Replacing Gen 3 Heads (Like a Virgin). Any Recommendation?

[DJPurdue]

Hi ExPo Community,

I had trouble with my car while travelling to the mountains. The whole story is in the thread below:

http://www.expeditionportal.com/forum/threads/158034-2002-Montero-Limited-Gen3-No-Start-Condition

After having the car towed to a shop, I was told that the cylinders #1 and #4 have lost compression. The shop wanted $3,200 to fix it. I had it towed back to my home and am now taking the head apart on both sides and going to replace them with good ones that I can source from a salvage yard from a low mileage vehicle.

I wanted to ask what precautions should I be taking in replacing the heads. I have never done this kind of repair. The most major repair that I have done to date is changing the timing belt on my friends Gen 2.5.

Somewhere I read that the head bolts need to be replaced once they are taken out.

Do I need to replace the head gasket? I think I should. Also what kind to get?

Would really appreciate any help.

 

[offthepath]

Although a rookie with monteros I've done a decent amount of engine work. Yes replace head gaskets and bolts.

Also a few thoughts, I'd have a machine shop still do a once over and check the used heads to make sure the valves, seats and guides are good and that the heads are level. Replace the valve seals while you are there.

Also did they do a leak down test in addition to the compression test? How did they determine it was the valves causing the issues? I'd just make sure there is not a broken ring or anything like that.

 

[DJPurdue]

Hi offthepath,

Thanks for the input. I could do the valve seal replacement although I haven't done it before just like replacing the heads on any car. It will be a good time to learn

The tech did say that he did a leak down test but kind of mumbled on the phone. I will pay him a visit and find out.

Thanks again.

 

[nckwltn]

you might also want to replace the exhaust manifolds... I have a cracked driver's side, and from what I've read.. they are commonly cracked.

 

[normal_dave]

Hi DJ,

I realize its nearly impossible for any of us to diagnose your Montero's condition online. With that said, I'm having a hard time accepting that you lost two cylinders in opposite banks, suddenly, on a road trip, without some sort of catastrophic incident. This may well be exactly what happened, but the number of times I've been lost chasing issues, only to find out it was a wild goose chase is approaching infinity.

It may be that the cows are out, and it's too late to close the gate, but I'm wondering if the mechanic pulled the upper intake and ran the compression test with a gauge on all 6 cylinders? or was it a computer diagnostic reading of cylinder activation. If you are that far along with the head swap, you may not want to consider this, but setup you air compressor with a disconnect and spark plug thread adapter. (I borrow the fitting and hose from my compression gauge), remove all the spark plugs and charge each cylinder with the rocker arms off and see where the air is escaping on # 1 and # 4. (exhaust pipe, intake runner, crankcase/pcv area (piston rings) adjacent cylinder... (head gasket) etc.) This will help isolate the issue.

I also find it curious about the firing order for our engines and the coincidence that # 1 and # 4 are paired cylinders in that they reach TDC at the same time, but one is on the compression stroke and the other is exhaust stroke. Not positive that this applies in terms of spark on the 6G74, but it sure has me thinking...Here's an explanation for the 6G72 sourced from JustAnswer:
------------
Mitsubishi 6G72 Timing Events

Cylinder numbering and arrangement
The 6G72 is a 60º V6 gasoline engine that displaces 2.972 liters. The cylinders are arranged and numbered as shown below.
Mitsubishi 6G72 cylinder numbers
Ignition Timing
The firing order is 1-2-3-4-5-6, with each numerically-successive cylinder reaching top dead center (TDC) 120 crankshaft degrees after the previous one. Paired cylinders have pistons at the same relative position, such as both at TDC, but they are 360º out of phase, such as one is in the exhaust stroke and the other is in the compression stroke. Paired cylinders are 1-4, 2-5, and 3-6. Spark plugs are fired simultaneously in paired cylinders, during the compression stroke for one cylinder and during the exhaust stroke for the other cylinder. The spark during the exhaust stroke is wasted because the basically inert exhaust gas cannot combust.
----------

With the above little tidbit, you know I'm heading out to the garage to swap coils and see if the problem moves to another pair of cylinders, right? Or at least be sure I don't have wires crossed or not seated properly, since I put new plug wires on before the trip (dohh!) I've done it boys, more than once, and lived to tell about it.

Another question might be did the timing belt happen to lose tension and slip just enough to disrupt the timing, (+valve seating) and still avoid piston to valve contact? Check the timing marks against TDC and both cams just for fun, you said you are going to replace the belt anyway.

You just bought the car a few months ago, and may or may not have a service history, but it sounds like it was running well enough to make your trip, so what caused both cylinders to fail, or maybe one was already down, and the second joined in and happily caused the no start?

