Had a weird issue today on my excavator one of my boom cylinders was making a hissing noise like crazy https://photos.app.goo.gl/5ScUjQUPNm7M6nPd9 It slowly lowered itself to the ground after a minute or so. It's never done this before. I ran it for a few hours afterwards and everything seemed ok just wasn't sure if it was something I should be concerned about. As always appreciate the feedback.
Bucket off the ground, engine off, lowers to ground, makes noise. Piston packing is bypassing. It is not likely to fix itself, so you can test it again to confirm.
I think I ran it for about an hour after this happened may be more. It's not leaking and my hydraulic tank is full. Is this something I can just run until something stops working? Or should I stop immediately and address this? I'm guessing repairing this is above my pay grade. Is this an expensive repair?
Internal boom cylinder packing failure is rare, IMHO. There's a valve on back of main valve bank that combines both pumps to operate boom up. Been too long for me to remember, but, it's just Orings. Old were black, new were clear. Can you actually hear the noise in the cylinder?
This is the video https://photos.app.goo.gl/AGaVUt6nMYYh9ocU9 That noise is with the machine off and the bucket in the air. It made this noise until it finally rested on the ground.
And, someone overhauled it before. That cylinder needs repacked. Left unrepaired, additional piston seal material will fluff off and possibly jam a valve or spool. Plus, the oil becomes very erosive when passing through a tear in the piston seal, possibly even damaging the the cylinder bore. Or, the rebuilder may not have properly tightened the piston nut onto the piston rod.
Yes, I would. Maybe, depends on what you consider as expensive, and how handy you are. Couple big trees and some come alongs/ chain falls, and you can have the cylinder right out. Could have piston damaged, which is going to cost $. If the barrel is damaged, going to cost a little more. If its damaged the barrel and piston, and contaminated the whole system with steel shrapnel, going to be even more fun. Won't know until you get it apart. Could just be seals. Merry Christmas.
If the boom cylinder leaks off steadily all the way to the ground, you should look at your line relief. If the cylinder is bypassing internally it would likely stop when the line relief catches it. You can easily test this by using compressed air to check the cylinder packing. Lower boom to ground, release hydraulic pressure on lines for cylinder, remove lines and used air on one side and see if it comes out the other line.
I have a big check in front of me .............I'm betting the piston nut has backed off and the piston is getting ready to come off. Cost of repair now?......$1500-2K maybe Cost of waiting until the piston comes off and destroys the cylinder, also contaminating the hydraulic system.........Yeah, I'll go with $30K +
Sorry man I'm not following you(amateur here). What will the results of this test indicate? So that I understand, are you saying if compressed air does not pass through the cylinder then the issue is the line relief valve? Would this then indicate normal operation? That it's just relieving excess pressure?
Line reliefs are pressure relief valves that prevent system damage due to an external force causing system pressure not created by the pump. For this reason, line reliefs are set higher than main relief pressure. Main reliefs are to control an entire system pressure and line reliefs are used to control the over pressure of a specific system, ie: the boom, stick or bucket function. From what I’ve seen on an excavator, if a cylinder is bypassing, you can boom the machine up, let off of the controls, the boom will slowly drop and then stop in the air. This is the line relief catching the pressure that’s bleeding from one side to the other. Once the boom stops, if you begin to raise the boom again and let off, it will slowly drop and stop again. When the line relief fails, it drops all the way to the ground as there is nothing to keep it from doing so. I’m not there with your machine so I cannot guarantee what is happing which is why I would advise you to check your cylinders with air pressure before you have them removed and disassembled. Be sure to check both ways (pressure both hoses separately) because if a nut has backed off, I’ve seen them hold pressure on one side due to the air pressure forcing the piston back against the rod.
It is easy to pinpoint the source of a sound with a piece of rod or a long socket extension or a stick. Get it set up, and then put the rod against the suspected location, and the other end in front of your ear above your jawbone. It transmits right in. you can figure out an alternator rear bearing from a nearby compressor, for example. I'm with @Vetech63 on the loosening nut. Been there and suffered that on the boom truck. As far as doing this yourself, that cylinder is massive. I can't say how heavy but I did the cylinders on the 120 by myself with a forklift. I was on pavement and had plenty of rigging. Your cylinder ~4x bigger. You'll need help and power tools to deal with it. The bill was $2000 to go through my little cylinder so any guesstimate less than that I would not make.