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I think it's good news. So the unloader valve was stuck in the control valve (yay!)
What should I clean it out with? Diesel, turpentine, WD40?
This pic was before I got the unloader valve out.
View attachment 74027
On the Yanmar forums, diesel is the go to for Japan tractors and hydraulics.

For o-rings, ensure the materials are compatible with hydraulics. There are 4 or 5 popular materials, but only 2 types will work.
 
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You beauty! ! !, I was worried I sent you on a wild goose chase after you opened the tranny and didn't see any problems with the unit, I am happy now that there was a fault and when you get this all cleaned up, you will have your tractor back.馃榿馃榿

You can clean it with diesel, and then rinse in unleaded fuel, this has no additives that will harm the pieces, if you want you could use unleaded to do the whole clean, but as you know, it is very flamable.

If you think it will be a little while before you get your parts, can I suggest that after you have cleaned the spool and valves and the control body, you place all of the pieces in a container that is deep enough and cover with clean diesel, this will prevent the chrome or polished areas from attracting rust, wrap the spool and valves is rag to protect the surfaces from being scratched or marked.

I will now try and find any dealer net works for you in Oz,
 

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Discussion Starter · #43 ·
Don't worry about looking for a dealer, I can do that later. I can get away with no parts needed at this stage. Very happy. No O rings look damaged at all, and the sludge in the unloader valve was obviously the problem. I will rinse with deisel then unleaded, air dry, then the whole control valve will be good to put back today/tomorrow. The only real hassle with this job was the heavy case cover, but I'll work out a way to get it back on without busting a muscle.
So good :) Thanks for your help, I will take a better photo of it after I get it out of the shed!!
 

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So good :) Thanks for your help, I will take a better photo of it after I get it out of the shed!!
Ah, your first out of the shed will have a better pix. Nice. :)
 

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Discussion Starter · #47 ·
Well, not great news lol. Hydraulics didn't work at all and oil was leaking a lot from the smaller "cover" (pump relief valve cover, 3 bolts, and mine has the 2 hoses to the fel hydraulics coming out of it) at the front section of the big cover. I also found a copper washer on the shed floor, I think it came from the short pipe on the side of the cover. So I removed the relief valve cover and applied gasket sealant, cleaned the 3 O rings, bolted it back on. I realise now I probably should have left the cover in place and just disconnected the two hoses, but since I had pulled it off, there was no gasket and no signs of sealant gasket so I didn't give it any when reassembling the first time. Now that should be sealed nicely, and I'll put the washer on the side pipe. When I removed the side pipe I looked for washers but didn't see any at either end of that short pipe on the side of the case (about 12cm length pipe, banjo both ends).
So, leaks hopefully sorted, and I have read through the manual hydraulics section, but couldn't find where to bleed air from the hydraulics system. I'm hoping that's why the hydraulics didn't work.
Can anyone tell me how to discharge air from the pipe line please?
74092
 

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Assuming that the oil is being pumped through the circuit, the 3 point should bleed through the control valve and bypass valve, and to bleed the lift piston and cylinder, you would just move the lift lever to full lift and lower at a steady pace over a period of time, like lift, pause, lower pause.
 

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Discussion Starter · #49 ·
Thanks Fred, I was just net searching for answers too. I'll try that, and after sealing the relief valve cover yesterday might get some movement. It was leaking oil so could have been sucking air aswell. I'll also try cracking the fel hoses to get air out of those lines.
 

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You don't have to crack the FEL lines to bleed air, you pull and push the raise and lower lever and the same with the crowd and dump lever, if the boom will raise, keep trying to raise to full extent a few times and same with lower, the full extent lowered which will lift the front of the tractor, and crowd and dump, full crowd and full dump and this will bleed the system.
 

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Discussion Starter · #51 ·
Thanks for your help Fred. I tried that over and over, slowly, got a very slight movement from FEL dump, but absolutely nothing from rear hydraulics. I can lift the 3PL arms up and down and there's no resistance at all, feels like no oil in the line at all. So I checked the hydraulic levels after last time I pulled the pump off and it was over the level bolt on the side so I didn't think that could be an issue... but checked hat again today and it is below that hole. So the tractor has 15W-40 in engine and hydraulics (that's marked under the seat by the importer for future reference), and I'm a couple hours round trip from the nearest oil seller. I am wondering if I can top it up with any of the oils I have on hand, because I have HEAPS of oil, just not 15W-40! Can I use, or combine any of the following just for a top up?
I need 15W-40,
have:
5W-30 full synthetic in both Penrite and Castrol brands
SAE 20W-60 full synth Penrite
5W-50 synth Mobil brand
85W-140 gear oil Penrite brand

Could I use either of those or blend two to top up the hydraulics?

I removed the rear implement to do the repairs, so was able to reverse it out for a pic, do a circle and reverse it back into the shed :) My DIY canopy and muffler extender give me fresher air and less sunshine or rain!
Tire Wheel Vehicle Tractor Automotive tire
 

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Please don't mix the oils, also do a internet check for what oil should be used in the tranny, I can have a look in a couple of hours, right now I have to head out and take my grandson to work.
 

