656 hydraulic problem

656 Gasser

New User
Hi everyone, first post here. I've been searching the site for a situation and problem my tractor is having but haven't found anything quite like it. So here goes I'll explain it as best I can.

I bought several tractors from my Mom after Dad passed away. One is a 656 that he rebuilt the motor and put a nice Waldon dozer on. Runs like a top. But I had always noticed that the hydraulic pump whined and growled a little on start up. Now it's gotten to where it doesn't always catch prime and work at all. During the recent cold snap it didn't work at all. I mean steering, 3 point, dozer, nothing. I added 2 gallons of hytran, bringing the level to maybe a 1/4" over full but it didn't help. So today it warmed up and after starting it twice it caught and worked, but whines some.

I pulled the filter cap off, expecting a lot of oil to run out but surprisingly wasn't that much really. A quart maybe? I don't understand the system obviously but don't understand how it can start pumping on startup without oil there?

Any advice on how this system works would be helpful. Thanks!
 
There is a suction tube inside the reservoir. That tube is made of plastic. Often when the tube ages cracks appear in the tube which allow it to suck air rather than hydraulic oil. Common practice is to overfill the hydraulic reservoir by a full 5 gallons. Doing so often covers those cracks and allows the system to work again. If you do add the 5 gallon of additional oil, that high mark on the dipstick should be marked and it becomes the new "full" mark. --Lee
 
I appreciate the response. Well I will give that a try. what is the procedure for changing that tube if a guy wanted to? Through the cap in the back of the housing or does the platform need to come off?

And if the extra oil doesn't help, would you assume the pump at that point, or does the fact that neither pump is working right mean that it's a supply problem for sure?

Thanks
 
No plastic suction tube on a 656. It is steel. There is also a section of hose connecting the return from aux valve directly into the suction tube to reduce cavitation. Some times the hose gets kinked, some times it bursts, sometimes people take it off completely. I doubt this is your priming problem though. Most likely restricted filter, weak pump, poor seal of suction tube on the pump or the o-ring on main suction tube which is in the split between transmission and rear case. You can look into rear to check hose and grab suction tube to see if it mount has broken loose through the 3rd arm plate. Far as amount of oil coming out with filter, the suction tube is above oil level so you will only get about that quart or so that you got, normal. If you over fill you will partially drain rear with filter off. If you see any crud on screen at filter that tells you oil needs changing and filter. The oil only goes through the screen with cold oil or plugged filter as it is easier to go through screen than paper when cold.
 

Thanks for the reply. I overfilled it, and so far it cured the problem. Thanks for the description on the filter, from what I could tell it looked ok. At some point I would like to tear into it and fix the real problem so I appreciate any info.
 

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