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Caterpillar 973 failure

Discussion in 'Track Loaders' started by mecaniquin, Oct 13, 2015.

  1. mecaniquin

    mecaniquin Well-Known Member

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    greetings to all forum members. first of all apologize in advance because my language is not English, but have started to work google translator to understand and communicate with you.

    I recently purchased a 973 serial cat 66g, at first glance the machine does not wear this because I never work with soil or rocks, but work in a warehouse storage of fertilizers.

    the initial problem of this charger is that it did not move. only 1 meter and stopped. got a manual and started work. adjustments made in linking the servos and many other things.

    Now the machine if it moves freely. forward back and sides, but after working 10 or 15 minutes the machine stops. enters the vent mode and guess. pulled the lever to park and then restart .and after stepping pedal and steering or try to push the bucket, it stops.

    I put clocks in the 7 systems. I have given adjustment screw cutting synchronization clockwise to these tests.

    venturi differential pressure.
    differential pressure in the filter.
    underspeed differential pressure valve
    servo supply.

    but .... when I test the machine with the clock connected in quick-connect charge pressure of 200psi drops to just under 100 psi which gives way to operate brake vent or spool start spool. that's just some of what I have gathered in this machine. to disarm the main control valve to a piece missing. 1u2604. check valve. the request and I came to miami. the mountain this week and the machine remains the same. not as if this piece he needed.

    note that this machine was brought from Italy in 1998 and worked until 2009 in many years.And stop there remain several "mechanical" and was not given the revised with failure ..

    I change oil and filters. first use a SAE 30. I thought the machine to heat lost all the oil viscosity change was equal to 15w40.

    what I really want to know is where I lost that this charge is for pressure. servo cylinder? Charge Pressure Check Valve? pump varible displacement? no engine tracks. I put a hose in each of them and does not drain oil.

    any comments that will help me to guide me I will be very grateful.;)
     
  2. Bob/Ont

    Bob/Ont Senior Member

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    The problem you are having is when you try to travel the drive loops lose so much of the charge oil that the pressure can not be maintained and the machine vents out stopping the drive. You most likely have a problem in the drive motors. Try to drive in reverse, then try driving one side at a time, both forward and reverse. If you have a 100 psi gauge hook it to the case drain pressure fitting of each motor and try to drive. If you have a bad drive motor the case pressure will go up to 70 psi when driving. A flow meter on the cooler line will tell all about drive loop leakage but you can get by with gauges.
    Later Bob
     
  3. mecaniquin

    mecaniquin Well-Known Member

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    Hello Bob. thanks for the interest. last week connects a hose to each track motor. the other two points put them in the cab on an empty 20-liter bucket. Nothing went through those hoses. not a drop of oil. -reverse-steering foward ... nothing. after 15 minutes the machine stopped. only it stops when you strain. Sometimes I stand 2 minutes. I go back to accelerate. and the machine moves and turns hard. this morning I went to make an adjustment to the governor and the valve override. all bad there. I hope that the problem is in that setting. morning after repair parts. start again and prove that happens. I see so many people worked on this machine without knowing. and they have managed to get out of control the entire system. I think all the relief valves have been moved. hopefully not. I would like to send photos or videos to the forum. Might video on a failure to appreciate better presented. tomorrow I mention what happened to the governor and setting override.
     
  4. mecaniquin

    mecaniquin Well-Known Member

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    What's up friends. Yesterday I finally turn on the machine. I made an adjustment to the governor linkage. underspeed also override the valve. working around 20 minutes without problems. then stopped 5 minutes. I went back to accelerate and try to turn the machine and vent again. However. if we speak of a load pressure drop. where to start looking? and will comment on the hoses that connect to the track motors. not pour oil. could disarm the main control valve. Charge pressure check valve? or you may have a cylinder leak? I also read that there is a check valve vent within charge valve.suppose you have a leak in the variable displacement pump. I do testing? as if the leak is there? .... or perhaps one of the relief valves defective or wrongly calibrated?

