MF135 without Pressure control valve

[Duncan135Tractor]

I'm trying to solve a problem with the lift arms on my 1974 MF135 (perkins engine). The tractor was being used to do some landscaping with a blade when suddenly the hydraulic lift arms wouldn't go up. The hydraulic oil was fine (full and clean). I suspected that something may have gone wrong in the pressure control valve. Removed the hydraulic lift cover (first time doing this). I have the MF135 Workshop manual, everything on my tractor looks the same except for the pressure control valve - there wasn't one. Do you know if some models of the 135 didn't have a pressure control valve? If so what controls the flow of oil into the cylinder?

Once I figure out how to upload a picture I'll include one of the hydraulic lift cover upside down as it came out of the tractor.

Thanks,

 

[DavidP, South Wales]

Hello Duncan,
Firstly we need to clarify a couple of points. You are talking about the "Pressure Control" valve. If your tractor is fitted with Pressure Control this will have little bearing on whether the 3-point linkage will work. The photo shows a Pressure Control quadrant. The inner quadrant is longer than the outer. If your tractor does not have Pressure Control, the quadrants will be the same length and pressure relief is by a fixed valve.
Its a pity that you removed the cover before doing the preliminary checks. Pressure Control was an option on MF 135s in the UK up to about 1971. The things that should have been checked first are for any excessive end float in the control spring linkage (where the top link fits),
removal of the RH side panel after partially draining the oil to check for correct operation of the pump control valve lever. Observe the vertical lever responding to commands from the quadrant levers. This can be mostly done with the cover removed but you will not have the loading of the pump valve lever in place. It will be necessary to push gently on the knurled screw or lever to imitate the pump lever pressure. Is the PTO working correctly? Does the PTO clutch appear to be OK?
DavidP

 

[Duncan135Tractor]

(reply to post at 15:03:46 09/09/10)

Hi DavidP

You are right my tractor doesn't have the pressure control quadrant. So that answers my question about the pressure control valve - don't have one.

Here are some answers to your other questions. There is no excessive play in the control spring linkage. I did check the linkage through the RH side before I removed the cover and just went out and checked it again. The vertical lever are responding as expected to the quadrant levers. There was no pressure at all on the hydraulic arms after it stopped working. Originally I thought the linkage may have broken.

Unfortunately, I realize now that I could have run the tractor with the standpipe cap off to make sure that the pump was working. However when I took the stand pipe cap off, the stand pipe came with it. There was a little bit of corrosion. It would turn in the hole put wouldn't come out. It had to be soaked in some WD40 to get the standpipe to come out of the cap. I'm not sure if that would create enough of an internal leak to prevent the hydraulic lift arms from rising.

How much oil would I need in the hydraulic case to run the tractor? Could I turn it on with the cover off and check to see if oil is squirting out of the hydraulic pump? I sure hope I don't have to replace the pump.

About the PTO - I thought the PTO ran off of the gear box. How is the hydraulic pump related to the PTO? Excuse my ignorance, this is the biggest tractor repair I've undertaken.

Thanks for your help

 

[DavidP, South Wales]

Hello again,
Have you now refitted the hyd cover? You would need around 4 gallons to enable the linkage to work. The requirement is that there is enough oil present to provide uninterupted flow of oil into the filter. Have you checked the filter? There is no problem in starting the tractor with sufficient oil in the casing. Only try this at min idle. At this speed you should see a 'fountain' of up to 2 inches coming from the pump. A small increase in eng speed will result in a significant increase in the 'fountain'.
If you still have the cover off the pump lever should be leaning rearwards under spring pressure from the control valve spring. As I recall you have not mentioned how old your tractor is. If it is a very early one it may have an aluminium oscillator. Later ones were made of steel. The osc works from an eccentric on the pump shaft and effectively rocks the control valve back and forth to prevent it sticking. Over the years I have replaced several aluminium ones that had broken. When this happens all hyd operation can be lost.
If all linkages appear to be OK this could be the answer. With the cover off pump removal is a small job and if it is the osc it can be replaced as a seperate item.
Regarding the PTO; The pump shaft is turning constantly except at the times when the clutch pedal is pressed fully. When you engage the PTO you effectively connect the pump shaft to the PTO shaft. My line of thinking was that if you had been using a mounted implement that was worked by the PTO and both failed together then it might be the PTO clutch at fault.

