slew brake problem

[mart1602]

got a bit of a strange one going on with the pc 138,everything was working fine,put tree shear on and pressed braker pedal but hadnt opened the valves on the ends of the hammer lines.so opened them up and off i went but now my slew brake wont hold and the machine turns about 20 degrees and the brake comes on with a bang, i dont know if the 2 things are connected or not but my track brakes have had a small delay before they come on for a while ,i have flushed the motors out with diesel and changed the oil but no improvement.would love to hear your thoughts please,martyn

 

[Mick-the-fitter]

Both track motors and slew motor are pilot operated, I would say it’s probable that there is a PRV issue on the pilot pressure side!

 

[mart1602]

thanks mick,what would the problem be?prv sticking ?

 

[Mick-the-fitter]

I don’t seem to have a hydraulic diagram for this machine but I would be looking at pilot pressure side of things, the brakes normally need pilot oil to release them, so they could be getting oil all the time and slow to release pressure! Or if the motors have cross line reliefs then they could be stuck ( I wouldn’t have thought both track motors would stick at the same time) if you have a hydraulic diagram, attach it, I can have a look.

 

[Mick-the-fitter]

Does your machine have a quick hitch added? And if so does it work? Correctly?

 

[mart1602]

yes got quick hitch and it works fine ,i dont have a diagram im afraid.thanks

 

[Mick-the-fitter]

I found a hydraulic drawing for the slew motor, it shows a separate pilot line for the brake, depending what model you have, so your problem could be low pilot pressure, or the brake pack it’s self has become ridged and sticks.

 

[mart1602]

thank you mick ,had the slew motor out a couple of weeks ago to change the shaft seal,was ok before and after will be back at the machine tommorow see whats happening

 

[mart1602]

quick update on this,been doing some testing valve is ok and so is check valve on top of the slew motor.
the machine seems to be slow to let the pilot pressure off so allowing the cab to rotate a bit before the brake finally comes on.
does anyone have an idea of what is going on?.thanks

 

[Shovelhands]

Check the hose on slew brake, possibly it’s collapsed inside and creating a blockage. Or there could be some other obstruction in the pipes, fittings or valves.

 

[Left hooker]

Pilot hydraulic filter blocked?

 

[Mick-the-fitter]

Change the brake valves around, it has two, see if it does it on the other slew, or is it doing it in both directions at the moment?

 

[V8Druid]

Pilot hydraulic filter blocked?

should be in the return to tank side so could account for slow pressure release/dump

 

[mart1602]

no pilot line filter acording to komatsu so will have to just go through it one step at a time,thanks for all the sugestions saves stripping it down completely

 

[Left hooker]

no pilot line filter acording to komatsu so will have to just go through it one step at a time,thanks for all the sugestions saves stripping it down completely

For that size machine I'm surprised it's not got one all my minis have one all be it a tiny little thing and my 18t has a large spin on canister filter

 

[mart1602]

Change the brake valves around, it has two, see if it does it on the other slew, or is it doing it in both directions at the moment?

doing it in both directions

 

[Mick-the-fitter]

Does your 138 have a tap and return line filter on the x1 circuit?

 

[mart1602]

its got a hammer line return filter and the main return in the tank ,no tap on it that i have seen anywhere

 

[Mick-the-fitter]

So hammer line can work both ways or just one way, I would remove hammer line filter and check hose and tank for filter debris.

 

[mart1602]

well finally got it sorted,pulled motor checked it over and put back still the same.
checked the spool over ,swapped lines from different spool,still the same.
pulled motor again and took it away to be tested and checked,got a call back nothing wrong with it apart from a small scratch on a poppit valve which wasnt enough to cause problem so just lapped back in.
couldnt get the idea out of my head that it wasnt letting the oil pressure out fast enough so before putting motor back in took the case drain pipe off the tank and blew through it and seemed as if something popped out ,there seemed like a restriction .put it all back together ,fresh hyd oil and bingo it is perfect infact better than its ever been .
cant put it down to one thing or the other but a result all the same and a very happy owner.
thanks to everyone for the input