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  1. #1
    JohnBarlow
    Guest

    Default Old Backhoe loosing hydraulic power


    I have a really old backhoe (1971 Chamberlain Mk3 industrial, Australian made). Recently it has started to loose hydraulic power after a short period (half an hour ?) of operation.

    It has many faults, but I would like to find a "main culprit" to attack and fix, as I can't justify fixing everything. I need some ideas/assistance to select/find the main culprit.

    When cold the system seems pretty good. After running for a while it starts to have less hydraulic power, and lifting the front yard bucket requires pulling the lever, wait three seconds, release the lever, wait three seconds, pull the lever ... (etc.) - it will only lift the bucket for a short time period (and only then an inch at a time).

    Possibly associated with the problem is an increasing tendency for the rear boom (main lifting ram) to lower the boom towards the ground (presumably oil seeping from one chamber into the other chamber of the ram, no huge oil loss onto the ground) - although it has always (fairly slowly) lowered itself towards the ground, just now it is notably worse.

    The hydraulics don't have much (any ?) power at low engine revolutions, so the engine is always set to rev fairly hard to achieve work.

    When I notice the hydraulics low on power I can touch & hold (but it isn't comfortable) the hydraulic return line (which goes into the filter just before entering the tank reservoir).

    I think the problem might be either:

    1) blocked hydraulic oil filter (changed it again last week)
    2) engine low on torque (head gasket leak, etc.)
    3) blockage in some of the hydraulic pipes/controls

    Known faults:

    Head gasket leakage (gas escaping around head bolts, excess pressure in crankcase).

    Diesel pump leakage (accelerator gland leaks constantly).

    Front yard bucket rams leak hydraulic oil (now at a rate of a drop every 8 seconds).

    Rear supports (sprags ?) leak oil.

    Hydraulic pump might leak oil (but it seems to mostly be the supply pipe).

    Hydraulic oil supply pipe (corrugated plastic, about 2 inch internal diameter) leaks a bit at both ends. How do you clamp a spiral-corrugated plastic pipe ?

    Diesel (overpressure ?) return pipe appears crimped mid-pipe.

    ... and lots more issues (but heck, it is fun to use, and I can't afford to buy a replacement).


    Do people think it is a worn out engine (Perkins 4-236 deisel), or a hydraulic blockage ? I am leaning towards the engine as the problem, as the hydraulics work pretty good cold, but I guess if the hydraulic return is partly blocked the pump could be working overtime pushing the oil around without me even trying to use the controls, and hence getting the oil really hot (hence thinner, rear boom lowers quicker, etc.).


    John Barlow, Bega Valley, NSW, Australia
    (owner builder doing a straw bale house)
    http://www.guru.com.au/farm/

  2. #2
    Elite Member
    Join Date
    Jul 2003
    Posts
    3,373
    Location
    Goffs Corner, KY
    Tractor
    IH 2444

    Default Re: Old Backhoe loosing hydraulic power

    "Hydraulic pump might leak oil (but it seems to mostly be the supply pipe)."

    If the suction/supply line for the pump is leaking oil it is probably also sucking air in, which will degrade hydraulic performance greatly.

    water in your hydro fluid will also cause poor performance and pump damage. What has the filter been plugged up with ? and where is it coming from ?

    Ben

  3. #3
    Elite Member
    Join Date
    Sep 2003
    Posts
    4,144
    Location
    New Brunswick, Canada
    Tractor
    Kubota L5030 HSTC, MF 5455

    Default Re: Old Backhoe loosing hydraulic power

    sounds like the pump is too worn and not developing sufficent pressure.

  4. #4
    JohnBarlow
    Guest

    Default Re: Old Backhoe loosing hydraulic power


    > If the suction/supply line for the pump is leaking oil it is
    > probably also sucking air in, which will degrade hydraulic
    > performance greatly.

    It could be sucking in air. The supply line is basically a gravity feed, comes out of the bottom of the oil reservoir (which sits higher than the pump), and the 2 inch ID hose goes down under the backhoe, then comes back up a bit to feed into the pump.

