MF40 Industrial 1976 Loader Backhoe Boom will not go down.

[Aussie54]

Hi all,
My MF40 Industrial 1976 Backhoe Boom will not go down.
When I pull on the control lever it goes up ok but when I push on the control lever, the lever has very little travel and the boom will not go down.
Any ideas as to what could be the cause of this? All other functions such as Dipper, Bucket, out riggers, Loader buck etc work ok. Oil if at correct level. 1st time I have come across this.
Your help and ideas would be appreciated.
Cheers,
Aussie54

 

[toxicjeeper]

On my new Holland 555e it was a broken linkage when it happened to meet last winter.couldnt curl the bucket..I just welded it back up and it's worked fine ever since

 

[TractorTech]

Sounds like the spool is getting jammed on something in the detent cap or the detent itself is rusted/broken

 

[rScotty]

Sounds like there is a problem in the control valve and the lever is not moving the sliding control valve far enough to open the return hose port. It there by any chance a relief valve on the bottom of the boom slider on the control valve? If so, I'd look there first.

If you loosen the boom cylinder return hose to check any of this, be careful because that boom will drop like a rock. Get it down somehow first. Do not ever loosen hydraulic hoses with engine running. High pressure oil will cut like a knife. In fact, even without the engine running a boom's self-weight can generate some pressure in the hydraulic hose.

On mine a similar problem was in the connector to the lever mechanism that works the sliding valve in the control valve array. It wasn't hydraulics, just a broken lever extension.

 

[Aussie54]

GUys, here is an update.
I got to it this morning and everything works OK. Go figure.
There was no binding and all the hydraulics worked.
I guess it must have cooled down?
It's a bit of a mystery to me.
I will again give it a run and see what happens.

There is very small leak under the spool for the boom. I will have to check that out.

Thanks for your input thus far.

 

[TractorTech]

That's good news, but still think that you take that detent cover off, you'll find out why it wasn't working. That also might be why you have developed a leak.

 

[Aussie54]

Yes, I intend to take that section all out and inspect and clean it.
I would like to see why this happened.
cheers.

 

[Sportsman762]

Not sure if I would pull the entire section out. I get nervous opening valves up. I would just take the end cap off and clean that up. Leave the spool in the bore less chances of inducing contamination. If I remember right some of the MF loaders had self leveling built into the valves. I know that 34A did, not sure what model your 40 has, and what loaders they used in AU.