Caterpillar 226B drive joystick testing

[GarrettJ]

Hey, my machine is a 2008 with 2700hrs. The left joystick is very slow to react and also overreacts. The right joystick is perfect and works like a charm. Both have very slight external sweating, but nothing I would consider a “leak”

From forward to reverse or reverse to forward, it has a full 1 second pause, which is painful when you need the machine to move. While waiting, the reverse beeper doesn’t come on till the machine starts moving, so I feel like it’s not sending oil pressure to line until it’s moving. Seems like something isn’t bleeding off or returning to neutral quickly enough.

It overreacts when turning left or right, usually by about 8-12” on the bucket. Imagine trying to work close to a car or house. Very annoying.

I've checked oil levels, changed the filter and would like to start testing pressures. I bought a manual online and seems to have all the ports labeled for me, just not sure exactly which ones to test and what numbers to expect.

I should say, it gets worse the higher you rev it, it seems to be worse the hotter the machine, and the reverse beeper operates normally.

Any help is appreciated, thanks!

 

[Chrisso]

226Bs were a 2004 model, yours is probably a series 2? To give any accurate specs we'd need a s/n, or at least a prefix.

 

[GarrettJ]

Hey, I’ll try and edit the title. It is a 2008 226B2.
Serial CAT0026BTMJH1268

 

[Chrisso]

226B Skid Steer Loader
Machine Serial Number - MJH01268
Machine Build Date - 2004/05/26

We're only interested in the last 8 characters, and I'm guessing you missed a zero also, but that's no biggie. Either way it still shows up as an '04 model according to sis.

Backup alarm is ECM controlled. I'm guessing the drive motor speed sensors are inputs to this so not necessarily pressure related. SIS is actually having a dummy spit at the moment so can't really pull out any good info.

We need to determine if the delayed movement is commanded or uncommanded by the joystick. Easiest way (and messyest) I can think of would be to remove a pilot line from the joystick (say the reverse signal) and run machine to replicate the fault. If there's a delay of oil flow from the joystick we would know straight away thats the problem. Failing this we'd do some baseline hydrostatic checks. Again SIS isn't having a good time ATM.

 

[GarrettJ]

Yah, it missed a digit, trying to post on my phone so that’s not awesome.

MJH12684

so I could disconnect the feed from the joystick, and see if the delay is in the oil being sent out, or if the oil is immediate and the delay is further down?

 

[Chrisso]

I think that's the only way to be sure. Depending on what tooling you have available, you could tee into it with a pressure gauge, or even just run a hose into a bucket. You obviously need to use caution as you'll have pilot pressure there (500 psi or thereabouts, would know for sure if my SIS was working).

The signal commanded from your joystick to your hydrostatic pump needs pressure and flow to work. If you can see a delay in flow, that's enough to condem the joystick valve in my opinion.

If it is the joystick there's plunger kits available that might be worth exploring. From memory the hydraulic section of the joystick is quite expensive.

 

[GarrettJ]

I’ll likely go pick up a pressure gauge set and check those pressures. I’ll keep those gauges/lines in a safe place.

with the updated serial number, does my machine show up as a 2008?

thanks!!

 

[Chrisso]

with the updated serial number, does my machine show up as a 2008?

Sure does, even SIS works properly with that s/n...
226B Skid Steer Loader
Machine Serial Number - MJH12684
Machine Build Date - 2008/02/19

So the travel alarm ECM input is just a pressure switch on the LH joystick. I wouldn't base any conclusions on this switch working before the machine moves, this switch may only need a small pressure increase to activate.

Pilot pressure should be 450 +/- 29 psi at 2550 +/- 25 rpm by the book, but what you're really checking for is the delay at this point.



FWIW I'm never satisfied with just good pressure. Where possible and safe to do so, I check for flow also... rules out internally damaged (restricted) hoses.

 

[Chrisso]

FYI pilot oil is supplied by the charge pump and tested here normally.

 

[GarrettJ]

So I just strapped a GoPro under the machine and tested it with that hose unhooked. Oil runs out of the hose at idle, and sprays the other way when I pull reverse.

the machine turns only to the left and left feels like it should. I’ll upload a video and post that in a few minutes

 

[GarrettJ]

 

[Chrisso]

Ok great video.

the machine turns only to the left and left feels like it should

Rear section of pump (when sitting in the operator seat) controls the LH motor and front section of pump controls the RH motor. So that's a good thing with that line disconnected.

Two things don't look normal to me. The fact that nothing comes out of that hose when commanding reverse makes me think something is going on with that joystick pilot valve. I think it's time to inspect or replace the valve. Pointless me pricing anything as it'll be in AUD, but I know they're not exactly cheap.

The other thing is the amount of oil coming out of that port in the pump. According to the schematic (sent you a copy), any oil coming out of that hole is either leaking internally from the pump... or exiting the joystick as a FORW/RIGHT command, then bypassing a spool. So, one more reason to suspect the joystick I guess.