Montero Down...
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Senior Member
Joined: Oct 2004
Posts: 2,045
From: Washington State
Montero Down...
Well folks, with 250k miles on the engine, I knew the day was coming, just didn't know when...
Today my Montero decided to give me a good scare and a ton of grief. I was driving along on the highway, cruising at about 70mph. I suddenly got a massive shudder that felt like the worst washboard possible. At the same time CEL came on. I pulled over, threw the code reader on the vehicle (yes, I carry one with me...) and pulled a single code - Cylinder 5 misfire. Nothing else out of the ordinary. fuel trims are within normal ranges. Engine idled fine with no discernible miss. The misfire would return any time engine would run at about 3k RPM. Anywhere below and above that range, it felt normal. With that I decided to continue driving (had to get to a family thing). About 50 miles later after a long hill climb, the engine felt like it was loosing power and transmission would not up-shift into higher gear when we got to the top of the hill. When I looked back to see if I was blocking any traffic up behind me, I was greeted by a nasty curtain of blue smoke instead. Those military smoke screen makers would be proud... I got off the road into a safe spot and looked everything over. There was a MASSIVE oil slick below my Monty and more oil was still dripping out. Oil was all over the exhaust crossover and the Y-pipe (hence the smoke) and entire bottom of the vehicle. I didn't have a good chance to look at where the oil was coming from, but it seems like there was more of it on the rear of passenger side head/valve cover. Dipstick was dry... The good thing is that the engine never overheated and the Low Oil light never came on. At this point engine would restart but it would idle very rough. I had a fiend come over and tow me to his home (our final destination). I was able to drive Montero on and off the trailer (it would run but with very discernible misfire).
Tomorrow I will try to tow it back to my home to get started on the detective work to figure out what a hell happened.
So, at this point I'd like to solicit bets and / or ideas as to what may have happened. If anyone guesses correctly you get a gold star and a pat on the back
Any takers?
Today my Montero decided to give me a good scare and a ton of grief. I was driving along on the highway, cruising at about 70mph. I suddenly got a massive shudder that felt like the worst washboard possible. At the same time CEL came on. I pulled over, threw the code reader on the vehicle (yes, I carry one with me...) and pulled a single code - Cylinder 5 misfire. Nothing else out of the ordinary. fuel trims are within normal ranges. Engine idled fine with no discernible miss. The misfire would return any time engine would run at about 3k RPM. Anywhere below and above that range, it felt normal. With that I decided to continue driving (had to get to a family thing). About 50 miles later after a long hill climb, the engine felt like it was loosing power and transmission would not up-shift into higher gear when we got to the top of the hill. When I looked back to see if I was blocking any traffic up behind me, I was greeted by a nasty curtain of blue smoke instead. Those military smoke screen makers would be proud... I got off the road into a safe spot and looked everything over. There was a MASSIVE oil slick below my Monty and more oil was still dripping out. Oil was all over the exhaust crossover and the Y-pipe (hence the smoke) and entire bottom of the vehicle. I didn't have a good chance to look at where the oil was coming from, but it seems like there was more of it on the rear of passenger side head/valve cover. Dipstick was dry... The good thing is that the engine never overheated and the Low Oil light never came on. At this point engine would restart but it would idle very rough. I had a fiend come over and tow me to his home (our final destination). I was able to drive Montero on and off the trailer (it would run but with very discernible misfire).
Tomorrow I will try to tow it back to my home to get started on the detective work to figure out what a hell happened.
So, at this point I'd like to solicit bets and / or ideas as to what may have happened. If anyone guesses correctly you get a gold star and a pat on the back
Any takers?
Thread Starter
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Senior Member
Joined: Oct 2004
Posts: 2,045
From: Washington State
Well, I'm a but disappointed that no-one wanted to play "guess my problem" game 
I finally had a chance to poke around my Montero. I believe my misfire and massive oil leak are unrelated. Misfire is caused by the failure of the valve seal on the #5 cylinder intake valve. Looking down the intake manifold, the valve is drenched in oil and spark plug is black with soot and wet. In fact it is so bad, that I suspect I was getting a misfire on #5 and #2 (waste spark system). I must have damaged the seal during install or didn't seat it properly.
Initially I was afraid that my misfire was related to the oil leak, such as some sort of weird head gasket failure (cylinder to outside, but only through oil galley) or compression ring failure. I tested compression ring theory by running engine and pulling PCV valve. There was no excessive blow by coming out from it. I also drained oil and checked for metal flakes/pieces. Oil had normal color and no foreign inclusions or metal of any kind. All together that eliminated the compression ring theory (good news). Poking around the engine some more, it looks like I had a slight oil leak from rear of valve cover on passenger side, but nothing at all from where the head gasket sits. Instead, I have a very big mess right where transmission mates to the engine. There is oil seeping on all sides of the bell housing and its all only on the transmission. My verdict - failed main rear seal. It is kind of a good news too (only in my weird world). I knew my rear main seal was going bad for some time - i had a small oil stain at the bottom of bell housing. Now I have an excuse to replace it.
So the good news, repair itself is relatively minor. The bad news is you got to pull engine or transmission to accomplish it. I have no way to pull/support the massive Mistsubishi transmission+transfer case, so I'm leaning towards pulling the engine. That will additionally give me a chance to examine the cylinders and decide if I want to do a bigger rebuild.