DavidP

 

[samn40]

Just check the pivot for the valve control hasn't come adrift.it is only
held with a small rivet ,this can be replaced with a bolt and nut.also
check the roller on the lever is still in place.this is the small roller
you should have removed before lifting the lid, if not search in the
bottom of the housing! other than that check the pto is driving as
David said if all these things are ok then your problem is in the lid
linkage/settings

 

[Duncan135Tractor]

Hi David and Samn40,

I've finally had some time to get back to the tractor. I haven't replaced the oil yet so haven't been able to test the pump running or the PTO. But I did find a couple of unusual things. First removed the filter to see if it was plugged. It looked pretty clean but there was no sealing ring under it, like the manual say there should be. I also checked the lever on the control valve and it moves in and out, but doesn't stay out. If there is no force on it should the lever be pointing in a backwards direction?
Lastly I found this spring in the bottom of the hydraulic/transmission case. It's obviously come off of something. The one end has been stretched open. It's only about 1/2" long. Any ideas?

Thanks

 

[Duncan135Tractor]

Hi,

Just realized I didn't answer some of the other questions that you had asked. The tractor is a 1974 model. Should the 1974 model have the steel oscillator?

The roller and pins for the lever were removed when the the cover was taken off. Where do I look for the pivot for the control valve? Is that the same as the lever?

Thanks again.

 

[DavidP, South Wales]

Hello,
Now we are getting somewhere with this spring. This is attached between the position control frame and 'dog' lever (look at the shape) between items 17 and 18. Without this spring in place your position control will not work as the 'dog' will not follow the rollers as it is supposed to do. A new correct spring should be fitted. Be patient it is difficult to fit. A piece of wire and very long nose pliers will help.

DavidP

 

[Duncan135Tractor]

Hi David,

It's taken a while to get a replacement spring, but it finally arrived. The spring isn't the only problem, I've discovered. The problem seems to be with the control valve. When the position control lever goes to the down position the vertical lever (10) pushes on the roller of the pump control lever (11) causing the pump to go to the discharge position. Just like it should work. However, when the position control lever goes to the up position, the bottom of the vertical lever (10) moves away from the roller on the pump control lever (11), but the pump control lever doesn't follow. It stays in the same location so there is no intake on the pump. If I manually push on the top of the pump control lever (11) by the roller, the hydraulic arms rise and there is plenty of force. It could easily pick up an implement. So I'm assuming there is nothing wrong with the pump. My guess is that the spring inside the pump (behind the control valve) is disconnected or broken and that's why the pump control lever doesn't follow the vertical lever. The spring I'm referring to is part 92 on Fig 51 if you have the service manual. Does that spring pulls the pump control lever in? If so it must be hooked into the control valve somehow. However, the manual doesn't seem to indicate the spring is hooked to anything. Or could the problem be the control valve itself? There seems to be a spring inside the control valve too (Fig 3 in service manual section 7).

I've had to put the tractor back together because I need to use the bucket for some jobs on the property. I hope I'm not risking damaging the pump by using the tractor. I can just imagine a spring getting ground up inside the pump.

Since I live on an island I have to order all parts and it takes a while to get them. I'd like to keep using the tractor until I get the replacement parts, but I don't know if I should go ahead and order a replacement control valve or just a spring. Have you ever seen this particular spring break? Is it possible to remove the control valve without removing the whole pump from the tractor? It doesn't seem like it from the manual.

BTW - there was another clue. Before the hydraulic arms stopped working completely there were a few occasions when the I'd lift the hydraulic arms to the top position and they would get stuck there. They would only lower after I lowered the draft control. The position control never got "stuck" in any position except the maximum lift position. But that problem may have been related to the "first" missing spring.

Thanks again

 

[Duncan135Tractor]

Hi All,

Some good news. I finally got brave enough to take the PTO shaft out, so that I could take the hydraulic pump out and have a good look at it. BTW - it wasn't so difficult, just like DavidP said. As I mentioned in my last post, the lever on the control valve was never going to the intake position on it's own. However, I could move it manually and the pump would pump oil out of the standpipe hole. When I got the hydraulic pump out and removed the oil strainer housing the control valve just fell out (which it isn't suppose to do). When I removed the oscillating body cap, the retaining ring (part 85 in diagram) fell out. So the whole problem was caused because the circlip or retaining ring had disconnected from the back end of the control valve allowing the control valve to float free inside the housing.

A lot of trouble for this little part:

The reason it may have come off is that there is a little bit of play in the control valve shaft. With winter coming I can always order new parts and spend some time in the garage!

The tractor is back together and the hydraulics are working fine.

Thanks for your suggestions and help.