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

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Originally Posted by DmaxMaverick

This.
It may not be that bad. Maybe a gasket or valve/seat. Think positive, for what it's worth.

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I suspect it might be a broken valve. Very similar symptoms to when I pulled this particular 506 engine out of the donor truck in the first place. If you recall, cylinder 1 had a busted exhaust valve and a piston that was banged up. I theorized that the engine had ingested a glow plug and caused the valve to break. Now I'm wondering if there are some hidden flaws in the valves themselves, or perhaps the valves got too hot and became brittle for some reason? Perhaps the original valve failed on its own without a foreign object. If so, I'm going to need to go through and replace all the valves to be sure. But that's just a theory at the moment; could be a broken piston as well. I'll have to pull the head to find out.

It may not be that bad, but it means a lot more work, again. I'm just really tired and don't feel like going through all this again. I still need to replace the torque converter (which just came in today... what timing), so I might as well pull the engine and see what's really going on and replace the torque converter while its out. I just don't want to do all of that again.

Casey

Gods speed....Sorry to hear of the failure.....

Most of us have been down this road a time or two...

Hope it is an easy fix.

I just listened to the video.

My bet is this is a valve issue.... or valve spring

A very common failure after a rebuild is lifter failure. The smallest amount of contaminates can and will cause lifters to seize or collapse. Such a cheap $12 part can cause such havoc. I heard your video with my eyes closed and recalled the same exhaust sound during one of my fun filled lifter failure adventures.

Is there any up and down movement on any of the rocker arms. If not, turn the crank 1/2 turn and check for play again to confirm it is not lifter failure.

If it is lifter failure, some lifters can be pulled easily without removing the head. The outer cylinder lifters are a pita if not impossible without the right tools.

Was there a kind of thumping noise coming from the intake?

There is the possibility that a cylinder got a crack in it. If you are willing to pull the pan and check for cracks into that cylinder, would help determine if that motor is garbage.

Possible the head gasket took a poop. Too.

Did you check for air bubbles or oil in the radiator? Check oil color?

Do not get discouraged! I know exactly how you feel! Spending thousands of dollars and countless hours on a motor only to find out it is **** once it is installed…

This very reason is why I sold all my motors and parts for $15,000 and simply bought an Optimizer with a warranty.

Good luck man! Keep us posted!

I already pulled the valve cover and checked the valve train; valves are opening and closing normally.

No air or oil in cooling system; no coolant in the oil.

I'll bet a valve broke.

Casey

Not that it makes any difference...
If a valve broke right off the valve spring should/could be higher then it's partner.

Well, you are already 1/2 there… I would pull just the head not the whole motor and check it out. You could be rolling again by tomorrow! Giterdun!

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Originally Posted by Yukon6.2

Not that it makes any difference...
If a valve broke right off the valve spring should/could be higher then it's partner.

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When I disassembled this motor to start with, it had a broken exhaust valve - about 1/2 the outer edge was missing, but most of the valve was still intact, and it still opened and closed normally, but would not allow the cylinder to hold compression. At the time, I thought the engine had ingested a glow plug and damaged the valve, but now I'm wondering if the valves were brittle for some reason.

Here's the original broken exhaust valve:


https://live.staticflickr.com/65535/...fa4447ef_b.jpg


I'm suspecting I will find something like this when I pull the head. If so, both heads are coming back off and all new valves are going in.

Casey

Turn the crank to TDC and put some air in the cylinder. You need to find where the leak is. This is free, and takes a few minutes for a priceless revelation.

I agree with Maverick......
The valve may not have lost enough pieces to damage the piston...and the part flew out the pipe..

I seem to remember reading that the valve have a hard face overlay (Two piece)

Your piccy clearly shows this.

The hard face portion broke and fell off.......

NEW VALVES FOR SURE.....

OEM valves are induction hardened since about 1980. They may be bi-metal, but still induction hardened. Who knows with aftermarket, though. The pictured valve looks like it parted at the hardened, bi-metal depth. A single failure can happen at any time, for any number of reasons, and it can be addressed on an individual repair. Multiple failures should change that approach. Any valve from the same lot would be suspect, so replacing the set would be right. A good, used OEM set would be as good, or better, than most aftermarket, in my experience.

The stuff from across the pond ....not so much.

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Originally Posted by Robyn

The stuff from across the pond ....not so much.

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No doubt. Even Clearwater complete heads use recycled valves, rather than sourcing them from the source of the heads, which may be cheaper. What concerns me is the foreign clones. It can be difficult to know if you have OEM, or an OEM clone from who knows where. Used valves, as well as many other parts, are a crap-shoot because of this. It's best to buy them from a known-good source, who sources true OEM or good, US quality aftermarket parts. There's a lot of good stuff out there, but there's also enough junk to mess the lot (bad apples).

I still have the valves from my original 1995 heads that (as far as I know) are the original, GM installed valves. Assuming I will need to replace all the valves, should I try to use those? They were functioning fine; just had 376K miles on them.

Still a lot of assumptions at this point, but if it is another broken valve, my plan was to take the heads back to the machine shop and have all new valves fitted; perhaps I would be better off to simply lap the 1995 valves and install them in the 1997 heads and reuse all the new seals that were recently replaced...

Really, before I get too far ahead of myself, I need to finish my diagnostics. It might be a couple of days before I have time to get back out to the shop, though.

Casey

Ya know....

You need to swap the converter out anyway...

If it were me, I would rip the hood off...yank the engine out and get it on the stand....

Far easier to work on that way too...

