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Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Sat Apr 20, 2019 4:28 pm
by housebus
Gentlemen good evening,

I just bought a Yanmar 1300 off of craigslist. The machine was pretty weathered looking, and it was apparent the former owners hadn't changed any fluids or filters in the time that they had it. It came with a hydraulic snow plow on the front end, and a rock carrier on the rear end. The rock carrier was built for a three point hitch, but had additional support pieces welded to it, and pinned to the tractor (so the 3 point hitch could not be moved.) Former owner said the hydraulics had only recently stopped working.

I believe I have two issues, and would greatly appreciate some help troubleshooting;

Issue #1; no pressure from hydraulic pump

Lift housing
Gross filter
Suction flex coupling

The fluid that came out was milky, and the screen filter had a solid layer of muck on it. Cleaned and reinstalled the filter. Replaced the trans-hydraulic fluid. When the machine is running, I see a oily mist coming out of the pressure line... but no oil. I pulled both banjo fittings (clean mating surfaces) and removed the hydraulic pump. The engine turns the driveshaft, and the pump turns with the receiving end of the driveshaft. The suction line on top, feeding the pump, was pretty dry. Looking at the flexible union between the two halves of suction pipe, I see a few slits and weather cracks. They are small, but would these be enough to let the pump suck air instead of hydraulic fluid? Is there a hole in my straw? Is there a good way to prime the pump with oil?

Issue #2; 3 point hitch lift cylinder seized

3 point lift housing
Piston soaking in PB blaster
cylinder exterior... I know, it's bad

Once I get hydraulic fluid pumping again, I still have a lift piston which appears to be rusted into the cylinder. My guess is all the warm water evaporating out of the dirty unchanged hydraulic fluid did this thing in. I pulled the lift housing off to investigate because the lift arms moved with no resistance. I was going to take a wire wheel to the exterior and give it a nice coat of AMLguard afterward. Anyone seen this part around the internet? Any techniques for freeing this up?

I also think I'll be replacing brake pads as both pedals offer no resistance. My shopping cart at Hoye is growing. But hey, the thing runs! Good thing I like projects.

Thanks in advance,


Re: Yanmar 1300 hydraulics problems

Posted: Sun Apr 21, 2019 5:18 pm
by winston
Sucking any air at all could cause a pump problem. The pump should be self priming with an air tight suction. I have heard of having to crack a discharge line just a hair in order to get them primed.

Might read through this thread on you lift piston. viewtopic.php?f=1&t=8631&p=32988&hilit=lift+piston#p32988

Best of luck with your project and keep us informed.

Re: Yanmar 1300 hydraulics problems

Posted: Mon Apr 22, 2019 7:50 pm
by housebus
Winston thanks for the link - read through that thread with interest. I think I have the same issues as Mr. Threeweight.

Parts are en route, so I'll be able to get a better seal once I have the new flex coupling. I have my cylinder soaking in vinegar to get some of the scaly rust off (same kind as described by threeweight.) The message I got from that thread was patience, penetrating oil, and a heavy hammer for the piston.

Will add more pictures for future reference and keep you guys posted.

Re: Yanmar 1300 hydraulics problems

Posted: Thu Apr 25, 2019 8:56 pm
by housebus
Lots of progress over the past few days. My order from Hoye came in, and I put the new flex coupling hose on my suction line. Snugged the two clamps, loosened the output banjo fitting on the pump, cranked it over and brought it to an idle, and... nothing. Brought the throttle up to about 3/4, and hydraulic fluid came gushing out! Happily closed everything up - that problem is solved.

fresh surface staining on vinegar soaked cylinder
unthreading cylinder from housing
gunk in between piston and base
steel brush on interior and exterior, then oiled
cleaned and dissembled cylinder housing, ready for install

On the lift cylinder, I let it sit in vinegar for 2-3 days, letting weak acetic acid take care of the scaly rust while the water snuck into the crevices. The cylinder unthreaded from the housing without any effort. The piston was stuck in there, but with a few punches from a framing hammer and a pin it moved. The only rust repair I did in the cylinder bore was with a wire brush and liberal application of oil. The piston moved through the cylinder without serious binding, but it took some force, so I elected to not further dissemble it and to just try it out on the machine.

I put the cylinder housing back in the lift attachment housing, and bolted the housing back onto the tractor. Running it up again, the hydraulics were lurchy at first, but I was able to go through several up-down cycles before, unfortunately, it got hung up again in the "full down" position where it had been. I'm going to have to take the piston out and thoroughly clean and oil both that and the cylinder bore. I was hoping a "if it ain't broke don't fix it" approach would work here but it just ended up stuck again. I'll throw some more pictures up for the next guy, when I get that apart.

But hey, the hydraulics are working! Thanks for the link Winston, that was exactly my problem.

Re: Yanmar 1300 hydraulics problems + engine oil pressure

Posted: Sat May 04, 2019 5:10 pm
by housebus
I guess I'm not done buying parts yet!

Firstly, I think my pump is bad. It occasionally pushes out fluid, but only after bleeding it at the pump doing the procedure above. The fluid is either a trickle(at idle/1000rpm) or a coughing push of air and fluid (1500rpm.) I checked this by pulling the lift attachment housing off, and connecting a flex hose to the solid steel line, and routing it back into the rear end's gearbox.

