PC78 Komatsu problem

NWH · Aug 22, 2019

I have a 2008 Komatsu PC78 u s-6 excavator that started giving me a problem It will occasionally lug the engine
when using the swing function or bucket curl function. Today it stalled the engine once. Any help or suggestions would be greatly appreciated. The cost of having our Komatsu service guy out is astronomical !

uffex · Aug 23, 2019

Good day
Suggest you begin with the engine - fuel - air - turbo - take a good note of exhaust colour when loaded. Any other machine working alongside have or had similar issues.
Kind regards
Uffex

NWH · Aug 23, 2019

The problem only occurs with certain functions of the machine. No problems with other machines using the same fuel source. I will double check fuel cap vent , fuel filter , air filter today. Thanks for the reply

SWR · May 8, 2021

NWH said:
I have a 2008 Komatsu PC78 u s-6 excavator that started giving me a problem It will occasionally lug the engine
when using the swing function or bucket curl function. Today it stalled the engine once. Any help or suggestions would be greatly appreciated. The cost of having our Komatsu service guy out is astronomical !

Did you figure out the problem?

NWH · May 8, 2021

Not yet. I have a man looking at it now. He is so busy with farm equipment that he has been slow to get to it. The Komatsu dealer is completely useless.

John C. · May 9, 2021

How many hours are on these machines. When was the last time the hydraulic oil filter was changed, the oil changed and the suction strainer removed for inspection and cleaning. A Dash 6 is an old machine now. Grit collects in the control valves of the pump and control valves. I'm seeing plenty of age and maintenance related problems now days. Most people want a fix by turn one of two screws and changing an electrical component. When they find out a pump or engine has to come out for teardown, everything just stops and the machine gets pulled out of the way or left where it died. We are at the twenty five year mark for the first EPA regulations and going forward I expect to see plenty of dead iron covered in berry briars with trees growing through the it.

NWH · May 10, 2021

The machine I own is 2008 model with 3000 hours. The filters have been changed every 1000 hours. I did this because there is only one hydraulic filter on the machine . It also has had a complete hydraulic oil change and tank flush. The local dealer tells me I need a new pump . I had an oil analysis done which showed normal .
The dealer also told 2 other fiends of mine the same thing about their machines even though they did no testing on them .As a result I have no confidence in them other than to supply parts at exorbitant prices .

John C. · May 10, 2021

Ya, I think I agree with you in not trusting the dealer at this point. The reason I asked the questions above is that number of hours is pretty light for being thirteen years old and I think the models were into the Dash 7 group by that time. Doesn't matter at this point.

Do you know how to get into the diagnostic package in the monitor panel? Have you had any alarms and fault codes show up?

NWH · May 11, 2021

I have had no alarms and was told by the Komatsu tech that there was no way to pull up trouble codes on these machines. This was contrary to what i
had been told about them He also told me that he had checked pressures on the pump. I do not beleive this to be true as he wasw only at the location for about 20 minutes and used no gauges of any sort. The pump on the machine is very strong and responsive until it starts choking the engine down which is very intermitant

John C. · May 11, 2021

Can you post a photo of the monitor panel in your machine?

heymccall · May 11, 2021

If the hydraulics are pulling the motor down, the exhaust will go black.
If the exhaust doesn't go black, it's a fuel supply issue.
I'd start by examining the supply side, including the tank outlet, looking for a screen. My bigger, older, komatsus have a screen in the tank outlet. If no screen is there, examine the water separator, including full removal and examining the inlet path for partial blockage. I dont have enough fingers and toes to count how many times I've had fuel restrictions before the lift pump on my smaller machines, Komatsu, Yanmar, Takeuchi, Kubota, Kobelco. The Kobelco had cellophane in the banjo fitting screen at the water separator @ 240 hours. The Takeuchi CTLs would collect debris in the tank outlet elbow. And the Kubota CTLs would plug the inlet elbow at the water separator. And my Cat SSL would plug the inlet path at the separator head/ priming pump.

NWH · May 12, 2021

It will be next week before I can get to the machine. I have checked the fuel system thoroughly, even replacing the lift pimp. It`s the kind of problem where you do something and think it is fixed only to have it pop up again ! There was a comment about the hours on the machine. The hours are low because I have 5 pieces of equipment and run them all pretty much myself. Also I turned 71 in February and have slowed down just a tick.

Jed Abair · Jun 10, 2021

I have the same machine which is a 2006 with 3,500 hours.It also has the same issue.I was wondering if you have any luck finding out the problem?

NWH · Jun 10, 2021

So far I have not. I have two friends with the same machine and having the same problem. Our dealer H&E Equipment tells us the pumps go bad at approximately
3000 hours. I had a oil analysis done and it showed normal. Because of this I do not think the pump is bad. It is hard to believe that Komatsu would allow a product
to be on the market with that poor of a life span !

John C. · Jun 10, 2021

When did H&E become a Komatsu dealer? No new machine dealer would ever say something like that. First off it isn’t true to my knowledge and second, it shows they don’t know how to fix them.

heymccall · Jun 10, 2021

It takes 5k hours for the stroke piston to start sticking in the main hydraulic pump in 544J and WA270-7 machines, but, not all of them.
And 5k hours before the slipper shoes self destruct in one pump on a 345CL.

Other than that, I've never had issues like you're describing, especially at that low of an hour meter reading.

Again, when the motor bogs, is the exhaust darker than normal?

NWH · Jun 11, 2021

The windows are tinted so it`s hard to tell. The H&E tech came and looked at my machine and a friends at the same time and told us the pumps went bad at 3000 hours. He also charged for testing pressures , which I don`t think he could have done because he was only there for 30 to 45 minutes and used no gauges. This was for two machines . Both machines were at the same location in order to try and save on the service call charge. I have had CAT an CASE machines in the past and have never had problems such as I am having with this machine and service.

Jed Abair · Jun 23, 2021

The exhaust is darker than normal on my machine when the issue occurs.

biggerhammer · Jun 25, 2021

I have replaced hydraulic pumps on 2 of these machines due to the same issue. Local pump shop advised its a bad design with it not backing off properly at full demand. New pump-no issues

A. Williamson · Jun 25, 2021

biggerhammer said:
I have replaced hydraulic pumps on 2 of these machines due to the same issue. Local pump shop advised its a bad design with it not backing off properly at full demand. New pump-no issues

so would adjusting the pressure compensator to a lower max psi or the swash plate endstop adjustment give the pumps more life?

PC78 Komatsu problem

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