CAT 279C forward and rearward motion slows to a creep

[timmonsg]

Hi all, please be nice as this is my first post on this site. I'm new to operating a CAT 279C with 5k current hours. Regardless which of the two speeds used, my machine slows down tremendously after only moving 10 to 20 yards. Engine RPM remains at the level set. Speed is set to max 10 MPH. I'm running a CID brushcutter that continues to run at operating RPM when this slowdown happens. Once I return the left joystick to the center neutral position and reapply forward or rearward direction, the machine appears to return to the speed desired only for another 10 to 20 yards before the slowdown in groundspeed begins until it comes to a halt/ creep. checked all fluid levels and all are maxed. filters appear newly serviced but could not tell you of the exact date or hour level changed. doesnt take long before the coolant and hyd temp starts to run in the upper one-third range. just spent $2500 on the AC with no good cooling results. speed sensor harnesses were replaced due to being frayed. first 5 to 6 hours of running on the job with these repairs done by the dealership were flawless. i hope i have not confused. Thanks again as im just looking for some hope. Greg (37-year Army Aviator Veteran recently retired)

 

[mark ingeman]

sounds like hydro filter is plugged

 

[timmonsg]

Thanks Mark. I will take a new one to the field.

 

[Mark250]

Can you check to see if the demand fan slows down at the same time as the machine speed slows down ? this will give a rough idea if the charge pressure is ok

sounds like hydro filter is plugged

As well as changing the filter, carefully cut the filter open and remove a section of the filter material. squeeze the oil out in a vice and open the cleats and see if there is any debris between the filter cleats.
let us know what you find

 

[timmonsg]

oddly enough, the dealership agreed to give a courtesy troubleshoot of my pro lem. i will let you guys know how that turns out. Shop Manager did offer that since this machine is an electric over hydraulic pertaining to the left joystick which he fills is the source of the problem i.e. losing connection for some unknown reason. reference the demand fan, is it a slowdown that i need to try and witness? As far as the hydraulic system as a whole, when the slowdown of travel occurs i see no noticeable drop in the speed of the lift cylinders or the curling of the same. If the filter is clogged, shouldnt i see a complete degradation of hydraulic movement of all attachments and cylinders as well? I appreciate you guys willingness help. Thanks Again, Greg

 

[Mark250]

Hi the left hand joystick was known to cause problems have changed out a few under warranty Cat ET is really the only way to check the current going to the pump solonoids and the sigals coming from the joystick
The fan hydraulic circuit runs off the hydrostatic charge pump and gives a quick and dirty check of charge pressure this can and will effect the drive system if incorrect
The work tool pump is a seprate system from drive circuit ( lift ,tilt etc )
Its good to see that your dealer will support you
Let us know how it turns out

 

[hermannea]

Hi all, please be nice as this is my first post on this site. I'm new to operating a CAT 279C with 5k current hours. Regardless which of the two speeds used, my machine slows down tremendously after only moving 10 to 20 yards. Engine RPM remains at the level set. Speed is set to max 10 MPH. I'm running a CID brushcutter that continues to run at operating RPM when this slowdown happens. Once I return the left joystick to the center neutral position and reapply forward or rearward direction, the machine appears to return to the speed desired only for another 10 to 20 yards before the slowdown in groundspeed begins until it comes to a halt/ creep. checked all fluid levels and all are maxed. filters appear newly serviced but could not tell you of the exact date or hour level changed. doesnt take long before the coolant and hyd temp starts to run in the upper one-third range. just spent $2500 on the AC with no good cooling results. speed sensor harnesses were replaced due to being frayed. first 5 to 6 hours of running on the job with these repairs done by the dealership were flawless. i hope i have not confused. Thanks again as im just looking for some hope. Greg (37-year Army Aviator Veteran recently retired)

Hey Timmonsg, did they ever figure out what it was?
My Cat262c is doing the exact same thing...

 

[Nige]

Whether he did or not, as Mark250 pointed out above, Cat ET is pretty much the only way of diagnosing the performance of the LH joystick.

 

[92U 3406]

I've seen wonky drive speed sensors cause similar symptoms. ET will be your friend on this one.

 

[hermannea]

Field Tech was out today again with Cat ET scanner, machine isn't throwing any codes or showing any events... LH joystick showed it was slightly out of calibration. Best guess was that it was LH joystick related...?
Is there anywhere to purchase a used joystick to confirm? Cat price is $660

 

[Nige]

A used joystick may be in no better condition than your present one - just saying .....
Unfortunately there are no repair parts sold by Caterpillar for them.

 

[mikebramel]

Thats not a bad price

 

[Mark250]

hi did the tech calibrate the throttle sensor or has any work been done on the throttle cable and linkage as that also can cause issues and not log a code
Mark

 

[hermannea]

Paid $700 for new joystick, installed this am(10/25/2018). Still having the issue...
Mark250 - Don't know that he calibrated anything on the throttle sensor,(he did say the LH joystick was 'out of calibration") nothing has been done to my knowledge with throttle cable or linkage. When i rev it up and drive it stays throttled up and just slows down.

 

[hermannea]

hi did the tech calibrate the throttle sensor or has any work been done on the throttle cable and linkage as that also can cause issues and not log a code
Mark

Would i hear it throttle down if it had anything to do with the throttle cable or linkage?

 

[Mark250]

Hi, it is not a matter of throttling down. The ECM uses the throttle position sensor as part of the under speed (Anti stalling) strategy. If the sensor is not calibrated it will get conflicting signals and can derate the transmission to the point where it will only crawl along
If the tech had ET connected he should of been monitoring the input signals to the drive solenoids and the under speed parameters in the status groups

 

[JRRod]

Paid $700 for new joystick, installed this am(10/25/2018). Still having the issue...
Mark250 - Don't know that he calibrated anything on the throttle sensor,(he did say the LH joystick was 'out of calibration") nothing has been done to my knowledge with throttle cable or linkage. When i rev it up and drive it stays throttled up and just slows down.

 

[JRRod]

Hey Buddy Did you figure out your problem sounds like my new issue Thank you !

 

[mars2222]

check the speed sensor on the drive units

 

[mars2222]

ckeck the fuel pressure on the Eletric pump
had the same problem with my 297C pump was only making 2 psi and it should be 10 psi