How can I tell if I have a bad pump, vs. a pump sucking air?

Next issue is low oil pressure light...

The oil that came out was dark and thick (I've done a few diesel oil changes, so I know it comes out looking like light sweet crude; this was darker than that) and it had a Fram filter on it. I changed the fluid and threw another cheap filter on it. After a half hour of run time I dumped half a quart of oil, added half a quart of diesel, and installed a Hoye filter. After I run it for a bit I will drain that and add some fresh Rotella 15w-40. After ten minutes of running, it still has a low pressure light. Other than degunking the motor, what measures can I take to get my oil pressure light to go out? RPM has no effect; I had read about some guys getting their oil pressure up at higher RPM.

Thanks in advance. Having fun and learning a bunch.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Sat May 04, 2019 5:39 pm
by winston
I think I would want to check oil pressure with a gauge to assure what you really have.

I can't know how clean your hydraulic sump is but have to wonder if your strainer has stopped up again. I would check it before ordering a new pump.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Sat May 04, 2019 6:29 pm
by housebus
Winston I was hoping you would answer and you delivered. I'll check both of those.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Sun May 05, 2019 5:14 am
by winston
For what it's worth (not much) my following these Yanmar forums has indicated your particular engine has a history of low oil pressure problems.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Thu May 09, 2019 6:02 pm
by housebus
Good news on the oil pressure - when I took the terminal off of the pressure sensor, the idiot light on the dash remained on. I installed the pressure gauge none-the-less and found pressure to be about 28psi at 2700 rpm. So there is pressure. I just drained the diesel/cheap engine oil cleaning combo, and will service it with some good Rotella 15W-40.

The hydraulics still have me miffed. Fresh fluid (second fluid change.) Verified that the screen is clean. Flex coupling has been replaced. No clogs that I can detect by tapping or prodding with zip ties into the suction tubes.

Running the machine for ~15 minutes between 1500 and 3000rpm I didn't get anything more than an oily mist from the cracked-open pressure banjo fitting. I know the thing turns, as I can see the teeth turning inside when I turn the mating face by hand on the workbench. Former owner said the hydraulics had just quit. I have only seen a trickle or a burp of fluid come out of this thing, and have read that a bad pump may still produce some minor pressures. Is this thing just smoked?

I have a slightly crazy idea of pulling the lines off of the pump again, rotating them 90 degrees out and using a few oil jugs and some duct tape to totally separate the tractor from the pump and the lines. The tractor motor could still turn the pump, and it would be easy to see how strong it is by watching fluid flow. Or I could just spend some money.


Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Thu May 09, 2019 6:30 pm
by winston
Might be possible the pump shaft key is sheared and pump turns from shaft interference but slips when trying to load up. Wouldn't be hard to check. or maybe you already have.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Fri May 10, 2019 3:49 pm
by housebus
Honestly, I hadn't. I'm ignorant of many of these things. Convinced myself that my pump didn't have that part until you mentioned it and I found it in the manual.

Gear lifted slightly

Gear lifted some more

Is this what a healthy key looks like?

I'm ignorant of this Woodruff key - I take it that the half-moon key will shear if the pump is overloaded? So a sheared key would not be lined up with the groove in the shaft, the shaft would be scored up by the spinning gear on a stuck pump, etc? Holding the interface and the gear, I can't make the thing budge.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Sat May 11, 2019 5:56 am
by winston
Looks like your key is good. I am confused by your pump pictures and comparing them with the pump this sight is showing for the 1300. Doesn't look the same.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Sat May 11, 2019 8:29 am
by housebus
I pulled the trigger on ordering a new pump (and some brake shoes, and the inline relief valve.) The pump on it right now is a "KAYABA" 10CK / 7A1, and if it had the Yanmar green on it under the aftermarket flat black paint I don't see any evidence of it now. My hunch is that the former owner's years of operating this poor tractor with a badly clogged filter screen did a number on the pump. I lifted up the rear end of this little Yanmar with my Ford 1700's loader, which helped prime the pump by giving it a gravity feed... but all I'm getting is oily air and a trickle of fluid. With the rear end elevated, at full power, and pressure line detached form three point housing, I was getting less than what your average garden hose would deliver. The fluid had the consistency of the dying android in Alien.

With the pump "primed" in this way my lift arms would come up alone, but when I pinned on the attachment arms it wouldn't even hold them without falling. At first I was thinking my O-rings were shot, but then I thought it might just be pumping the piston full of air, so it has no strength.

Will keep posting updates and pictures for the next guy when the parts come in.

Thanks again for the help Winston.


Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Thu May 16, 2019 6:48 pm
by housebus
New pump installed w/ new paper gasket and new O-rings - left the output line cracked to bleed air on startup. When the engine caught I got a steady flow of hydraulic fluid out of the pump, instantly. Three point goes up and down just fine, and can easily lift me.

I think this tractor has been restored back to health. Many days of work ahead, but I think the big issues are resolved. Thanks Winston for the guidance, and thanks Aaron for hosting such a great resource for these machines.

Re: Yanmar 1300 hydraulics, engine oil pressure problems

Posted: Thu May 16, 2019 7:07 pm
by winston
Good to hear you are up and going.