bobcat 643 hissing cylinder?

Hey guys, Ive noticed with my 643 the lift function of the bucket has lost some power, I get alot of leakdown and the ram on the right hand side of the cab makes a hissing sound when operating. I was lead to believe all I needed to do was the piston seals but the more I research the more confused I get? Could it be my control valve? Is there a way to check? Any help much appreciated Cheers, Dave

if it was the seals youd see some leakage on the machine itself, the fluid that escapes by

[email protected] said:

if it was the seals youd see some leakage on the machine itself, the fluid that escapes by

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Could be the piston seal or sometimes the nut holding the piston on the rod comes loose and fluid leaks thru the piston.
Here's how to test for a internal leakage.

OldMachinist said:

Could be the piston seal or sometimes the nut holding the piston on the rod comes loose and fluid leaks thru the piston.
Here's how to test for a internal leakage.

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ok i have done some tests and i think the lift load check is faulty. Any ideas on an easy solution? can you just take it out with the control box still in place?

d_calabria said:

ok i have done some tests and i think the lift load check is faulty. Any ideas on an easy solution? can you just take it out with the control box still in place?

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anyone know how to repair a leaking load check valve? cheers

d_calabria said:

anyone know how to repair a leaking load check valve? cheers

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Some had Orings and backup rings in them, others were just poppets and springs. If the seats were badly worn, there is nothing you can really do.
Remove them one by one and have a look.
It is possible it is the relief for the lift rams, The main erlief is closer to the front, the lift one is near the back of the control block from memory