Unrelated to your no start, but handy for your project: I recently did valve seals on my wife's 3.5L Sport, and bought a wonderful valve spring removal tool from Lisle corporation, that actually allowed me to replace the seals while the engine was still installed, with relative ease (as far as Mitsu's go...)
https://www.youtube.com/watch?v=b1DmJQ4Fods

All of this may not be of any use to you, but even with some of the Mitsubishi design issues, the 3.5L is a pretty tough engine, and I hate you are struggling with yours as a new owner. Be strong and of good courage, you'll be back on the road soon enough, inquiring minds want to know the root cause, since you've drawn us in.

Edit: so I'm reading through this post again, and I completely forgot I also had a no start condition on our '03 Sport a few years back. I'm sorry I can't remember the exact reason I determined it but the ignition control module had failed. It is located near the coolant bypass pipe, top/left, mid-engine. Bought a generic from Advance auto with a coupon code, swapped it in and presto, been running fine on it ever since.

Good Luck, keep up posted.

 

[DJPurdue]

Hi DJ,

I realize its nearly impossible for any of us to diagnose your Montero's condition online. With that said, I'm having a hard time accepting that you lost two cylinders in opposite banks, suddenly, on a road trip, without some sort of catastrophic incident. This may well be exactly what happened, but the number of times I've been lost chasing issues, only to find out it was a wild goose chase is approaching infinity.

Those are my thoughts too exactly. Never had it happen before on any car. People say that Mistu's are different. I guess that is so.

It may be that the cows are out, and it's too late to close the gate, but I'm wondering if the mechanic pulled the upper intake and ran the compression test with a gauge on all 6 cylinders? or was it a computer diagnostic reading of cylinder activation. If you are that far along with the head swap, you may not want to consider this, but setup you air compressor with a disconnect and spark plug thread adapter. (I borrow the fitting and hose from my compression gauge), remove all the spark plugs and charge each cylinder with the rocker arms off and see where the air is escaping on # 1 and # 4. (exhaust pipe, intake runner, crankcase/pcv area (piston rings) adjacent cylinder... (head gasket) etc.) This will help isolate the issue.

He did say that he checked the compression on all 6 cylinders. The upper plenum/intake was removed when I brought the car back. So I am assuming that he did do a physical compression test. He was also showing me the piece of paper he had the numbers written on for each cylinder.

Unfortunately, I don't have an air compressor. I rent so I have to do all my work on the street. Its not the ideal situation but its what I have. I read on a Mitsubishi-forums.com that someone changed their engines valve seals and the compression came back. I will start with that and then check compression and then see how it goes.

Another question might be did the timing belt happen to lose tension and slip just enough to disrupt the timing, (+valve seating) and still avoid piston to valve contact? Check the timing marks against TDC and both cams just for fun, you said you are going to replace the belt anyway.

The timing belt marks are exactly where they should be. I have had timing jump on my Honda Civic before but that was before I was really getting on it. (Like 9000 rpm with every shift for hours going from Maryland to Ohio). But the car still ran. Did run like #### but it was running. With the Montero, the engine was not even under any stress. Worked fine till we reached the hotel and then wouldn't start at all.

You just bought the car a few months ago, and may or may not have a service history, but it sounds like it was running well enough to make your trip, so what caused both cylinders to fail, or maybe one was already down, and the second joined in and happily caused the no start?

Yes, I dont have any service history. It was running great till it didn't run at all.

Unrelated to your no start, but handy for your project: I recently did valve seals on my wife's 3.5L Sport, and bought a wonderful valve spring removal tool from Lisle corporation, that actually allowed me to replace the seals while the engine was still installed, with relative ease (as far as Mitsu's go...)
https://www.youtube.com/watch?v=b1DmJQ4Fods

That is a great tool. I saw a video by Eric The Car Guy yesterday and he was also recommending this tool. I am going to order it so that I can get it this week to change the valve seals.

All of this may not be of any use to you, but even with some of the Mitsubishi design issues, the 3.5L is a pretty tough engine, and I hate you are struggling with yours as a new owner. Be strong and of good courage, you'll be back on the road soon enough, inquiring minds want to know the root cause, since you've drawn us in.

I will keep posting as I keep going and let the community know. It might help someone a lot of pain in the future.

 

[DJPurdue]

Hi nckwltn,

The exhaust header is fine on the passenger side. I will check on the driver side and replace if needed. No noise issues as yet. Right now the focus is getting it up and running. Thanks still for the input.

 

[normal_dave]

So it sounds like the mechanic did a reasonable compression test, but I'm still holding out for better news. If you don't have a compression tester, you could cut a piece of plastic pipe similar in size to a spark plug, hold it down into the spark plug tube sealing the opening, maybe cover the top of the pipe with your thumb, have someone turnover the engine and verify those two cylinders aren't generating pressure.

