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Thread: Trouble with a Clark Lift model C500's hydraulics

  1. #1
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    Trouble with a Clark Lift model C500's hydraulics

    My old Clark Lift C 500 fork lift's main cylinder was leaking very badly so I took it into a hydraulics shop and had it rebuilt. After installing it again, the carriage will not go all the way to the floor under its own weight, nor will the carriage rise very far. Is there any special thing I have to do to bleed the hydraulic system? I tried opening the small plug on the top of the cylinders, and a bit of air came out, but the lift only goes up a few feet and then stops. Does anyone know the procedure to bleed the cylinders? Or anything else I might try to get the thing to operate properly.

    Thanks for any help. It's an old unit and I don't have any manuals to go with it.

    Jerry O

  2. #2
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    That's a very complex multi-stage, lift cylinder on that old C500. It's made up of about 4 barrels sliding in each other. Very possible the shop who rebuilt it got some things a bit too tight. The packing is adjustable however.

    There are two bleed screws, one on the front of the ram where the collar is, one on the top.
    Here's the bleed proceedure:

    1) Raise carriage about 4ft off the ground or until side bleeder screw is accessable
    2) Loosen side bleeder screw using an Allen wrench. The piston will drop a few inches as
    the air comes out. When air stops and oil starts, re-tighten bleeder screw.
    3) Loosen top bleeder screw using Allen wrench. The piston will drop a few inches as
    the air comes out. When air stops and oil starts, re-tighten bleeder screw.
    4) Check oil level in sump and add if needed

    I have no idea why or how but Clark built forlifts from about 4000lbs to 25,000lbs capacity and called them all C500. Is yours a big one or a little one?

    Good luck & welcome to the Forum

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    Clark Used the C500 as a model designator, like Biscayene or Impala in Chevys. Prior to C500 it was C20,30,40 etc.
    The C500 is followed by more numbers"
    C500 235-01-0001 would be a C500 model, 2000 to 3500 capacity,truck number 01 of production run 0001.

    Lets say over the years Clark has run 9780 production runs.
    In this run, they were making 5500 lb trucks and were running a quanity of 321 trucks.
    You would have C500 355-01-9780 thru C500 355-321-9780.
    The C500(model) 355 (3000 to 5500 lb cap) truck number 321 coming down the line, during production run 9780.
    The data plate listed the capacity based in the counterweight put on it at the factory,
    A 235 is the same truck but CW/d to carry 2000m 2599, 3000 (S30), 3500 ibs.

    Similarily a 355 would be a 3500,4000,4500,5000,5500, etc based on CWT on it.

    Every C500 has this info stamped in the right hand side of frame, down 6 to 10 inches, and front to back
    area between dash base and seat pivot fasteners. In 1 inch+ high letters, Depending on number of times
    repainted, you may scrape half a blade of a good pocket knife away to clear them. (I reccomend Case knives)

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    Thanks for the response and the bleeding information. I got frustrated with trying to get the cylinder to collapse and took the cylinder back to the hydraulics shop. They couldn't get the clyinder down either and decided to take it apart again. I got a call last night, and the shop guy said when they took it apart they found something inside the called a "bushing" that had been left inside when it was reassembled. I'll get it back tomorrow and go from there. The bleeding procedure will be a big help.

    The unit is a small one, probably in the 4000 # range.

    Again, Thanks for the good advice.

    Jerry O

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    Hi TD24,

    Thanks for the tutorial on the model numbers. I'll dig the old paint off the frame and see what I've got. The original problem seems to have been caused by a part left inside the cylinder when the shop rebuilt it.

    Again, thanks -- the model numbers will help if I need to get work done on the unit in the future.

    Jerry O

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    Quote Originally Posted by Jerry O View Post
    Thanks for the response and the bleeding information. I got frustrated with trying to get the cylinder to collapse and took the cylinder back to the hydraulics shop. They couldn't get the clyinder down either and decided to take it apart again. I got a call last night, and the shop guy said when they took it apart they found something inside the called a "bushing" that had been left inside when it was reassembled. I'll get it back tomorrow and go from there. The bleeding procedure will be a big help.

    The unit is a small one, probably in the 4000 # range.

    Again, Thanks for the good advice.

    Jerry O
    I've got a "Planned Maintenance and Adjustment Proceedures" manual laying around for the small C500-Y50 (Y355-31-1245 to be excact) An operators manual, and a parts manual too. Some people just never throw things away

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    Hi OFF,

    Do you have any interest in selling the manuals you referenced above, or parting with a copy of them?

    Let me know. My email is obuy@q.com

    Thanks,

    Jerry O.

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    Yours for the cost of shipping. Just message me a mailing adress.

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    Hi again OFF,

    Sorry I'm late getting back to you, but I had to do my share at eliminating the overstocking of Walleyed Pike in a fine Manitoba Lake and just got back to Duluth.

    Let me know what the shipping costs are and I'll send you a check. You can send me an email at obuy@q.com
    The manuals can be sent to:
    Gerald Ostroski
    5504 Lakewood Road
    Duluth, MN 55804

    Thanks for all your help.

    Jerry Ostroski

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    Help with old Clark forklift

    Took the plunge and bought an old Clark forklift. Need help with identification and a few questions. Looks like a “Carloader” from comparison to photos saw posted on web.
    Has 4 cylinder Continental F163 flathead gas engine looks like original paint on engine is medium blue. Seems to run well. Seller said it was 3500 lb capacity, but don’t think they knew anything about forklifts beyond what who they bought it from told them. I worked as a ASE certified auto tech for a few years back in the 70’s and have pretty good mechanical knowledge overhauling engines, transmissions, machinery, electric motors etc., but this is my first forklift.