    I want to start on Monday, removing the main control valve and review the charge pressure check valve. but any ideas you can give me is very useful .. greetings
     
  5. Bob/Ont

    Bob/Ont Senior Member

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    Don't take anything apart until you do a complete pressure test and know what to fix. If you take it apart first you will complicate things for yourself.
    Get the pressures across the front of valve. Upstream, venture and servo supply and the charge, near steering levers and brake on top. The LH drive is on the valve body and the RH drive is on a block very low near the back of fuel tank. A low pressure gauge in each drive motor will tell condition. A flow meter on the cooler line would help but charge pressure will tell a lot. Lock the brakes by removing and plugging the release line. Leave end towards the brakes open to air. Check the brakes will hold then heat up oil and check pressures at full stall forward and reverse. Maybe someone can post the test sheet for you.
    Later Bob
     
  6. mecaniquin

    mecaniquin Well-Known Member

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    IMG_20151018_022104.jpg IMG_20151018_022116.jpg IMG_20150831_140306.jpg IMG_20151016_150437.jpg IMG_20151016_150522.jpg

    I try to put the pictures of the pressure tapping points
     
  7. mecaniquin

    mecaniquin Well-Known Member

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    ok here we go.


    1. Pressure tap for underspeed pressure valve throat.

    2. Pressure tap valve upstream pressure for underspeed.

    3. Pressure tap for brake pressure.

    4. Servo supply pressure.

    5. Venturi throat pressure.

    6. Venturi upstream pressure.

    7. Charge pump pressure (filter relief valve).

    8. Charge pressure

    9. Right side drive pressure (forward & reverse).

    10. Left side drive pressure (forward & reverse).


    I have no flow meter. I have only indicators. from 60 psi to 5000 psi.It is that in points 9 and 10 exceeds 5000 psi. as did those tests. You tell me which points to begin Monday. the other photographs are of the machine today. hood side panels. and protectors below are saved.
     
  8. Bob/Ont

    Bob/Ont Senior Member

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    You need to check pressure at 3 4 5 6 8 9 & 10. You can take the brake release hose off or the valve and cap the fitting to load the drive for testing. Test complete system as it is, then test with RH and the LH pedals half way down so you can see how it drives on each side. This will show if one side is bad only, then I take the drive hoses to the motors off and plug them, run the test again and see if the problem is in the pumps or motors.
    Later Bob
     
  9. mecaniquin

    mecaniquin Well-Known Member

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    OK. First. Let me see if I understood. you want me to take the pressures at points 3 4 5 6 8 9 & 10. This will I do when the oil has the normal operating temperature. (I close the synch shutoff valve for this test ???) or (I condemn "close" the hose releases the brakes ???)

    IMG_20150819_084147.jpg

    the black hose that is in the hands of the Lord. you want the closure for testing? if you shut the machine will not move. The tests conducted are made with the parked machine?
     
  10. Bob/Ont

    Bob/Ont Senior Member

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    Yes check and record the pressures at the points I mentioned. Lock breaks and make sure they will hold the machine parked at full power. Pressure readings are taken with machine parked. The sync shut off can remain open for this test, it is closed to adjust the machine travel straight when finished. Forgot to mention to put a tach on the engine for this test. Load the drive and watch the gauges, pull as far as you can without the drive venting out, then back off, do a few times in forward, then a few times in reverse. Observe gauges and record readings. Try to get to full travel if you can. If you have vent out then try again but with one steering pedal half way down to get ZERO drive pressure on one side, compare charge pressure when loading half system and full system. Repeat with other side at ZERO drive pressure and again compare charge pressure to the pressures read with other tests. Do these tests and post results.
    Later Bob
     
  11. mecaniquin

    mecaniquin Well-Known Member

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    OK. then in points 9 and 10 I put indicators 5000psi. put the governor in high idle. and pull the lever foward and reverse. without placing the brake hose. then foward and I pressed the pedal steering. a side. then the other. just in reverse. Indicators should then get to 0 ... or what would be the expected result in this test?
     
  12. Bob/Ont

    Bob/Ont Senior Member

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    You can zero out one side at a time in forward and reverse. By doing this you only load one side at a time and if one side is bad and the other good you will see the drive not vent out when driving the good side. If they are both just worn and leaking a bit they may not vent out driving one side. We will see. This effectively tests each side on it's own. You know condition of RH and LH. To test deeper take off the main drive hoses and plug them, repeat the tests and you now know the condition of each pump and motor. Watch charge pressure as you test. It will raise and fall as cooler flow does. Cooler flow indicates drive loop leakage.
    Later Bob
     
  13. mecaniquin

    mecaniquin Well-Known Member

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    a greeting friend bob. Today I started testing ...

