Construction and other equipment - Allis H4 hydraulic control block

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Allis H4 hydraulic control block

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=112924
Printed Date: 25 Jul 2025 at 5:03pm
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Topic: Allis H4 hydraulic control block

Posted By: pinball
Subject: Allis H4 hydraulic control block
Date Posted: 05 Oct 2015 at 9:37pm

I have oil coming out around the bucket spool on the top. Has anyone ever taken these hydraulic blocks apart. Looks like 4 bolts and taking the lines off will let me remove it but ive never had one apart so I need some advice on it before I start. I suspect bad o rings. Thanks Norm

Replies:

Posted By: Coke-in-MN
Date Posted: 05 Oct 2015 at 10:00pm

yep the valves are a stacked body of individual valves with "O" rings between the sections , also "O" rings in valve body - can replace just the rings and get good results or buy a kit for 3 times the price and get the same rings .

No big deal - just take some pictures if you have doubts if your memory is good .

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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."

Posted By: pinball
Date Posted: 06 Oct 2015 at 6:17am

Thanks. I am going to try to fix it. I didn't know if I had to worry about springs tension when I open them up. I do have a service and parts manual . Norm

Posted By: BCPaul
Date Posted: 06 Oct 2015 at 10:26am

Although I am not familiar with this particular set-up, most hydraulic components are fairly easy to work on. Safety is key. Oil under pressure hurts. Relieve all pressure by working valves after shutting down energy source. As the man says, take pics if you aren't sure. Another important point: buy a good set of seal picks. They usually come in sets of four, with different angles/shapes of points and hooks. Be very cautious of not scoring or scratching any surfaces. Valve bodies are pretty straight forward, and although there may be a spring or two, if you are careful, parts won't fly too far. Watch for the tiny ball bearings used under some springs (relief valves). Keep it clean! Disassemble on bench covered with a rag. It keeps things from rolling around. Keep it clean! Wash your hands, tools and parts twice before re-assembly. You don't want to do all that work only to find the spool jams on a piece of dirt, then scores the bore as it moves. Sorry for the long post, but I've seen too many good jobs go bad just because the mech wasn't as anal as I am.

Posted By: pinball
Date Posted: 09 Oct 2015 at 6:19am

After a few choice words I finally got the control block off. Took it all apart. Couldn't find the small oil rings between valve bodies. Did find correct oil rings for the pistons and the return line. Replaced the top and bottom o rings, Cleaned it up pretty good. Put it all together and crossed my fingers and put my rain suit on. Fired her up and lo and behold everything works correctly with no leaks. Took the h4 out for about an hour doing some dirt work. Adjusted the tracks to 1 1/2 and they seemed to work fine. Both steering clutches and brakes seems to work fine with the right better than the left. OIL LEVELS in finals still full. Only think I have to do now is get the charging system working as I am not sure it is now. With the price of batterys now that needs to be done. NOTE----If any of you have a leaky control block that is leaking from the top or bottom you don't need to take it apart. You can remove the piston from the bottom of each compartment without taking it apart. Learned the hard way. Take care Norm

Posted By: BCPaul
Date Posted: 09 Oct 2015 at 6:36pm

It's always nice when a plan falls together

Posted By: Coke-in-MN
Date Posted: 12 Oct 2015 at 12:29pm

Charging system is easy to fix - 10SI Delco alternator - and they are cheap to find and repair .