299d2 slow track speed when hot

[hvguy]

machine: 2017 cat 299d2 MDH04684 1980hrs
I maybe chasing my tail here but my machine is slowing down about 30% of track speed when the engine and hyd. Oil gets hot (200 engine, 150 hyd) according to the track motor speed sensors, it'll be 3200 or so normally but slows down to 2650 or so when it's angry.

Normally this doesn't happen because I do pretty small jobs, however on larger jobs that require tracking material 500ft 1 way, it because a pain.

Does anyone know if the ECU is derating the hydraulics to compensate for engine and oil temp?

I have a brand new high pressure fuel pump (old one locked up ) new lift pump, pre and after fuel filters and the rail pressure on the machine is keeping up with demand. (26k demand, 25990 actual)

 

[Nige]

We've been here before. From your description of the symptoms the problem is with the underspeed system.
First look at your TPS (Throttle Position Sensor). What Part Number is it.? There has been an update on it because of reliability problems with the former P/N.
It sounds like you have access to ET. Have you tried checking that the TPS is giving a 100% signal when you have the pedal on the floor.? If it is then the next step would be to do a TPS calibration.

Lifted from @Chrisso's explanation in another thread regarding how the control of the hydrostatic drive system functions..........
"These are electronically controlled hydrostatic systems that use a software "underspeed" strategy. The underspeed is basically a calculation made by your machine control ECM software that sets a target RPM just under (hence the name) the desired engine RPM. As loads on the machine increase, actual RPM drops below this calculated underspeed RPM. As a result, the ECM starts easing up on the hydrostatics (slows track speed) until either...
1) Loads decrease, engine RPM increases back to above the underpeed RPM, hence tracks speed up again, or
2) Loads keep increasing, track speed keeps slowing to a stop while the engine keeps running nicely.

If your TPS signal is bad, your ECM won't know you're pushing the pedal to the floor, so underspeed kicks in.

If your governor cable isn't set correctly, the engine isn't getting a max RPM command to begin with, so underspeed kicks in.

If you have a sticking park brake, the hydrostatic system can't overcome the load, so underspeed kicks in. You get the drift."

 

[hvguy]

We've been here before. From your description of the symptoms the problem is with the underspeed system.
First look at your TPS (Throttle Position Sensor). What Part Number is it.? There has been an update on it because of reliability problems with the former P/N.
It sounds like you have access to ET. Have you tried checking that the TPS is giving a 100% signal when you have the pedal on the floor.? If it is then the next step would be to do a TPS calibration.

Lifted from @Chrisso's explanation in another thread regarding how the control of the hydrostatic drive system functions..........
"These are electronically controlled hydrostatic systems that use a software "underspeed" strategy. The underspeed is basically a calculation made by your machine control ECM software that sets a target RPM just under (hence the name) the desired engine RPM. As loads on the machine increase, actual RPM drops below this calculated underspeed RPM. As a result, the ECM starts easing up on the hydrostatics (slows track speed) until either...
1) Loads decrease, engine RPM increases back to above the underpeed RPM, hence tracks speed up again, or
2) Loads keep increasing, track speed keeps slowing to a stop while the engine keeps running nicely.

If your TPS signal is bad, your ECM won't know you're pushing the pedal to the floor, so underspeed kicks in.

If your governor cable isn't set correctly, the engine isn't getting a max RPM command to begin with, so underspeed kicks in.

If you have a sticking park brake, the hydrostatic system can't overcome the load, so underspeed kicks in. You get the drift."

Hmm, that all makes sense except the commanded and actual engine rpm are keeping up, it'll damn near kill the engine if you plunge into a pile of dirt, dial back the track motor speed to a crawl, then start spinning the tracks or push the material, whichever comes first.

The parking brake is hydraulic, so perhaps it's dragging, but I highly doubt both of them would start dying equally at the same time at just 1900 hours.

It even does with with the bucket empty.

Sometimes you and push the joystick left or right, depending on what it feels like; then it'll start to speed up. Almost like the hydraulic valve controlling the motors is... Sticky?

Kinda hard to explain.

 

[Nige]

commanded and actual engine rpm are keeping up,

if the commanded and actual engine RPM start to fall at the same time when the RPM decreases that again sounds like the TPS.
Please do the checks on the TPS P/N and whether or not it is registering a 100% signal when the pedal is to the floor and report back.

 

[hvguy]

if the commanded and actual engine RPM start to fall at the same time when the RPM decreases that again sounds like the TPS.
Please do the checks on the TPS P/N and whether or not it is registering a 100% signal when the pedal is to the floor and report back.

Will do, should I also check the engine speed knob on the right column below the computer? Because that's what we're using to hold the engine speed.

I'll try and check the part number on the floor pedal when we get done. It's 100 outside right now

 

[Nige]

I would check both TBH. See if you get a different TPS reading from the floor pedal or the hand control. You shouldn't, but.........

It's all a sequence and as each item is checked and ticked off it will eventually lead to the culprit.