Manitou MLT741 no hydraulics.

[kukiits]

As i have seen question for @ACEngineering , of course if someone could help, please.
I have a MLT741-120 LSU with serialnr 225677.
Problem is that suddenly all hydraulic functions stopped working, measured pressure at test port near SX14 block, max pressure what i get with 3 functions active lift/tilt/telescope is about 80bars.
Got a new LS pump, standby pressure is 19bar.
Put another clock in ls line, basicly it looks like each function gives 20bar in ls line, when you activate 3 and steering till end it will bounce to 110bar. Pump ir working correctly by ls pressure.
Where could be leakage in this sx14 valve ? Got out the ls safety valve, orings are good and valve too, could it be that ls flowregulator valve ?

thank you

 

[ACEngineering]

As i have seen question for @ACEngineering , of course if someone could help, please.
I have a MLT741-120 LSU with serialnr 225677.
Problem is that suddenly all hydraulic functions stopped working, measured pressure at test port near SX14 block, max pressure what i get with 3 functions active lift/tilt/telescope is about 80bars.
Got a new LS pump, standby pressure is 19bar.
Put another clock in ls line, basicly it looks like each function gives 20bar in ls line, when you activate 3 and steering till end it will bounce to 110bar. Pump ir working correctly by ls pressure.
Where could be leakage in this sx14 valve ? Got out the ls safety valve, orings are good and valve too, could it be that ls flowregulator valve ?

thank you

should be getting 270 bar on main functions, 19bar is standby pressure as you say.

you can clean the LS flow regulator valve on the spool block and the filter on the end of it but nothing to really go wrong with that unless its full of crap.

Next to the LS reg valve on the spool block is the main relief valve, take that out and make sure its not stuck open with a bit of broken ram seal or something.

some of these machines have a joystick isolator switch which is a little dump solenoid block next to the pump and dumps the Pilot line pressure to joystick also there is often a inline filter for the pilot circuit located just next to the main hyd filter.

 

[kukiits]

Problem is not only for Pilot pressure operated valves, but there is bassicly no steering, and telescope doesnt work too.
Thats the trick, i cant get to those 270bar. LS flow regulator is like small hole or like a valve, i think maybe its stuck open.

In hydraulic diagram i dont see main relief valve, i just see 270bar ls pressure relief valve.

 

[ACEngineering]

The LS reg valve has a little piston that rattles up and down it. And a metal gauze filter in the end you pull out with pliers.

 

[ACEngineering]

Problem is not only for Pilot pressure operated valves, but there is bassicly no steering, and telescope doesnt work too.
Thats the trick, i cant get to those 270bar. LS flow regulator is like small hole or like a valve, i think maybe its stuck open.

In hydraulic diagram i dont see main relief valve, i just see 270bar ls pressure relief valve.

Have you looked at the splines that drive hyd pump? There common to wear through so you pump might not even be turning.

 

[kukiits]

Have you looked at the splines that drive hyd pump? There common to wear through so you pump might not even be turning.

Good idea, didnt looked at them. But then why with one active function i got 45bar with two 65 with three 85bars, and when three activated and steering till end 100-115bar ?

 

[ACEngineering]

Good idea, didnt looked at them. But then why with one active function i got 45bar with two 65 with three 85bars, and when three activated and steering till end 100-115bar ?

Because it's a manitou

Dont know but 115bar on steering still isnt enough as I think its 160bar.

Sure I read that you fitted a new pump? If so you would have seen the splines.

 

[kukiits]

Because it's a manitou

Dont know but 115bar on steering still isnt enough as I think its 160bar.

Sure I read that you fitted a new pump? If so you would have seen the splines.

Yes its not enough, its my problem.
Yes fitted new pump, but didnt pay attention to splines in angle gearbox.

 

[kukiits]

Problem was ls flow divider, which is next to ls pressure relief valve. It was stuck.