    I began to block out the brake. and place the hose in points 9 and 10. and the track motors. at first when the oil is cold the indicator exceeded 5000 psi. Here the images. IMG_20151019_105528.jpg IMG_20151019_113046.jpg IMG_20151019_125314.jpg IMG_20151019_113324.jpg IMG_20151019_125331.jpg
     
  14. mecaniquin

    mecaniquin Well-Known Member

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    after moving fwd and rev lever several times at intervals of 30 seconds ... the machine began to vent. I guess you meant to do these tests. Note that I have no tachometer. So I put it in high idle. flowmeter have not ok. only indicators.

    IMG_20151019_112924.jpg IMG_20151019_113203.jpg

    with the lever in park and high idle 230psi 230psi lh rh ... then take 2000psi and was reduced to take one of the two to 500psi. both they stopped at 500psi. no pressure differences.but......
     
  15. mecaniquin

    mecaniquin Well-Known Member

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    IMG_20151019_163212.jpg IMG_20151019_171425.jpg


    pressures made today are not equal to the comparison table ..

    I track of motors nothing came of oil. the right leaving a drop every ten seconds. in all ranges of acceleration and movement of the lever fwd and reverse ..

    another thing I noticed was that before starting the machine oil in the transmission was in the middle level between add and full. start and after more than an hour and turned the brand is in full. should not be the other way around? if the cooler is higher than the transmission should level off at. I did not upload it. do you think there is any restriction ???

    another thing I saw when the idling high and lever in the park. the left pedal pressed and held in 230psi but when I press the right pedal pressure in the pump up to 420 psi. you may just need adjustment?

    That's what I saw damaged. apart from all the pressures that are wrong. Hahaha. remember that synch cutting screw is open. I always did the tests with closed screw. you tell me where do we start .. or maybe sell it for parts lol. joke.
     
  16. Bob/Ont

    Bob/Ont Senior Member

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    Could you try another gauge on the servo supply tap, something is wrong, servo pressure must drop over it's valve to charge pressure. Servo must be more than charge/brake pressure. Are you sure the hose ends are open on the case drain fittings. Something is not right there.
    Later Bob
     
    Last edited: Oct 20, 2015
  17. mecaniquin

    mecaniquin Well-Known Member

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    Hello Friend. I am going to change the meter. and change the hoses on the track motors. but I have a suspicion that this defective one cylindro. not you think? mind you. the drive pressure to reach 4500 psi in fwd lever and then vent. but when the lever is in rev only reaches 3500psi and vent the left side. 4300psi for the right side in rev. should vent in the same psi both fwd and rev ??? That could explain why once the machine is start the oil level in the transmission goes up instead of down ??? or maybe I'm wrong? is there any test that he can do to cylinders?
     
  18. Bob/Ont

    Bob/Ont Senior Member

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    The HPCU shouldn't vent out, this is caused by low charge pressure. Low charge pressure is a result of drive loop leakage. I suspect you only need the drive motors rebuilt but need to be sure. Try to get plugs for the drive lines to block off the HPCU outlets and test again as you have but without the motors. A big improvement would say motors are problem.
    Later Bob
     
  19. Mobiltech

    Mobiltech Senior Member

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    I'm wondering how you have no case drain at all. I've never seen one of these machines without a little case drain. Are you sure you did the test right or did I miss something else that has shown actual case drain.
     
  20. mecaniquin

    mecaniquin Well-Known Member

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    I changed the hoses and oil pressure came not there. drops only. place a direct indicator. and I do not get the needle.

    IMG_20151020_104936.jpg IMG_20151020_104958.jpg

    I suppose you want me to close the HPCU outputs. you want me to block these ??? both sides? or one side at a time?

    IMG_20151020_133748.jpg IMG_20151020_133756.jpg

    I lock the small hose down too? or is it just the greatest? (thick)...

    Today I returned to position the pointer in making the servo supply pressure. in this indicator she had a pressure drop of 340 psi to 140 psi ..

    it is normal to lower the pressure in the servo by the load pressure drop?

    another question. You have no idea of the cost to repair one of these bombs? Thank you. later