Rip both heads off and gitterdone....

Spending time fooling around trying to nail it down is pretty much a moot point......
It has a dead hole.....Ya need to swap the converter anyway.....

The engine is easy to yank out.....Far easier to work on the heads out on the stand too....

Just my 2 cents worth.

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Originally Posted by Robyn

Ya know....

You need to swap the converter out anyway...

If it were me, I would rip the hood off...yank the engine out and get it on the stand....

Far easier to work on that way too...

Rip both heads off and gitterdone....

Spending time fooling around trying to nail it down is pretty much a moot point......
It has a dead hole.....Ya need to swap the converter anyway.....

The engine is easy to yank out.....Far easier to work on the heads out on the stand too....

Just my 2 cents worth.

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Pretty much what I had planned on doing!! :D

Casey

Small block heads are not bad in the chassis.....These suckers are just too heavy.

Out on the floor you can get right after it and gitterdone without wrecking your back jumping the heads....

Plus you can clean the decks easily and be sure everything is spiffy going back.

The used valves from the 95 heads....I would not be opposed to using them.
Grind them and lap them to the seats in the fresh heads....

The only Caveat might be any damage to the one head.....LETS HOPE IT IS NOT HURT......

Do you have std pistons ????
IF you wind up and need a piston....I think I have some std size ones on the shelf.

If ya need one....let me know...Getcha one in the mail....They need a new home...

Hang in there. I know how horrible that can be - the good feeling of getting a job done and then things go south again.

I feel for you.

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Originally Posted by arveetek

As of 9 pm last night, this is the current status of the ol' Tahoe:
...clip...
So after 4 months and thousands of dollars, I'm essentially right back where I started. I still need to swap out the torque converter, so it looks like pulling the engine (again) is in my future.

I'm nearly sick to my stomach at this point and really discouraged. I can't imagine what went wrong, or what I missed. I did everything by the book to the best of my ability.

Casey

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Bummer Casey.... Sorry this happened. :(

I don't have any exhaust valves. But they aren't that expensive. I think the engine shop charged me about $20 for a replacement a few months ago. That may be all you'll need. I know that in the early 1990s I had a local diesel shop install new head gaskets in my first 6.2L diesel pickup. I was called in when they got the heads off, and was shown the top of one piston that had been beat up by a loose glow plug tip at some point in its history (happened before I got the truck). We chose to ignore it. A couple years later we did a full rebuild - unrelated to the piston crown.

I have images somewhere in the archive of a valve failure just like the one your engine developed. The material GM used for the exhaust valves is an alloy called "Stellite", which is likely some alloy of stainless (resistant to heat). You can read more about the alloy here: stellite alloy steel exhaust valves

I mentioned to my daughter the possibility of a problem developing with the engine even before we attempted the first start. It's the nature of the beast. I wanted her to be prepared, and we even talked about a way(s) forward if that happened. So many things have be right for success, let alone avoiding a lurking wild card like the valve problem.

The original lifters used in our 6.5 Blazer had been laying horizontal on towels for 12 years. I considered new lifters when put back together this summer, but I didn't want to chance getting cheap imports. I thought the 187K mile GM originals were a better gamble. They were all cleaned and checked before going in. The only thing I didn't do that I should have was pump them up using 10W oil or ATF before installation. I suspect it took some seconds of running to accomplish the same thing. BTW - our 6.5TD Power Project engine got its original lifters when we rebuilt it... It ran another 300k before I sold it - still running great... Jim

Casey

I have been down this road myself....
It is disheartening for sure.....
You have valves from the 95 engine to rob for parts....A good thing.

A set of head gaskets and bolts are the big items (A known quantity)

Take a deep breath....let it out slow and if the personal need is there....A few expletives are certainly understandable....

I am pretty sure that you did not miss anything......It is real tough to catch the sort of stuff you are dealing with unless you just SPEND $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ and replace everything.....still.....CHIT HAPPENS.

Ask the Boys that were running Chernobyl how it feels when your parts fail....OMG

Get the engine out.....Get the RH side head off and see wassssssup....

Stop beating yourself up.....This sort of thing happens....especially when you are trying to keep things on a tight budget....

Gods speed......EVERYTHING WILL BE FINE.....AND IF ITS NOT FINE....IT'S NOT EVERYTHING :D

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

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):



https://live.staticflickr.com/65535/...f523c7a1_b.jpg

https://live.staticflickr.com/65535/...a5c85f98_b.jpg




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:


https://live.staticflickr.com/65535/...e5e8a414_b.jpg



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:


https://live.staticflickr.com/65535/...d1ed3615_b.jpg

https://live.staticflickr.com/65535/...77d8c44e_b.jpg

https://live.staticflickr.com/65535/...85a7f827_b.jpg

https://live.staticflickr.com/65535/...6d5e5746_b.jpg

https://live.staticflickr.com/65535/...eae9be44_b.jpg



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

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...

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Originally Posted by Robyn

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

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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

Copy..

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

https://www.thedieselpageforums.com/...7&d=1640195529

https://www.thedieselpageforums.com/...8&d=1640195568

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...

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Originally Posted by More Power

https://www.thedieselpageforums.com/...7&d=1640195529

https://www.thedieselpageforums.com/...8&d=1640195568

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...

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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

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

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Originally Posted by 2INSANE

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

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

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Originally Posted by DmaxMaverick

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

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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.

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

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Originally Posted by 2INSANE

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.

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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.

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

Looking forward to hearing it run.....

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

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.....

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

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

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......

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.

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