The ol' Tahoe is down for the count - coolant in cylinder(s)

[arveetek]

Thanks for the kind words and encouragements everyone!

Robyn, yes this engine has std pistons. I still have my original 95 engine for parts, so I'm good there. In fact, I already swapped in one piston from the 95 to replace the banged up piston in cylinder one. Thanks for the offer though, I appreciate it.

I haven't had a chance to touch it all weekend; in fact, the way things are going, I may not be able to get to it until this coming Saturday. I'll keep you updated on what I find out.

Casey

[arveetek]

Finally had time to work on the ol' Tahoe this weekend. Took off Friday to get a head start, and by the end of the day Friday, she looked like this (again):










After pulling the passenger side head, my suspicions were verified: the exhaust valve broke in the exact same manner as it had on cylinder 1:






I found the exact same damage as before in cylinder 1; bits of the valve had imbedded into the top of the piston and banged it up pretty badly, along with the head. There was also some slight scoring on the cylinder wall:














When I first disassembled this engine (if you recall, this is my spare 1997 506 block, not my original 1995 929 block), I assumed it had ingested a glow plug and that is what caused this damage. Apparently, that is not the case. For some reason, the exhaust valves are self-destructing on their own.

I have both heads and off and will be dropping them off at the machine shop tomorrow morning to have all new valves installed.

I spent quite some time honing the damaged cylinder yesterday afternoon; looks like it will clean up okay. I already have a good piston pulled from my original 1995 engine to swap in.

Casey

[Robyn]

At least we know what happened.....

Strange things as to why the valves are going away like that......?????

Looks like the short block is still fine.

Just a thought here.......Look at the cost of the repairs on these GM heads....then take a good look at a set of Fresh AMG 6.5 heads.

New BETTER castings, new valves, new springs....ZERO time on them.

I used a set of AMG heads on the Dahoooooley when I did the engine...Those are lovely heads.

Just swap your Rockers and push rods.....

The new AMG heads are gonna be a tad more $$$$ but used heads on a 6.5 is a time bomb IMHO

If you decide to go with AMG heads...be sure to specify PICKUP/SUV heads...The P400 for the Hummer/Van use different intake bolt angle...and will not work with pickup/suv intake manifolds.

This mistake is how I ended up with a set of the P400 heads...

[arveetek]

The new AMG heads are gonna be a tad more $$$$......

I would love to, but I've already blown a huge wad on this project and can't justify spending that much more. Other than the valves, these heads are actually in really good shape, and crack-free.

I decided to go ahead and replace the lifters while I'm at it, though. I was staring at the lifters with the heads off, and thought, "I better replace those too while it's easy to do." I don't want to take any more chances at this point.

Casey

[Robyn]

Copy..

I understand fully.........If the one head is not hurt....should be OK

[More Power]

Ghost of Christmas past...

Here are a couple of images sent to me in 2013 by member Bob Farley.

In combination with your experience and one or two others I've heard about, are these the result of a bad production run or a change in subcontractor? It's not inherent in the design or this problem would have been epidemic.

Glad you have a plan Casey...

[arveetek]

Ghost of Christmas past...

Here are a couple of images sent to me in 2013 by member Bob Marley.

In combination with your experience and one or two others I've heard about, are these the result of a bad production run or a change in subcontractor? It's not inherent in the design or this problem would have been epidemic.

Glad you have a plan Casey...

Wow! You're right, that's the exact same failure! The only conclusion I can come up with is what you stated: either a bad production run or a change in subcontractor. Probably no way to find out.

My advice to anyone reading this: if you find a valve failed in this manner, go ahead and replace ALL the valves. If one has failed, the others are not far behind.

My machine shop stated that the intake valves would probably not fail in this manner, but I'm not taking any chances. All the valves are being replaced. I hope to have the heads back the first of next week. I am off all next week, so hopefully she'll be back on the road next week!

Casey

[2INSANE]

Is it possible some valve metal pieces got past the piston rings into the oil?

[DmaxMaverick]

Is it possible some valve metal pieces got past the piston rings into the oil?

How would that be possible, with piston, rings and cylinder intact? It wouldn't.

[2INSANE]

How would that be possible, with piston, rings and cylinder intact? It wouldn't.

If there is heavy scoring on the rings, I thought it could be a possibility. I would hate to see Mr Casey have future problems.

[arveetek]

I didn't see any evidence of metal in the oil. The rings didn't look damaged, either. Only the cylinder wall had one scuff, which I was able to get out with honing. I was tempted to reuse the rings, since they only had 931 miles on them, and I didn't see any visible damage. However, I was able to locate a matching set of rings for one piston, and got them installed.

