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4 broken newer rockers, one cylinder, no impacts! ???
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=92627		 Page 1 of 1
Author:  Mountainman [ Wed Mar 22, 2023 7:50 pm ]
Post subject:  4 broken newer rockers, one cylinder, no impacts! ???
Well, I have this strange CRD I got from a lost member a few years back. It finally made its way to the front of the inventory, and it ran like one or 2 cylinders were dead. I pulled the cover to find all 4 rockers on #2 snapped. I figured failed rod bolts like I've seen before, so I pulled the head to confirm, and the cylinder looks great, so do the valves.
The only thing I can think of is that maybe they knocked off a rocker or two when they reassembled it, that maybe the pressure eventually snapped the others. Wouldn't the intake valves have tremendous pressure placed on them if the exhaust valves failed to open?

The last test I can think of is to turn it over with the head off to listen for knocking, but the carbon ring at the top of that cylinder shows me that the piston hasn't been rising too far upwards. Hmm, I'd appreciate any ideas before I go and throw the head back on with new exhaust valves (200k miles), -and cross my fingers that it's not a huge waste of time... :banghead:
Author:  WWDiesel [ Wed Mar 22, 2023 10:35 pm ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
I am assuming you have the injectors removed since you already have the valve cover/cams removed. All the valves will stay fully shut and you could spin the crankshaft over with the starter all you want without any danger of valves hitting pistons. This way you could listen for any abnormal noises in the bottom end. Some oil will get pumped out in places, but you can clean that up.
With the injectors all removed and all valves closed, any suction or pressure made by the pistons will vent out through the injector holes. :D
Author:  Mountainman [ Wed Mar 22, 2023 11:29 pm ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
Hmm, yeah, I was going to try that, but then I convinced myself that a piston must have slapped the valves to break the rockers, so I pulled the head. This will be my first attempt to turn one over with no head :|
Author:  WWDiesel [ Thu Mar 23, 2023 3:24 am ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
If you pull the head, you MUST install some hold downs to keep the piston liners from moving when you turn the engine over.
Item #2 in the drawing below. You can make some hold down clamps out of some flat stock or angle iron.

Image
Author:  Mountainman [ Thu Mar 23, 2023 10:31 am ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
Thanks for the reminder, I have the factory tools, but I never use them while turning them over by hand anyhow, but I sure will for cranking speed.

- one more note, that piston was putting crazy forces on the bearings with no open valves. What a gamble it would be to put the top back on...
Author:  WWDiesel [ Thu Mar 23, 2023 1:24 pm ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
Mountainman wrote:
Thanks for the reminder, I have the factory tools, but I never use them while turning them over by hand anyhow, but I sure will for cranking speed.
- one more note, that piston was putting crazy forces on the bearings with no open valves. What a gamble it would be to put the top back on...

Vary simple remedy, just pull the injectors or glow plugs and no pressure can build even with all valves staying closed. :wink:
Author:  layback40 [ Thu Mar 23, 2023 7:16 pm ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
Mountainman wrote:
Thanks for the reminder, I have the factory tools, but I never use them while turning them over by hand anyhow, but I sure will for cranking speed.

- one more note, that piston was putting crazy forces on the bearings with no open valves. What a gamble it would be to put the top back on...



The force would not be that great. Much less than when it fires. Unless it was hydrolocking on fuel being injected.
Author:  Mountainman [ Thu Mar 23, 2023 9:32 pm ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
layback40 wrote:
Mountainman wrote:
Thanks for the reminder, I have the factory tools, but I never use them while turning them over by hand anyhow, but I sure will for cranking speed.

- one more note, that piston was putting crazy forces on the bearings with no open valves. What a gamble it would be to put the top back on...



The force would not be that great. Much less than when it fires. Unless it was hydrolocking on fuel being injected.


Good news. So it just pulls a vacuum? There was about 2 tablespoons of diesel in the piston bowl.
But I only ran it for a minute to pull it in the garage. Was shaking violently and barely staying running
Author:  geordi [ Mon Mar 27, 2023 10:41 pm ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
There's no combustion OR pressure if there is no air exchange. Even with two broken on the same side, the air in the cylinder never changes position. The fuel is a small amount, and likely just washed into the oil. No pressure on the bearings at all.

They probably had the cams out of time when assembling.
Author:  Mountainman [ Sun Apr 02, 2023 1:03 am ]
Post subject:  Re: 4 broken newer rockers, one cylinder, no impacts! ???
Thanks for the confidence! I turned it over by hand and it felt normal, but with 200k, it needed valves anyhow, so nothing lost. One more saved from the crusher! :JEEPIN:
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