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Cat 304C Cr pump oil leak

Discussion in 'Compact Excavators' started by hvguy, Oct 13, 2019 at 1:37 AM.

  1. hvguy

    hvguy Senior Member

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    Conroe TX
    I was out digging some drainage ditches and ended up sinking my machine up to the exhaust in mud. The stupid intake hose design allowed the engine to suck in some water but not quite hydrolock. Got it started again, finally got the unit free and back to safety. Loading it on the trailer, I noticed a black puddle under it. Pulled the cover plate and it's coming from between the engine and pump. My first guess is rear main, but after driving it quite a ways, the oil level in the engine is fine, and this particular oil isn't hot? So it's the pump case oil?

    1 Do these pumps have lubricant other than the hydraulic oil.
    2 What would cause this to fail after getting wet.
     
  2. uffex

    uffex Senior Member

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    Good day
    May have some internal damage maybe worth dropping the pan and having a look many engine have run with bent piston rod.
    Kind regards
    Uffex
     
  3. Mobiltech

    Mobiltech Senior Member

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    I think the cavity between the pump and engine is a dry area with a pump drive coupling but probably full of dust and some seeping oil from pump or engine. If water got in there it would come out black. I wouldn’t be too concerned but keep an eye on oil levels.
    You will probably want to change engine oil in case it took on water.
     
  4. hvguy

    hvguy Senior Member

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    But, does the hydraulic pump have a separate gearbox? And oil sump? Or is it like a normal pump that just flows hydraulic oil and that's all.
     
  5. Cmark

    Cmark Senior Member

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    The bellhousing doesn't (usually) contain oil. Given your story I would be looking to see if the breather pipe is plugged. The crankcase may be pressurising and pushing oil past the rear main seal.
     
  6. hvguy

    hvguy Senior Member

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    Genius! I'll check when I'm home. I'm out in the middle of nowhere and my 277b decided to split a drive hose. Woohoo!
     
  7. hvguy

    hvguy Senior Member

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    Didn't leak for 30min, I put it to work digging a random hole for 20 min and no leaks, went to the front gate to meet pizza guy, came back and it's pouring. Checked blow by, no issues.

    Pulled covers, pulled counterweights, drained hydraulic fluid, pulled pump, jacked up engine and pulled the bell housing, splined coupler, flywheel, THEN I see the rear main is leaking. Woo! Only took 5hrs lol. Ordered, it came in today.
     

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  8. hvguy

    hvguy Senior Member

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    Conroe TX
    Success! It would appear that when the machine went for a dip, some dirt and crud got between the 2 lips of the seal and wore it out.

    IMG_20191016_131212.jpg IMG_20191016_131215.jpg