I am most confident just replacing valve seals won't help the compression issue, their only job is to keep oil from getting into the cylinders via the valve stem. Replacing the seals was a small miracle on my engine, but only in terms of the "ol smoky" issue at extended idle and the excess oil consumption.

I'm still optimistic, however... If you have a multimeter, break it out (if you don't, then get one), and read through this post a few times. This tells in detail how to test the ignition module, I now recall how I discovered mine and I'm, pretty sure this was the test. As you will see, you could have a good coil pack, and still not be able to start the engine. I might add that this "Doug C" is quite the Mitsu specialist, and I believe well worth whatever you would pay him for the online mechanic advice he sells through this service, I've used his advice before and it was spot-on.
http://www.justanswer.com/mitsubishi/6ce0h-mitsubishi-montero-sport-ls-2002-montero-sport-3-0-v-6-rough.html

At the end of the day, you may still end up pulling the heads, due to low/no compression, but it sure would be nice to knock this issue out, with an ignition module, or something similar. By taking time and working through some of this you avoid throwing parts at the problem, and gain great satisfaction that you have identified the real issue by determining what isn't wrong first.

"The mind is a terrible thing", getting older, but I'm just about positive that my ignition module from Advance in the generic box actually was an oem with the Mitsu logo and part number. I remember being pretty satisfied that I ended up with a genuine part for around $ 100.00

BTW, how in the world can I get a paragraph double space to show up in a post? If I'm so smart, how can I be this stupid that I can't type properly!!! Edit: well we can ignore this now can't we...it has to do with screen size, laptop=no paragraphs, desktop and larger screen= easy reading.

 

[coffeegoat]

DJPurdue,

I have absolutely no help for you on the compression/head work, however, I have been working on a parts list you may find useful. I'm working on a rebuild/refresh on a 2001 limited and instead of starting with a build thread I'm trying to put together a google doc spreadsheet with all the parts, resources, etc all in one place and linked to tutorials, forum threads etc. Eventually I'll see if I can it reviewed by the collective for complete accuracy but for a start it should be a pretty good estimation of costs to do an engine refresh (timing belt, gaskets, plugs, etc). Someday I'm hoping it'll be a nice one stop shop to figure out what parts, what tutorials/guides you need to do various projects.

https://docs.google.com/spreadsheets/d/1gbUj5RziJTqk-i_Fs9HughXCmFE77CWoFsiUOkFfF0c/edit?usp=sharing

If you see anything you want updated or that I should change just let me know, cheers

 

[DJPurdue]

Hi coffeegoat,

The list looks great. I think you pretty much captured it all. I really like that you have the links and part #'s in it as well. Great job!!!

 

[DJPurdue]

Hi normal_dave,

I got the heads pulled out. I was hoping to get the heads from the salvage yard, have them inspected and just put them on. But then I talked to the tech that had diagnosed the no compression issue on cylinder 1 & 4 and he said that is not how you do it. He said that I will have to send it to the machine shop and have them clean it (he said they boil it for 2 hours) and then lubricate and check everything and if all is good then reassemble. They could do valve grinding as well but it would cost more. I will change the valve seals myself. The Lisle tool is on the way

My objective right now is not to get the car up to a 100% but to just get it running. Its already taken up about a $1000 (if not more) between the towing and diagnostics so I am trying to get it up and running.

What would you or anyone here recommend? What way can I save some money but still ensure that once I put the car back together that the compression issue will be resolved?

 

[montypower]

Have the heads rebuilt by reputable shop.

I did full head rebuild on my 03 Montero at 93k. It ran fine. However, these OHC motors wear hard. Guides were worn. Really brought the motor back to life doing the refresh. Used all OEM dealer parts. Great time for plugs, wires, injector rebuild...

 

[normal_dave]

I agree (generally) with the tech, but let's not get the cart before the horse. If you have pulled your heads, can you visually see the damage on the valves that is causing compression loss? You are assuming the head is the problem, and if #1 and #4 are at "0" compression, then you should be able to see a burnt valve, broken spring, crack or other opening allowing the compression to leak out while cranking. What if the heads are fine, and the piston rings are broken or worn out?

On your old heads, if you can't see damage to the valves, (crack, burn, or a gap letting air get by a valve), then we need to check for leaks another way. Turn the head with the cylinder dome side facing "up" and level, use something to brace the head so the combustion chamber/head surface is level. With the valve springs and spark plugs, still installed, then carefully pour a pre-measured amount of water, mineral spirits, etc. until you cover fill the combustion chamber of the head, covering the valves and spark plug hole. Wait and watch for the liquid to leak out through an intake runner, exhaust port, etc. Repeat this for the questionable cylinders, and the others if you are having fun by this time.

