Bucket truck losing pressure...

   / Bucket truck losing pressure... #1  

mrcaptainbob

Platinum Member
Joined
Mar 21, 2002
Messages
593
Location
Jackson County, Michigan
Tractor
Bolens HT-20
A friend has an old, c1970's, bucket truck with a 30 foot lift. It's losing height after the rise. It's now to the point that it slowly settles back down even though the control is used to raise. Can't even maintain height. There are two sets of controls, one set in the bucket, the other on the swivel post at the truck bed. When the bucket controls are 'maxed', there is an intense squalling at the post controls. Does not appear to be any noise at the bucket controls. Neither set of controls have ever been rebuilt to our knowledge. But the friend/neighbor said that they do have 'O' rings, but are square shouldered and he cannot find them. What source might we find these under? I'm sure square edged/shouldered 'O' rings are available. Also....when near the upper limits of extension, the cylinders tend to chatter, as if low on fluid. The tank is about 3/4 full when cylinders totally collapsed. There is a large, 8" (approx.) diam pancake shaped item fitted right at the tank and then connected to the suction pump. Is that a filter of sorts?
 
   / Bucket truck losing pressure... #2  
What brand is it? doe's he have the manual? Most hydralic suppliers have square cut O-rings. Sounds like it could be the selector valve for upper/lower controls, leaking by. Most lifts have a safty check valve on the lift cylinders, incase of hose or valve failure. May be to old? If you cannot find O-rings locally, just Google square cut O-rings.
 
   / Bucket truck losing pressure... #3  
Post some pictures of resivor/ filter asy. Older units have accumilators charged with nitrogen. You do not want to take these apart, could get fluid bath or worse.
 
   / Bucket truck losing pressure...
  • Thread Starter
#4  
No manuals are available from what we can find. I will find out more info today and get some pictures as well and post back. Thanks for the help....
 
   / Bucket truck losing pressure...
  • Thread Starter
#5  
Okay. The info on this is that it's a 1973 Ford with a Stelko model C27SSG 1179, 27 foot bucket lift unit. The following pics show the truck and bucket lift, the pedestal and lower controls and the third is of the Stelko tag.
 

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   / Bucket truck losing pressure...
  • Thread Starter
#6  
Don't know how to add words after pictures, so I'll just do a reply note. The bucket can be lifted from the bucket controls to maximum height. It starts chattering near the end of the extension. Then it slowly lowers on both cylinders, even if the bucket controls are held to maximum open! Found that the 'pancake' looking device on the hydraulic tank is in fact a CharLynn model 240 oil filter. After cracking it open, the copper screen appears pretty clean, minor debris. The edge gasket needs replacing and I'm now searching the net for a new one of those. The flow control valves are accessible. Should those be removed, are there any spring loaded check balls in there to be careful of? What do we expect when that valve is removed from the cylinder end? Thanks for any help.....
 
   / Bucket truck losing pressure... #7  
CaptBob,

You need someone with experience with bucket trucks.....ya don't wanna mess around with something like this when lifting people at these heights..

That said, you'll be needing someone with a flow meter/load tester to rule-out pto/pump problems and work from there......the squalling you are hearing is most likely the pressure relief valve on the lower controls....but with proper guages installed inline on the pressure line it will be easier to see just what the reliefs are set at.....

the square type orings you are looking for may be quad-rings......they are avail using standard oring charts to determine the size......avail at your local hyd shop
 
   / Bucket truck losing pressure... #8  
The cylinder itself maybe bypassing causing the drift.
 
   / Bucket truck losing pressure... #9  
What do we expect when that valve is removed from the cylinder end? Thanks for any help.....

Cartridge valves installed in cylinders should not be removed when up and not supported......immediate collapse will happen if you don't take the proper precautions......I would advise not to pull them out unless you have new ones cuz very few of them can be serviced anyways.......

theoretically the cartridge valves job should be to hold the cyls up when the truck is off and hyd power is dead......if you blow a hose the cyl will still hold a load......

If your cyls are leaking down when the truck is off then if will either be the cartridge valves or cyls need repacking (more common)
 
   / Bucket truck losing pressure... #10  
Does it drop at all heights, or just at end of stroke? If it drops at all heights, could be internal cylinder bypassing, or safty checks. If just at end of stroke, there could be air in system, low fluid, or internal cylinder leakage. Is fluid clean, if it has water in it there may be pitting in cylinder. May want to have a hydralic shop diag and repair, due to liability issues.:(
 
 
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