Farm Equipment - D21 magnetic filter

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D21 magnetic filter

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=210593
Printed Date: 02 Apr 2026 at 3:23am
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Topic: D21 magnetic filter

Posted By: whatscooking
Subject: D21 magnetic filter
Date Posted: 01 Apr 2026 at 6:03am

Just got my I&T manual for a D21 and see the filter asembly inside the left frame rail is to be serviced every 200 hours. Had one shop say to get rid of it.

Replies:

Posted By: DrAllis
Date Posted: 01 Apr 2026 at 7:30am

That filter was used on D-21's s/n 1001 thru 2520. From then on, it wasn't there. The earliest One-Ninety's and XT's also used a similar filter up to s/n 14,965 and it too was discontinued. As I understand it, there were times the hydraulic pump would lose its prime after an overnight shutdown the next morning. Also, the filter hampered oil supply in cold weather. They found the elimination of this restriction seemed to improve those situations. Do as you want. But, if you chose to keep it, clean it regularly.

Posted By: whatscooking
Date Posted: 01 Apr 2026 at 2:24pm

DrAllis wrote:

That filter was used on D-21's s/n 1001 thru 2520. From then on, it wasn't there. The earliest One-Ninety's and XT's also used a similar filter up to s/n 14,965 and it too was discontinued. As I understand it, there were times the hydraulic pump would lose its prime after an overnight shutdown the next morning. Also, the filter hampered oil supply in cold weather. They found the elimination of this restriction seemed to improve those situations. Do as you want. But, if you chose to keep it, clean it regularly.

So would you remove it. I am trying to figure out why my power steering is acting the way it does.
I have removed the valve at the rear of the pump and have it sliding freely in the bore. I warm the tractor up steering effortlessly for 20 minutes and park in front of my shop. Working on the left brake linkage for 45 min or so and then fire her up and immediately feel the steering wheel is tight best I can describe it, somewhat not hey. Don't hear the air in the system howel and the three point acts normal. Drive it around max turn several times and park it still tight. Start it up next day and she steers as good as any car.
Can that orbital valve act this way? When it messes up the feeling in the steering wheel has a tight then when spinning the wheel there is a slight notchey feeling.

Posted By: DrAllis
Date Posted: 01 Apr 2026 at 3:52pm

Removing the magnetic screen filter and replacing it with a piece of exhaust pipe and short hose from an Auto Parts supplier will for sure eliminate the filter as the problem. If it still acts up, it's something else, like the pump. I've never had an orbitrol bother.