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

[arveetek]

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

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

[Robyn]

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.

[Robyn]

I just listened to the video.

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

[2INSANE]

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!

[arveetek]

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

[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.

[2INSANE]

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!

[arveetek]

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

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:





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

[DmaxMaverick]

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.

[Robyn]

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.....

[DmaxMaverick]

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.

[Robyn]

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

[DmaxMaverick]

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

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).

[arveetek]

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

[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.

[arveetek]

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.

Pretty much what I had planned on doing!!

Casey

[Robyn]

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...

[trbankii]

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.

[More Power]

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

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

[Robyn]

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