Mitsubishi 12-Valve 6G72 Head Overhaul

[Falcon_LS]

Some pictures I took of the cylinder head I started overhaul today. Took about 4.5 hours to remove the cylinder heads, and even more effort to remove the really hardened valve seals. They were literally rock hard, despite 4 ARX treatments. I haven't done anything to the pictures other than shrink them, I'm about to hit the sack.

Anyhow the heads are now at the shop, they've put them in a tank for cleaning and they will be installing the new valves and valve guides tomorrow morning. I've also got an overhaul kit, so I'm replacing everything right down the the exhaust manifolds and head gasket whilst the head is off. Going to be running Motorcraft 10W-30 for a while with some MMO prior to the OCI, and make the switch to M1 0W-40. That should clean up all the dust, sprays, etc. used during the process. Thanks to StevieC for the suggestion!

No more smoke, no more oil consumption.

Good news is, the spark plugs and injectors were quite clean - thanks to MMO and TC-W3.

Here are some pictures I thought I'd share:

 

[Falcon_LS]

 

[panthermike]

That's some heavy varnish, sounds like you have a good plan.

 

[Gary Allan]

While I'm sure that this engine was available in something like a Montero, this is the first time I've seen it in a North:South installation. I've only ever seen it transversely mounted.

 

[Falcon_LS]

Mike, the varnish actually surprised me a bit as well, but I'm hoping Mobil 1 will be able to clean that up.

Gary, this engine was available on 1991-1996 Monteros in the North American market. It's so much easier to work on when it's longitudinally mounted!

 

[addyguy]

That is some nasty, nasty varnish on that head!

It's going to take WAY more thn M1 to clean it up - why not clean it while you have it off?

 

[Falcon_LS]

The heads are actually in a cleaning tank right now.

Originally Posted By: Falcon_LS
Anyhow the heads are now at the shop, they've put them in a tank for cleaning and they will be installing the new valves and valve guides tomorrow morning.

 

[JohnBrowning]

If you can still get them try ebay get bronze valve guides for it. I have always replaced Toyota,Honda and Issuzu OEM valve guides with bronze guides and have always enjoyed better life and durability. IF the engine sits for a long time less chance of any corrosive interaction sticking the valve stem to the guide!

 

[CivicFan]

How many extra parts do you think you will end up with when you reassemble it?

 

[tom slick]

What's it like getting that level of automotive work done in Kuwait.

Just to clarify, you did 4 ARX treatments to that engine?

BTW ARX does not claim to soften seals, only clean the sealing surfaces.

 

[c3po]

My background is in from another field of Auto-Rx type chemistry application. The machinery treated with this chemistry is composed of "Ferrous Metal" and post copied here is correct. Truthfully I never made the connection as to why stains are not being removed from certain engines. Thanks Steve
Toyota Steve
Junior Member
Member # 1791

posted September 11, 2003 09:24 PM
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Drew - your dipstick is steel. I have come to find that Autorx cleans all metals, but does better at removing varnish color from the cast iron and steel parts than it does from the aluminum. It must have something to do with the porosity of aluminum, and the ease with which aluminum varnishes. Because your dipstick is ferrous metal, like your block, crank and rods, it REALLY cleans up well with autorx. steve
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Auto-rx as a varnish cleaner
Frank Offline


Registered: 05/28/02
Posts: 2164
Loc: Jacksonville Beach Fl
Auto-Rx will clean varnish off of cast iron most
metals during application process. Aluminum is the exception eventually it will come clean however not during the Auto-Rx application. Varnish is a cosmetic issue and does nothing to performance level.

I found these 2 old posts in the oil additive section.
I did see an old post about Schaeffer's Neutra and this product seems to do a good job of cleaning up the valvetrain.

 

[Gary Allan]

While mine wasn't that dirty, I would have thought that you should have it looking like this. I can't see the treatments being long enough.





Here's the pistons @ 180k after a massive dose of MMO shortly before the tear down.





Heads - well, one of them..

 

[StevieC]

Wow that is some heavy varnish Falcon_LS. I would definitely be using synthetic for the rest of its life if your climate is doing that to the engine.

My dad's van which has the same engine looked more like Gary's engine and I did an AutoRX clean/rinse both for double the mileage on the bottle and it is clean as brand new.

I think these engines need more time with the AutoRx in order to clean it up.

Can't wait to see the results after...

Steve

 

[Chris142]

Make sure that you replace the O-Ring on that tube that runs from the rear of the water pump and out the valley.

I bet 90% of the coolant leaks on those engines is from that stupid tube.

 

[Gary Allan]

Yeah, that O-ring is the usual suspect in the unexplained leak source mystery.

I know some people have done enough of these engines to think that they have a zipper on them, but the thought of taking the intake off to service that O-ring is just ..well, it's just not right for such a simple service procedure otherwise. That's about a $150-$200 job. Doing the valve seals is only a little more expensive.

