Author Topic: Look Inside My 6v92 Cylinder Liners (VIDEO)  (Read 783 times)

Offline GnarlyBus

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Look Inside My 6v92 Cylinder Liners (VIDEO)
« on: June 24, 2018, 03:28:39 PM »
While thinking about the work ahead of me to repair the cylinder liner seal on my 6v92 that is leaking coolant out of the air box drains (see my other thread), I decided to stick my endoscopic camera through the liner ports and see what could be seen. I was curious to see the condition inside as I was told when I bought the bus that the engine had been rebuilt 25k miles before of which I've added 12k in 3 years.

You'll hear in the video I was thinking that the light from the camera was reflecting off oil and making it look burned and ashy. Now, I'm pretty sure that the pistons and valves look burned. From my research this probably happened when the engine overheated at some point.

I'm now thinking I have an inframe in my future. I'm trying to stay positive as I would have had to remove all this stuff anyways to fix the liner seals.

Can anyone confirm that the pistons are shot? Are the liners or valves gonna need replaced? Is this video too shaky and my breathing too loud to tell what's going on?! :)

https://youtu.be/QHFbpLsYTPE
1984 MC-9 w/ 6v92TA & Allison 740
Oregon Summers & Arizona Winters
Full-Time since 2015

Offline eagle19952

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #1 on: June 24, 2018, 03:42:00 PM »
looks like low compression (to me), need rings.
possibly over fueling..leaky injectors too.
Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.

Offline Oonrahnjay

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #2 on: June 24, 2018, 05:14:09 PM »
  looks like low compression (to me), need rings.
possibly over fueling..leaky injectors too. 

      Lotta scuffing on those cylinder bores.  Definitely will need rings and I wouldn't bet any money that the pistons walls are in good shape, either. 
Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long

(New Email -- brucebearnc@ (theGoogle gmail place) .com)

Offline eagle19952

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #3 on: June 24, 2018, 05:38:02 PM »
      Lotta scuffing on those cylinder bores.  Definitely will need rings and I wouldn't bet any money that the pistons walls are in good shape, either. 
I did not look long enuff to see the thrust sides :)
Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.

Offline GnarlyBus

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #4 on: June 24, 2018, 05:51:40 PM »
looks like low compression (to me), need rings.
possibly over fueling..leaky injectors too.

School me on what tells you this. I'm looking to learn how to inspect the pistons and cylinders.
1984 MC-9 w/ 6v92TA & Allison 740
Oregon Summers & Arizona Winters
Full-Time since 2015

Offline GnarlyBus

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #5 on: June 24, 2018, 05:52:56 PM »
      wouldn't bet any money that the pistons walls are in good shape, either. 

Are you saying the sides of the piston might be damaged or the liner walls? Thx.
1984 MC-9 w/ 6v92TA & Allison 740
Oregon Summers & Arizona Winters
Full-Time since 2015

Offline Oonrahnjay

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #6 on: June 24, 2018, 06:04:17 PM »
  Are you saying the sides of the piston might be damaged or the liner walls? Thx. 

     The scuffing on the cylinder walls means that the lubrication broke down.  Probably the rings rubbed dry (or in the presence of overheated, burnt oil) and rubbed grooves in the cylinder walls.  I'm going to guess that the scuffing can't be honed or bored out -- or maybe it wouldn't be worth the experiment to try.  Once the rings and cylinder walls are damaged, there's a very good chance that the pistons were damaged by rubbing on the rough areas that appear scuffed; this is not a 100%, it may vary on different overheated engines but since it's hard to know exactly how bad it is, it's probably a smart thing to just overhaul that cylinder -- new piston, rings, and liners.  If you guess wrong and decide to use damaged parts and they're too damaged to function properly, you've just bought yourself another overhaul either immediately or soon just down the road. 
     Sorry for bad news, but I'm going to guess that that's the way that it's just going to work for you.  If your cylinder walls had been perfect, I'd have said that maybe there's change you got away with it.  Your cylinder walls aren't perfect and that's just the way it is; I can't imagine that the pistons got away with no (or minor enough to ignore) damage.
     All this is just a WAIG, but it's what I think, based on your video.
Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long

(New Email -- brucebearnc@ (theGoogle gmail place) .com)

Offline eagle19952

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #7 on: June 24, 2018, 06:20:21 PM »
School me on what tells you this. I'm looking to learn how to inspect the pistons and cylinders.

low compression makes an incomplete burn.
the piston tops are flaked//built up with something, (fuel and oil is all it can be)
there should be a visible injector spray pattern on the piston top.
Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.