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Discussion Starter · #53 ·
This is the note under the seat. It currently has 15W-40 in the engine and hydraulics. I can't read the rest of the gearbox oil, 80W?

I'll head into town tomorrow and get some 15W-40 unless someone thinks I shouldn't use that.
Good news is there are now no leaks from Relief valve cover or the side connecting pipe, but I will pick up some O rings when I go to town. There was oil coming from the FEL hose connections when I loosened them but I didn't let a lot of oil go, just to check if there was oil there (engine running).

74147
 

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Discussion Starter · #54 ·
This was in my repair manual. Refers to the 670 and 670D but apparently thats the D2350 also. The SAE 20 seems to be 15W-40 equivalent (from my reading today).
74148
 

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I have tried to find information on the oils used in your tractor, but it is like bashing your head against a brick wall, even trying to work out the "hydraulic oil equivalent to SAE20" which is in your temperature range, at best, this means hydraulic oil with the viscosity of SAE20, some more searching coming up.

Please don't put 80/90 in the transmission from where the hydraulic pump has its pick up, this will be to heavy for the remote pump to pull from the tranny, older tractors like the David Brown series used 80/90 in the tranny and for the 3 point hydraulics, the pump was internal and designed for the heavier oil.

The 80/90 mentioned would be ok in the front axle.

This is not helping you of course.
 

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Discussion Starter · #57 ·
It all helps Fred, thank you for trying! I will go with the 15W-40 as that's what is in it. Id only put the 80W-90 (thanks Bill) in diffs at this stage but not broke, so not touching them. I might not get to town till next week, but tractor is all back together and in the shed so no rush - except all the jobs are adding up without it!
My concern is, after topping up hyd oil, still no hydraulics. The unloader valve in the control valve was definitely stuck, and that's definitely sorted. It was a build up of gunk, possibly dust/fibres/sludge from a previous cover off or 40yrs service.
Could the relief valve or another valve also be stuck? Is there a next best culprit?
 

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You haven't got much to check now, 1-the relief valve, 2-the pump, and 3-the strainer filter in the transmission housing, I remember you saying that you cleaned the filter, was this one a wire strainer in the housing, or a proper paper filter?, I know you also pulled the pump, did you strip this down and check the internals?, did you remove the drive gear from the pump shaft and check that the key hadn't sheared?.

For the hydraulics to work and as you know, the oil has to be pumped through the circuits, I would attack the pressure control valve, is it possible to disconnect a hose that comes from the pressure relief valve and goes to the tranny, (not sure where those two hoses run too) place this in a bucket and crank the engine, (not necessarily starting the engine, oil everywhere) just to see what volume the pump is putting out, better still would be a hydraulic pressure gauge to check the pump output.

When the engine is running, does the hydraulic circuit make funny noises like sucking or slurping?, did you bleed the suction line to the pump when you first pulled the pump?, did you oil the internal gears when you re-assembled the pump, this helps with suction.

I tried to find the manual on this site so I could have a read but I cannot find it and I know has placed one on this site, anyway we have to beat this shortly.
 

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Discussion Starter · #59 · (Edited)
The relief valve has me confused now. I thought it was the small cover at the front of the hydraulics case cover. Pictired here:
74171

But on the next page, it should be at the spot with red dot:
74172

But I don't recognize the Fig 7-26 "Cylinder Relief Valve". They aren't the same thing?
A few months ago the hydraulics stopped, just like they did this time. Last time, I pulled out the oil filter "15", drained the oil, pulled off the hydraulic pump, all looked fine, put it all back, and hydraulics were working perfectly from the first time I started it up.They haven't played up at all for a couple of months, then stopped again. I did pull the pump lid off, seals looked ok (I took a picture too), but only "test" was to blow through it, blocking off outlets, turning the shaft with holes blocked and there seemed to be good suction. The fact it has been working perfectly since makes me think it was never the pump or filter (I didn't take out any gears or check internal gear teeth). That's why, this time, I went for the Control valve and it was definitely stuck.
There were no unusual noises at all. Weren't last time either. Hydraulics have been working perfectly for a couple of months since I pulled the pump off. I didn't even prime the pump when I put it back (I meant to but forgot, luckily it worked fine).

So now, if I can confirm which Relief Valve? Are there two? I don't recognize Fig 7-26 at all :unsure:
 

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Discussion Starter · #60 ·
ok, so what I thought was my Relief Valve, I don't think is. The Relief Valve in the manual, pic 7-24 and diagram 7-25, is not the same as mine :(
Here are a couple of pics of mine. Doesn't appear to be any valve/shaft, but just a cover? Certainly isn't the same as in the manual I have. Located in front of the seat on top of the hydraulics cover I removed to fix the Control Valve (I think directly under this, what I thought was the "Relief Valve".

74174

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Pic with the Flow lever under the seat. I will check the manual, see if there is anything in there that could be stuck of blocked to possible cause hydraulics to stop working. Its currently set to high in this pic, but I generally leave it on middle flow.
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