 

[Falcon_LS]

Originally Posted By: CivicFan
How many extra parts do you think you will end up with when you reassemble it?


None.

Originally Posted By: tom slick
What's it like getting that level of automotive work done in Kuwait.

Just to clarify, you did 4 ARX treatments to that engine?

BTW ARX does not claim to soften seals, only clean the sealing surfaces.


It's not really common. In Kuwait, people tend to go all the way and do a complete overhaul. But I did a compression test, and hence only went with the head overhaul. The bottom ends on Mitsubishi 6G engines are near indestructible, so I only went with the partial overhaul.

Also, that is four ARX treatments. 4,000 km clean and 5,000-6,000 km rinse applications. Prior to that, the engine has always had 5,000 km oil change intervals until it was switched to synthetic in May of this year. I've been running 10,000 km oil change intervals since with a British synthetic (Morris Multi-Life Full Synthetic 10W-50) and Lexus 5W-40 Full Synthetic. Although the ARX has helped give the engine more get up and go.

I was following the oil burning application, which is said to rejuvenate seals. But the seals were rock hard as I said.


Originally Posted By: Gary Allan
While mine wasn't that dirty, I would have thought that you should have it looking like this. I can't see the treatments being long enough.


I understand this is pretty much a splash area, and the real work is in the ring packs. But that's really what I was hoping for, so it was quite a shock to see the state of my heads when the covers were pulled off.

Originally Posted By: StevieC
Wow that is some heavy varnish Falcon_LS. I would definitely be using synthetic for the rest of its life if your climate is doing that to the engine.

My dad's van which has the same engine looked more like Gary's engine and I did an AutoRX clean/rinse both for double the mileage on the bottle and it is clean as brand new.

I think these engines need more time with the AutoRx in order to clean it up.

Can't wait to see the results after...

Steve

Steve, Mobil 1 0W-40 is all this engine will see from this point on. Hopefully the next time I pull the covers off to replace the rocker cover gaskets, they will look CLEAN!

Originally Posted By: Chris142
Make sure that you replace the O-Ring on that tube that runs from the rear of the water pump and out the valley.

I bet 90% of the coolant leaks on those engines is from that stupid tube.


I've purchased a complete gasket overhaul kit, which includes cooling system o-rings, etc. as well. I wasn't going to tear down the engine to reuse old parts, especially having thrown $800 at it.

More pictures to follow tonight, as everything will be reassembled today. Having said that, I do have a question. I'm running a sludge application in a 1MZ-FE ('02 Lexus ES300). Would it be worthwhile extending the clean and rinse to 10,000 km (6,250 miles) EACH?

 

[Silk]

I haven't seen a Mitsi engine that dirty for awhile...we need to go back to the '80's to see that much gunge.Mind you,we don't pull them apart that much - valve guide seals means the car is off to the wrecking yard.But pulling rocker covers off gives us a good idea of what they are like - did a rocker cover gasket on a '94 L200 petrol today,just shiny alloy inside.

Maybe using 15/40 is the way to go?

 

[StevieC]

The reason the Mitsu engines & Chrysler 3.0L's which are virtually the same, had that level of "gunge" is because they weren't using EGR valves and were running extremely high cylinder temperatures causing extreme cylinder head temperatures and oil coking.

I'm not sure if Falcon_LS's engine has an EGR valve but he certainly has the climate which will produce high heated cylinder heads and cause oil coking with mineral oil.

In 93/94 Mitsu & ChryCo they came out with the EGR equipped 3.0L and this problem was drastically reduced and also the oil consumption problem due to hardened valve seals also reduced because they weren't being baked hard in the engines due to the lower cylinder head temperatures.

Also because emission testing was around and Chrysler 3.0L's without EGR's were failing left/right/center due to high NOX.

Most of my dad's customers would bring him the car and we would super-retard the timing so it would pass and then we would put the timing back again, or we would add a small pipe to the exhaust and pipe it back into the air box. They would run the car with this pipe until the test was over and then seal the pipe off until the next test.

The car would chug like crazy when cold and sometimes when idling in gear with this pipe feeding exhaust back into the engine so this is why it needed to be sealed off after the test.

We did it in a "hidden" way that the technician didn't know what we were doing and didn't see how we were cheating...

 

[Kestas]

Originally Posted By: Falcon_LS
Originally Posted By: CivicFan
How many extra parts do you think you will end up with when you reassemble it?


None.

I think that's why he wisely took lots of pictures before disassembly.

 

[Silk]

NZ has never had emission testing,and many vehicles (all in the early days) didn't have EGR,and most EGR systems are blanked off here soon as they give trouble.The only sludge engine here is the Nissan SR18/20....Mitsubishi are no more prone to gunge than any other....but valve guide seals certainly give trouble on early V6 engines,SOHC and DOHC.