Anyone here ever pull the engine from the full size Gen 3 Montero? Would love to hear your hints and "watch out for..." before I get going on making the same mistakes
I finally had a chance to poke around my Montero. I believe my misfire and massive oil leak are unrelated. Misfire is caused by the failure of the valve seal on the #5 cylinder intake valve. Looking down the intake manifold, the valve is drenched in oil and spark plug is black with soot and wet. In fact it is so bad, that I suspect I was getting a misfire on #5 and #2 (waste spark system). I must have damaged the seal during install or didn't seat it properly.
Initially I was afraid that my misfire was related to the oil leak, such as some sort of weird head gasket failure (cylinder to outside, but only through oil galley) or compression ring failure. I tested compression ring theory by running engine and pulling PCV valve. There was no excessive blow by coming out from it. I also drained oil and checked for metal flakes/pieces. Oil had normal color and no foreign inclusions or metal of any kind. All together that eliminated the compression ring theory (good news). Poking around the engine some more, it looks like I had a slight oil leak from rear of valve cover on passenger side, but nothing at all from where the head gasket sits. Instead, I have a very big mess right where transmission mates to the engine. There is oil seeping on all sides of the bell housing and its all only on the transmission. My verdict - failed main rear seal. It is kind of a good news too (only in my weird world). I knew my rear main seal was going bad for some time - i had a small oil stain at the bottom of bell housing. Now I have an excuse to replace it.
So the good news, repair itself is relatively minor. The bad news is you got to pull engine or transmission to accomplish it. I have no way to pull/support the massive Mistsubishi transmission+transfer case, so I'm leaning towards pulling the engine. That will additionally give me a chance to examine the cylinders and decide if I want to do a bigger rebuild.
Anyone here ever pull the engine from the full size Gen 3 Montero? Would love to hear your hints and "watch out for..." before I get going on making the same mistakes
Last edited by HunterD; Dec 26, 2019 at 01:14 AM.
Thread Starter
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Senior Member
Joined: Oct 2004
Posts: 2,045
From: Washington State
For some reason I couldn't upload a photo from PC. Here is what the bottom of my Monty looks. As you can see, engine is pretty clean, but anything after bell housing is a total oily mess. Exxon Valdez would be proud
Senior Member
Joined: Oct 2015
Posts: 348
From: Northern VA
I too would be inclined to pull the engine. You will have better access for other leak repairs.
I would think engine removal would be quite similar to the Sport which I posted details on. Use the factory engine pick points to balance the engine with your leveler.
In all honesty, removing the converter bolts was the hardest part of the job to get the engine out. Access sucked. Use new bolts going back in as I am sure you will damage the corners during removal as I did.
Lack of metal in the oil is a very good thing!
I would think engine removal would be quite similar to the Sport which I posted details on. Use the factory engine pick points to balance the engine with your leveler.
In all honesty, removing the converter bolts was the hardest part of the job to get the engine out. Access sucked. Use new bolts going back in as I am sure you will damage the corners during removal as I did.
Lack of metal in the oil is a very good thing!
Senior Member
Joined: Oct 2015
Posts: 348
From: Northern VA
Pictures of where I attached the leveling bar chains when I pulled the 3.5L out of the Montero Sport. You have full size so may be different. Don't do it like this. Instead follow what I did when putting the engine back in. https://mitsubishiforum.com/forum/mi...01/#post313219
Pictures of where I attached the leveling bar chains when I put it back in. Much better balanced.https://mitsubishiforum.com/forum/mi...13/#post316406
Guess you decided to pull the engine...
Thread Starter
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Senior Member
Joined: Oct 2004
Posts: 2,045
From: Washington State
Thank you. This is very helpful.
Yes, I decided to pull the engine. It will give me a chance to check internals on it as well and likely to put in new bearings. I doubt I will be as good as you are at taking photos during work. I do try to take some snapshots to remember how to put together vacuum lines and some brackets/wiring. I'll try to be better Will keep you posted.
Yes, I decided to pull the engine. It will give me a chance to check internals on it as well and likely to put in new bearings. I doubt I will be as good as you are at taking photos during work. I do try to take some snapshots to remember how to put together vacuum lines and some brackets/wiring. I'll try to be better
Will keep you posted.
Senior Member
Joined: Jan 2019
Posts: 483
Im not getting email notifications for some reason, so I just read your first post.........trying to guess. Ok, maybe the rear cam shaft seal gave out, and the oil is pouring out of that area? But why would that cause the thick blue smoke to pour out the exhaust? Unless the smoke was from the oil burning off on the exhaust manifold/tail pipe? But then, why the misfire? This knucklehead is stumped.
Senior Member
Joined: Jan 2019
Posts: 483
OK......so its the rear main seal. I will want to follow you on this repair so I can learn some tips in case I am forced to do it on one of my Montys. Good luck with it, and keep the black oil off your digital camera.....
PS.....Yesterday I posted a 1999 Monty SR with all options on the "For Sale" tab. Its in Va.......any interested parties? ($1,000)
PS.....Yesterday I posted a 1999 Monty SR with all options on the "For Sale" tab. Its in Va.......any interested parties? ($1,000)