Burnt valve on 6.2

[dependable]

A lot of threads about 6.2 heads lately, thought I'd add one. Am working on another low mileage M-1008, when I got it from GSA, it had what I thought was a bad lifter. After taking valve cover off and compression test, it turns out to be exhaust valve. 400 or better PSI three cylinders on that side, and one that would barely register. I have never seen one valve seat so bad on a otherwise low wear motor. I guess it could have had a bad spring, but spring seems OK. It did not eat a glow plug, seen and repaired that before, no dents in top of piston.

Am going to use an NOS head I bought, as this one looks too far gone to fix. I don't think there is any way a bad lifter could cause this, anyone think other wise? I would have to delay reassembly to get a new lifter. New head comes with new valves and springs, so they will be OK. Push rod and rocker arm look fine.

My guess would be some debris got stuck in valve, any other ideas of cause?

First picture shows the bad valve compared to a good valve, second is close up of badly pitted valve seat. It must have been run like this for a while. Fortunately, piston and cylinder wall look fine. Would probably have worn some if it was a gas motor.

 

[Chaski]

What did the injector look like?

 

[Stonepicker1]

It could of been a bad injector that put to much fuel in the cylinder and also could of melted the glow plug(anything in the top of the piston?). This could of been changed out buy the previous owner and just ran the engine with a dead cylinder.

 

[cucvrus]

That looks like water damage to me. Like it had water sitting in it and rusted. Maybe a leaking head gasket at that cylinder. Just thinking out loud. Lower left looks like the compression seal was leaking and allowing water to seep in. Low mileage means it sat a lot and had time to corrode.

 

[dependable]

Thanks, I'll check out the injector, I have some new nozzles and a tester.

Top of piston has no impact marks. When they suck a glow plug, there is a pattern of the plug hitting top as it disintegrates, and the piston and wrist pin need to be replaced, as there is usually knock.

I see what you mean by the corrosion and possible gasket leak.

 

[cucvrus]

I you can zoom in on these heads they have the same pock marks from corrosion. These came off a 13K motor that sat with no hood. I had them machined and everything gone over on them. They are back on my M1008 project. I am a firm believer in replacing the original head gaskets at this point in time. The mileage matters very little. It is the time that has corroded away at them. Good Luck.

 

[dependable]

After testing injectors,(they test good, and pretty much all the same) I have to conclude damage was caused by head gasket leaking coolant into cylinder for a long time. This truck was a garaged fire company truck, so external source of water unlikely.

Something to keep in mind if you have to top off radiator, even a little, on a regular basis.

Kind of dangerous for me to get out pop tester today though, almost put me into Mercedes mechanic mode, and I do not have time for that now. Ha ha.

 

[cucvrus]

The heads you removed my still be serviceable. I would take them to a reputable machine shop and have the checked out. The valve seats can be re-seated and the heads can be useful again. I am sure there are a lot of guys driving CUCV's with bad head gaskets at this point in time and hardly even notice it. The few I had would run great and never gave any real issues. The most was no heat in stop and go traffic and the radiator would hold massive pressure and push the coolant into the overflow bottle. I would just un bolt the overflow and poor it back in the radiator. That worked good for a few years till winter came and I was driving a steam engine out of just the drivers side pipe. That I knew was game over. Since then pulled the engine went over the top end and all seals reinstalled and ran it 10K more miles. Still running good today. Good Luck.

 

[dependable]

Well, the the plot thickens. Everything up and running great, notice a very slow drip of coolant coming from under engine. At first it looks like it might be leaking from under new head, but I know that could not be true. Hoping it is the nearby freeze plug, but no, it is a hairline crack in block, just under head. Adjacent to the same cylinder that had the burnt out valve. I have no idea if the two are related, but they must be.

Anyone see this before? Still wondering what conditions caused this.

My only fix for now is probably some dreaded leak stop formula. I don't have time to pull engine and try to weld it.

 

[cucvrus]

Get it good and dry and clean it up. i would try JB Weld. Maybe. That stinks bad.

 

[snowtrac nome]

get it good and clean use belzanna super e-metal

 

[dependable]

I thought about what may have happened to motor: Coolant did not have much anti freeze, probably had some, or it was just on verge of freezing, water in block started to freeze.

What is different about that cylinder? The dip stick is there wicking some heat out of block. The freeze started there first and made the crack and wrecked the head gasket right above.

 

[cucvrus]

WOW. I never seen a dipstick that went into the block. My dipstick goes into the oil pan and connects to the exhaust manifold. I have a few CUCV 6.2 engine blocks laying around if you want to start over and build an engine during the winter months. I liked your analogy of the situation. All that really matters is that it is cracked. I would not trust the entire block at this point. It is cracked there and all most cracked thru at other places that are not visible. Like on the top side between head and block and in the cylinder. That would explain a lot. Good Luck.

 

[dependable]

Proximity of dipstick the only reason for ice crystals to start there and not somewhere else, just speculation, it is right under that part of block.

At this point going to try a block sealing product by 'blue devil', nothing to loose, it only weeps slowly, and only under pressure. I'll post how it works after a while.

Thank for offer of block, but I have some here as well. I had a tree chipper I ran for years with cheep over the counter leak repair, it leaked worse than this motor. I can always try a surface patch later, but doubt I will have to.

 

[dependable]

Following up here; I bought a bottle of Blue Devil Block and Radiator Sealer. only used half the bottle, and so far so good after 100 miles. The stuff is the color of windshield washer fluid, not full of goop or solids like some coolant system sealers.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjIuLHuv-TWAhVG34MKHfCABxEQFggxMAI&url=http%3A%2F%2Fstore.gobdp.com%2Fradiator-block-sealer-directions%2F&usg=AOvVaw2M5wD5ZU7hrIE4--tGencA