yes bbforks
that is exactly why i put that comment at the bottom
NONE of this job should be done by a novice period!
let the professonals do it ;o)

Have a forklift mechanic pack the lift cylinder. The mast can hurt you real bad. Dont try it!

Jplayer- you're absolutely right. I'm just afraid to have folks start removing hydraulic lines when the forks are up in the air. I've learned the hard way that sometimes what you say is not what is heard.

Khans- if you decide to remove hydraulic lines- the hydraulic line that is connected by hose clamps is the return line. DO NOT- I REPEAT- DO NOT- Remove any hydraulic line that is secured by a nut that is part of the hydraulic line. All pressure type hydraulic lines have built in hex head connectors. SERIOUS injuries can happen when hydraulic lines under pressure are suddenly disconnected.

-nuff said

if its dropping 10ft in 10 seconds you have a serious issue
my guess is since it is what you say a "single cylinder" that it is a multistage telescopic cylinder? or is this just a simplex mast freelift (does not go up very high)

my best guess is you have some packing issues in the cylinder allowing the rod packing to bypass.
The thing about it slowing down when you pull the lift lever is only that it is applying pressure to the cylinder trying to raise it back up. But if it is still falling down while you have that lever pulled it sounds like an internal cylinder issue. (packing).

If when you raise it all the way up and leave it for a while see if it bleeds down then, when raising it up to the top it might be putting enough pressure on the cylinder to hold it there temporarily? or just applying enough pressure on the packing to expand it and then it holds.

There is one test you can do, when you have it raised up pull the return line off and see if there is any drainback. You may get a slight bit but it shouldnt be alot. If you get more than a trickle then you may have a bad control valve or check valve issue. Now when i say return line i DO NOT mean the line going from the control valve to the cylinder, i mean the big hose going from the control valve back to the tank. By all means DO NOT loosen the pressure line while it is up in the air, that is very dangerous and will get you wet with oil in the process. Not to mention the forks will be comming down quickly too!

If your not sure about any of this hire a professional tech to troubleshoot it and repair it.

Having the same problem... just replaced the spool valve it's a little better but the load drift is 12" every 5 mins... I think there may be a check valve I over looked. Does anyone have access to a manual or hydraulic print?

I need to kknow what type of lift cylinder you have. Can you send a picture to my e-mail?

my c500 is a single lift cyylinder with two tilt cylinders, one control valve with two levers.
any help
thanks

What kind of upright is on the machine? Could be either a faulty hydraulilc control valve or packings in the hoist cyl. The symtoms will be different depending on the upright cylinder.

If I lift the mast anywhere ohter than all the way to the top, then I release lift the forks they fall to floor, 10 seconds per 10 foot.
If I hold on lift they fall slower. my question is is there a check valve or a bad cylinder.
thanks Ken

Don't understand your question- you'll have to make it clearer what you want to know