    I can understand the use of spiral-coil hose for the supply line (less likely to collapse from internal suction), but the spiral appears to be a bugger to seal (hose clamps done up tight don't "cut the mustard").

    > water in your hydro fluid will also cause poor
    > performance and pump damage.

    I suspect (given the 60 litres or more of) oil leakage will have taken out most (if any) water contamination. Are there any obvious signs for this ? (such as a white deposit on the tank filler, similar to water contamination of a car engine oil system).

    > What has the filter been plugged up with ?
    > and where is it coming from ?

    This is might be a sad tail, but I asked the previous owner what oil I should use in the hydraulics (thinking manufacturer and type might be specified), but he said "any old oil will do, used sump oil, whatever you have". I think the reservoir has accumulated a lot of crud over the years, and maybe I am just sucking it into the system.

    Of note, the hydraulic power / temperature problem is only fairly recent, and I have been moving dirt with the beast for a while (several months on and off), so my gut reaction is that something has changed recently.

    The hydraulic system has simple spool valves in it (simple lever, pull to lift, push to drop), and the first lever in the hydraulic system is the front yard bucket raise/lower, and this is the spool valve I have most recently fiddled with.

    The problem with the spool valve was the hole that the lever connects to (simple bolt acting as a pin through the end of the spool "rod"). This hole had become worn over the past 30 odd years, and eventually a chunk broke out and the lever could no longer operate the spool. I did a simple weld (on the end of the spool, not near the polished shaft section, having removed it from the valve casing) and got the spool looking good for use. Easily replaced, glided into the vavle body (which looked to have internal O-rings to seal onto the spool). Re-attached the spring self-centering mechanism on the other end, and under testing works fine.

    I have a nagging worry that I may have cut an O-ring (or whatever else I could have done wrong) such that the pump is constantly working to push a small lump of crud onto the next spool valve, and using up power (hence generating extra heat) constantly.

    I guess I should bite the bullet and pull that spool valve apart!


    Thanks, John

  5. #5
    New Member
    Join Date
    Nov 2002
    Posts
    14
    Location
    Central Florida
    Tractor
    Massey Ferguson 40B

    Default Re: Old Backhoe loosing hydraulic power

    Here are my guesses from experience with a Massey Ferguson:

    1. Clogged filter(s) I had a “hidden” intake filter as well as a return filter in a canister
    2. Pressure relief defective / held open with some crud
    3. Worn pump

    Hydraulics really like it clean.

  6. #6
    Elite Member
    Join Date
    Mar 2002
    Posts
    2,829
    Location
    Iuka Mississippi USA
    Tractor
    3550 Fard Backhoe and a 1948 Farmall Cub,

    Default Re: Old Backhoe loosing hydraulic power

    John another thing to listen for is the pump whining or squalling. Thats a sign of air getting into the system. Or the suction line could be collapsed on the inside. I had one collapse on the scraper i run at work and it dove me batty. It happened last week on one of the roll off trucks we operate to. THe line gets a weeak spiral and it sucks together.

  7. #7
    Member
    Join Date
    Aug 2005
    Posts
    36
    Location
    canada
    Tractor
    135MF ,265MF, 820 belarus

    Default Re: Old Backhoe loosing hydraulic power

    We had pretty close to the same thing .We tightened the pump intake hoses and made sure there was no leaks but it still would not work right. Then one day the backhoe just stopped moving because the pump had gone it had been the pump all along .The thing we found out later was that the person who had it before us used any oil he could find which in the end killed the pump.The pump had a filter and all but crud still got to the pump. I would check the cheaper stuff first and hope its a air leak in the pump intake hose or a relieve valve problem. good luck

  8. #8
    Platinum Member
    Join Date
    Nov 2003
    Posts
    800
    Location
    Winn Parish, LA
    Tractor
    Case 380B, Super C

    Default Re: Old Backhoe loosing hydraulic power

    With temp performance variation, sounds like a pump problem, besides the cylinder piston seals. Do you know if that backhoe has a charge pump? Odd suction line would be leakinf oil.

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