Jimna 284 hydraulic problem

adpl · Sep 13, 2011

I have just replaced the hydraulic filter housing and outletpipe (broke the housing and bent the pipe with a tree stump impact...whoops). the FEL is working (hesitant but works) but the rear power lift will not operate. The tractor is spewing quite a bit of foamed hydraulic fluid from the resivoir vent when the FEL is lowered (under the seat, has been topped off). The only thing I can think of is the the filter might be in backwards. There is no arrow to show install direction on the new housing...does the philips head screw in the housing go toward the pump or the cotter pin on the opposite side go towards the pump (I have uploaded photos, hopefully they will embed.....new to this site). Do I need to prime the pump/line? I used AW 32 fluid to replenish the resivoir....I am guessing the foam is a funtion off air escape from the system and or reacting with the old fluid. Any ideas? Any and all help will be much appreciated!!!

Bob Rooks · Sep 13, 2011

The cotter pin side is the inlet. That is the by-pass relief valve.
The aerated oil is a function of an air leak in the lines on the suction side of the pump. All hydraulic oils are miscible.

greg_g · Sep 13, 2011

And once you remedy the suction leak, recheck the sump level once the bubbles settle out. If the loader and/or rear lift is/are raised, make sure the engine is running when they're lowered. If you lower them with the engine off, the sump level will rise - possibly to the point of overflowing.

My Jinmas had only one hash mark on the hydraulic dipstick. I took that to be the full mark. I never added any fluid unless/until the stick came out dry. And when you check levels, don't screw the stick back in. Just unscrew, wipe, set in hole, remove and check. Top up if required, then screw back in when done.

//greg//

Affordable · Sep 14, 2011

The foam is air getting into the system,I would check all the fittings from the pump on pressure and return. The fittings on the pump have O-rings that seal them ,did you use teflon tape on the fittings when you added them to the filter head ? Also check all the hard lines for cracksThe hydraulic fill is behind the seat ,that is where you refilled it correct ?
I have had alot of customers that said the refilled the fluid only to find they filled the wrong area.

Tommy
Affordable Tractor Sales
"Your Jinma PartsSuperstore"
Home of compact Jinma, Foton, and Koyker Tractors and Parts, Wood Chippers, Backhoes - Affordable Tractor Sales Company

RonMar · Sep 14, 2011

Is that spin-on a filter or a mesh strainer cartridge? If it is a filter, it may be too restrictive for a suction application. IE: You cannot put a 10 micron filter on a suction side of the pump. It should be around I think a #100 mesh, which I think works out to be around 150 micron. Strainers on the suction side, filters on the return side...

adpl · Sep 14, 2011

Thanks for the advice, so....if the cotter pin side is the inlet, then the cotter pin side would go toward / facing the resivoir and not the pump?
I used some thread / gasket sealant I found at the auto parts store, do you think the teflon tape is better?

Bob Rooks · Sep 14, 2011

RonMar posted a good question. Is the filter a suction filter for the pump or a return line filter to the reservoir? If it is a return line filter then it's okay, nominal rating is 10µ (btw. it's a pleated paper media filter). But if it is a suction side filter for the pump it is the wrong filter, should be a Wix #51553 33µ or equivalent.
Don't use Teflon tape on hydraulics. Pieces of it can tear off on the inside and get stuck in your relief valve.

greg_g · Sep 14, 2011

adpl said:
do you think the teflon tape is better?

Not unless it's installed competently. Because many owners have tracked down hydraulic problems to choke points obstructed by loose pieces of improperly applied teflon tape. My general rule is that compounds are for metal threads, tape is for non-metal threads. But if you like teflon, there is a compromise; teflon compound.

//greg//

biggerten · Sep 14, 2011

RonMar said:
Is that spin-on a filter or a mesh strainer cartridge? If it is a filter, it may be too restrictive for a suction application. IE: You cannot put a 10 micron filter on a suction side of the pump. It should be around I think a #100 mesh, which I think works out to be around 150 micron. Strainers on the suction side, filters on the return side...

The OP pictures a NAPA 1551, a google serach shows that to be a 10 micron filter. Furthermore, he asks which end goes towards the pump. If it's on the outlet side, it would explode. So it MUST be on the inlet/suction side.

Your point about the 150 micron is a good one. He has a 10 micron filter on the suction side. I wonder what happens. Does the pump just cavitate? Does the vacuum created overcome the seals and let in air? Does the bypass come into play?

Bob Rooks · Sep 14, 2011

If this filter assembly were used on the suction side of the pump it would only be marginally effective. While it has a nominal flow rate of 12 - 16 gpm, that has a lot to do with the viscosity of the oil at a given temperature. So when the oil is cool the filter by-pass will be open, rendering the filter useless.

I would use it on the return line to the reservoir from the valve block.

But if it were to be used on the pump suction then a different element must be used. However, it's your pump not mine. Your call.

RonMar · Sep 14, 2011

Yep, 10u is the wrong filter for the suction side. Way too restrictive, especially when the fluid is cold. There is no place to put a return line filter on the 284, at least easilly, as the final return from the 3PH valve is back thru the sidewall directly into the reservoir. Everything upstream of that point back to the pump is subject to full system pressure.

The relief/bypass may or may not open under vacume, and any type of weak spot or leak is probably allowing air to reach the pump. Or it is sucking it thru an internal pump seal. Pressure rated seals often are very poor at resisting vacume. It could also be sucking in around the filter cartridge seal...

At any rate, I think that is the wrong filter element for this application... They make coarser mesh or paper cartridges for this type installation.

