Komatsu PC220-7 issue

[rockfall]

Hi,

What I know is when single travel lever is operated forward or reverse only one oil pressure switch/sensor located on the merge-divide valve of the control valve designated for that particular side of pump should display pressure on the screen. Why is that when I operate the right travel lever the screen displays pressure on both 011 & 012, but when the left travel lever is operated only 011 entry on the screen displays pressure approximately 375 bars while the 012 entry shows only 40 bars, which I guess is normal.

Does this mean that both pumps work on the right track? Is this something to worry about?

Thanks

 

[John C.]

Does the machine travel straight? Do both tracks have power? Does the travel shift speeds up and down automatically?

 

[rockfall]

Thanks John. The machine travels straight. But the left track is a little bit stronger than the left. Dont know how to check the travel speed shift

 

[John C.]

Put the machine in high range and travel it up a hill. As the hill gets steeper the machine travel should shift from high to mid speed to low speed if the hill is steep enough.

 

[rockfall]

Tried it. The tracks stops moving. It has only two speeds. Hi and low

 

[John C.]

So it must be stuck in high range. Have you checked for fault codes?

 

[rockfall]

Yeah. There are no fault codes. Plus sometimes I need to push the hi or low button several times to shift speed. I have checked each an every spool in the solenoid valve. None of them are stuck. But for some reason I sometimes suspect the solenoid valve for all issues with the machine like issues with travel speed, arm in is slow, I replaced all inner parts of the right travel motor which was weak now the left track is acting weak just like the right track before replacing parts.
The pistons in solenoid valve had issues like getting stuck before so I had to polish it manually with a fine sand paper.

 

[John C.]

Sound to me like you have a little bit of a dirty hydraulic system. How long has it been since you changed hydraulic oil and filters? How many hours do you have on this machine? Possible issues that affect travel might be high hours on the travel motors themselves (both may have needed to be rebuilt), leaking swivel joints, unbalanced pump outputs, differences in spool travel between the two track functions and dirt under the travel pedals. This are in no particular order. I like to work from the least expensive fix to the more expensive items. Dirt under the travel pedals being the easiest to check and work from there.

 

[rockfall]

Hi John,

Tried all that you pointed at but now used. I think there is something in the control valve or the solenoid valve itself because two functions are slow. The arm digging and the left track. When track sticks are operated opposite to each other together for steering the tracks become so weak and turn slow. Im thinking of buying a brand new solenoid valve because there were some spools getting stuck from time to time and I had it polished manually.

 

[John C.]

How many hours do you have on this machine? Has the hydraulic system had any component failures recently?

 

[rockfall]

No failures recently. The machine has 23000 hours on it.

 

[John C.]

That's a whole lot of hours! I am agreeing with you on stuff being in the system. But it is likely considering the age of the machine and time on the components.

Lets go back to your original question about the merge divider valve. Its purpose is to allow the machine to travel straight when other functions are operated at the same time. So if you are traveling and pick up the boom the merge divider opens and combines the flow from both pumps so that you keep traveling straight. When only traveling, the valve is closed and the pumps are isolated to each track. What you can check is pressure on the monitor when the machine is traveling straight. The readings should be about the same. So if you operate the right travel lever and nothing else you should read high pressure only on 12 in the monitor and not both 11 and 12.

Your comments on the travel power and range changes brings up another issue. Since you state you don't have any fault codes and you have to shift the button several time in order to change the travel speeds, I'm thinking you have some problem wiring. I have seen plenty of wiring issues on those machines as the insulation deteriorates when soaked with hydraulic oil for long periods of time. Sun shine will also degrade the insulation and turn it hard and prone to cracking. I would probably check the merge divider and the solenoids for the travel with an ohm meter first and then start tracing the wiring back towards the cab looking for chafing and wet spots. Bad insulation will allow cross talk in the harnesses making for some real head scratching when odd things start to happen.

 

[rockfall]

Checked the readings on 11 and 12. The numbers are changing so fast between 150 and 180 on both so cant figure out the exact reading. Plus John I was reading the manual they talking something about regeneration valve for boom and arm. Where is this located?

 

[rockfall]

Also John can you explain what is the function of this regeneration valve and how can I know if its working good or not. Keeping in mind my arm in function is also slow and it stops like 2 to 3 secs midway.

How can I check LS pressure to know whether the pump is stroking up or not?

 

[John C.]

The regen valve for the stick is in the engine side of the main control valve on the Dash 6 machines. I don't know if they had changed that in the Dash 7 line. The purpose is to help improve speed and reduce the possibility of cavitation on the piston sides of the cylinders. Some of the oil from the rod sides of the cylinders are routed to the piston sides as make up oil. I didn't know they put one on the boom circuit sides as they are always working against gravity. It's in the stick circuit because an extended stick with a loaded bucket can fall faster than the pump might be able to supply oil. Instead of putting some kind of restriction in the rod return oil circuit to prevent a negative pressure in the piston side, Komatsu has put a poppet type valve in the return which routes the oil to the piston side. When the stick reaches a vertical position and there is now positive pressure on the piston side the regen valve and it will close.
Komatsu used a differential pressure gauge to read the LS pressure. Basically you read the pressure coming out of the pump and the LS pressure from the valve at the same time and there should be about a 300 PSI difference. I don't recall right now where to plug in to get the LS pressure so I'll have to find and review some of my notes from years ago.

 

[rockfall]

Got it. John can you search for me where it is exactly located in dash 7 because I have searched the back side of the control valve a lot for this valve but couldnt find it. Is it next to the back pressure valve somewhere?

This is how it looks like from the back.

 

[John C.]

The regeneration valve is a poppet and spring that is held in by a plate that was accessed from the engine side of the valve. On the Dash 6 machines that I worked on the main body of the valve was in a horizontal position with the spools pointing straight up and down. In you photo the valve spool are horizontal. What I would do is find the spool that controls the arm circuit and look for a plate or plug that might be holding in the check valve.

 

[rockfall]

Hi,
There are some safety-suction valves on the control for each actuator. How do I check or calibrate if needed. There is a big valve named as 2-stage safety-suction valve for the service valve on top. How would I know its calibration is OK hence no need to play with it.

 

[rockfall]

I have seen komatsu pc200 dash 7 and 8 overheating. I have done a lot like roding rads, cleaning hydraulic oil cooler, installing thick sponge everywhere so the air coming from the fan doesnt escape but no use. Is there something else I could do for the overheating issues. In addition, is it mandatory to have oil in the bell housing because I have checked the housing its dry.

 

[John C.]

The biggest issue with heating is dust and debris getting in between the hydraulic oil cooler and the radiator. Komatsu used to have a plate in the bottom of the house just under the radiator/cooler but did away with it on the Dash 6 line. I built an air lance which is a half inch piece of pipe with a butterfly valve on one end and a drilled pipe plug on the other end. It's about an eight inch hole for the air to blow through which seems to bust up the dust clogs pretty well.
Another reason for over heating is people who turn the screws on the pump trying to make the machine work faster. Run a cycle time test on the boom up function. Stretch the bucket and stick out and sit it on the ground. Max out the engine speed and make sure panel is in the fastest mode. It should take about four seconds to go from the ground to topping out the boom. If it is faster than that, you might have an issue.
The damper case is suppose to have about a pint to a quart of oil in the Dash 6 and older machines. An operation and maintenance manual would tell you what they require in those machines.