Engine Knock

[gumps10]

Hey everyone. Just picked up a 95 Burban for my wife and am tryin to diagnose were the knock is coming from.

Here's what we have so far....

Turbo is siezed, it appears to be the bearing. We now have it removed.

Knock occurs with or without the belt. Bearing was shot on the tensioner, and is replaced. Although, it does appear that something is wrong with the alternator bracketetry, as its twisted a little, and is driving the belt into the front edge of the pulley, just tearing it up.

With enough disassembly, we were finally able to get to the injector line on #4. This seems to be the cylinder creating the noise. We swapped injectors with #1, and the noise stayed at #4. We removed the glow plug looking to see its health, thinking maybe part broke off and was getting smashed into the top of the piston, and it looks fine. We even ran it without that glow plug, and that seems to confirm that we have the right cylinder, as you cant hear the knock over the air noise (ie is timed the same).

It seems the next step in the project will be to pull a valve cover. At this point, it has to be one of three things....

1. Valve issue... bent, collapsed lifter, etc
2. Something on top of the piston
3. Bad rod bearing causing the piston to hit the head.

I figure if its 2 or 3, its just time for the engine to come out and get a 'run through'

Any tips on fixing the turbo? I'm more concerned about the knock before the turbo but I'll take what I can get.:)

Thanks in advance
Dave

[Husker 6.5]

Hey everyone. Just picked up a 95 Burban for my wife and am tryin to diagnose were the knock is coming from.

Here's what we have so far....

Turbo is siezed, it appears to be the bearing. We now have it removed.

Knock occurs with or without the belt. Bearing was shot on the tensioner, and is replaced. Although, it does appear that something is wrong with the alternator bracketetry, as its twisted a little, and is driving the belt into the front edge of the pulley, just tearing it up.

With enough disassembly, we were finally able to get to the injector line on #4. This seems to be the cylinder creating the noise. We swapped injectors with #1, and the noise stayed at #4. We removed the glow plug looking to see its health, thinking maybe part broke off and was getting smashed into the top of the piston, and it looks fine. We even ran it without that glow plug, and that seems to confirm that we have the right cylinder, as you cant hear the knock over the air noise (ie is timed the same).

It seems the next step in the project will be to pull a valve cover. At this point, it has to be one of three things....

1. Valve issue... bent, collapsed lifter, etc
2. Something on top of the piston
3. Bad rod bearing causing the piston to hit the head.

I figure if its 2 or 3, its just time for the engine to come out and get a 'run through'

Any tips on fixing the turbo? I'm more concerned about the knock before the turbo but I'll take what I can get.:)

Thanks in advance
Dave

Being seized, you won't know much until you diassemble it as to how much damage occured. Could be just the bushing, or there could be shaft damage, the vanes of the impeller or compressor could have contacted the housing, the internal passages could be filled with metal shavings. Your knock could be a chunk of compressor vane bouncing around in a cylinder. If it was me, use it as a core for a reman like
walt sells.

Husker 6.5

[deerefanatic]

Or put a Garret VNT turbo on!! :D

Seriously, if you don't see a bent valve, I say "Off with it's head!!"

:D

[gumps10]

Being seized, you won't know much until you diassemble it as to how much damage occured. Could be just the bushing, or there could be shaft damage, the vanes of the impeller or compressor could have contacted the housing, the internal passages could be filled with metal shavings. Your knock could be a chunk of compressor vane bouncing around in a cylinder. If it was me, use it as a core for a reman like
walt sells.

Husker 6.5

I plan on diassembling the turbo just as soon as I figure the KNOCK out. It doesn't apeart to be missing any vanes or such...it may just be siezed from sitting.
Any suggestions on removing the valve cover with out diassembling all the injector lines? This would help to diagnose more.
It is just such a steady consistant knock its hard to diagnose as a bad rod bearing or such. The last time I spun a rod bearing (small block 350) I seem to remeber it being a different sound..almost nonexsistant at idle getting louder and more rapid with throttle.


Here are some clips of the sound...ignore the video more for sound.

Vid 1: http://www.youtube.com/watch?v=Vwh6mjVod4I
Vid 2: http://www.youtube.com/watch?v=2GFGMaui4bE
Dave

[grancito]

I'll go with a piece of something stuck on top of the piston, have seen it, see if you can look in through the injector hole, may be able to remove it, have a scratch around in there, worth a try. My 11 cents worth, getting more expensive. Grant

[Husker 6.5]

Worn wrist pin. Did the knocking become louder with the glowplug removed? If so, the lack of compressive resistance is allowing the parts to "slam" harder at the TDC travel limit.

Also, what kind of oil pressure are you running at idle and 2000 rpm? While scary, Walt has said that the engine was designed to idle at as low as 10psi! Mine, with 225K, idled at 35-38 psi hot and ran 44-48 psi at 2k hot. Really low (<10 at idle) could indicate that it is a rod bearing going out.

Hope this helps.

Husker 6.5

[Husker 6.5]

Just listened to both of your clips. Man, does that sound like a rod about to go bye-bye. It sounds just like the HT4100 motor (a real piece of crap!) in my 82 Coupe d'Ville just before it put a rod through the aluminum block. If your turbo is siezed, there's no telling what bearing/shaft crap wound up in your crankcase and pumped through the engine.

Husker 6.5

[gumps10]

Well Husker,
After pulling it's valve cover last night we decided to pull the motor. Didn't see anything that would tell us anything of value. When we had the #4 glow plug out the knock couldn't be heard over the comppression coming out the hole, plus with the turbo off the whole thing is getting kinda loud any how:D

Now the decision will be which direction to go after final diagnoses :rolleyes:

1) Fix this motor ... The only problem I see here is expense and the fact of how much I want to put into this with the rest of the truck being an Unknown. ie...if this was a truck that I had put the miles on this would be a no-brainer.

Or
2) Drop the 6.2 in there... however this may need some work also as I'm just finding out...

[grancito]

Keep us posted, this is interesting.

[gumps10]

Well,
I started to pull apart the front of the motor yesterday in prep to pull out. When I got down to the balencer I checked again for flex, none in the main balencer, some in the secondary/pully.
What struck me as odd though, was the secondary/pully was bolted on with 3 of 1 size bolt head and 1 of another size.
I just thought this was a little odd unlles its some sort of indexing thing.
I couldn't persue further cause my 2 year old wanted to go in and eat. I will look further tonight. Just was wondering if this was SOP or not.
Thanks
Dave