MF168 hydraulics failure

[john maddock]

Oh dear! The venerable MF168 is having a hissy fit.

Today, it would barely lift an empty bucket on the 3-point linkage - but there is some intermittancy. (I hate an intermittent problem!). Sometimes it will lift a little, but then settles down again, spontaneously. The auxilliary pump seems to be unaffected.

Last time I saw anything like this, I think it was a leaking O ring in the hydraulics - a pissy little ring about 4mm in diameter costing less than a dollar. From memory, it was something to do with a small pipe leading from the Pressure Control valve to the lift pump standpipe, so I've order what appear to be the necessary O ring and washer, hoping it will solve the problem.

Has anyone dealt with this problem in the past?

JV

Update: the problem is *not* related to the top link causing movement of the control valve; the lifting problem exists without the top link connected - which leads me to suspect a leaking O ring, the amount of leak varying with the load applied.

Second update:

Success! I was correct, new O rings solved the problem. I changed both the O ring and its helper washer on both the bottom of the stand pipe (the top set were OK) and the bleed to the Pressure Control valve, so I don't know which one was the problem. I suspect the Pressure Control pair coz they are still a loosish fit on the bleed-off pipe, even though the O ring on the standpipe was abraded slightly.

I think it is a dud design, a quick & dirty solution. The MF engineers fitted a steel block which tapped into the oil supply from the pump, installed an O ring and helper washer in it, then simply pushed a small pipe into the O ring, thus bleeding a supply of oil to the Pressure Control valve. From there, they used another small pipe, but this one has compression fittings both ends.

If the O ring in the block leaks, pressure to the lift cylinder is lost, either partially or completely, depending on the severity of the leak - and that's why I observed a reduced lift capacity and also a variable lift capacity i.e there would be some lift, then the linkage would fall.

I think the MF engineers should have gone to SpecSavers! They might have come up with a decent design as a result.

JV

[john maddock]

[QUOTE=john maddock;312121]Oh dear! The venerable MF168 is having a hissy fit.

Today, it would barely lift an empty bucket on the 3-point linkage - but there is some intermittancy. (I hate an intermittent problem!). Sometimes it will lift a little, but then settles down again, spontaneously. The auxilliary pump seems to be unaffected.

Last time I saw anything like this, I think it was a leaking O ring in the hydraulics - a pissy little ring about 4mm in diameter costing less than a dollar. From memory, it was something to do with a small pipe leading from the Pressure Control valve to the lift pump standpipe, so I've order what appear to be the necessary O ring and washer, hoping it will solve the problem.

Has anyone dealt with this problem in the past?

JV

Update: the problem is *not* related to the top link causing movement of the control valve; the lifting problem exists without the top link connected - which leads me to suspect a leaking O ring, the amount of leak varying with the load applied.

Second update:

Success! I was correct, new O rings solved the problem. I changed both the O ring and its helper washer on both the bottom of the stand pipe (the top set were OK) and the bleed to the Pressure Control valve, so I don't know which one was the problem. I suspect the Pressure Control pair coz they are still a loosish fit on the bleed-off pipe, even though the O ring on the standpipe was abraded slightly.

I think it is a dud design, a quick & dirty solution. The MF engineers fitted a steel block which tapped into the oil supply from the pump, installed an O ring and helper washer in it, then simply pushed a small pipe into the O ring, thus bleeding a supply of oil to the Pressure Control valve. From there, they used another small pipe, but this one has compression fittings both ends.

If the O ring in the block leaks, pressure to the lift cylinder is lost, either partially or completely, depending on the severity of the leak - and that's why I observed a reduced lift capacity and also a variable lift capacity i.e there would be some lift, then the linkage would fall.

I think the MF engineers should have gone to SpecSavers! They might have come up with a decent design as a result.

Success! I was correct, new O rings solved the problem. I changed both the O ring and its helper washer on both the bottom of the stand pipe (the top set were OK) and the bleed to the Pressure Control valve, so I don't know which one was the problem. I suspect the Pressure Control pair coz they are still a loosish fit on the bleed-off pipe, even though the O ring on the standpipe was abraded slightly.

