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Terex TL842C Hydraulic Info

Discussion in 'Forklifts/Telehandlers' started by John C., Jun 2, 2020.

  1. John C.

    John C. Senior Member

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    I'm working on another basket case and need some information to cut down on the head scratching time. The machine hasn't been run for around a couple of years. It was parked and then wouldn't move. I got the electrical issue with the parking brake sorted out and can now move the machine. The hydraulics wouldn't work at first when I checked and set all the pressures. I raised the pilot pressure from 300 PSI up to the factory spec of 500 PSI and got some movement on the boom. At least it would go up enough to be able to move the machine. It barely goes down though and the carriage tilt function doesn't work at all. When I raised the pilot pressure the pump started rattling and does that all the time now. Main pressure was at 2,700 so I raised it to 3,000 PSI. I'm thinking that the stroking mechanism on the pump is bad and probably some bad things are going on with the swash plate. Parts depot for these things is in Tigard, Oregon and there are few people around here that will even talk about one. I have a parts book for the machine but not been successful on finding a service manual yet. Any info would help out my customer.

    Thanks in advance.

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  2. mikebramel

    mikebramel Senior Member

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    Should be easy for you to get pump parts. What is the signal pressure when you're trying to lower the boom
     
  3. John C.

    John C. Senior Member

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    This one is only pressure compensated. According to the hydraulic schematic in the parts book, the pressure compensation is internally ported in the pump. As far as I can tell, the pump either works or it doesn't. The max pressure is set on the pump and there is an external block for the pressure controls for steering, brakes and implements.
    Terex has a parts order center in Tigard, Oregon but the parts warehouse is in North Bend, Washington. I talked to the people in Oregon yesterday and the pump is obsolete but they do have an updated pump for around $2,100. I'm going to do some more checks today before I drain the system and pull the pump for teardown.
     
  4. mikebramel

    mikebramel Senior Member

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    From what I remember DR control is pressure comp. DFR is load sensing. DFLR is load sensing w hp control.
    Are you sure it is a problem with the pump and not a leak downstream causing the pump to load/ unload. They are very reliable.... but maybe that is why it was parked
     
  5. John C.

    John C. Senior Member

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    It was parked because the park brake would not release. Apparently there was a problem with the tilt control on the forks and then someone pulled some wires loose on the park brake relay and didn't put them back on the proper lugs. The park brake pressure switch was shorted through as well.
    When I ran a search on the model number I noticed the DFLR as well and checked the pump for a load sensing line and didn't find one. All that is there are the case drain, suction and discharge hoses. The pump looks original so I was wondering if all the functions could be in it and not used?
     
  6. mikebramel

    mikebramel Senior Member

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    Yes if you run the margin pressure in (small adjustment) it will act as a PC pump
     
  7. excavator

    excavator Senior Member

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    We have a Genie dealer here in town that works on a lot of lift trucks, I should be able to swing by there in the next day or so and talk with the service manager to see if he knows anything, even if there is anyone local who has a like machine. When the 2 companies merged alot of Terex models got painted Genie blue so there might be a possibility there is some Genie info available. Terex info is more than a bit of a pain on their older machines, most of this I'm sure you already know. Is the date on the pump tag 04/02? I believe 2002 was when the merger happened. so if that date is correct that's right when the merger happened.
     
  8. John C.

    John C. Senior Member

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    Went to the machine and plugged in a gauge and got no pressure this morning. I pulled the pump and brought it back to my shop and tore it down.

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    The seal plate has a couple of small marks but it isn't the reason the pump didn't work.
     
  9. John C.

    John C. Senior Member

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    The barrel assemble also didn't look bad either.

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    The swash plate has a touch of fretting though where the piston feet ride but that wouldn't cause it to quit pumping.

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  10. John C.

    John C. Senior Member

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    I got to looking close at this point and looked at the end of the stroke limiter rod. It looked a little worn from something.

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    I checked the socket where it's sits in the swash plate and found what looked like two sockets.

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  11. John C.

    John C. Senior Member

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    Next item was to push the piston out of the bore in the pump housing. I had to push it to the inside because it got stuck in the threads trying to come out towards the head end.

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    Low and behold what I found.

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    I'm waiting for prices now to see what the client wants to do next.
     
  12. excavator

    excavator Senior Member

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    I did a bit of checking and it's actually a TH842C not a TL842C. When Terex took over Genie it became a GTH842 and the manuals are available on the Genie site. I just checked again and the actual Terex parts manuals are also on there.
     
    Last edited: Jun 6, 2020
  13. John C.

    John C. Senior Member

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    You are correct and I hit the wrong key when typing. I've got a parts book. I couldn't find the service manual on a google search. Thanks for the new model numbers.
    I got a new pump today from Genie and instead of the Rex Roth unit, it's now a Saur pump. I gave the old numbers to the Rex people who said they would get back to me. Didn't happen. I'll install it tomorrow but won't have the machine running until sometime next week. I need to changes all the oils and filters that are years old.
     
  14. John C.

    John C. Senior Member

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    Well I cleaned the hydraulic tank and flushed the hose to the hydraulic pump and bled the air off the case as much as could be done. The case drain fitting is on the side of the pump in this layout and I couldn't turn the body because of the four wire hoses with the flange type fittings. Anyway I started the engine, got a little chatter for a few seconds and then shut down to bleed any air that might still be in the case. Hooked up the gauge and started the engine up again. At any rate all I could get for pressure was 1,500 when the spec pressure is 3,000 PSI. This pump has a different regulator and I think I saw Sauer on the casting. There are allen headed caps on the ends of the regulators instead of the usual adjustments that were on the old pump. Does anyone recognize this mess and is there an adjustment I can make if I remove the caps. On the old Rexroth pump I found where you bottom out the load sense valve on the top and then set the pressure on the lower valve. Here is a photo of the pump and regulator.

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  15. excavator

    excavator Senior Member

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    Do you have a complete Sauer part number for the new pump? I've messed with Sauer Danfoss pumps a bit and might have some info. Since this is probably an update from the Rexroth pump, did you happen to look at the GTH842 service manual? Does this look at all similar?
     
  16. John C.

    John C. Senior Member

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    The only number I have is the Terex number (234953GT updated number). There are no tags on the pump and the only reason I mentioned Sauer was because it was on the bill. I beginning to believe it is a knock off of the RexRoth. I've been into the service manual which provide no information on the pump itself. The operator's manual shows adjusting the original pump controls.
     
  17. John C.

    John C. Senior Member

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  18. excavator

    excavator Senior Member

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  19. John C.

    John C. Senior Member

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    It worked just like the book said. I went through the rest of the stuff while I had the gauges installed. Couldn't get the carriage tilt to work. Somebody prior did some make work wiring. They took power off the park brake relay so the carriage tilt won't work with the park brake set. I haven't been able to find the tilt relay and when you touch the pump destroke it blows a fuse. I'll put my own relay in and take power from somewhere else but I have to follow the wires from the shift solenoids to find a convenient place to tap in.
     
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  20. John C.

    John C. Senior Member

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    Got everything to work yesterday I had to butcher a hole in the cover over the transmission in order to clear the pump control valves that are in a different place. All well and good except now the valve hits the engine air cleaner. A piece of oak and two longer bolts all worked fine. This machine had been sitting for three years or more. Brought it back to life again to move pallets of cut sand stone around.

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