41b Hydraulic issues

   / 41b Hydraulic issues #21  
Well welcome to my world, full of many unknowns....

Best thing is to be patient and not break anything more than what you have...having the exCat guy can be your best bet yet...

as far as the hydraulic valve and every component on that machine is serviceable....a hydraulic schematic from Cat may help the guy with you ,(assuming he can read it) the unloader valve could be a possibility, without proper guages on the machine you won't know if it works OK when something goes back on .....be carefull taking things apart, they're not impossible, maybe difficult for you but not impossible....that's where the manual will allow you to understand how they are put together.....

The odds are that it is going to be something really stupid when you find it.....KEEP DIGGING>>>>>;)
 
   / 41b Hydraulic issues #22  
Also, hydraulic valves and components should be completely removed from the machine to dissect, one part missing or put back in wrong will add to your problems(very common mistakes), that way a nice clean bench will show extra stuff upon reassembly....:eek:
 
   / 41b Hydraulic issues
  • Thread Starter
#23  
Ive cooled down a bit on the matter.... Im thinking about taking the valve assembly somewhere and just paying to have it rebuilt. Can this be done with out the machine present, or will they have to make adjustments to it on the machine after a complete rebuild? Also, any idea what a complete rebuild would cost to pay someone else to do?
 
   / 41b Hydraulic issues #24  
Can you add pics of valve?
 
   / 41b Hydraulic issues #25  
1st of all put your spanners away, and dont touch the machine anymore, until you know what your playing with. Im sorry to say, but you are going to have to buy yourself a manual ( if you want to do this yourself ) and a pressure guage ( 5000 or 6000 PSI guage ).
If the CAT mechanic comes out to your machine, he is going to have that manaul and read it twenty times over, so that he fully understands on how it works. So you might as well do it yourself !


-The steering works great with no problem
-The outriggers go down and up with no problem, but once they hit the ground wont lift the weight of the machine
-The front arm will come down, but has to be worked ALOT to get up
-The front buket will not tilt at all (all the way down at the moment
-the back swing seems to work fine
-the back arm works on one cylinder but not the other
-the back bucket seems to move ok.

Ok the steering should be its own seperate hydraulic system ( safety ), so that seems to be ok.

The rest the hydraulic problems are part of the same hydraulic system.
From reading your problems and what you have done, to me your pump is OK, it is just the pump management side of it.

2nd pic. This valve has a few different names depending on what machine they are. Pressure Compensator valve, DR/FR valve, plus many others, however they are all the same. They are all plumbed up differently depending on how the manufacturer wants his Pump management system to work.

The rear valve of this pic, is what sets your maximum system pressure, about 3000PSI.
The front valve is your minimum pressure, which could be set around 300 PSI.
Now the pipe going into the front of the valves is hyd pressure from the system. Now depending on how much pressure there is, will determine your system pressure.
Eg. If that small hydraulic line has 1500PSI in it, then add 300 PSI (minimum pressure set with spring pressure ), then the system pressure will be 1800PSI .
Therefore they system pressure can be set anywhere between 300PSI and 3000 PSI.

1st Pic: So what I have just said about the 1st pic, then I will take a guess and say its a regulator or a flow restrictor. Thinking more a regulator.

Ok why differnent pressure's? Im thinking it could be for starting up.
The pump has spring in it so that the pump is in the fully swashed position ( Swash plate is at full angle therefore pistons will be moving full stroke- ie Full flow ).
So poor old starter motor on the engine when cranking the engine over also is turning the pump over when its at full stroke trying to get the system to 3000PSI before the swashing back to a no flow position.
Therefore starting speed is going to be very slow and will eventually burn out motors.

So if the pressure is very low on start up ( 300 PSI ), the pressure will be met very quickly, and the the pump will swash back to a NO flow position, and the starter motor will be able to turn the engine over a lot quicker !

Now when you go to operate your hydraulic system, you then provide 300 PSI on top of the set low pressure (300PSI spring pressure ) therefore the system pressure will be 600 PSI, then 600 PSI on top of 300 PSI you will get 900 PSI now this will keep going until it gets to the maximum set working pressure of 3000PSI ( very quickly ! ).

Ok I hope your are not to confused as it quite hard to explain.
I have seen these same valves plumbed all very differently from Earthmoving machines, ROV's, test benches etc. And what I just explained earlier could be wrong. This is why you need to manual, so you can read what CAT have done in there Pump management system.

I hope you picked this up for a good price, because personally I think these valves just need a little adjusting, and you have one fantastic machine.
So hang in there mate, but the bare minimum you need here is the manual and a pressure guage.
The CAT manuals are pretty good. They will tell you how the system works and how to adjust them so that you get the correct pressure.

All the best
Duff :thumbsup:
 
   / 41b Hydraulic issues #26  
Agree with you Duff!!

I prepped a few pic's for clarification.....but decided take a step back and "watch", when I saw he took the valve apart...which was stupid, because now we can even get a gauge on.....LOL....

This is a perfect example of what happens when you think you know more than you do.......

There is NO way around this with out more information. A MANUAL!!! Period!!


cat_pump_compensator_text.jpg


cat_pump_type_plate_100_3259_text.jpg
 
   / 41b Hydraulic issues
  • Thread Starter
#27  
Agree with you Duff!!

I prepped a few pic's for clarification.....but decided take a step back and "watch", when I saw he took the valve apart...which was stupid, because now we can even get a gauge on.....LOL....

This is a perfect example of what happens when you think you know more than you do.......

There is NO way around this with out more information. A MANUAL!!! Period!!


cat_pump_compensator_text.jpg


cat_pump_type_plate_100_3259_text.jpg

Aside from the problem that is keeping the pump from getting to full pressure, the valve for the front bucket was definitely bypassing and letting the bucket leak down, so I know that needed worked on. The cat mechanic was about 99% sure that my problems were in the front valve assembly, so I took the assembly out.... Looking back on it I dont know if it was the right choice, but they are out, so they are getting worked on now.
 
   / 41b Hydraulic issues #29  
Aside from the problem that is keeping the pump from getting to full pressure, the valve for the front bucket was definitely bypassing and letting the bucket leak down, so I know that needed worked on. The cat mechanic was about 99% sure that my problems were in the front valve assembly, so I took the assembly out.... Looking back on it I dont know if it was the right choice, but they are out, so they are getting worked on now.

bucket_valve_text.jpg
 
   / 41b Hydraulic issues
  • Thread Starter
#30  

I tried taking those bottom caps off and one of them looked manageable, but the other had a bunch of ball bearings that tried to fall out and didnt look like it would come apart. So, you are saying that there are no O-rings on the spool, what seals it?

I was told that I needed to take the small hex head screws out (on the top and the two on the face) that are shown in this pic and check for debris in them. Was this advice corrrect? What I am starting to think is that maybe you guys think I shouldnt mess with the valves and the problem can be there..... Im at the point where im not going to mess with the valves for myself, but take them somewhere and have them re-built and just bolt them back on the machine, but I would hate to do that if its not the problem.
100_1663.jpg
 

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