If you've already bought junkyard heads, then they too are an unknown and should at least be checked and freshened up by a machine shop. Whichever heads you use, since you are going to do your own valve seals, consider taking a sharpie, and number each valve to each cylinder 2-I, 2-E, (intake/exhaust) etc. so that the machine shop can provide everything back to you to assemble properly. I guess if they do a full valve job, it won't matter if you number them anyway. With this said, there may be no reason to buy junkyard heads, just take yours to a local machine shop, and get them checked and repaired, see if you can save money re-assembling them yourself, since you have the tool and seals coming.

I have in the past bought valve lapping compound and the drill mounted suction cup tool and "lapped in" the valves myself, but it really shouldn't cost a lot to get a machine shop to go over the heads.

What scares me is you do all this work, re-install and still have the compression problem or worse yet another issue causing the problem the whole time that hasn't been pinpointed yet. You've really jumped in with both feet, hopefully you are on the right track.

Let us know what you find. I'm still concerned about verifying why those two cylinders aren't showing compression, although it may already be obvious to you. The hardest part about the valve seals for me was getting the old ones off. Installing the new ones requires a little plastic cap that goes over the valve stem as a guide, comes in the kit, a little oil on the inside of the new seal, and a matching deep well socket or pipe, that you can push the new seal in place by hand. You should feel two "clicks" or steps as the new seal sits into place.

EDIT:
BTW, did you run the full test on the ignition control module yet? I'll sleep better knowing it checked out ok...

 

[DJPurdue]

Hi normal_dave,

So the heads have come off the car. Visually I cant seem to tell any damage and that maybe my lack of experience doing this kind of job. Here are the pictures I have taken:







It just looks really bad inside so I found a shop that can refresh them for around $500 and since I am this deep into the project anyway, I will have the ones from the car redone.

For the ignition module test, I still havent done that. Since the plenum was already out of the car and I had taken the timing belt off too to replace with a new one and water pump and all tensioners, I will just wait to get the heads back from ths shop and reinstall. If the car fires up then all good otherwise ignition module test it is.

Also then I will go back to the tech and ask him to redo all the tests since he got paid.

Question: I have uninstalled everything on the timing marks (crankshaft and cams). Once I get the head back from the shop, it should just be a matter of aligning the marks and reinstalling, right?

Also would like to clean up the pistons while I am at it. What would you suggest I use and what method is best?

Thanks so much for your inputs. Really appreciate them.

 

[normal_dave]

Ok, since you've determined to get the heads serviced, that's good, but I'd still like to verify why you didn't have compression. I would pull the rocker arms, and inspect the valves as previously described to determine if #1 and #4 are the cause of the compression loss. You'll want to temporarily re-install the spark plugs of course. I know I seem hung up on this, but you said you wanted to get it running, and that means absolutely verifying the cause of the issue. Why was there no compression on those two cylinders?

I think it would also be a great time to clean/bleed your lifters. This is a time consuming, but not costly procedure. It will allow you to be sure of proper oiling, and no noisy ticking lifters in the engine later. When you go through this procedure, you'll want to look for broken/cracked black plastic rings on the lifters, and replace the lifters that have the broken parts, or won't hold pressure as you pump them with diesel fuel.

There's a great write-up here, I did this on the wife's Montero Sport, ended up replacing 7 lifters using OEM parts only, and it made a tremendous, lasting difference.
http://www.club3g.com/forum/maintenance/165458-how-bleeding-lifters-v6.html

As far as cleaning pistons, re-install your crank bolt, use the wrench to rotate each piston to TDC, then use a putty knife/scraper and a wire brush mounted in a drill to clean the scale off of each piston. Don't get too aggressive of course.

As far as the timing marks, basically yes, you will just re-align everything, but use the factory service manual directions for this. Mitsubishilinks.com I also like the Rock Auto Aisin timing belt kit, It has the Mitsuboshi belt, but it appears it is a high quality timing belt, and oem idler, adjuster, and water pump.

Also consider new rear cam seal O-rings, use Mitsubishi genuine, also replace the front cam seals at this time, I used aftermarket National, hopefully the machine shop has included this in their price. You will also want Mitsubishi valve cover gaskets. I use RCHillmitsubishi online parts, and have gotten good service, and the lowest prices that I could find, at least.

Edit: Forgot to add, be sure to inspect, clean, and replace your pcv valve, and piping as this is a potential source of excess oil usage, and your exhaust ports show some extra carbon deposits, this is not unusual.