Catastrophic Failure

[Leejohn]

That looks like there is water in you oil and some was on top of your piston. Cold weather freeze up.

[yelbike]

That looks like there is water in you oil and some was on top of your piston. Cold weather freeze up.

I don't see the water in oil. There may be water on the oil outside the case from precipitation. I doubt very much that a freeze crack as the tractor was warm and the oil would have been completely milky in colour.

The repair doesn't look to intensive compared to the jd 2305 case failures. Look up the for posts on it, it really sucks, trust me, don't ask how I know! As long as there is no internal parts damage, it looks like a relatively easy fix for a skilled FIYer. I would guess something physically pressed against the case(like an over extended cylinder) rather then a high hydraulic pressure. I would guess that a high hydraulic pressure would leak at seals before a catasrophic case failure. Just my uneducated guess though. Keep us posted please.

[DFB]

Wow looks like just behind where the rockshaft control valve bolts up. I would think your system pressure relief valve must be nearby. Mines located right below it

[Leejohn]

The reason I posted about freeze up is because my brothers BH just blew the top out of one of the L & R cyls. When it went it ended up about 60' away. The metal is about 1/2" thick.
Also the bucket is on the ground and it moved it about 2' until the dirt pile got to big.

[yelbike]

The reason I posted about freeze up is because my brothers BH just blew the top out of one of the L & R cyls. When it went it ended up about 60' away. The metal is about 1/2" thick.
Also the bucket is on the ground and it moved it about 2' until the dirt pile got to big.

Curious, was his oil milky in colour?

[Leejohn]

There was a little water that hadn't drained out of the piston. The BH was been setting for awhile, we well have to open the drain plug and see if water comes out now. I would say it is. It wouldn't take a lot of water if trapped on top of the piston like his was. What got me was how far the boom moved. If I think of it I'll try and get a picture.

[Chilly807]

Would this relief valve also protect the system if one closed the descent-rate control valve on the three-point and then attempted to raise the hitch?

It doesn't work that way, all the descent rate valve controls is the rate of fall. It's a check valve of sorts and is spring loaded. It has no effect on the raise part of the cycle, even if it's closed completely the valve will lift off the seat and allow oil to enter the cylinder unrestricted. Once it's in there, however, it's trapped and has no way out past the valve. I would think the safety valve would be plumbed directly into the cylinder to allow excess pressure to escape if the need arose. In other words, it shouldn't have to also pass through the descent rate valve to get out. That's the way it's shown on mine anyway.

The attached pics are from the WSM for my tractor, an L3400. It shows the cylinder safety valve being set for roughly 3000 psi (2845-3277 psi), which is well above the normal relief setting of 2250psi, and the hydraulic diagram shows where everything is plumbed in relation to each other. The lowering valve (6) is shown in green, the cylinder (7) is in yellow, as is the safety valve (8).



Sean

[Chilly807]

Wow.. quite the failure. I've never seen anything quite like that before. Sure looks like an overpressure situation, if that's the weakest point of the casting.

Sean

[radioman]

Wow.. quite the failure. I've never seen anything quite like that before. Sure looks like an overpressure situation, if that's the weakest point of the casting.

Sean

My thoughts exactly. You can see a clear line all the way where it broke. It appears to be following the thickness of the cast iron from the inside. I am willing to bet that once you get that cover off and inspect it from the inside with a strong light, you will see a dark color metal spot indicating an old fracture that was there way before you got the tractor and the gray paint covered it on the outside. If you dont see a spot of an old long time fractured spot, then either you have quite possibly found a manufacturing design defect or definately a failed relief valve. Time to inspect it too. By the way, its good to know that your oil was not milky- but even with contaminated oil you would noticed sluggishness with hst or loader as its using the same oil.

[DFB]

On my machine the thermal/shock safety relief ball check is located right inside the control valve itself.

Looks like a high pressure blowout to me. I once experienced a CAT skidder pump housing crack under pressure upon start up. It was freezing cold out.

Looking foward to seeing more diassembly