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Cat 955 L

Spyros33

Spyros33

Well-Known Member
Joined
Aug 22, 2020
Messages
130
Location
Korinth, Greece
Occupation
Mechanical engineer, machine operator
Hi guys! It has been one oh the hottest summer of the Last 100 years in Greece, so working outside was out of the question.

So now that it cooled down a little i started working with my 955.

I was clearing some land for a pond project and suddenly i heard a baging noise coming from the engine. I immediately shut it down and checked engine for any appearing obstacles.
Then i tried to start again but engine wouldnt turn over. I turned engine the other way by hand almost 1 turn and then it would stop again.
My first thought was that the turbo blades Broke and got in the cylinders.
I Took the intake hose out but turbo seemed fine.
Started tearing engine appart and after taking out valve cover the mystery was solved!
IMG_20210822_161356.jpg IMG_20210822_160022.jpg

The spring was broken and valve dropped in the cylinder.

Going to remove cylinder head to see how big is the damage
 
5

56wrench

Senior Member
Joined
Dec 4, 2016
Messages
2,123
Location
alberta
Ouch! That is certainly disheartening. Was this the new cylinder head you installed? If the valve dropped all the way into the cylinder, I'm suspecting you will need at the minimum, a new piston, liner and head. If that is indeed the case, you might as well rebuild the engine because you have already put so much time, money and effort into this machine and want it to be reliable for many years
 
W

Welder Dave

Senior Member
Joined
Oct 11, 2014
Messages
12,548
Location
Canada
Didn't go back to see but if the head was rebuilt by someone else, shouldn't any damage caused by the broken valve spring be a warranty issue?
 
Spyros33

Spyros33

Well-Known Member
Joined
Aug 22, 2020
Messages
130
Location
Korinth, Greece
Occupation
Mechanical engineer, machine operator
Yep that was the new cylinder head.
IMG_20210822_170730.jpg IMG_20210822_170725.jpg
Like 56wrench predicted i ordered new piston, new valves and 8 new valve springs. Fortunately the liner was unharmed.
Because the machine is left in the middle of nowhere, i have to put it together tp move it so overhaul will not be done at the time.
 
W

Welder Dave

Senior Member
Joined
Oct 11, 2014
Messages
12,548
Location
Canada
What would cause the spring to break, just old age? The shop that rebuilt my engine now has a policy to always put a new oil pump and gear on when doing a rebuild (even if the original meets specs.). I had a couple gear teeth break off and they covered it on warranty but had to had to pull the engine to fix it. It did cost me $300 to have it hauled there though.
 
AllDodge

AllDodge

Senior Member
Joined
Apr 2, 2011
Messages
2,312
Location
Kentucky
Looks like there is a piece missing from the spring. Can see the top and bottom but the middle doesn't match

Did ya find the keepers and rest of the valve stem?
 
kshansen

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,165
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
I almost had that happen on a Cummins KT19. Still can not believe we?I was so lucky that the valve keepers stayed in and only put a couple minor marks on top of piston.

Now this was not on a rebuilt engine, but one with 23,865 hours on it! I did pull all six heads and had repair shop replace all springs and most of the valves and guides.gt

Put it back togeather and had another 1,000 hours on it when I reited in 2015. Last time I talked to someone there they were still using that Komatsu WA600 for a stand by machine with no major problems.
 
Spyros33

Spyros33

Well-Known Member
Joined
Aug 22, 2020
Messages
130
Location
Korinth, Greece
Occupation
Mechanical engineer, machine operator
Alldodge actually the spring pieces match, it Just Broke in two pieces. Keepers and rotocoil were laying next to the spring and valve pieces were jammed on the piston
 
Spyros33

Spyros33

Well-Known Member
Joined
Aug 22, 2020
Messages
130
Location
Korinth, Greece
Occupation
Mechanical engineer, machine operator
Rod is straight but the shop mechanical said that it could be shorter than it should as a result of the impact.

I will get a new Rod as well to be safe

Can someone provide me the torque specs of the connecting rods?
 
Spyros33

Spyros33

Well-Known Member
Joined
Aug 22, 2020
Messages
130
Location
Korinth, Greece
Occupation
Mechanical engineer, machine operator
Can someone with SIS access give me the connecting Rod torque specs?
Searching on google i find
30lbft + 90°
But i'd like to hear it from the experts
 
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