Bob Rooks · Sep 14, 2011

RonMar said:
Yep, 10u is the wrong filter for the suction side. Way too restrictive, especially when the fluid is cold. There is no place to put a return line filter on the 284, at least easilly, as the final return from the 3PH valve is back thru the sidewall directly into the reservoir. Everything upstream of that point back to the pump is subject to full system pressure.
Ok, did not know that.

The relief/bypass may or may not open under vacuum (Yes, it does. At approx 10" Hg), and any type of weak spot or leak is probably allowing air to reach the pump. Or it is sucking it thru an internal pump seal. Pressure rated seals often are very poor at resisting vacuum. It could also be sucking in around the filter cartridge seal...

At any rate, I think that is the wrong filter element for this application... They make coarser mesh or paper cartridges for this type installation.

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J_J · Sep 14, 2011

There is some erroneous data being passed out here. My Power-Trac which uses a VSP pump has a 10 micron suction filter, and has been using filter like this for over 30 years. The only problem with suction filters is they have to be changed to keep the fluid clean. These filters were designed to be in these systems, and have been working as advertised. We all know about the filters blocking the flow of fluid when cold or dirty, and the pump may cavitate and could damage itself. A lot of hyd system also use return filters, and that is by design, so you have to go with the flow, if it is in your system, continue to use it unless you can design a better filter system.

If he is sucking air, then it is a leak in the fittings or cracked parts.

Bob Rooks · Sep 14, 2011

J_J said:
There is some erroneous data being passed out here. My Power-Trac which uses a VSP pump has a 10 micron suction filter, and has been using filter like this for over 30 years.
The Variable Speed Peristaltic (VSP) pump is a whole different animal and not subject to the same issues as gear pumps.

The only problem with suction filters is they have to be changed to keep the fluid clean.
This is not a problem, it is routine maintenance. Suction side filters would have a vacuum gauge to show the amount of restriction.

These filters were designed to be in these systems, and have been working as advertised. We all know about the filters blocking the flow of fluid when cold or dirty, and the pump may cavitate and could damage itself. A lot of hyd system also use return filters, and that is by design, so you have to go with the flow, if it is in your system, continue to use it unless you can design a better filter system.
And this can be easily accomplished.

If he is sucking air, then it is a leak in the fittings or cracked parts.
Agreed.

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biggerten · Sep 14, 2011

If the OP had the filter head installed backwards (I'ts not clear to me whether he did or did not) the bypass wouldn't work. It seems to me that that would increase the chance of drawing air into the system.

I've had my Jinma for 5 years, and been all over the Chinese tractor boards. The consensus is to use a 150 micron filter on the suction side, a lot of these originally came with a screen in the tank that doesn't hold up well, and started to be replaced or augmented by the filterheads around the 2005 time frame.

Ron's statement about the three point return being internal is correct, that is why I figured the filter would explode if on the output side, it's NOT designed for the pressure.

Bob Rooks · Sep 14, 2011

biggerten said:
If the OP had the filter head installed backwards (I'ts not clear to me whether he did or did not) the bypass wouldn't work. It seems to me that that would increase the chance of drawing air into the system.
What it would do, assuming everything else is air tight, is to draw oil in reverse flow through the filter media (in this case, pleated paper) eventually causing early failure and filling the hydraulic system with paper bits. There is no screen on the outside of the filter media, only the inside. I've looked at several. In addition, it would cause aeration from cavitation because of the relatively low velocity.

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RonMar · Sep 14, 2011

It is not erroneous data for a gear type pump. They do not respond well to suction side restrictions. In fact, there is a whole school of thought to do away with inlet side filtration alltogether, adding instead, a good return filter, filler neck filtration and air vent filtration and dessicant. If the reservoir is kept clean and dry, and any fluid added is filtered/screened, there is really no need for a suction strainer. Any particulates generated internal to the system are most likley going to come from the pump or points downstream. Those particulates are much more effectively trapped by a small micron return line filter, returning cleaned fluid to the reservoir... What does this do for you? Well in cold climates, it should extend pump life on systems that must endure cold starts, by reducing pump cavitation due to restricted flow...

The factory intank strainer on my 284 was pretty cheesy. I replaced mine with an off the shelf #100 mesh stainless model designed to be screwed into a NPT bung in the side of a reservoir. I rebuilt the original pipe with an elbow on the end and put the new strainer horizontal in the reservoir at the bottom of the pipe... I have thought about adding an internal pipe fitting to where the fluid returns to the reservoir, piping it outside to a 10u filter cartridge and then returning it back to the reservoir. Sure would be nice to have time to try all my hair brained ideas

I did make a maintenance filter that connects from the aux port on my system thru a return line filter and back to the reservoir, to filter most all the fluid to 10u. but when it is in place, I cannot use the 3PH, so it only gets run occasionally, or when the BH is in place.

adpl · Sep 15, 2011

Thanks everybody for your input! Much appreciated! I have reached the conclusion that the cotter pin side goes towards the resivoir, it would appear that the only way the bypass would engage is with suction from the pump end (at least that is my best guess). I have found and repaired one obvious leak and that has helped a little but I am still getting heavy foaming. Any advice as to how to trace were the other air leaks are comming from (aside from the obvious dripping of fluid)? What is the consensus / best recomendation for sealing the connections......teflon plumbing style tape or some sort of liquid sealant compound?

greg_g · Sep 15, 2011

I've already weighed in on the type of thread sealant, but I can comment on the fluid. When advised to use AW32 hydraulic fluid in their 200 Series Jinmas, a few owners mistakenly purchased AW32 machine oil instead. Machine oil does not have the anti-foam properties that are typically found in hydraulic fluid.

//greg//