Oliver 77 Cracking Hydraulic Pump Center Plate

[ctk3473]

Hi, I have a 1951 Oliver 77, when I got the tractor it had a cracked center plate, but it had been sitting outside for 10+ years and the hydraulic boots were cracked and worn so I chalked it up to water getting into it and freezing it.

I replaced the center plate with one from a parts tractor which had also been outside but I didn’t see any cracks or in the plate so I put it in, when I had it apart I didn’t notice any wear to the gears and the bearings were fine, I replaced the seals in it as well at the time.

I put the pump in, put fluid in it and let it sit for 2 weeks and didn’t notice any fluid loss, and it worked fine with my 3-point cylinder.
Fast forward a few months (December to March) I took the tractor outside to use the 3-point and realized I had no fluid in it. The tractor was stored inside and the lowest temperature it could’ve reached would’ve been 45°.

I disassembled it recently and the plate was cracked again. If anyone has any ideas about how it could’ve cracked under those circumstances I would appreciate them. I’ve read that it could be related to the pressure relief but couldn’t understand how to check any of that so instructions for that would also be appreciated.

Thank you in advance.

 

[GermantownGreen]

Hi, I have a 1951 Oliver 77, when I got the tractor it had a cracked center plate, but it had been sitting outside for 10+ years and the hydraulic boots were cracked and worn so I chalked it up to water getting into it and freezing it.

I replaced the center plate with one from a parts tractor which had also been outside but I didn’t see any cracks or in the plate so I put it in, when I had it apart I didn’t notice any wear to the gears and the bearings were fine, I replaced the seals in it as well at the time.

I put the pump in, put fluid in it and let it sit for 2 weeks and didn’t notice any fluid loss, and it worked fine with my 3-point cylinder.
Fast forward a few months (December to March) I took the tractor outside to use the 3-point and realized I had no fluid in it. The tractor was stored inside and the lowest temperature it could’ve reached would’ve been 45°.

I disassembled it recently and the plate was cracked again. If anyone has any ideas about how it could’ve cracked under those circumstances I would appreciate them. I’ve read that it could be related to the pressure relief but couldn’t understand how to check any of that so instructions for that would also be appreciated.

Thank you in advance.

Reach out to Centerplate. He makes new plates and has excellent deals, etc.
From Wisconsin.
GG Wes

 

[greg krush]

Hi, I have a 1951 Oliver 77, when I got the tractor it had a cracked center plate, but it had been sitting outside for 10+ years and the hydraulic boots were cracked and worn so I chalked it up to water getting into it and freezing it.

I replaced the center plate with one from a parts tractor which had also been outside but I didn’t see any cracks or in the plate so I put it in, when I had it apart I didn’t notice any wear to the gears and the bearings were fine, I replaced the seals in it as well at the time.

I put the pump in, put fluid in it and let it sit for 2 weeks and didn’t notice any fluid loss, and it worked fine with my 3-point cylinder.
Fast forward a few months (December to March) I took the tractor outside to use the 3-point and realized I had no fluid in it. The tractor was stored inside and the lowest temperature it could’ve reached would’ve been 45°.

I disassembled it recently and the plate was cracked again. If anyone has any ideas about how it could’ve cracked under those circumstances I would appreciate them. I’ve read that it could be related to the pressure relief but couldn’t understand how to check any of that so instructions for that would also be appreciated.

Thank you in advance.

I would guess that the centerplate that you put in also had a hairline crack but you could not see it, after you put some pressure on it when you started the tractor the crack opened up. If your parts tractor sat outside it most likely got water in it and cracked. I have have had some that the crack is not visible to the eye, can use dye to check for cracks. Centerplate or Korves has new ones.

 

[Centerplate]

Greg Krush could be correct and the center section from your parts tractor could had had a very small crack not easily visible.

The other possibility is the relief valve seat could have worked loose, but still held in place by the relief valve plunger. When your cylinder deadheaded the pressure would increase trying to push the plunger to release oil. The seat being loose could have slid out but not enough to release oil. The excess pressure could then crack the center plate. I had that happen on a 770 once. I would inspect that carefully.

 

[ctk3473]

I took the pressure relief apart and it had over 1/8th inch of shims in it so I’m going to chalk it up to the replacement center plate I had had a crack I didn’t see and the higher pressure finished it off. Thank you all for your help.

 

[Centerplate]

When you put it back together, I would check the pressure on the system. No more that 1100 PSI.