Komatsu pc200-5 slow operation after hammer hooked up.

[davecampbell]

You have a piston stuck in the TVC valve. Get a hold of a parts breakdown so you can see how it comes apart. You can pull off the end plates to get access to the piston. I believe there is a spring on the opposite side of where the solenoid plugs into and you have to push the piston out. Make sure you note the orientation of the piston when it comes out. I can't recall if it has to be in the right direction or not, but I seem to remember that it does.

looks like that is a pretty easy job with the exception of draining hydraulic tank. Is it possible to improvise some plugs to put into the side of the control block while I disassemble and clean the tvc valve? If I'm reading the schematic correctly, looks like 4 passageways to plug.

 

[davecampbell]

Looking at schematic, it does not look like the tvc valve is between charge pump and the control block that I have my guage tapped into. I got 500 psi coming out of charge pump so I'm losing a bunch of pressure between those 2 points. Looks to me like there are some screens in the control blocks, I'm thinking when I tear into it, I'm going to need to tear apart both control blocks too.View attachment 208199a

 

[John C.]

The TVC valve is the first valve in the pump control circuits to get pilot oil. Pilot oil then is routed to the other valves in line. You aren't loosing flow, it's just not being opened up to flow down the line because that regular is stuck. If you tear off both blocks on each pump, which I think you need to do, you will have to drain the tank. There is a lever that goes down into the servo piston area which is open to the hydraulic tank. There are button screens in the blocks that will need to be replaced.

 

[davecampbell]

I got the blocks of and started with the tvc. There is a plunger that sticks and does not slide freely.

 

[John C.]

I used to blow the block out with ether and then air. I'd chuck the spool in a lathe or even a drill press if the chuck was big enough and polish it with crocus cloth. Even a Scotch Brite pad with work. Plenty of oil on things when you put them all back together.
Nice Work!

 

[davecampbell]

I'll buy some crocus cloth tomorrow and get after it with that. I also found a pressure tap that I did not recognize as one. I'm thinking it's on the bottom of the servo adjuster. What pressure would that be reading?

 

[John C.]

If you watched the Dash 5 tune up video, that is the fitting on each pump you tie into to read the actual oil pressure on the servo piston. The pressure reading will be situational. When the Jet Sensors are at 300 PSI difference on their end, you set the NC pressure at 70PSI coming out of that fitting. When setting the cut out, you put a function like boom or stick over relief with the mode in H0 and H and the main reliefs set at 4,500 PSI, the pressure there should be at 70 PSI. After those are set in the right situations you can set the TVC for how much RPM you want to pull out of the engine. I'll add or subtract TVC pressure to get about 150 RPM drop on the engine. After all that I go back and check and reset the NC and Co as needed.

 

[davecampbell]

I was very careful to not change any of the settings when I disassembled and cleaned everything. It has better pilot pressure now, but when I go full lever on tracking it pulses the speed of the tracks. If I push the levers a little less I can track smoothly.

 

[John C.]

Do all the functions on the machine work now except the surging part? You are going to need the gauges and then set up the hydraulics like I did on the PC400 in the video.

 

[davecampbell]

Do all the functions on the machine work now except the surging part? You are going to need the gauges and then set up the hydraulics like I did on the PC400 in the video.

Yes, and I still have my guage hooked to the back of the front control block. It pulses with the tracks. I haven't actually tried using it, but everything else cycles good. I need to go buy 2 more hoses and one more guage so I can do what is in the video.

 

[davecampbell]

The surging seems to have gotten better. Could it have been air in the system? Trash that I missed?

 

[John C.]

There are a whole bunch of little passages and small spools and lands in those valves that anything is possible. If it get better over time, I think that's a great situation.

 

[davecampbell]

I put in 9.3 hrs with it yesterday and track surging is completely gone now.

 

[John C.]

That is super news! Nice work. Is the machine performance what it was before?

 

[davecampbell]

I've used this machine for several jobs with it working well. Yesterday I blew a hose on the hydraulic thumb. I had an old hose that I used as a temporary fix and within 5 min it displayed the symptoms of slowing down. I could let it set a few minutes and it would work good for a couple min. I thought my screens had plugged up in the pump control blocks again, so I drained the hydraulic fluid and pulled them off. I boiled them and blew ether through them. Reinstalled and still has same symptoms. I plan to hook a guage up to pilot pressure again to verify, but feels like it is losing pilot pressure to me.

 

[keif]

Could it be air in the system, some machines you have to pressurize the hydraulic system after cracking it open....

 

[John C.]

So you installed an old hose and now you have problems again?

 

[John Sarappa]

Where exactly are these screens that you cleaned? Thanks

 

[davecampbell]

So you installed an old hose and now you have problems again?

Yes the first time it did it was the first and only time I used the hammer. This time I blew a hose on the same circuit, but it was being used for the thumb.

Where exactly are these screens that you cleaned? Thanks

the screens are located between the control blocks mounted to the hydraulic pump.

 

[John Sarappa]

So you have to take the control block off to get to the screens?