allis challmers 715D backhoe/loader power steering

mculley · Jan 6, 2016

I have a 1975 allis challmers 715D backhoe/loader with a 65HP perkins diesel. Was using the hoe for plowing snow and all was working well. On the drive back to the barn I noticed that I had to continue working the steering wheel in one direction to just keep the tractor going straight. The next day when I tried to go out and plow roads I had no power steering. Temps were down to mid teens so I thought it was moisture in the hyd. oil that had froze in the lines or valves. That wasnt it, next I pulled the bypass/relief valve assembly to make sure it was operational and all seemed fine. I wasn't sure I had enough hyd fluid in the tank so I added an additional 5 gallons which brought the level up to within 4 to 5 inches from the fill spout.
All the rest of the hydraulic functions work fine....any ideas would be appreciated.
My next try is to see if I can prime the power steering pump from the pressure side where the hoses go to feed the steering wheel motor. Would that work if I lost my prime and cant get it to reprime? Do I need to bleed out air in the pressure lines up by the steering hyd. motor?

Tool Box · Jan 6, 2016

If it has the standard steering orbit motor at the bottom of the steering column that is likely your culprit. They can fail internally and cause the oil to bypass. You shouldn't have to worry about air in the lines, those hydraulics should be self bleeding. I am not familiar with allis but suppose if they have priority valve for the steering, there could be some issue there but I think the likely cause is the orbit motor.

mculley · Jan 6, 2016

(quoted from post at 21:12:55 01/06/16) If it has the standard steering orbit motor at the bottom of the steering column that is likely your culprit. They can fail internally and cause the oil to bypass. You shouldn't have to worry about air in the lines, those hydraulics should be self bleeding. I am not familiar with allis but suppose if they have priority valve for the steering, there could be some issue there but I think the likely cause is the orbit motor.

Thanks for that insight, is there any way to test that and any ideas of where to go to find another one?

Bob Bancroft · Jan 7, 2016

I used to have to continually turn one way on the road. The more weight in the bucket, the faster I had to turn. So, I eventually rebuilt the older steering cylinder. (The other one was obviously a newer replacement). No difference. Then more recently, I rebuilt the newer cylinder. I liked the original cylinder better. The newer one has some of those "plastic" type rings. The one which was really bad wasn't in the kit! So, after waiting a couple more days for one little part, the problem was finally fixed. It was the newer cylinder the whole time!

mculley · Jan 7, 2016

Not what I'm used to, but the power steering decided to start working again today. I suspect that I may of had some moisture in my hydraulic fluid and it froze in the very tight tolerances of the steering cylinder. Today was the first day we've been above freezing and that along with my attempts to thaw may have finally taken.
My question, you talked about rebuild kits for the steering cylinder... are those still available and if so, where? You know....just in case.

allis challmers 715D backhoe/loader power steering

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