384 Weird Auxiliary Hydraulic problem

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atk_nut
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Joined: Tue Apr 03, 2018 1:18 am

384 Weird Auxiliary Hydraulic problem

Post by atk_nut » Tue May 14, 2019 6:04 pm

Hey there.

Last year, I was starting to have issues with my aux hydraulic. It was getting sticky and would not operate. When I had the tombstone off to clean the interior filter, I took the valves apart and cleaned everything up. It seemed to operate much smoother and I was happy...until I tried it. Now, it does the same thing, it just seems to "deadhead" in the lift position. Once I engage the "lift" lever for my mower, the aux lever just pops back to neutral. I was able to get it to work sometimes last season, but not at all now. I'm wondering if I assembled something wrong. Anybody run into something like this before?

There were a couple of aluminum "discs" at the top of the valve, I'm just wondering if I got those in wrong.

The main lift works well. I've checked the linkage adjustment, it's all good.

I notice in the service manual, it has an "auxiliary adjusting screw" (part 15 in the image) Looks internal maybe? I can't find anything about that.

Also, is there supposed to be a detent in the aux? If so, it doesn't work.





Image



atk_nut
Posts: 6
Joined: Tue Apr 03, 2018 1:18 am

Re: 384 Weird Auxiliary Hydraulic problem

Post by atk_nut » Wed May 15, 2019 6:11 am

So it's definitely a matter of the aux circuit kicking out. It just seems to go high pressure, then kicks to neutral. I can hear the relief valve if I try to hold it in position. How does the kick out work?

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JohnP
Posts: 132
Joined: Fri Mar 30, 2018 8:05 pm
Great Britain

Re: 384 Weird Auxiliary Hydraulic problem

Post by JohnP » Thu May 16, 2019 7:08 am

The Auxiliary spool valve is a simple device with “Lands” to cover or uncover ports inside the valve chest. It has two fairly close fitting floating washers at the top retained by a circlip. Inside the bottom of the spool valve there is a simple “Drop limiting valve”.

When the auxiliary spool valve is moved downward to “Lift” oil flows into the valve block and flows to the high pressure relief valve (Closed circuit) .

The top land of the spool valve closes the port to the main circuit. The auxiliary circuit now has total priority over the main lift circuit. The bottom land of the spool valve has moved downward allowing oil to flow out, via a non-return valve, to the auxiliary tapping point on the right hand side of the hydraulic casing.

If the hydraulic pressure increases above 2600 psi the high pressure relief valve will operate (Audible noise) oil exhausting will then be fed into the low pressure circuit (50 psi), through the low pressure relief valve, back to the transmission reservoir. This low pressure oil also flows between the two washers at the top of the spool valve. The washers are moved apart forcing the spool valve upwards returning the auxiliary spool valve to neutral.
JVP

If it ain't bust don't fix it!

atk_nut
Posts: 6
Joined: Tue Apr 03, 2018 1:18 am

Re: 384 Weird Auxiliary Hydraulic problem

Post by atk_nut » Thu May 16, 2019 2:01 pm

Thanks JohnP.

That makes sense to me. So since I'm hearing the "audible noise" I am reaching high pressure. So either there's a blockage somewhere, or the high pressure relief is opening at a pressure lower than what is required to operate.

I guess I really need to get a pressure gauge in there to tell for sure.

atk_nut
Posts: 6
Joined: Tue Apr 03, 2018 1:18 am

Re: 384 Weird Auxiliary Hydraulic problem

Post by atk_nut » Wed May 22, 2019 3:31 am

Issue solved!

The high pressure and low pressure springs were swapped in the relief valve.

ooops :)

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JohnP
Posts: 132
Joined: Fri Mar 30, 2018 8:05 pm
Great Britain

Re: 384 Weird Auxiliary Hydraulic problem

Post by JohnP » Wed May 22, 2019 7:15 am

Glad you found the problem!
JVP

If it ain't bust don't fix it!

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