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Caterpillar 955L Engine Rebuild delema

Discussion in 'Track Loaders' started by Bryant_955L, Oct 4, 2014.

  1. Bryant_955L

    Bryant_955L Well-Known Member

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    I am hoping I can get some answers and I know that I have come to the right place. After several months working part time on my 955L, I finally have my 3304 PC engine apart. My biggest concern is cylinder #1 and the crank. In cylinder #1 there is a piece missing at the very bottom of the linear. The missing piece is about 1" long by about 1/4" high. The block is also broken in the same location. I can't tell if when they installed the linear they did this damage. Cylinder #1 is a true Caterpillar piston and liner and all the other pistons and linear's are IPC. I have attached a picture showing the liner and block. I am hoping to learn from this forum if I should be looking for a new engine block or if my engine block is fine once I install new linear's. Cylinder Linear #1 top view.jpg
     
  2. kshansen

    kshansen Senior Member

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    Not sure how to answer. It appears something got between the rod and cylinder wall while it was running or it had a bent rod. Hows the rod look?

    Guess it gets to be a big judgment call. If you can find a good used block that would be the best option.

    Now one option that only you can decide on is to decide that this cylinder has three seal rings and only the lower one has been compromised so you could just leave that one out and run it as is with new parts.

    Guess it comes down to how you intend on using this machine and how much of a risk you are willing to take.
     
  3. overworked

    overworked Senior Member

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    I'll second KS, would like to see other parts, and block without liner in it.
     
  4. Nige

    Nige Senior Member

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    I looked at that photo and my first thought was "get the liner out of it first". If the #1 piston is Cat and the other three are IPD what are the chances that hole had a failure (hydraulic locked maybe?) at some time previously and the engine has been given a partial repair..? Good I would suggest.

    Also I'd like to see a photo taken from directly above of the #1 connecting rod laid right on top of a rod from one of the other holes so that it's obvious if the rod is even slightly bent. Are all the four rods identical, either Cat or aftermarket..?

    Those 3304s are tough (and forgiving) engines. A good used block would be one thought but I'm pretty certain that even just replacing the #1 liner could produce an acceptable end result.

    You mentioned a concern regarding the crank. What's wrong with it and on what journals..? Is it a genuine Cat crank or aftermarket..? Do you know if it has standard or undersize journals..? How about posting some photos of it also..? At the very least I would say that bearing in mind the ding in the block the crank should be checked for straightness by a reputable crank specialist if you have one close to where you are. Even if you don't it should be checked anyway IMHO.
     
  5. 02Dmax

    02Dmax Senior Member

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    Sure looks like a broken o-ring in that pic so I'd bet that using the bottom o-ring is no longer an option. I'd also look real close at the cam. Something knocked that chunk out and was very close to the camshaft when it happened. Looks like a thrown rod at low rpm to me.
     
  6. lantraxco

    lantraxco Senior Member

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    I'll guess the other way, they rebuilt with IPD but broke that liner trying to remove it so they just left it in there. :rolleyes:
     
  7. DMiller

    DMiller Senior Member

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    I wouldn't hesitate to remove that liner and see what else awaits, the hairline I see at the web of the block to the bottom left does disturb me a little. Cracked water jacket never fix well, if there is any potential for coolant to enter the crankcase junk the block and buy another. Being as that was in the rotation throw of the crank(cam bore showing) I would also suspect a previous hydro lock and bent rod in a previous incident.
     
  8. Bryant_955L

    Bryant_955L Well-Known Member

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    First, thank you for your responses. I have limited funds and really no knowledge or experience, so any information I receive is greatly appreciated. I placed the rods over each other and they seem to be very straight ( see attachment). Rods_Stacked_ for comparison.jpg In my first post I mentioned the crank. I was worried that the crank my be bent for what I saw from cylinder #1. Since that time, I placed the crank back into the block with only the main bearings in position 2 and 4. With the other mains removed from the block I rotated the crank viewing the gaps in the other main bearing location to see if the crank wobbled. I saw no movement and so I am now thinking the crank is not bent. In both the cam and crank there is no scares or pits in the journal locations they seemed only polished. My next step will be to remove the linear's. I am still trying to figure out how to remove the linear's.
     
  9. Bryant_955L

    Bryant_955L Well-Known Member

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    Several of you mention a hydro lock. What does that mean? Does that mean that your cylinder totally filled with water or does that mean it over heated and seized the piston inside the cylinder?
     
