boom packing diagnosis
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=47554
Printed Date: 23 Jun 2025 at 12:53pm
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Topic: boom packing diagnosis
Posted By: doctorcorey
Subject: boom packing diagnosis
Date Posted: 19 Mar 2012 at 9:27am
| need some opinions here; I have a problem with my HD7G in where after raising the boom, it settles down a ways but then holds normally. If I then move it up or down, it will once again settle a ways then stop. Now, accompanying this, the boom control will get "frozen", and require a lot of force to move it, then be normal. If I keep using the boom control and not let it sit, it works pretty much normally. It feels like a hydraulic lock. When I got this tractor the controls were almost frozen solid from disuse. I did the hose check on the lift rams, and fluid will force out under pressure from the head end, so I believe I have a bad packing. I just thought that a bad packing wouldn't cause the drop and then stop; wouldn't it just drop at about the same rate all the way down? This leads me to believe I have two problems, the packing and something in the valve body bad. I'm going to try to power these rams up one at a time (possible with my MF tractor aux hydraulics) to isolate the bad ram. I guess I could just block one ram lift hose and use the shovel hydraulics. Heck, it might be both rams, but it's so hard to do major service at my ranch that the avoidance of extra labor is critical. Any help would,well, help. |
Replies:
Posted By: D-17_Dave
Date Posted: 19 Mar 2012 at 9:59am
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You have a problem inside the valve. Remove it and do a careful clean area dissasseble and see where the rust and dirt is. There should be a spring return assembly on the opposite end of the spool from the handle, normally under some type of cap screw. These return to center springs can get full of rust or broken ad not allow the spool to properly return to neutral. Also pay attention to scratches and such on the spools themselves. ------------- Yea, I can fix that..... |
Posted By: doctorcorey
Date Posted: 19 Mar 2012 at 1:41pm
Yeah, Dave, I agree with that, probably that spool check valve not working smoothly. I do get a bit of that hesitation/slight drop before the boom lifts. Lifting speed seems alright, although I have no other machine to compare with. Add to it, the detents in the boom control are not well defined, even weak.
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Posted By: HD6 Merv
Date Posted: 19 Mar 2012 at 3:33pm
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Hicorey, the slight drop/ hesitation in the lift to me points to the check valve in the spool not seating correctly, also is a sympton of boom dropping slightly then stopping. If it was a piston seal then ram will keep creeping. When checking rams you can block oil supply to piston end. And pressurise the head end. If piston seal is leaking; oil will leak past to piston side and ram will extend due to greater surface area. But if rams creep quite noticably when extended you can bet piston seals are faulty. and is only neccessary for 1 ram to leak for this to happen. ------------- tits tyres and tracks they all cost you money |
Posted By: DMiller
Date Posted: 20 Mar 2012 at 7:47am
| One other possible is trapped air, I have bled out hydraulics on a few older Cats that did that and cured the problem, you cannot always expect the system to flush out air pockets. |
Posted By: doctorcorey
Date Posted: 20 Mar 2012 at 2:35pm
I'm going to pull the valve off this weekend and bring it home for cleaning and inspection. With the poor detent feel, there's got to be something sticking or dirty. Thanks for all your help.
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