well there you go
found a problem, bad cylinder
get er fixed and see how she does then ;o)

There is no "motor" in that hydraulic accumulator. It only stores a limited amount of hydraulic oil pressure by compressing a spring in the accumulator when the truck engine runs the hydraulic pump. The hydraulic pump pressurizes the accumulator and the accumulator stores the energy until it is needed. The accumulator assists the brakes at times when there may not be enough hydraulic pump pressure available, like at idle when you are also operating some hydraulic cylinders. The accumulator only has enough energy stored to affect a few brake applications before being depleted.
Once depleted you have no power assisted brakes. The brake application then becomes a matter of how hard can you push on the brake pedal because at that time, the brake valve has switched over to being a master cylinder to provide back up for the brake system. There is no back up brake booster pump.

Ouch!
I suspected late 70's,...well Elvis was still rockin!
There is an accumulator, traced it to the steering and brake unit. Bypassed it to test, no go. Checked for a fuse, or flow control valve, but none was found at base of free lift cyl. Dont know if one should be there?
Blocked free lift cyl to test for bounce, it's gone! sending cyl to rebuilder, possible seal breakage.
I'm wondering about the brake accumulator and motor. Never heard that motor come on, no power to it. We pumped the brake 50 times to deplete the reservoir. Then a warning light came on with buzzer upon re-start.. It went away when i pumped the brakes with engine running. that's normal and Had nothing to do with Hyd cyl, but wondered if the brake unit was not functioning properly because the electric motor never had power.
Will keep you posted on Cyl repair.
Thanks for the tips!

If there's no numbers before the FGC35- this would be a first series lift- making it a '70's model. If there is indeed an accumulator mounted in parallel with the hoist circuit than that can make the carriage "bouncy". If you're not carrying fragile material (glass etc) the accumulator can be removed with no other adjustments needed to the lift.

Thanks for the replies!
It's model FGC35. It also has "TOYODA LOOM WORKS" on another decal at the roll cage. I think it's a restored classic....maybe from early 80's with inline 6.
I will try the full lift deadhead again. I did that but only once. Will try several times as suggested. There are no screws at tops of cyls at all. If i have a bad accumulator, i'm sure it's not fixable. Must be a huge spring inside there, like old brake accumulators on GM trucks?
Will check tomorrow if I can dig out from the snow storm!

If you can't find a bleeder screw, you can do this.
You must make certain the hydraulic oil is filled to the correct level before doing this.
Tilt the mast as far back toward the truck as it will go, this is to ensure the carriage and telescoping sections can drop completely to the bottom end of travel when lowering the mast in this operation.
Raise the mast as far as it will go and raise the engine RPM enough to force the hydraulic lift circuit into bypass without killing the engine.
Then lower the mast completely.
Repeat this a few times.
By pressurizing the lift circuit this way (forcing into bypass) some of the air can be encouraged to be entrained into the oil. Lowering the mast quickly and completely after each pressurization helps transport the entrained air back to the tank in the returning oil.
The entrained air will want to come out of the oil pretty fast, so it is important that the mast be lowered completely and quickly each time when you are doing this.
I have used this practice many times on systems that have no bleeds and it has always provided good results.

if you have a 'bounce. in the mast & carriage when you stop raising or lowering it is most likely air as you suspect.

2 things i would do
- check to see if the hydraulic system has an accumulator, a bad accumulator can cause this.
- try and bleed the air out of the cylinders. The older cylinders usually had a bleeder screw near or on top of the cylinder.

Forgive me- tellies? Are all the hydraulics slow to respond? How many hoist cyl's are there? Is the hydraulic oil in the tank foamy while the engine is running? The model # is stamped into the frame on the right (as seated) side of the machine.