.

Back to the spark plug seals. If you did not change them, then the oil will eventually swell up the plug wire tips. When this happens, the tips will swell and can potentially expand enough that the wire will pop off the spark plug. I've had this happen not that long ago. I've got a "cylinder misfire" error code. At first i was panicking and thought it was something major, but then noticed that one of the wires was not seated all the way down. Once i realized what was causing this, i got the valve cover gaskets and the spark plug seals replaced at the same time.

I did not realize you can take both halfs of the plenum together. Can you post the picks showing which bolts will let you do this. Thanks.

 

I did replace the spark plug seals, it took me a couple of minutes to figure out that they were not an integral part of the valve cover as they had hardened to a point where they were stuck to it. I had really let the valve cover gaskets go. The felpro kit came with replacement spark plug seals. If the gaskets leak again I will probably just go ahead and replace the spark plugs at that time if it's before the 60K interval. As far as the two halves of the plenum, I had to crop and compress the picture to show you one of the fasteners, the nut and stud combination on the front right, the rest are not visible (the nut is partially obscured by the vacuum hose in front of it). I could e-mail you a larger picture if you'd like (250 KB). It's easy to see, if you are standing in front of the vehicle these are the smaller 10 mm bolts between the upper plenum and the middle plenum, they are on the right side on each side of the plenum tubes diagonally opposed. the first and last are nuts on studs the rest are bolts. I actually assembled these pieces together off of the vehicle to ensure gasket alignment (couldn't make it work putting it all together on the vehicle). I'm sure I was just a few miles from a misfire code......good thing it didn't happen as this is my wife's daily driver!

 

Thanks for the info on the plenum. Next time I'm working on it, I'll try to remember this. I've always took off two parts separately. So far it worked for me, but worth a try to see if it will be easier this way. If you can PM me the full photo, I'd appreciate it.

I'm glad you replaced the the plugs. Mine were also so hard, that they did not flex at all and it looked like they were molded into the valve cover itself. Took a pop with a back of screwdriver to get them off. I figure I got many many miles to go now till i have to worry about this next time

 

this will be my next project on our 03 Montero. Im planning to do the spark plug seals as well. May i ask where did you order your seals from? I'll change my spark plugs and wire too.

What was the torque specs? I certainly dont want to over tighten. Thanks

 

I think that doing the timing belt was actually easier than doing the spark plugs. I got the gasket kits online and doesn't come with the rear cam seals which always flood the rear of the motor with oil. Just sayn.

 

The torque on the valve covers is only about 30-35 in-lb. I don't remember where i ordered my valve cover gasket set - it was too many moons ago

 

I got mine from Rock Auto Online...

 

Don't forget when you remove the upper intake plenum, put tape over the 6 ports of the lower. Bolts and debris have a magical way of finding these openings and can cause catastrophic damage if not seen. FYI, the rear seals for the cam is not actually called a "seal". I bought cam seals and it turned out all you need are the "O" rings. If you do drop something down the lower ports, you can remove by using a magnetic wand (bolts) or by using compressed air. If wand or air from the top does not work, remove V/C and spark plug, thread air line into spark plug hole, charge cylinder then open intake valve, (pry bar usually works) then watch debris shoot out lower intake. Over the years, this method has saved myself some incredible grief.

 

I think my rear cam seals are leaking as well, after I replaced the valve cover gaskets now I have oil streaming down the rear of the engine on the passenger side, though I did a crappy job torqueing the valve cover bolts but now I see this post. 7-UP Bill, where did you get the O-rings and can they be installed without pulling the camshafts? Looks like I'm pulling the freaking manifold again!!!