bobcat 643 lifting problems

[lemming]

hi i am working on a 643 and it is has fine flow, but is low on hydraulic pressure, 1500 psi. it should be making 3000 psi, so i am suspecting a faulty pressure relief valve. The markings/numbers on it says SUN 8FQ6 8I01 17A, but i cant find anything from that. can anyone tell me the bobcat part number, or similar?

 

[mike_belben]

Raise cab. Find main valve block and remove the relief, its on the top front where the control rods attach to spool stubs on a 743. Like 27mm socket i think? Remove it, watch for an o ring to be left inside the cavity. Clamp valve in vice, unscrew the cap, pull out spring and shims and pintle. Inspect seat, clean up with sandpaper, lapping compound.. Ive even fixed them with a hand file in a pinch. Reinstall and try again. Shim if still too low. If it dont respond, pull charge pump and recondition the guts.

 

[Tazza]

Raise cab. Find main valve block and remove the relief, its on the top front where the control rods attach to spool stubs on a 743. Like 27mm socket i think? Remove it, watch for an o ring to be left inside the cavity. Clamp valve in vice, unscrew the cap, pull out spring and shims and pintle. Inspect seat, clean up with sandpaper, lapping compound.. Ive even fixed them with a hand file in a pinch. Reinstall and try again. Shim if still too low. If it dont respond, pull charge pump and recondition the guts.

Excellent advise right there.
If you do need a new one, talk to the dealer for a new one. The pressure should be around 2,400-2,600 PSI