# MF135 Detroit power steering leak from vent



## tkrlyon1 (Apr 5, 2016)

I have a 1970 MF135 with Perkins Diesel Engine. When I turn the steering wheel while running the tractor fluid pours out the vent located behind the steering column. 

Could this be a symptom of a plugged up power steering filter?

Also is ATF the best fluid to use in power steering?


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## RC Wells (Dec 26, 2008)

A leak from the steering column usually indicates the power steering valve assembly is due for renewal or replacement. Sometimes as simple as a new seal kit.

Massey originally recommended ATF or non-foaming hydraulic oil. The modern universal tractor fluids are perfectly suited to the power steering application, and contain additives that lubricate and preserve the O rings and seals.


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## sixbales (May 18, 2011)

Howdy tkrlyon1,

There is a very good discussion on this forum entitled "MF 135 Power Steering Issue". Here is one solution:
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"After much playing around and changing the column seal the fluid was still pushing out the top of the steering column. It seemed to worsen when the steering was used hard like with the front loader.

The problem is a worn power steering valve at the base of the steering column. The valve has sliding parts that are a lapped fit with no seals. When the valve wears fluid seeps out between the spool and the body. The steering still works but you lose all the fluid and then have no power steering.. Your foot is also wet with fluid.

I figure out a fix in stead of buying the $700 if you can get one power steering valve.

I replaced the steering shaft seal in the bottom of the column. While I had the column off I drilled and tapped a hole below in the cast base the seal for 1/8 npt.
Next I placed a compression Tee in the return line to the power steering pump. I made a pat to return the leaking fluid to the pump by connecting the port I drilled to steering fluid return line.

Photo is attached. It works great!"


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## tkrlyon1 (Apr 5, 2016)

Yes, sixbales I saw that post. 
I have seen many post regarding this problem.....
Everything from the filter is stopped up, to the power steering valve is bypassing, to using the wrong oil, even that the transfer lines were to small to handle the flow / pressure needed...
I was just wanting to know if anyone has confirmed exact source of this problem and the best fix for it....
I am not opposed to modifying my equipment but I want to verify that this is the best and most reasonable fix.


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## tkrlyon1 (Apr 5, 2016)

From what I gather the vent is on top of the steering box was meant for the gear oil, right??
I went ahead with the modification from the post above. 
Instead of running the hose onto the steering box, I ran the hose all the way to the pump reservoir. I used 1/4" heater hose and two hose barbs along with a 90degree elbow on top of the steering box. I used a die to turn the 1/8 npt on the brass hose barn to make it a 3/8 nf, that way I can hold it onto the back of the reservoir can with a nut. 
Seems to work ok so far but have not had a lot of time to verify it's a good fix.


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## tkrlyon1 (Apr 5, 2016)

Thanks sixbales,

Power steering works great


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## willys55 (Oct 13, 2016)

interesting indeed


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## Chuck Webb (Jan 24, 2018)

I have a question about this thread. Do you seal off the vent that is leaking after installing the discussed by-pass? I am concerned about blowing the seals.


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## Busted Tractor (May 22, 2018)

When that vent leaks my experience has been the cylinder mounted on the front of the steering box is damaged and leaking power steering fluid into the gear box. This usually has happened when the tractor is used with a loader or other heavy front end equipment. Have not usually had an issue with the valve leaking.


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