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Cat 312D L

Discussion in 'Excavators' started by 90plow, Jan 16, 2020.

  1. 90plow

    90plow Senior Member

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    Hey guys decided to move on from my cx130. Found a nice 312d L with 7200 hours, quick coupler, heat /ac, camera, aux hydraulics. Aside from a few scratches here and there it’s very clean. I have a cat tech coming out to check the machine out. here’s what I’m going to have checked.
    -travel motors seem weak when turning (fine when going straight)
    -one button broken in the cab I don’t know what it is
    -upper wiper works intermittently
    -motor hours (verify)
    -hydraulic pressures (if possible)
    -squeaky belt

    any thing I should look out for?
     

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  2. John C.

    John C. Senior Member

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    Most of what you are looking for can be found in the monitor panel without the expense of a Cat wrench. Here is a video that shows how to access the information.

     
  3. Cmark

    Cmark Senior Member

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    Checking the hydraulic pressures thoroughly should show up any issues with the travel motor circuits. Tell them your concerns before they leave the workshop to make sure they bring the tooling to block the sprockets.
     
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  4. 90plow

    90plow Senior Member

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    There was a tech on site while we were there. He mentioned the tracks looked too tight which could give the tracks issues turning. Separately the manager came out and he said the tracks looked too tight like someone over greased them and it would create that issue. Thoughts?
     
  5. Nige

    Nige Senior Member

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    Correct track tension has a lot of bearing on how a machine will move, especially on how it will turn.
    By "over-greased" I assume that you mean someone pumped up the track tensioners too much.?
    Did you take any photos of the tracks.? If so post them here.
     
  6. 90plow

    90plow Senior Member

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    Here’s what’s posted online. I forgot to grab more.
    I’ve seen cats properly tensioned and they usually have a double sag one on each side of the top rollers.
    And by too tight I mean over greased.
     

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  7. Nige

    Nige Senior Member

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    That first photo the track is like a bowstring. It ought to be slacked off.
    If the track on the other side of the machine is similar it needs slacked off too. T'is not hard, but no use testing propel & turning functions until the tracks are correctly tensioned.
    Track sag measurement is done by placing a long straight edge on top of the tracks. It needs to be long enough span the distance between one carrier roller and the other.
    Specification is between 40 and 55mm of sag measured at a point wherever the sag is the most between the two carrier rollers. This point may not be exactly in the centre between the two rollers.

    The sprockets (assuming the one on the other side is the same) have seen better days too.
     
    Last edited: Jan 17, 2020
  8. Cmark

    Cmark Senior Member

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    Yes they do look a bit tight, however guessing that this is making it hard to turn wouldn't wash with me. Checking the drive pressures would add no more than 10 minutes to the job if the other pressures were being checked.
     
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  9. wornout wrench

    wornout wrench Senior Member

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    The question is why are they that tight?
    Is there an issue that they are trying to cover up by over-tightening.
    I would be having a good look at the undercarriage too, have they been having issues throwing tracks.

    My industry tends to run tracks tight, when they are out shovel logging they don't want to loose a track, so the operators will constantly tighten the track a bit more then you really should. A tight track will really accelerate the track wear.

    The other thing to look for, I can't see it in the pictures, are the rock guards hitting the pads, that will really cause turning issues.
     
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  10. 90plow

    90plow Senior Member

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    Thanks guys. I will have the tech spend some time on it. Not overly concerned about replacing the sprockets or putting a couple bucks in the machine. Just don’t want to spend thousands on pumps.
    Both sides are super tight.
    Machine climbed a 20’ tall mountain of asphalt millings no problem. Just on flat ground it would not turn as fast as I thought it should and when only one track was operated it seemed to struggle too much.
    Rock guards are not hitting the tracks.
    I also read on another post it could be a PRV calibration issue. I guess it controls the track Hydraulic pressure
     
  11. 90plow

    90plow Senior Member

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    Worn out wrench. My theory on the tight tracks...
    When it was traded in someone wanted to make it look good, cleaned it and thought man these tracks look too worn out. Let me pump them up.
    Just a theory.
     
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  12. rmllarue91

    rmllarue91 Senior Member

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    Good straight travel poor turn is usually sign of rotary manifold. If its got 5000 plus hours hydraulic oil is dark Amber with associated aroma or used in hard travel areas ( excessive drive circuit heat ) mud side hills. I just reseal without verifying and haven't been wrong yet....
     
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  13. 90plow

    90plow Senior Member

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    Thanks, so is that a major job? Just want to have an idea of what I’m talking about with the tech, is the rotary manifold something with hydraulics?
     
  14. Nige

    Nige Senior Member

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    Search here in the excavator forum for "swivel". That's what it's most commonly called.
    It is the rotary manifold right in the centre of the machine that supplies oil from the upper frame down to the travel motors and brakes.
    See the attachment. I picked a 312DL at random but yours won't be that much different if at all.
     

    Attached Files:

  15. 90plow

    90plow Senior Member

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    That’s good because it is a 312dl haha. Thanks!!
     
  16. Nige

    Nige Senior Member

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    Yes, but there are 10 different versions of the 312DL. I picked the first one on the list so I only have a 1 in 10 chance of being correct.
    Always quote the machine Serial Number if you want the most accurate information.

    upload_2020-1-18_14-45-38.png
     
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  17. 90plow

    90plow Senior Member

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    Got it thanks.
    Looks like more work to get it out than to actually re seal it. Not too bad though.
     
  18. Nige

    Nige Senior Member

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    Absolutely right.
    There's also detailed info available on how to disassemble & reassemble it. I didn't want to go down that rabbit hole without a Serial Number.
     
  19. 90plow

    90plow Senior Member

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    So had the cat tech out on site today. Motor pressures were fine loosened the tracks and it seemed a lot better. He suggested re doing the rotary valve. Also found out one motor isn’t going into high speed. It’s getting pressure from the machine but the valve is stuck on the drive motor. So a rebuild or a new motor is needed (not the end of the world).
    Decided to go ahead with the purchase because there aren’t too many machines like this for the money. It’s got every option you can order and it’s been taken care of. Got the seller to throw in a 36” cat bucket as well as the 24” that’s on it. I’ll keep you guys posted on how it goes. Thanks for the help!
     
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  20. Nige

    Nige Senior Member

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    First thing on your shopping list IMO ought to be an Operation & Maintenance Manual (the one in the pocket behind the seat probably got lost years ago) & a Parts Manual. You can download the pair in Adobe pdf format from a Cat web site for probably $100 or so.

    Post a Serial Number and I can walk you through the process.