Hello, I am new to the forum but I have been an outsider looking in for years and usually can view threads to help with most problems on my machine but recently I've been stumped. Not familiar with hydraulics so any help is great. I picked up a 1991 1845c that was in rough shape. Went over the motor, maintenanced entire machine. Installed a new hydrostatic and boom/curl hydraulic pump. When I started the machine it drove like new lots of power. The problem is the bucket curls fine but it only booms up when the auxiliary foot pedal is fully disengaged (opposite of when spring is closed). But when I do that the curl does not work. It will boom normally but extremely slow and will not stay up. I have checked all the linkages/cage is in right spot. Case dealer tech said replace relief valve. Sound right? The left boom piston was previously repaired (weld) and cause of high pressure (i think) sprung a pinhole leak. I've repaired the leak but still can only boom(lots of power) when I mess with foot pedal. Any help would be greatly appreciated.
Check the springs in the valve are centering the spools otherwise any function after the first wont have any volume left
On the relief valve? Or motor valve? Thanks this is really bothering me. If the relief is stuck is the pressure building too high and blew a pinhole in the weld on the boom cylinder? Thanks Matt
I just noticed a small leak from the seal on the the left boom cylinder. So let's just eliminate everything else and say the issue is solely weak boom operation, would that leak be the cause of the problem? If the curl works fine, does that mean the relief valve (whole block) is working correctly?
I took off the lines and the caps on the motor valve to check the springs. They checked out fine, not broken, plenty of spring. Any other ideas? Thanks, Matt
I would check the max pressure you can obtain. There's probaby a 1/4" pipe plug somewhere in the vicinity where the inlet of the valve is (where the pump would feed in). That would give you weak boom lift and weak bucket lift
I see the plug but don't have my own gauge that goes that high yet. My question is that why does curl work fine but boom does not. Only works if I push auxiliary pedal wrong way...and that blew out my hydraulic pump seals. Would bad relief valve do this? Also could a bad seal on one boom piston cause this? Wouldn't the other side be able to lift the empty bucket?
Well you'll want to know what the pressure is to detemine if that is why you blew the pump and the cylinder apart and at the same time to determine you have a low pressure problem across all functins or one or two to narrow it down. Did you buy the machine like this?
The machine needed new hydrostat pump. I installed that and had new hydraulic pump put on. Machine drives fine and curls fine. No boom though. But if I push the auxiliary pedal opposite of engaged the boom works fine (thought previous owner did this for some reason). The hydraulic pump seals blew because it was idling for a half hour with that pedal pushed the wrong way and was making way too much pressure. So relief valve is shot? I'm pretty clueless with hydraulics and thought maybe I could figure this out but doesn't look that way.
Without the gauge readings its just speculation
Thank you much. I will do this and update Matt