MF40b O-ring keeps failing

[AlanSun]

I have a 1970s MF40b still mostly going strong, but have a recurring problem with the o-ring on the output flange of the Dowty hydraulic pump. This splits every few weeks and costs me a flood of oil every time. Is this problem familiar to anyone else? Solution? Thanks for any help.

 

[M5farms]

ive just had a similar exp on a NH tractor blowing oring and come to find out there is a plastic seal that goes around the outside of the oring the supposed to fix it . Go to your dealer and have them pull the schematics and if it doesn't require any seal get a high quality Oring

 

[airbiscuit]

Here is a good thread. See if you can get advise from Shona13.

http://www.tractorbynet.com/forums/parts-repairs/372472-massey-ferguson-230-little-tractor.html

 

[AlanSun]

ive just had a similar exp on a NH tractor blowing oring and come to find out there is a plastic seal that goes around the outside of the oring the supposed to fix it . Go to your dealer and have them pull the schematics and if it doesn't require any seal get a high quality Oring

Thanks for the suggestion but there's only space for a standard o-ring.

 

[M5farms]

as you can see the seal is thin I'm not sure what ur dealing with but I never TG thought that this little plastic ring would be effective but so far no blown oring

 

[AlanSun]

That looks possible, thank you! See attached photo of where it has to go. I'll go back to the dealers and see if he can find something similar.

 

[M5farms]

That flange looks like what I was dealing with.

 

[Dave M7040]

I have a 1970s MF40b still mostly going strong, but have a recurring problem with the o-ring on the output flange of the Dowty hydraulic pump. This splits every few weeks and costs me a flood of oil every time. Is this problem familiar to anyone else? Solution? Thanks for any help.

Is their an information label on the Dowty pump that you could post?

Dave M7040

 

[Spanner]

Och Alan, away wi' ye...
(Just kidding!)

Welcome to the forum.

As Dave asks - do you have any 'numbers'?

Also - Are you buying replacement O-rings from your dealer as specific OEM Part Numbered items, or is he supplying a 'generic' o-ring from the 'Assortment' box?

Sometimes the generic items are often 'near enough' but not 'good enough'.

 

[Dave M7040]

Could you please look at the page 53 with this link and tell us if you see your pump there.
There are more pumps on page 54.

http://www.crosscreektractor.com/customer/crcrtr/pdf/Massey Ferguson.pdf

Dave M7040

 

[LD1]

I think you have an issue with o-ring sizing.

A captured o-ring like that shouldnt be blowing out.

It looks like the o-ring groove is ALOT wider than it is deep. May be a problem. Maybe it wasnt supposed to be an o-ring? Maybe it is supposed to be a flat rubber ring....kinda like whats on a oil filter?

What size or number o-ring are you using?

 

[Spanner]

I think you have an issue with o-ring sizing.

A captured o-ring like that shouldnt be blowing out.

It looks like the o-ring groove is ALOT wider than it is deep. May be a problem. Maybe it wasnt supposed to be an o-ring? Maybe it is supposed to be a flat rubber ring....kinda like whats on a oil filter?

What size or number o-ring are you using?

Agreed.
That's why I was asking about the 'sourcing' of the o-rings...

 

[Dave M7040]

View attachment 523487
That looks possible, thank you! See attached photo of where it has to go. I'll go back to the dealers and see if he can find something similar.

I think you need to step back a bit if I understand your situation.

The photo of the flange with two bolt holes you posted, is connected to the pump by bolting to another flat surface on the hydraulic pump.
Is this correct?

The last time I dealt with a similar connection was on a large road grader.

What I found was that the two surfaces, the pump one and the flange one were no longer flat.

The flange, like the one on your knee, was bowed so where the bolt holes are, the flange and pump body touched when the bolts were tight but the flange was bowed and the other two corners of the flange, where there are no bolt holes, did not mate to the pump surface. This bowing did not support the seal and it was constantly blowing out.

This grader situation was a sort of emergency one so I carefully used a fine flat file to make the surface flat again.

A piece of thick glass with a sheet of emery paper on it would provide a better flat surface where you could rub your flange back and forth until the entire flange surface was polished and flat.

I think if your try the glass and emery paper technique you will see immediately that the surface is not flat and there will be areas of the flange which are not being polished.

Continue polishing and the high spots will be worn down and eventually the face will be flat. A machinist could do an even better job.

I doubt from the photo, an O ring is the proper seal for the joint. Your local hydraulic shop may have square edged circular seals that just fit in the flange groove.

Dave M7040