Lift Bucket Problem

[Mike Eagle]

I have a 1964 MF 165 with a MF 235 front end loader. The bucket seems to have a mind of its own. When I try to scoop it either digs in or rides up over the pile. When dragging with the loader the bucket releases and does not stay in position when the tractor moves. I have replaced all seals and O-rings in the bucket cylinders. The Cross, 4-way control valves for the lift and bucket have been inspected and no problem areas found. The lift valve has a float position. All equipment is original. No leaks in hydraulics. It has a separate fluid pump driven by the engine. Anyone have any suggestions as to how I might solve this problem. Thanks.

 

[J_J]

I believe I would put a pressure gage in the system and use the data to analysis the problem.

 

[kennyd]

What you are describing sounds like a spool valve problem to me, not sure how you "inspected" it, but if it's 46 years old...

 

[Mike Eagle]

Good idea JJ. Any suggestions where to put these gages? Thanks

 

[J_J]

First check the pressure at the input to the valve, and then check the pressure at the cylinders. Activate a lever until it goes into relief, and that is your tractor pressure.

 

[Mike Eagle]

Thanks JJ. I'll give it a try this weekend.

 

[Mike Eagle]

Thanks Kennyd. When I inspected the valve I looked for wear, scratch marks, broken or deformed O-rings or other deformaties. Yes, the valve is 47 years old but the material used was cast iron. The two valves were machined out of one block of cast iron and the valve weights a "ton". The spools looked like the day they were machined, shinned like they were chrome, with no scratches, dings or wear marks. O-rings were stiff but not brittle and in this valve they are only used to hold the hyd oil inside the unit. Guess that is why the old tractors are so popular - they were built solid to take abuse and keep on running.

 

[wdchyd]

Mike,

unless your valve is machined for work port reliefs (which I don't believe Cross valves are), then I would check your cyl seals again...I know you don't want to here that but I would suspect them....do they hold a load when just lifting?? Do you remember if the seals on the piston head were orings and backups or urethane seals or 2 piece piston seals??there are ways to test them but you'd have to prove them out separately (we use a test machine with meter-out flow valves)...

Other than that the control valve could be cracked internally between porting in housing(rarely see that tho)....

 

[Mike Eagle]

Thanks for your reply wdchyd. To answer a couple of your questions. The control valve does have two work port relief valves. The seats on these valves show no signs of wear. No way to check the springs that hold the valves in position. The seals in the cylinders are O rings with backups. The cylinders have been checked in a cylinder repair shop with no apparent problems. There is no drift on either the lift or bucket cylinders after you get a load into the bucket. It is just darn difficult to get the load into the bucket. An internal crack in the control valve is something no one has mentioned before. I am in the process of putting some gages in the system to help with this problem. This is proving to be not as easy as I first thought. Thanks again.

 

[J_J]

The hyd gage should be installed on a tee at the input to the FEL valve. Then it will indicate the pressure for any hydraulics utilization. I would suspect the valve is sticking in the float mode. Can you raise the front wheels off the ground using the bucket, or does the loader arms leak down.

 

[wdchyd]

Thanks for your reply wdchyd. To answer a couple of your questions. The control valve does have two work port relief valves. The seats on these valves show no signs of wear. No way to check the springs that hold the valves in position. The seals in the cylinders are O rings with backups. The cylinders have been checked in a cylinder repair shop with no apparent problems. There is no drift on either the lift or bucket cylinders after you get a load into the bucket. It is just darn difficult to get the load into the bucket. An internal crack in the control valve is something no one has mentioned before. I am in the process of putting some gages in the system to help with this problem. This is proving to be not as easy as I first thought. Thanks again.

Mike,

you'll have to do a little process of elimination...more than likely the control valve but do not jump to conclusions w/o proving it out.....

the way I would prove out work port relief is disconnect from cyls....attach porto power hand pump w/guage and pump up to system pressure with control lever in neutral position (this should hold a load to whatever setting is used...) do both a & b ports separately.....if either one does not hold load then swap work port relief valves to rule out valve....if pressure loss moves to other side then you have bad work port relief valve......if one side still does not hold a load but the other side holds a load after swap out then you have an internal crack in housing....don't mix up relief valves as some are set at different values...