  10. trackdoc

    trackdoc Well-Known Member

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    A hydro lock is when the piston is on it's way up on the compresion stroke, and there is a fluid blocking its passage ie fuel, coolant or oil
    As both valves are closed the fluid has no place to go, something has to give.
    Normally the con rod.
     
  11. trackdoc

    trackdoc Well-Known Member

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    If you put the crank in the block, install all the main bearings and torque them in steps while turning the crank you will know if it is bent.
    ie torqe all mains to 30 lb/ft and turn the shaft, then 50 and turn the shaft.
    If the shaft is bent you will at some point feel the tight spot.
     
  12. trackdoc

    trackdoc Well-Known Member

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    There is nothing holding the liner other than o ring seals and corrision.
    Use someting like a piece of brass or aluminum and drive it out from the bottom upwards
     
    Last edited: Oct 5, 2014
  13. 02Dmax

    02Dmax Senior Member

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    I had a crank twist in a 3406 once. I'd play it safe and have a machine shop check it. It would be affordable for a 3304 and money well spent in my opinion.
     
  14. Nige

    Nige Senior Member

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    I agree with you that the #1 rod does not appear to be bent, so the thought goes back to a problem in #1 that has since been repaired which is why the engine has different pistons in different cylinders. Are all 4 rods the same brand, i.e. all Cat or all IPD but not a mixture..?

    Regarding getting the liners out, as others have said - a bronze drift and brute force. Once they are out post pictures of what they look like on the outside. The corrosion will probably be spectacular if you're having that much difficulty moving them.

    Back to the crank. The only reliable way to prove it's NOT bent is to have a specialist crank shop put it in a pair of V-Blocks, spin it and check the journal runout against specification with a dial test indicator. As DMax says, a crank that small it shouldn't cost much for your peace of mind. At the same time the crank shop could measure all the journals and see if they are standard or undersize and also whether they are are within specification as regards journal diameter. I can probably find the maximum runout tolerance specification somewhere if you need it. I can assure you that you will not be able to see a crank that has a bend in it more than the permitted maximum with the naked eye unless it's REALLY bent. You have already discounted the possibility of a severe bend, the possibility of a very small bend is still there.

    A hydraulic lock can be as a result of having either fuel (from a defective injector) or coolant (often from a head gasket leak or the PC chambers in this particular engine). Usually what happens is that when the engine is stopped the affected cylinder fills with fluid from wherever and if the valves are closed when you crank it over on the starter motor the fluid has nowhere to go. The power of a starter motor is plenty to bend a connecting rod if forced up against an immovable object - in this case a fluid-filled cylinder above the piston. Result - banana-shaped rod.

    Another question - was the engine using a significant amount of coolant before you stopped it and tore into it..?
     
  15. kb9tci

    kb9tci Senior Member

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    I think I'm setting with a bent rod in my 955L due to leaking precups. It has not reached catastrophic failure, but I am not trying to find it either. I've got it parked until I can find time to tear it down again. It's going to be a while until I can get my house wrapped up.

    I would be on the fence with using the old block, too. If I had the time to fix it if it failed again, I would probably use the old block with a new liner and hope for the best.

    Good luck!
     
  16. Andrew_D

    Andrew_D Senior Member

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    Nige: Since he has the crank in with bearings 2 and 4, couldn't he then use a dial indicator on the remaining bearing surfaces? That should give the same result as putting it in v-blocks shouldn't it? Maybe even go so far as to follow up by doing the procedure a second time using 2 different bearings?

    Andrew
     
  17. Scrub Puller

    Scrub Puller Senior Member

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    Yair . . . Andrew_D. I believe that even on a small engine like this oil and running clearances could interfere with the absolute truth of the readings and throw up some odd numbers . . . should be able to get some idea though.

    Cheers.
     
  18. Nige

    Nige Senior Member

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    the problem with running it on the main bearings is that no-one can guarantee what part of the babbit in the main bearing shell it's actually running on. With the crank supported on a pair of guaranteed ground V-blocks there would be no doubt.
     
  19. Bryant_955L

    Bryant_955L Well-Known Member

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    Okay I found a long block online but in order to get a refund for a core the block has to be repairable. From the information and the pictures would the block be repairable?
     
  20. Bryant_955L

    Bryant_955L Well-Known Member

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    What if you can't even turn the crank?