Swapped in piston from my original 929 engine, and replaced the lifters for good measure. I got the heads back on Tuesday morning. Engine is now repaired and reassembled and my son and I got it dropped back into place this morning. Hope to have it started and running tomorrow.

Casey

[DmaxMaverick]

If there is heavy scoring on the rings, I thought it could be a possibility. I would hate to see Mr Casey have future problems.

That would suggest broken rings and piston, at least. As Casey said, the cylinder wall damage wasn't bad, and would have to be a lot more than he found. If it were to happen, it would destroy the engine, entirely. A gouge in a cylinder deep enough to pass a chunk of valve past the piston, compression and oil rings would push it beyond recoverable (short of a sleeve, which is not at all practical with this engine). I've seen similar damage in engines ran well beyond time for overhaul, and that was the result. That's one you leave swinging in the tree.

[Robyn]

Sounds like you are almost there......

Looking forward to hearing it run.....

[arveetek]

https://www.youtube.com/watch?v=scr4pe6Lxng

Got her back on the road yesterday around noon time.

The correct torque converter makes driving much nicer, as the engine doesn't have to scream to get moving. However, there is not as much turbo whistle now since the engine RPM remains much lower most of the time.

For the easiest first starts, I followed the recommended procedure: I left the glow plugs out (with the plugs out, there's no compression and therefore little resistance on the starter) and cranked the engine over to build oil pressure, and then continued cranking until fuel mist starting coming out of the cylinders; then I installed all the glow plugs, cranked it over again, and she lit right off! No drama at all when using this procedure, as this naturally bleeds the fuel injection system easily.

Casey

[Robyn]

So happy that your rig is back up.

I learned that priming procedure years ago when I fooled with the Old's 5.7 diesels.
After frying a couple starters and draining batteries...GOTTA BE A BETTER WAY.

Yup...yank the plugs and spin it over....

The Turbo does make it a little bit tougher....but still much easier than draining batteries and melting starters...

Also the fuel system does not have to battle compression to get the fuel to shove the air out of the fuel lines.....


Good deal.....

GOTTA BE A GOOD FEELING TO HAVE THE RIG UP AND GOING.....

[trbankii]

Great news for the New Year! I'm happy to hear it!

[arveetek]

The Tahoe is still running great, but I do have one small issue: there is a vibration that is engine RPM related that is really annoying me. At first I thought I was being paranoid, but I can definitely tell it's there. I can feel it the most between 1500-2000 rpm, even sitting still in park. It feels a lot like a bad u-joint feels at highway speed, but it's obviously engine related, and it wasn't there before (right after the initial engine rebuild).

Today I decided to verify if it's in the engine or transmission. I unbolted the torque converter from the flexplate and then started the engine; she was smooth as silk (or at least as smooth as a 6.5L diesel can be). I tried several times to replicate the vibration and could not detect it. That relieved my fears that there might have been some sort of slight misfire or other engine issue. I bolted the torque converter up 180 degrees from where it was (just to see if maybe there was some harmonic issue between the TC and flexplate that might be resolved by clocking the TC at a different spot), but the same vibration returned. It appears the new torque converter is out of balance.

It's really not that bad, and a lot of people might not even notice it, but it's driving me up the wall since I know it shouldn't be there. At just the right RPM, I can see the rear view mirror start to shake in rhythm to the vibration.

I have reached out to the torque converter supplier to see what the next step is.

Casey

[Robyn]

Torque converter is junk.

I had a batch of junk converters years ago.
What happens is the hub that goes into the tranny was replaced and the damned thing is not concentric.....
Allow to run as it is will tear up the front pump on the tranny and it will also add stress to the crank shaft...

Only one way to fix it....

Get that bad boy out and take it back to the seller.

I had six I believe that were bad.....

I had one that would literally shake the mirrors.

I dragged on out of the rig after doing what you have done....Grabbed it in the lathe by the hub and spun it..

Damned thing wobbled like a button on an outhouse door....

I was running out 1/8" or more..

All manner of hell came loose when I discovered the issue.
The rebuilder tried to convince me that it was a bad vibration damper.

He did not was to do a thing..

I threatened to burn his outfit down.....He finally gave me my money back.....I replaced it with a different brand...also spun the replacement in the lathe first.

Sorry to hear of the issue.

Get that bad boy out of there......

[DmaxMaverick]

It's great to hear the good news. However, an unbalanced converter is no small thing. Serious damage (and starting all over again, again) can happen as a result. The problem could also be a cracked flex plate, which is much more common, but often difficult to see.

[arveetek]

Yes, long-term damage from bad harmonic vibrations has me concerned. I don't think it's the flexplate; it wasn't cracked before the install, and the vibration has been noticeable since startup after the engine/torque converter swap.

Casey