Old Clark C500-30
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  1. #1
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    Default Old Clark C500-30

    Hello, we have an old Clark C500-30 that has been running well for a long time. Now we are having the issue of the mast not staying up at any height, with or without load. There is no real leaking from the main mast cylinder. Just very very minor weeping on the piston surface.

    It is a single stage mast with side shift. It has large cast steel cups at the top over the end of the piston and a large cup housing at the bottom. It has been kept inside all the time and maintained well.....but it is old. Other than this issue it is a great machine.

    So, we are interested attempting what we believe will be a cylinder seal replacement. We have another forklift to help lift up the piston and remove it as well as an overhead gantry.

    We have reviewed the previous threads on this machine on this forum. But most of them refer to a 3 stage mast, ours is a single stage (rather tall) mast. Overall lift of the forks is up to 4.15m. So it has a tall single stage mast.

    Some of the threads refer to a set of special tools that are required to be used to get the old seals out etc....any help would be appreciated.

    Thanks peter

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    Hi, I have added some photos hope that helps with any replies

    Thanks20180119_091318.jpg20180119_091311.jpg20180119_091250.jpg20180119_091235.jpg20180119_091225.jpg

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    The only special tool that it looks like you need is a big spanner for the gland nut. If you look at see that big ring at the top of the cylinder, that is the gland nut that will allow the rod and the piston to be removed. The spanner wrench goes in the holes you see. That being said, sometimes the holes are deep enough to where you can just insert some round stock in the hole to screw the nut off, or it you don't mind a little teeth marks cosmetically, you can just use a big pipe wrench. I have made spanner wrenches for these big cylinders, it's not very hard if you have the tools.

    A couple of words of caution, most of these gland nuts have a set screw (or more) holding the nut from coming loose. If you try to remove the nut before loosening the set screws, you will ruin the threads. Also, if you go the pipe wrench route, make sure it doesn't slip and bang the the rod.

    This is just general cylinder repair, based on your pics. I have no specific knowledge of this particular lift.

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    Before I started tearing apart the mast and cylinder I’d rule out the valve first. The lift/lower spool maybe worn out or cracked. The easiest way to check it out is.....Get a couple hydraulic fittings and some hose. Move the lift cylinder pressure hose to another pressure port on the valve. If it’s acting the same, you know it’s the cylinder packing. If it works like it should, it’s the spool in the valve.

    Andy

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    I agree with Andy. Being a single acting cylinder, they have a vent located on the top of the cylinder (dead side) with a small hose that trails down to the bottom of the cylinder and vents to atmosphere. If the seals are bum and leaking you will see this hose puke hydraulic fluid if you do a full cylinder extension. You're seeing fluid that has slipped by the seals and is sitting on top of the ram and is being pushed out the vent.

    More often than not it's the control valve that the culprit...but not always!

    Stuart

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    I third that, there may also be a relief valve in the lift circuit thats leaking internally......as I remember the old Clarks had all valve functions in one body.....but if the valve is badly worn ,you can replace the whole lot with a good used two spool valve from a wreckers.Most mechanical people have several multi spool hydraulic valves ling around waiting for a project.A multi valve can be reduced to two spool by simple reassembly..........before anything though.....look for a "anti drop valve" thats been added aftermarket,they often cause trouble.

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    On most of our lifts, the cylinder vent hose goes back to the tank, so if you have a leak it goes back to the tank. If this is the case, you'll have to remove the hose and see if it has fluid in it.

    Some cylinders just have a rod in them with no piston, any leak by on them will be readily apparent, as it will be running down the outside of the cylinder.

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    Thanks for all the help. We did the diagnosis today and the low pressure return hose from the top of the mast cylinder spewed forth a good 1 litre of fluid and then repeated it again. So it appears that we are reconditioning the mast cylinder.

    Not sure if we should also get the Spooling Valve looked at at the same time??

    thanks

    Peter

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    Pull the cylinder apart first....its so old theres a good chance of a leather bucket.......theres also a good chance of a fair ammount of corrosion pitting inside......if seals arent available,just get the piston head machined to fit polyurethane seals......these seals can also cope with a fair ammount of pitting or scoring inside the cylinder.

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    Quote Originally Posted by CMRL View Post
    Thanks for all the help. We did the diagnosis today and the low pressure return hose from the top of the mast cylinder spewed forth a good 1 litre of fluid and then repeated it again. So it appears that we are reconditioning the mast cylinder.

    Not sure if we should also get the Spooling Valve looked at at the same time??

    thanks

    Peter
    I'd start with a cylinder rebuild first. If you still have leak down problems after a cylinder rebuild, you'd want to look into the valve.

    I'm going to bet a cylinder rebuild will solve your problems.

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    Hello and thanks to everyone who replied. We are starting the tear down week after next.


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