I think it is a dud design, a quick & dirty solution. The MF engineers fitted a steel block which tapped into the oil supply from the pump, installed an O ring and helper washer in it, then simply pushed a small pipe into the O ring, thus bleeding a supply of oil to the Pressure Control valve. From there, they used another small pipe, but this one has compression fittings both ends.

If the O ring in the block leaks, pressure to the lift cylinder is lost, either partially or completely, depending on the severity of the leak - and that's why I observed a reduced lift capacity and also a variable lift capacity i.e there would be some lift, then the linkage would fall.

I think the MF engineers should have gone to SpecSavers! They might have come up with a decent design as a result.

JV

[john maddock]

[QUOTE=john maddock;312121]Oh dear! The venerable MF168 is having a hissy fit.

Today, it would barely lift an empty bucket on the 3-point linkage - but there is some intermittancy. (I hate an intermittent problem!). Sometimes it will lift a little, but then settles down again, spontaneously. The auxilliary pump seems to be unaffected.

Last time I saw anything like this, I think it was a leaking O ring in the hydraulics - a pissy little ring about 4mm in diameter costing less than a dollar. From memory, it was something to do with a small pipe leading from the Pressure Control valve to the lift pump standpipe, so I've order what appear to be the necessary O ring and washer, hoping it will solve the problem.

Has anyone dealt with this problem in the past?

JV

Update: the problem is *not* related to the top link causing movement of the control valve; the lifting problem exists without the top link connected - which leads me to suspect a leaking O ring, the amount of leak varying with the load applied.

Second update:

Success! I was correct, new O rings solved the problem. I changed both the O ring and its helper washer on both the bottom of the stand pipe (the top set were OK) and the bleed to the Pressure Control valve, so I don't know which one was the problem. I suspect the Pressure Control pair coz they are still a loosish fit on the bleed-off pipe, even though the O ring on the standpipe was abraded slightly.

I think it is a dud design, a quick & dirty solution. The MF engineers fitted a steel block which tapped into the oil supply from the pump, installed an O ring and helper washer in it, then simply pushed a small pipe into the O ring, thus bleeding a supply of oil to the Pressure Control valve. From there, they used another small pipe, but this one has compression fittings both ends.

If the O ring in the block leaks, pressure to the lift cylinder is lost, either partially or completely, depending on the severity of the leak - and that's why I observed a reduced lift capacity and also a variable lift capacity i.e there would be some lift, then the linkage would fall.

I think the MF engineers should have gone to SpecSavers! They might have come up with a decent design as a result.

JV

The Cure!

After ordering a new bleed -off pipe (the only one in Aus.!), and being told new Pressure Control valves are no longer available, not to mention an extensive discussion with the service manager in case a re-adjustment of the control levers was required, I went to a non-genuine site to see what was available. It was there that the penny dropped, coz the listing for a plain standpipe had the warning that using it disabled the Pressure Control. Solution found! I un-ordered the bleed-of pipe and ordered a plain standpipe.

I'm pleased to report that with a full bucket, the linkage now has the ability to lift the front wheels ever so slightly, and can make the pump relief valve crack off! The tractor is used mainly for loader & backhoe work, so losing the Pressure Control is irrelevant - and I now have a tractor I can trust - after about 13 years, coz I now think it came with the problem already existing.

Happy Daze!

JV

[Footsfitter]

Dunno what you bought that 360 machine for, you seem to be playing with old faithful most of the time !!

[john maddock]

Dunno what you bought that 360 machine for, you seem to be playing with old faithful most of the time !!

Good question Footsfitter, the answer to which is: horses for courses! Moving 3000+ cubic metres of soil for a new dam(n) (!) wall was likely to be just a tad too much for the Venerable 168. On tother hand the 14t 360 was just a tad too big to take inside the Farm House to dig new footings, remove spoil & backfill with rock!

And of course, there is a season for everything

JV