IH Control Valve problem

[Harley T]

I have a '58 International 350 Utility with separate hydraulic control valves for the front and rear. Suddenly, the front (plow blade) won't go up, but will still go down. The rear works fine. No external leaks anywhere. Fluid level OK. Accidentally, I found out that while trying to raise the plow, if I engage the rear control valve at the same time, the plow will then go up. Since the rear and power steering work fine, I figure it's not a pump problem. Don't know why it works when the rear is engaged, since they are separate. Any ideas? Bad spool in the front control valve? TIA

 

[Harley T]

Problem solved.

 

[J_J]

I would be much appreciated, that when you guys find the problem, please post the results of how it was fixed.

 

[Harley T]

After eliminating several possibilities, countless searches on the internet, and phone calls to every tractor service/parts place within 100 miles, it ended up being something simple and stupid that I was able to figure out myself.

The control valves are two way valves. The pin on the control valve indexing bushing was bent, and bushing had been partially turned toward "S", or single action from "D", or double action. By being only partially turned, it was still able to work part time, and also in conjuction with the rear, or second control valve. The second was acting as a "helper".

Took some needlenose pliers, pulled and straightened the pin, reinserted it, then turned the bushing all the way towards "D". Now it works like a charm.

Just wish it hadn't taken so long to figure out such a simple fix.