Followup M hydraulics

[Steve Santini]

Hello Everyone
On Monday I asked about causes for weak hydraulics on a 41 M with live hydraulics with two newly rebuilt rams.(two way rams done at machine shop and tested by them, so thats probably not my issue) As a recap the hydraulics are slow and weak; a suggestion was made by two helpful members that I plumb a gauge into the pressure sideband get a reading.
I uploaded a picture of the tractor with the gauge in the pressure line coming from the live pump. the first valve is just letting fluid pass through, the second is the one my lines come off to go to the control valves to raise the loader and tilt the bucket.
so at 3/4 throttle I get about 200 lbs. pressure. then when i open the valve all the way for either the bucket or the entire loader i get 350 lbs. raising the loader, and almost 450 or 500 psi
while lowering.
my questions-should the pump be at hardly any pressure when no valves are open and it is just recirculating? Did I test it correctly by opening one of the valves for a bit ? Thanks for any feedback you can share, sorry for the long post. Steve

 

[David G]

You can have two ways it is weak, either flow or pressure.

If you look at the pressure gauge when the loader is against the stops, it will show you the maximum pressure, please test and post back.

Low flow will cause slow operation, but the loader will still lift a heavy weight.

 

[Mike in Wisconsin]

If I am following your testing correctly, have you held the control valve in one direction untill that cylinder has come to the end of its stroke and dead ended? If you don't your pressure reading will only be the pressure needed to move the cylinder, not you system maximum pressure. Hold the control valve all the way for a while after the cylinder dead ends and see what pressure you get. You may hear a chattering or high pitched whine noise which would be the pressure relief valve in the control valve popping off its seat. If the pressure you get is low when testing the cylinder dead ended it could be a worn pump or the pressure relief valve is set low or has a weak spring in it.

 

[Steve Santini]

David when you say against the stops do you mean wide open with the lift handle against the stop?

 

[Steve Santini]

Mike
Thank you for the explanation . On my way out to check it. I will post back shortly.

 

[Steve Santini]

Mike and David
Here is what I got for pressure. 400 psi while lifting the loader at high throttle. Only went to 500, maybe 550 after deadheading the valve open with the Rams fully extended. I do know it doesn't have much power for having new 3 in. rams because I did a little lift test on it the other day.
I am just trying to make sure it isn't something simple before I settle on the pump being at fault.
I did deadhead the first valve in the series when I first tested it (this is the first spool valve probably plumbed in for a rear implement line, but has no lines currently coming off of it) So I opened (pulled) the handle on that valve and pressure jumped right up to 1000?
But the loader Rams fully extended and held open only give me 100 more pounds than when they are lifting.
Steve

 

[Mike in Wisconsin]

What you might want to do is to run your hydraulic lines to the first valve instead of the second valve and see what happens. Each of your valves may have a pressure relief valve in them. Maybe the first valve has a higher pressure setting than the second one. Another possibility would be that the valves spool valves could be worn or scored up and leaking by some pressure. I'd swap the loader hoses to the first valve in line and see what happens. The worst that happens is you'r out a little time and thread seal tape.

 

[Steve Santini]

A good idea Mike. When I accidentally deadheaded the system against the first valve there was a lot of pressure. Doesn't make sense for it not to e the same when deadheading the second valve against the end of the Rams-unless I'm leaking pressure by somewhere. I will try it when the light is back. Thanks for the info .

 

[Highwayman]

Best be careful when fooling around with increasing live pump pressure on an M if it still has the original cam gear you could easily break it by deadheading the live pump at high pressure. I wouldn't get carried away

 

[Mike in Wisconsin]

Steve, do you know what the pressure the M live hydraulic pump originally ran at?