Sany SY35U main control valve

[melia]

I bought a 2014 Sany SY35U and when it gets warmed up the hydraulics start slowing down and in about 15 to 20 min the hydraulics stop working. i had someone
look at it and they are saying its the main control valve. i have only found one online and it's about 5K. does this sound like the main control valve? can that valve be rebuilt?
does anyone know where to get this valve and is there any info on taking that valve out.

thanks.

 

[LouNY]

No idea on a Sany but most hydraulic systems when that happens it's a weak pump or flow getting past a valve as the fluid warms up.
Do you have a service manual for it?
That may have some test procedures and locations.

 

[melia]

i do not have a manual. i have been trying to find one.

 

[oldnslo]

Lou is correct. You need to perform more tests before determining what is at fault.
A simple test is check what component gets hot quickest since loss of flow creates heat. May not be exact but can point you in the general direction of failing component.

 

[Harry in Ky]

No idea on a Sany but most hydraulic systems when that happens it's a weak pump or flow getting past a valve as the fluid warms up.
Do you have a service manual for it?
That may have some test procedures and locations.
View attachment 769445

Weak pump? That's what I thought at first too, until I saw this.

SY35U - SANY America

Everyone’s favorite mini, the SY35U packs powerful lift and dig performance in a compact design. SANY’s outfitted this excavator with all the standard features youRead More

www.sanyamerica.com

Having never heard of the machine I was curious. I don't know if his machine (2014) has all these features, but when I got to the part about "Independently developed intelligent control system" and "matching pump output to available engine power" then I have to wonder. If you put a computer, a gaggle of sensors, and a mile or so of wires in charge of all that, then what can go wrong with THAT system?

 

[oldnslo]

Harry
That “intelligent control” does add another level of potential problems like Some sensor getting weak when warm

 

[Seven Gables]

I bought a 2014 Sany SY35U and when it gets warmed up the hydraulics start slowing down and in about 15 to 20 min the hydraulics stop working. i had someone
look at it and they are saying its the main control valve. i have only found one online and it's about 5K. does this sound like the main control valve? can that valve be rebuilt?
does anyone know where to get this valve and is there any info on taking that valve out.

thanks.

Your main control valve or MCV is a whole stack of valves , pretty sure that’s not the fault. How many hours on the machine? Have the filters and fluids been been maintained properly? I think the best thing to do is find someone who knows what they’re doing run some hydraulic pressure checks . With the symptoms you’ve described i would be inclined to test your servo system pressure first, if that is low you won’t have enough pressure to move any of your MCV spools. You should have around 450-500psi of servo pressure. Be a good idea to put a new servo filter in , you can very easily do this yourself. Possibly it’s plugged up and causing your issue.