Another 3pt wont lift question Yanmar 336

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sutto55
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Another 3pt wont lift question Yanmar 336

Postby sutto55 » Mon Jan 11, 2021 12:14 am

I recently changed the Transmission/Hydraulic oil in my 336 tractor. Cleaned the suction screen. Replaced the Filter. Checked the oil level and topped it off to full.

The 3pt would lift but slowly before that and the items above did not really make any difference.

Since then it has been getting slower and slower and more jerky when lifting. going down was fine. Today no lift at all.


Cracked the high pressure line at the valve and had fluid there under pressure when engine was running.


I removed the control valve and find the orings in each part a bit flat, but no flatter i guess than they were a week ago when I had movement. I didnt see any crud in there blocking anything after dismantling the whole valve. Put it back on and still no movement. I removed the cover from the back of the cylinder and freed up the stop valve that had been stuck in the full open position since I have had the tractor and nothing looked clogged in there either.

One thing that I noticed and the main reason for the question is I removed the plug on the top of the valve that shows the spool moving back and forth when the control lever is moved from the up to the down position and when the control lever is in the up position I see a bit of oil in the bottom where the spool is and when I move it the down position I get a lot more oil as well as a lot of air bubbles. So the question is, what should I see here and where can the air bubbles be coming from?

Thanks
Andrew

winston
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Re: Another 3pt wont lift question Yanmar 336

Postby winston » Mon Jan 11, 2021 6:53 am

You had posted back in 2015 about your lift being jerky. I had mentioned the possibility of sucking air anywhere on the suction side of the pump. You didn't comment anymore on the thread, do you remember the conclusion of that incident? This one sounds like same possibilities.

sutto55
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Re: Another 3pt wont lift question Yanmar 336

Postby sutto55 » Mon Jan 11, 2021 2:24 pm

Hi Winston,

I didnt do anything at the time. The 336 was fairly new to me at the time and I think it was just the difference between the YM165 that the hydraulics was a bit slower and smoother and when I got used to the difference I didnt see it as such an issue.

In this instance before it stopped moving completely I would move the position control lever to raise the 3pt and it would take 15 to 20 seconds to move from down to up and not at all smooth.

sutto55

winston
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Re: Another 3pt wont lift question Yanmar 336

Postby winston » Mon Jan 11, 2021 6:29 pm

I see from the 336 parts list it has an inner strainer. I have never read of that before and never heard of an inner strainer being stopped up. Something to ponder. I cannot see from the parts drawing how the fluid gets from the strainer to the pump suction line. Having said all that I guess I am concerned about your bubbles you are seeing. To me that indicates sucking air someplace.

sutto55
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Re: Another 3pt wont lift question Yanmar 336

Postby sutto55 » Tue Jan 12, 2021 4:41 pm

Hi Winston,

I agree the bubbles are a concern. The only point I can find that is doubtful is Item#53 below. This is a rubber hose that connects to the suction line going to the pump that has a coating of oil on it. There is no oil dripping from it though when engine is stopped.

The other rubber hose #54 looks clean.

HYD Hoses.JPG
HYD Hoses.JPG (149.81 KiB) Viewed 87 times

sutto55
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Re: Another 3pt wont lift question Yanmar 336

Postby sutto55 » Thu Jan 14, 2021 6:01 am

OK. Problem solved.

I removed the suction hose #53 between the Filter and Pump and I cleaned it up found this.

One thing that did surprise me was that when I pulled the line off the filter, I was all ready with funnel and bucket to catch all the oil and none came out. I had a bit from the other end that went to the pump, but just enough to fill the line. Any reasons why it didnt run out? I expected the filter to slow down the flow, but wouldnt think there was enough restriction to stop all the oil. I mean after the initial draining of the hose there was not even a single drop leaked out.

hose.jpg
hose.jpg (120.15 KiB) Viewed 59 times

winston
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Re: Another 3pt wont lift question Yanmar 336

Postby winston » Thu Jan 14, 2021 6:29 am

Sounds reasonable to me less restriction for pump to suck air than suck fluid through the filter. In any event, glad you have the problem solved.


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