    Questions:

    SERIAL NUMBER LOCATION FOR ID
    I read somewhere serial number was on frame, someone posted was :”under battery” which looks to be in original carrier on right side inside the access door. Took out battery and took a quick look, did not find anything under the accumulated crud in that area. Before I scrape too much, am I looking in the correct place?

    BRAKES
    When I got it home, the brake pedal did nothing – went to floorboard with no resistance or braking action. Looked in master cylinder and it was about ˝ full of fluid. That was yesterday. Today I went out in garage and pumped the brake pedal a bunch of times, and now it has resistance, firm not spongy near the top of it’s travel. Did not have room or time to start it up and move it, but I could hear something moving inside the right front wheel when I pressed on the brake pedal and I put the machine in neutral and rocked it fore and aft a little with a 2x4 and pressing the brake pedal stopped me being able to rock it, so maybe the brakes do work? I’m not one for fixing it if it ain’t broke so will add some brake fluid and try things out when I get some time. Any ideas on why no pedal yesterday, OK today?

    HYDRAULIC OIL MILKY COLOR
    The oil in the hydraulic tank which is in front of the motor, sort of under the front of the seat looks milky. Any idea why it is this color? I suspect some water and some posts say same. Some say “normal” to get some condensation, but leery of running with water in it.

    How high in the tank is the level supposed to be, and what oil to use? Can I get the 5 gallon pail of tractor hydraulic fluid/trans fluid at Tractor Supply and use that? How many gallons to refill whole system and should I try to flush out all the old stuff or just drain and refill the reservoir tank. The lift seems to work OK and it has no major leaks, the lift cylinder area especially is dry. The little bit it does leak somewhere leaves a few drips on the floor at right front of the machine, maybe a few inches spot overnight. The radiator coolant looks clear light green like someone did use an antifreeze mix in it, so there does not appear to be comingling of coolant, though I don’t even think these systems are interconnected anywhere.

    STEERING
    The unit has about 1/3 of a turn free play in the steering. Have not looked underneath to see where the play is – probably stack up of all linkages and box. Is this “normal” for a machine this age? Any suggestions where to look first?

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    Welcome theycallmedoc! That sounds like quite a project you've got there.
    Normally the serial number is stamped on a plate that's attached to the dash or the front face of the machine.
    Should also include capacity. Brakes use common hydraulic parts, just find a good partsman with a buyers guide
    (picture book) and match things up. Bleed that old brake fluid out of there, I'm sure it's full of water too.
    Hydraulic oil that's milky is contaminated, usually with water, drain & replace. Pretty well any oil will work in a
    machine that old, ATF, hyd oil - somewhere about 22 to 32 in weight, or 10W30 motor oil.
    Steering might have a ball & socket joint that's adjustable, just tighten it up. Other than that they have a
    steering box like a car, usually a GM car about the same vintage as the forklift. It will never steer like your
    cadilac but you can do better that 1/3 turn slop.

  12. #12
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    Common place for water ingress is mast lift cylinder. Most all straight mast trucks use a single acting hyd cylinder for mast, the difference between various designs is some used a piston seal and some did not. If yours uses a piston seal on mast cylinder you will see a small hose attached to top of mast cylinder to bleed off any oil that goes by piston seal and send it back to tank. Problem with this design, if the wiper seal on cylinder has failed it will let rain water enter via failed wiper seal, then when you raised mast it forces water in cylinder back to tank via that vent hose.
    A good mechanic isn't expensive, he's priceless!

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    Please don't respond to spammers...makes our job tougher mopping up their mess

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    Thanks to all who responded with info on my forklift. I found the serial number which was stamped on the outside of the right side “frame”” the big ˝” plate slab side of the machine near the floorboard intersection. I contacted Clark equipment and they sent me a brochure on the machine a 1955 model year Carloader 4024 it turns out to be. 4000 lift capacity with curb weight 6800 pounds. It is a 1 mb file so don’t think can attach but if anyone wants it PM me. They also sent the original build card with all the part numbers in the machine and the name of the original dealer and purchaser which was pretty neat. When I get time I am going to flush/change the brake fluid and the hydraulic oil. The Clark literature says there is an electric parking brake actuator/lock for the hydraulic brakes as one poster mentioned but that button if there was one is gone from my “instrument panel”. Will check that out someday when I get time.

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    Quote Originally Posted by theycallmedoc View Post
    The Clark literature says there is an electric parking brake actuator/lock for the hydraulic brakes as one poster mentioned but that button if there was one is gone from my “instrument panel”. Will check that out someday when I get time.
    Also known as a "Micro-lock". Basicly just a normally closed hi-pressure solenoid valve controlled by a toggle switch. You step on the brake, hit the switch, it closes and locks in the brake pressure, keeping the brakes applied. 1955......wow that's an oldy.

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    Thanks for info. If that was ever there, the button/wiring is long gone from the instrument panel. Will look and see if the solenoid valve is down near the master cylinder when I get time and the area cleaned out. Other problem will be the machine has been converted to 12 volt and this solenoid would have been 6 volt. I guess I can rewind it, find a new coil, or make a resistor or voltage regulator set up to operate it at 6v, if the device still works at all. Then there is always the wheel chock option, which probably makes as much sense as anything for as much as I will need a parking brake.

    Quote Originally Posted by OFF View Post
    Also known as a "Micro-lock". Basicly just a normally closed hi-pressure solenoid valve controlled by a toggle switch. You step on the brake, hit the switch, it closes and locks in the brake pressure, keeping the brakes applied. 1955......wow that's an oldy.

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