front bucket dropping in minutes

[intheground]

Hi guys new to this site. I have a jima 284 with a hydraulic problem that has got me talking to myself. When I put the bucket in the up position within 5 minutes the bucket is down. There are no signs of leaks all fittings are tight. I changed the hoses around from lift to curl and when I did that the lift was fine in the curl fittings in the valve. (so I think the valve is working) I loosened the fittings one at a time worked the hydraulics to try to get out any air but still no change. I also put the bucket down so it lifted the tractor a few inches and it held fine. the cylinders look good no leaks or scracthes. all the rest of the hydraulics work fine. Any suggestions? thanks

 

[George2615]

It sounds like you may have an internal leak in your joystick valve. Putting the bucket down and lifting the tractor uses different valving ports inside the valve than those needed to hold the bucket in the up position. The internal port check valve most likely has some dirt, a speck of rust, or an deteriorated O-ring seal preventing it from seating properly. If you are unsure how to take it apart to check and clean I'd recommend taking it to a tractor dealer or hydraulic shop to have them check it for you. It could also be inside the lift cylinder ram seals. I had a similar problem with my tractor that was less than a year old but it only dropped about an inch an hour, not as fast as yours. Mine was an internal leak in the joystick valve which was replaced by the dealer under warranty.

 

[AKKAMAAN]

If you have a double acting cyl with rod ends connected to tank (single acting), it can be cylinder piston seal...Disconnect rod end and lift till you get relief valve opening...if is oil coming out...piston seal bad..... (I have seen valves with special spool connecting rod end to tank aswell),
If you have true single acting cylinders it must be valve internal leak...

 

[intheground]

when I switched ports with the lift and bucket and the lift held fine in the up position wouldn't that indicate that the valve is working?

 

[LD1]

By switched ports do you mean that you hooked the raise up to the dump ports. If you did and it held up fine it indicates that your cylinders are fine and the lift valve is what is faulty

 

[intheground]

when I say I switched ports I mean I took the 2 hoses for the bucket and placed them in the ports for raise and lower and took the raise and lower hoses and put them in the rollback and dump ports so raise and lower became rollback and dump and rollback and dump became raise and lower. so whichever of the 2 ports the bucket was connected to it still dropped in the up position and the raise and lower of the boom worked fine in either position.

 

[LD1]

well if the bucket still dropped when raised no matter which ports it was hooked to I'd say the seals in the cylinders are shot. The only other possible cause is that you have two faulty valves which is unlikely

 

[AKKAMAAN]

if you have a true double acting cylinder, the oil volume for the piston rod have to leak out when bucket go down......that will be out thru the valve....then both piston seal and valve are leaking....lift bucket to top, all extracted cylinder, disconnect the rod side, plug port on valve, keep try to lift.....relief will open.....IS OIL COMING OUT OF THE ROD SIDE HOSE????????????.....
if so piston seal is bad....

 

[intheground]

thanks akkamaan, will have to go find a couple of plugs and try your test. Just another question (unrelated) if you hold the bucket in the full up postion will the prv open and release oil? as you can tell not to familiar with hydraulics.

 

[bruceatlam]

This may or may not apply to this case, but, I do know that many Jinma dealers replaced the "double lever" Chinese loader valves with better joystick valves before even selling the tractor for the first time. The Chinese loader valves are noted for problems ----------

 

[AKKAMAAN]

thanks akkamaan, will have to go find a couple of plugs and try your test. Just another question (unrelated) if you hold the bucket in the full up postion will the prv open and release oil? as you can tell not to familiar with hydraulics.

Yes Sir, prv will open....if the piston seal is not super bad and can't hold pressure....then the all oil will come out thru the rod side....

But if your test show piston seal is bad.....there is still a problem in valve, unless rod side is connected to tank internally in the valve.....

 

[intheground]

well I plugged the rod side port on the valve like you said and I held the the joy stick in the curl position and the prv opened and some oil ran out of the rod side hose. I then curled the bucket plugged both fittings on 1 cylinder and disconnected the other cylinder from the bucket raised the bucket off the ground to see if it would hold. did this to both sides . one held the other not so lucky it dropped at the same rate as before. I really don't understand why if 1 cylinder is holding it won't hold the bucket up , if you don't hit the joy stick the good cylinder should hold pressure?? first I know I have to rebuild the cylinder is it a difficult thing to do and do you know of any online instruction thanks for all your imput guys could not of got this far without your help

 

[AKKAMAAN]

Can you take a few pic's on the rod sidetop of the cylinder....to sy how the top is locked... you can definately do it your self if you have a some tools and a heavy duty wise plus have time to upload pics so we can see whats going on... first step is to get piston out...second step is to take piston apart....3rd step replace seal...you can buy them online or order thru your local hydr shop...4 step put it all together...

 

[intheground]

Can you take a few pic's on the rod sidetop of the cylinder....to sy how the top is locked... you can definately do it your self if you have a some tools and a heavy duty wise plus have time to upload pics so we can see whats going on... first step is to get piston out...second step is to take piston apart....3rd step replace seal...you can buy them online or order thru your local hydr shop...4 step put it all together...

thanks akkamaan, certainly can use your help... Found the seal kit online at affordale tractor. Will definatly upload pics later on this week when I start this project could really use your help.. once again THANK YOU.........

 

[George G]

Lets say it's the left cylinder that you found was leaking past the piston seals. As the oil leaks past the piston, oil from the right cylinder moves through the hose over to the left cylinder, past the piston to the cap end of the left cylinder and through the hose back over to the cap end of the cylinder on the right. Thus, Both cylinder drift at the same rate.

 

[intheground]

thanks George G.
diagram and explaination very, very helpful!!!