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relief valve

  1. D

    Relief valve o-ring question

    How many orings are inside a relief valve, -have replaced 3 (red arrows) Now dripping from adjuster (green arrow) Is there another oring accessible by removing the lock nut and hex screw?
  2. J

    John Deere 490 travel issues

    Hey all I’m new to the forum but have been lurking for years. I’ve run into a problem I can’t figure out. So I just bought a 1990 490D and all the electronics have been bypassed I didn’t do it I bought it like that. Engine runs great all dig functions work great so when I’m traveling it all...
    • jchand4
    • Thread
    • 490d deere final drives relief valve
    • Replies: 8
    • Forum: Excavators
  3. H

    Boom Cylinder Extends But Will Not Retract

    Cat 304CR (NAD00987) I've got a boom cylinder that will extend but will not retract. In other words, boom goes up but won't come down. When I try to boom down, I hear noise from the relief valve, but the cylinder only moves about 1/4". I don't have a way to test flow, but I have adequate...
    • Howey Matt
    • Thread
    • 304 304c 304cr boom boom cylinder cat caterpillar cylinder excavator relief valve
    • Replies: 34
    • Forum: Compact Excavators
  4. B

    PC120-6 weak hydraulics

    I have a Komatsu PC120-6 that the hydraulics get really weak after 45 minutes of run time. It’s so weak it barely picks up the bucket. I just had the hydraulic pump professionally rebuilt last week ($4500.00) I also changed out the relief valve on the main valve block. The relief valve that’s...
    • blanchb
    • Thread
    • hydraulic pressure hydraulic problems pc120-6 relief valve weak hydraulics
    • Replies: 153
    • Forum: Excavators
  5. G

    Relief Valve Help - Yanmar B32-2

    Good day all Looking for a little help with my machine. very week blade and swing operation, swing motor and pilot system gear pump are new. I can hear the fluid bypassing over the pilot system relief valve at idle. Took it apart and it looks like one o-ring is gone. In the attached photo there...
  6. M

    case 580k relief valve?

    Just got a Phase 1 580k When digging my bucket operates normal but when it hits a root or obstruction it just stops as if a relief valve dumps pressure . Is there a relief vale? I'm used to old backhoes that bog down under pressure this never does that . What should I check?
  7. L

    Cracked hydraulic pump on an 863 - how to avoid a repeat?

    I have a 1997 Bobcat 863 which cracked the hydraulic gear pump. I found that and have a new pump on order, arriving in a couple days. Now I'm trying to figure out what could have caused this issue in the first place. The crack goes directly through one of the bolt holes holding the pump onto...
    • LessWhole
    • Thread
    • bobcat bobcat 863 hydraulic relief valve
    • Replies: 11
    • Forum: Skid Steers
  8. Troy4500Industrial

    Relief valve? Rebuild?

    Hey guys, My 74’ Case 580B has been leaking from this for a while ... I unthreaded it and replaced the o rings last year, but it’s leaking internally from under cap/c clip ... is this a relief valve and how difficult is it to repair? I can’t seem to find any schematics on it
  9. J

    Cat 302.5 Hydraulic Thumb Relief

    Hello, first post here but I've been following along for a while. Very helpful forum! I recently installed a hydraulic thumb on our 2000 Cat 302.5 (4AZ01260) and have been reluctant to use it yet because I think we need to incorporate some form of relief into the system to avoid having the...
    • JHead
    • Thread
    • 302.5 hydraulics mini excavator relief relief valve thumb
    • Replies: 17
    • Forum: Excavators
  10. J

    Excavator humming/buzzing noise

    I just purchased a 2008 JCB 8060 Excavator. Everything seemed normal when testing it out. After having it shipped 600 miles to my house I have started to notice a noise. After it is running for a short time I get a humming/buzzing noise that seems to come from under the floorboard. The tone...
    • Jessie H
    • Thread
    • buzzing excavator humming hydraulic jcb noise pump relief relief valve
    • Replies: 0
    • Forum: Excavators
  11. D

    T300 spool valve sticking after replacing seal

    Hello to everyone and thank you in advance for any help you provide. I do most of my own wrench turning and do the best that I can with the self taught knowledge I have to keep my equipment running and my business operating. The machine in question is a 2002 bobcat T300 that runs and operates...
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