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D311 compression release

D311 compression release

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90212
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I am currently converting two 9t212 graders to one useable machine and was wondering what the fix is when the comp. release buttons on the intake rocker arms don't contact the release shaft. The operators manual says to contact your Caterpillar dealer when this problem occurs but there is no place to plug the computer into. From reading all the information that appears on this forum I am sure someone has experience with how to mend this machine. Thank you for the help.
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Thu, Nov 11, 2010 4:05 AM
ccjersey
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Is the problem that the shaft doesn't rotate to the correct spot? The lever installed on the end of the shaft incorrectly? Take linkage loose and see if you can get it to work by hand.

Or is there wear on the contact parts? Not sure why this would ever occur.
D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time😄
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Thu, Nov 11, 2010 9:18 PM
90212
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Reply to ccjersey:
Is the problem that the shaft doesn't rotate to the correct spot? The lever installed on the end of the shaft incorrectly? Take linkage loose and see if you can get it to work by hand.

Or is there wear on the contact parts? Not sure why this would ever occur.
The compression shaft rotates to the correct position and is free to turn even by hand but three of the buttons on the rocker arms clear by 1/64th and the fourth one misses by 1/8th. So far I am totally stumped. I will look at some others that I have and also plan to swap out the rocker arm assembly with a known good one to see if that will change anything. I will also reset valve clearance to make sure that is correct. Any and all ideas will be appreciated. Thank you. Chuck
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Fri, Nov 12, 2010 12:54 AM
ccjersey
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Has this engine been running lately? I'm wondering if there's enough carbon underneath the valves to hold them open enough that the decompression cam cannot touch the rocker arms. Might need to spin it over for a while and spray the valve stems with some kind of penetrating oil to get them to seat properly.

Another possiblility is that the seats have been replaced and ground to a higher profile or the valves replaced with some with slightly larger heads so the valve stem height is no longer in a correct range. I cannot find an installed height spec on the valves in any of the information I have on any CAT engine, so I wonder if they ever published that number.

We have some old D318's that have pretty severe wear on the rocker surfaces where they contact the top of the valve stems, and they still decompress OK, so I'm wondering if wear is the problem.

We reinstalled the head on a IH RD450 when I was a teenager and forgot the rotators, Had to adjust the rocker studs a long way to set the valves! The next time I was at the machine shop, the guy handed me the set of rotators and it all began to make sense. But the parts book I have (D318 which should be similar) doesn't show any rotators, so that wouldn't be it.
D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time😄
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Fri, Nov 12, 2010 6:50 AM
edb
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Reply to ccjersey:
Has this engine been running lately? I'm wondering if there's enough carbon underneath the valves to hold them open enough that the decompression cam cannot touch the rocker arms. Might need to spin it over for a while and spray the valve stems with some kind of penetrating oil to get them to seat properly.

Another possiblility is that the seats have been replaced and ground to a higher profile or the valves replaced with some with slightly larger heads so the valve stem height is no longer in a correct range. I cannot find an installed height spec on the valves in any of the information I have on any CAT engine, so I wonder if they ever published that number.

We have some old D318's that have pretty severe wear on the rocker surfaces where they contact the top of the valve stems, and they still decompress OK, so I'm wondering if wear is the problem.

We reinstalled the head on a IH RD450 when I was a teenager and forgot the rotators, Had to adjust the rocker studs a long way to set the valves! The next time I was at the machine shop, the guy handed me the set of rotators and it all began to make sense. But the parts book I have (D318 which should be similar) doesn't show any rotators, so that wouldn't be it.
Hi Team,
I think CCJ has nailed it with the valve stem heights/lengths above the upper head face are too short/low. This puts the rocker arm at an incorrect angle so as the button on the lower arm is too far away from the de-compression cam bar.
Maybe in the past, with pocketed in/worn valve seats, the stems were ground shorter to allow the valve to close onto it's seat in the full compression position.
If I recall correctly, some Cat Engines had hardened caps to fit on the ends of the valve stems, but, I do not think the D311 was one of them. These may or may not help here to reset the rocker into an operable range.
Only other Bodge would be to build up the de-compression buttons on the rocker arm and grind to get into range.
Hope this helps.
Cheers,
Eddie B.
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Fri, Nov 12, 2010 11:27 AM
90212
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Reply to edb:
Hi Team,
I think CCJ has nailed it with the valve stem heights/lengths above the upper head face are too short/low. This puts the rocker arm at an incorrect angle so as the button on the lower arm is too far away from the de-compression cam bar.
Maybe in the past, with pocketed in/worn valve seats, the stems were ground shorter to allow the valve to close onto it's seat in the full compression position.
If I recall correctly, some Cat Engines had hardened caps to fit on the ends of the valve stems, but, I do not think the D311 was one of them. These may or may not help here to reset the rocker into an operable range.
Only other Bodge would be to build up the de-compression buttons on the rocker arm and grind to get into range.
Hope this helps.
Cheers,
Eddie B.
At some point in time the head has been worked and or replaced because there is no paint on it. If they cheaped out on paint they may have cheaped out on the valves and or seats. When time and weather allow I will dig into this thing and solve the problem. It may involve a different head or maybe just building up the buttons on the rocker arms. Thank you CCJ and edb for the brain power. Chuck
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Sat, Nov 13, 2010 2:50 AM
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