My Hydraulic Pump Cracked or Broke!

My Hydraulic Pump Cracked, Blew Out The Front Seal, Or The Shaft Broke Off!

There are really only 2 things that cause this to happen:


1)- The pump was "dead headed".
This is very common. Probably 99+% of pump failures that we see are because of this. This style hydraulic pump will pump oil any time the engine is turning and that oil MUST have somewhere to go (liquid does not compress). If the oil flow from the pump gets restricted then it starts to (very quickly... less than a second) build up pressure. The pressure can almost instantly hit 6,000psi or more before something gives. Usually it is the pump shaft or the pump housing... sometimes it is the key on the pump shaft.

What causes the restriction?

If you have a loader then it was caused because either: 

a)- You disconnected a quick-disconnect fitting while the tractor was running or tried to start the tractor with a fitting disconnected. Maybe a branch caught the line and pulled it loose or you unhooked the lines to get better access to do maintenance. 

b)- Your loader valve is defective causing too much pressure to build up. Could be a stuck or broken relief valve or a small piece of o-ring lodged in the valve and plugged up a port.

c)- Your quick disconnect couplers are not completely opening. This happens when the valve mechanism inside the coupler (usually a ball) gets wore down over the years. If the couplers do not completely open when you hook them up then the oil will have nowhere to go.... cracking the pump housing or twisting off the shaft.

d)- Your loader or power steering is just not hooked up correctly.

No Loader...
Then there is likely a problem with your three point valve causing too much back-pressure

 

Question )- If this was caused by "dead heading" then why didn't my original pump do that? 

Answer )- Well... something must have happened to the original pump or you would not be buying a replacement pump in the first place. It is VERY unlikely that you wore out your original pump unless the hydraulic system was seriously neglected (lots of fine grit in your oil for long periods of time). I have customers with 10,000+ hours on their tractor and the original pump is still going strong. 

You are replacing your pump because SOMETHING went wrong and that SOMETHING was probably not fixed the first time. More than likely you are replacing your pump because "the loader was lifting really slow" or "the three point lift was really weak" or something along those lines. Both of these things are caused by a restriction in the system. Your original pump had enough wear on it that it could tolerate a restriction in the system and "bleed" enough pressure back through the pump that it did not hurt it. This causes the 'slow to lift' symptoms. The new pumps are very efficient and are tight enough that they can not "bleed" that pressure back through the pump and something has to give. Usually a shaft, housing, or keyway.   

 

2)- A defective pump casting.

This is very uncommon (the other less than 1%). In fact we have only seen this one or two times in the last decade. The pumps we sell and the Yanmar original pumps are a very high quality product. A defective casting is very easy to see. The walls will be much thinner in the spot where it broke or there will be a sandy material or air bubbles in the casting.

 

 

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