If both a & b ports (Extend & Retract) do hold a load then you proved out the valve.....then....(you probably don't want to here this)take your cyls apart and repack them again.....

I know, I know, I know......those Orings and Backups are the poorest excuse for piston seals ever...EVER....I've been rebuilding Hyd Cyls for 34+ years and we NEVER use Orings & Backups for a reciprocating pressure seal....I don't care what OEM's use....we have 3 different styles of piston seals that fit in standard oring grooves without any retrofitting.....Higher pressure rating and last longer.....

By proving valves, cyls, (and pumps for that matter) you'll at least know what IS working properly then make decisions , repair or replacement will be much easier....Don't rely on taking things apart to see inside unless you prove that component out and it fails(nothing to lose if you goof it up).....you may end up with another problem if there was nothing wrong with it and it goes back together wrong ,it may not work after you find the original problem (makes troubleshooting worse cuz you have two things wrong )

Remember, "When in Doubt, Prove it Out":thumbsup:

Bill

 

[Mike Eagle]

Thanks JJ. Yes I can lift the tractor front end using the bucket but I have no held it long enough to see if it leaks down. I will try that. Thanks for the info on the location of the gages.

 

[Mike Eagle]

Thanks wdchyd. Lots of good sound advice in your reply. Gives me a lot to do this weekend but the testing procedures that you and JJ have given me are great. I do not have the experience both of you have so this is a real learning experience for me. The solution will be found - this is becomming an obsession.

 

[wdchyd]

Thanks wdchyd. Lots of good sound advice in your reply. Gives me a lot to do this weekend but the testing procedures that you and JJ have given me are great. I do not have the experience both of you have so this is a real learning experience for me. The solution will be found - this is becomming an obsession.

Great, make it an obsession:thumbsup:, it all gets easier once you are sucessfull, the more you do yourself the more you'll learn (and the easier it gets).....don't give up....I always thought it is much worse when you can't find the problem vs when you find the problem and can't do anything about it.

wdchyd

 

[Mike Eagle]

Happy to report that the problem is solved for now. When I put the gages in place on both the bucket lift and tilt control valves I saw a drop in system pressure when both valves were activated. I then removed the system pressure relief valve and found one of the two smaller O-rings on this assembly was missing. On the parts diagram this was called the backup O-ring. (There are two O-rings in the same groove) This was replaced along with the other three rings on the assemble. I also disassembled the detent mechanism that holds the valve in the float position and found it badly rusted. From it's condition I am not sure the control valve was going fully into the float position. After cleaning and greasing, the lift bucket control valve is definitely going fully into float now. Pressure in now holding steady and the bucket tilt is working as it should. Thanks for your help everyone.

 

[kennyd]

Happy to report that the problem is solved for now. When I put the gages in place on both the bucket lift and tilt control valves I saw a drop in system pressure when both valves were activated. I then removed the system pressure relief valve and found one of the two smaller O-rings on this assembly was missing. On the parts diagram this was called the backup O-ring. (There are two O-rings in the same groove) This was replaced along with the other three rings on the assemble. I also disassembled the detent mechanism that holds the valve in the float position and found it badly rusted. From it's condition I am not sure the control valve was going fully into the float position. After cleaning and greasing, the lift bucket control valve is definitely going fully into float now. Pressure in now holding steady and the bucket tilt is working as it should. Thanks for your help everyone.

Glad to hear you got it fixed. I suggested the valve when I first replied

 

[Chilly807]

Glad to hear it's working now. Something else to consider, if it starts doing it again, is the "floppy bucket syndrome". Usually you only see it on the bucket cylinders, the main lift cylinders don't seem to be affected as much.

What happens is that when you dump a full bucket of something heavy, the weight in the bucket tipping ahead causes cavitation in the cylinder, trapping air. A regenerative valve helps, but doesn't always work 100 %.

Afterwards, the bucket control is "soft", or "floppy". There's a lot of threads here about it.

To cure it, simply hold the bucket fully curled (over the relief valve) for about 10-15 seconds, then fully dumped for the same period. That will help purge the air out of the cylinders.

It will come back in time, but at least you can deal with it.

Sean