Komatsu PC78us-6-n0 Motor Stalls while moving bucket and swing arm

[Casino Acres]

Hello,

I have recently purchased a 2006 PC78us-6-n0 serial # 10051 with 6900 hours on it.

This machine has sat for almost a year prior to me purchasing it, and filters thus far have been quite dirty.

I brought it home and started digging. Once it warms up, the motor will stall while doing normal functions and not under heavy load. The machine still has the power to pick and lift itself with no issues and no issues tracking the machine around and using the blade. If careful, I can use the machine and back off when it wants to stall. I have only ran the machine for 45 min or so before I noticed the issue and stopped not to cause any further damage. I have cleaned fuel filters, water separators, oil filters, and air filters, and I am waiting for a hydraulic filter. Once the Hydraulic filter comes in, I will change that along with draining the tank and cleaning the suction filter in the tank.

I have been reading past threads and have encountered similar issues, with the answer seeming to be that swash plate sticking is common. Is this something that can be farm fixed, or is it a big expensive bill at a shop? I have also read that the compensator sometimes gets dirty and sticks. Is that something I could fix or am I up sh!ts creek with this machine?

Thank you.

 

[Casino Acres]

I have now noticed that my pto seems to be making oil. It was blowing out of the check valve on the filler tube. We cleaned check valve, drained oil, we had way to much in there. The hydraulic pump had also gotten quite hot.

Would this cause damage to the pump causing it to act up?

Problem hasn’t gone away since draining/changing PTO oil.

 

[JKidder]

We're you ever able find the issue? I have a pc78us-6 with similar symptoms.

 

[Simon C]

We're you ever able find the issue? I have a pc78us-6 with similar symptoms.

Post your serial number and more details and what has been changed versus cleaned. Mention anything else that has been done, how many hours.
Simon C

 

[John C.]

Describe the symptoms that you have please.

 

[JKidder]

Thanks for the quick responses. Machine is a PC78US-6 serial 5565 just over 12k hours. Motor starts up great, machine operates amazing until you use a function with substantial flow. (Rapid boom down, tracking, and multi function). It will load the engine, seems like a pressure relief sticking, and any function will stall it. No hydraulic input and engine will maintain RPM. A few on/off cycles later, machine will operate as intended, until a higher flow function. When machine is running well it does great with high pressure situations(pulling a stump).

 

[John C.]

You have an intermittent problem then. What kind of monitor panel do you have? I seem to recall those have a different monitor panel. Do you know how to pull service codes?

 

[JKidder]

This is the monitor. I do not know how to pull codes on this one.

 

[John C.]

Here is the description from the book. Unfortunately I don't have a video showing how it it done.

Function of displaying "service code"
All trouble information items of the controller are sent to the monitor panel. All of the information items which must display "user codes" and those which do not need display "user codes" are saved as "service codes"in the monitor panel.
If the following operation is executed, the service code is displayed on the display of the monitor panel and the letter "E" to indicate that the trouble is happening currently and the lapse time (service meter reading) are displayed on the service meter unit.

1) Method of displaying and deleting service code
i) The service code is displayed by the following procedure:

(1) Push and hold the "Buzzer cancel switch (8)" and "Working mode selector switch (7)" for 2.5 seconds.
(2) Push the "Buzzer cancel switch (8)" and "Mode selector switch (UP)
(3)" [or Mode selector switch (DOWN)
(4)] and set "01" tothe 2nd and 3rd columns from the left on service meter unit (2).
(3) Push the "Set switch (5)". Since the switches "3, 4, and 5" are not indicated on the panel of model
US, operate the same parts as the panel of model UU.
Example 1)"01" is displayed on service meter unit (2).
Example 2)"E213" happened 6 hours ago. a If "E213" is still happening, the letter "E" is displayed in the 2nd column of service meter unit (2). If "E213" has been repaired, "E" is not displayed.
a The lapse time is displayed in the 3 columns from the right of service meter unit (2).

DISPLAY AND SPECIAL FUNCTIONS OF MONITOR PANEL
(1) Display
(2) Service meter unit
(3) Mode selector switch (UP)
(4) Mode selector switch (DOWN)
(5) Set switch
(6) Travel speed switch
(7) Working mode selector switch
(8) Buzzer cancel switch

 

[John C.]

Here is a list of the possible codes.

2) Service codes list
Error Code Abnormal System User Code
E101 Error history data are abnormal —
E108 Engine coolant temperature is 105°C —
E112 Short circuit in forward system of wiper motor drive —
E113 Short circuit in reverse system of wiper motor drive —
E114 Short circuit in windshield washer drive system —
E115 Wiper does not start wiping in 10 seconds —
E116 Wiper is not retracted in 10 seconds —
E203 Short circuit or grounding fault in swing holding brake solenoid system E03
E206 Short circuit or grounding fault in 2nd travel speed selection solenoid system —
E213 Disconnection in swing holding brake solenoid system —
E216 Disconnection in 2nd travel speed selection solenoid system —
E224 Defective pump pressure sensor system —
E227 Short circuit or grounding fault in engine speed sensor system —
E232 Short circuit or grounding fault in TVC-EPC Solenoid system E02
E233 Disconnection in TVC-EPC Solenoid system E02
E258 Grounding fault on power source side of all angle sensors —
E304 (*3) Short circuit or grounding fault in engine stop solenoid relay system —
E306 (*4) Defective governor feedback potentiometer —
E308 (*4) Defective fuel control dial system E05
E314 (*3) Disconnection in engine stop solenoid relay system —
E321 (*2) Grounding fault in governor control motor drive relay system E05
E323 Grounding fault in governor control accelerator relays system E05
E325 Grounding fault in governor control decelerator relays system E05
E328 Abnormality in governor control motor stal E05
E401 (*1) Disconnection on boom angle sensor (-) side E40
E402 (*1) Grounding fault or disconnection on boom angle sensor signal side or disconnection on (+) side E40
E403 (*1) Defective correction of boom angle sensor —
E404 (*1) Disconnection on arm angle sensor (-) side E40
E405 (*1) Grounding fault or disconnection on arm angle sensor signal side or disconnection on (+) side E40
E406 (*1) Defective correction of arm angle sensor —
E407 (*1) Disconnection on offset left angle sensor (-) side E40
E408 (*1) Grounding fault or disconnection on offset left angle sensor signal side or disconnection on (+) side E40
E411 (*1) Defective correction of offset left angle sensor —
E421 (*1) Short circuit or grounding fault in boom raise EPC system E41
E422 (*1) Disconnection in boom raise EPC system E4
E423 (*1) Short circuit or grounding fault in arm-in EPC system E41
E424 (*1) Disconnection in arm-in EPC system E41
E425 (*1) Short circuit or grounding fault in offset left EPC system E41
E426 (*1) Disconnection in offset left EPC system E41
E431 (*1) Short circuit or grounding fault in PPC basic pressure lock solenoid system E41
E435 Emergency stop —
E441 (*1) Defective correction of interference prevention (Front) —
E442 (*1) Defective correction of interference prevention (Side) —
E443 (*1) Defective correction of depth display —
E501 Machine model not set —
E502 Defective machine model selection signal

*1. PC78UU only
*2. Serial No.: PC78US: 4001 – 5500, PC78UU: 22832 – 23500
*3. Serial No.: PC78US: 5501 and up, PC78UU: 23501 and up
*4. Serial No.: PC78US: 6501 and up