Cracked my lift cylinder, why?

I was in the process of re-assembling the 3 point on my 202 and making some adjustments. I started the tractor and immediately the arms started to rise. Before I could do anything they reached the top and I heard a loud "BANG". Then they would not respond. Took it apart to find the lift cylinder had cracked in two places, one down it's whole length.
My guess is that the relief valve did not open when it should have and I had excessive pressure built up in the cylinder. I know I need to back off the nut on the pump that controls the valve, anything else I should be looking at before ordering parts and putting it back together?

I had the same thing happen on one of my MF50s. The controls where not properly adjusted which allowed the arms to go up to high and split the cylinder. I put in a new relief valve, new cylinder and redid the control adjustments and all is good now. Did you go through the control rod adjustments on the top cover before you installed it? John UK can send you info on how to do it correctly.

Dan

Thanks Dan, yes I do have John's instructions and I thought I had followed them correctly but I definitely want to re-check everything before re-assembly. I think my problem had to do with the adjustment of the nut on the pump which adjusts when the control valve is actuated. Things seemed to be working ok so I don't know why I messed with it. I also think the stopper on the position control was too high.
I am just sick about it because I have been working on it for almost two months and having a hard time finding the time to get it finished. Now I could really use it for some yard cleanup and I can't.

There are NO adjustments for the pressure on this system, the safety valve is pre-set and it operates automatically when the pre-set pressure is reached.If the valve has not been operated for sometime then it may have stuck and that is your problem. It tells you in the Operators Book to discharge the Safety valve at least once a month, this serves two purposes, it makes sure that the valve is free and opening as it should do and it also sprays oil over the inside of the Housing to prevent rust. To discharge the Safety valve, you should lift the Draft lever to the Top Of the Quadrant with the Engine idling and allow it to Blow off for a few seconds. It is a Safety Device and not meant to be discharged continuously as some operators seem to allow.
All the Control Linkage will need re-setting, you can't just replace the cylinder and hope that it will be OK. The tolerances on this system are small and need to be checked at all stages. The Valve you refer to, that you say needs re-setting, is the Control Valve, this controls the actions of the Hydraulic system and has no relation to the Safety Valve and does not influence it, except when you move the Draft lever to external pressure and then it will blow off if it has nowhere to send the oil.
If the oil is the incorrect grade and is too thick and heavy, this can also be due to the cold weather, the oil will not discharge quickly enough through the Safety Valve and it will build up a back-pressure which could have the same effect as the Safety Valve not opening. The Lift Cylinder must have been weak for it to break like that and it is possible that the tractor has been driven too quickly over rough ground, this would allow the implement to bounce on the 3 point which would impose tremendous shock loads on the system when it crashes down. You should not hear any sound of movement from the implement as you drive, if you do, you are driving too fast for the conditions and you should slow down (change down a gear)to prevent shock damage.
If you need help, email me.John(UK)[email protected]

Thank you John, that confirms my suspicions. The pump I rebuild and installed was from another tractor of which I do not know the history so in hindsight I should have just replaced the safety valve as a precaution.
My reason for saying I need to adjust the nut on the pump is because the arms lifted before I raised the position control lever. I did not think the cylinder should have broken that easily but being as how the pump is all rebuilt and it is fresh GL-1 it was likely making a good amount of pressure. The temperature was not too low, the tractor has been sitting in my heated shop for the past couple of months and I have the heat set around 65°F. To the best of my knowledge the hydraulic life was never used on this tractor because the backhoe was always in place so I don't think the cylinder was weakened by misuse.

I now have a couple more questions. First of all, it is not the oldest style pump, it disassembles by removing 4 bolts which run front to rear but it does not have a strainer. Which relief (safety) valve should I put in?
Also it looks as though there are at least 3 different cylinders for this tractor. I have ruled out one of them because my piston is 3" in diameter. I believe my tractor already has 9/16" mounting studs with 3 3/4" and 3 3/8" spacing. I think I should be using the 190859M1 cylinder, which is good because it is the least expensive one.
In the up position of the arms, is there still pressure applied by the pump to hold them up or is it simply the control valve that does not allow fluid to flow back through it that holds them up? I'm assuming that when you put the control to the down position the valve in the pump allows the fluid to follow the path back to the pump and it drains out there.

That nut that you refer to, you should only JUST remove any free play between the two levers hanging down and the Pump Control Lever which comes up out of the oil. There is nothing else to do with this setting other than that. If the system still does not perform as it should then the problem lies within the Top Cover and how that linkage has been set. If you need more assistance with this, email me direct and I will try to work out what you should do next to correct the problem, tell me what it is doing and what you have done from this point on...John(UK)..fergusontractorshotmail.com

So the bottom line is that the safety valve should have opened which would have (in all probability) prevented the cylinder from cracking, unless as you say it was weakened previously.

The 190859M1 cylinder is the one I used for my 1964 MF50. I had to drill the top cover holes out for 9/16 studs but after that everything else lined up and worked fine.

Dan

Good, that is the one I ordered. I also ordered some 9/16" fine thread stud material and nuts.
Which relief valve did you use? There is a 2750psi or a 2800psi valve. Not too sure how much difference 50psi would make but it may be significant.

I don't remember which relief valve I ordered, but I know it was the lower PSI of the ones available.
I didn't want to take any chances.
Dan

And I cracked my MF 65 hydraulic top cover something like 33-35 years ago. Replaced the hydraulic pump with a brand new one, and the new one had a steel plug in the pump instead of the safety valve. My father and I did not know about those kind of things, and the dealer said nothing. Well, the dealer said the pump was ready to put in, because we asked about that.
Lifted it up, and cracked the entire cover straight over, between the front and the rear bolts of the cylinder.
Cover welded, and have held up nicely so far, with a bit lower pressure. I have a used uncracked cover I might put in if for some reason the resistance for working lessens... ha ha.

I think it is quite a difference in pressure between a MF 165 Mk II pump and a 202 which I think may be from the 50ties, or am I wrong. The first FE 35 or TO 35 I think had quite a bit lower pressure.


Bill

Hi Bill, yes it's from the late 50's and uses the same/similar pump to the 35 tractors, I think around 2800psi. Freshly rebuilt pump and new GL1 so it was making some good pressure! Everything was working great up until that point. Lesson learned, I thought about replacing the pressure relief valve but I guess I didn't put enough thought into it to think it all through to the end where excessive pressure will start to break stuff. Hopefully all the parts will arrive before the weekend and I can put it back together and maybe hook up an impliment or two this weekend.

For the MF 35 made in England the correct pressure is 2500 psi, or around 175 kg/cm2.

And, the FE 35 the cylinder was 2.5" in dia, while for the later MF 35 it was 3". And the hydraulic cover was strenghtened, and the bolts holding the trumpets was increased from 7/16" UNF to 1/2" UNF. The pump was also altered if I am not too messed up in my memory.

Bill

This story has a happy ending. I ordered the lift cylinder from this site along with a new pressure relief valve and got it all back together Friday evening. After mounting up a rear blade and doing some work with it I am happy to report it is all working great!
With instructions from John(UK) on adjusting all the critical points it seems to be functioning 100% as it should, the draft and position controls do what they are supposed to. If you can't tell, I'm pretty pleased with it!