Offline TomC

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #8 on: June 24, 2018, 07:45:20 PM »
With that much carbon build up on the top of the piston and the valves-either the engine is running too cool, or you're not driving it hard enough, or both. Cylinder walls look good except for three-with that scuff mark on the wall. Doing a ring job, honing the cylinders, cleaning up the carbon deposits and rolling in new bearing shells might be all that's needed. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline luvrbus

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #9 on: June 24, 2018, 08:36:10 PM »
Not a clean burn at all,that is a lot of carbon for engine with 35,000 miles the spray pattern looks ok, without pulling a head and knowing for sure it looks like some shop screwed the angle grind on the valves and seats ,the glazing between the ports on number 1 is not normal they will glaze the port height .On that one I would be looking at set of pistons and liners  and having the heads rebuilt and besides he is only seeing 1/2 the liner     
« Last Edit: June 24, 2018, 08:55:25 PM by luvrbus »
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Offline GnarlyBus

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #10 on: June 24, 2018, 10:43:32 PM »
Thanks for the observations everybody. About how much does it cost to have the heads rebuilt?
« Last Edit: June 24, 2018, 10:58:14 PM by GnarlyBus »
1984 MC-9 w/ 6v92TA & Allison 740
Oregon Summers & Arizona Winters
Full-Time since 2015

Offline luvrbus

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #11 on: June 25, 2018, 06:13:37 AM »
I have a place in Phoenix I trust to do my work, heads are around $500.00 ea to bring back to DD specs. if not cracked.I wouldn't do liner kits without head work I have done it a few times and they came back to bite me in the @$# every time with a injector tube leaking.It a tough call Jordon but you never know till you open one up I would budget $4000.00 for parts and roll it out and replace the rear main seal too and fix all the oil leaks that is JMO .I tried to post a photo for you of a head from a 8v92 with 365,000 miles it has a no build up   
« Last Edit: June 25, 2018, 07:11:24 AM by luvrbus »
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Offline chessie4905

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #12 on: June 25, 2018, 07:09:48 AM »
I will be surprised if you don't have a cracked head.
That residue on top of piston looks like ash from oil burning to me. Just tear it down and figure the cost now as Cliff said. You'll regret just a patch job. After repair, verify accurate temp gage readings and especially verify hot light operation and temp setting along with proper operation of overheat shutdown. Consider adding a mister system. Do your first short trips at night in cooler temps and avoid any mountain climbing till you have some easy miles to verify everything is working properly. Radiator and cooling system in good condition.
GMC h8h 649#028 (4905)
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Offline luvrbus

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #13 on: June 25, 2018, 07:13:12 AM »
I will be surprised if you don't have a cracked head.
That residue on top of piston looks like ash from oil burning to me. Just tear it down and figure the cost now as Cliff said. You'll regret just a patch job. After repair, verify accurate temp gage readings and especially verify hot light operation and temp setting along with proper operation of overheat shutdown. Consider adding a mister system. Do your first short trips at night in cooler temps and avoid any mountain climbing till you have some easy miles to verify everything is working properly. Radiator and cooling system in good condition.
I think that is his problem now someone did a patch job in the past
Life is short drink the good wine first

Offline windtrader

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Re: Look Inside My 6v92 Cylinder Liners (VIDEO)
« Reply #14 on: June 25, 2018, 09:20:57 AM »
Thanks for the observations everybody. About how much does it cost to have the heads rebuilt?
The PO of my bus took the patch and go route against the advice of his mechanic. After a number of patch jobs receipts piled up, he finally conceded then installed in a reman motor. Always an expensive and difficult decision but the better path in the long term. Not saying this is for you but something to have on your radar.
Don F
1976 MCI/TMC MC-8 #1286
Fully converted
Bought 2017