2004 Cat 257b Drive problem

[crowe2007]

Please can you create a new thread in the Compact Track/Multi-Terrain Loader section and mention the machine Serial Number. It makes it easier to look up information. For information on how to create a thread, click this LINK

The sn is cat0299DPBX903102

 

[92U 3406]

The sn is cat0299DPBX903102

Start a new thread for your issue. Trying to diagnose 2 very different machines with 2 different issues in the same thread leads to nothing but confusion for everyone.

 

[Gregory A White]

After you guys suggestions and what I have done, I am leaning toward an internal leak. That isn't going to be an easy one for me. Is there a "most likely" suspect? I am going to start with the LH joystick valve. There is a tiny bit of oil around the plungers just under the handle. Could this be classified an internal leak? I'm having a blast dealing with this thing (I love tinkering) and learning so much from all of you.

 

[Gregory A White]

This issue has been going on for a couple of years (approx 250 hrs) and not getting any worse. I'm having a difficult time believing that drive motor is the problem.

 

[Nige]

After you guys suggestions and what I have done, I am leaning toward an internal leak. That isn't going to be an easy one for me. Is there a "most likely" suspect? I am going to start with the LH joystick valve. There is a tiny bit of oil around the plungers just under the handle. Could this be classified an internal leak? I'm having a blast dealing with this thing (I love tinkering) and learning so much from all of you.

Resealing the joystick should not be a difficult task provided you are reasonably handy with tools. Just remember that it is a hydraulic compone built to tight tolerances. Don't go bashing the internal, or external for that matter, parts with hammers.....!!

@ThreeCW did a really good write up of how to strip and rebuild a pilot control valve. He put a link to it in Post #11 on Page 1. You could do far worse than copy exactly what he did. Attached is what the service manual covers, but that does not include the actual disassembly of the guts of the pilot valve. However I did find rebuild instructions for a track dozer pilot valve that uses the same repair kit as the skid steer.

Before you do that though, I think you should investigate thoroughly the suggestion from @Mobiltech in Post #15 on Page 1 regarding the possibility of a missing track drive lug or lugs.

 

[ThreeCW]

Gregory,

My pilot valve leak repair was eventually addressed by changing one "O" Ring in the middle of the pilot valve assembly.

If you are going to address a leak in the top part of the pilot valve assembly, a MUST READ from a top contributor and an Administrator of the HEF, Willie59, is located here:

https://www.heavyequipmentforums.com/threads/repairing-a-leaking-joystick-control-valve.21529/

In this thread, Willie59 points out: "Remember, when you disassemble the unit, be sure and note which spring/spool set came from which hole, don't switch the location of those parts or mix them up."

I did not have to go into the top end of my pilot valve but did read this post a number of times before attempting my repair. Very good advice indeed Willie !!

 

[Gregory A White]

Thank you Nige. I will follow your suggestions. I respect your knowledge.

Gregory,

My pilot valve leak repair was eventually addressed by changing one "O" Ring in the middle of the pilot valve assembly.

If you are going to address a leak in the top part of the pilot valve assembly, a MUST READ from a top contributor and an Administrator of the HEF, Willie59, is located here:

https://www.heavyequipmentforums.com/threads/repairing-a-leaking-joystick-control-valve.21529/

In this thread, Willie59 points out: "Remember, when you disassemble the unit, be sure and note which spring/spool set came from which hole, don't switch the location of those parts or mix them up."

I did not have to go into the top end of my pilot valve but did read this post a number of times before attempting my repair. Very good advice indeed Willie !!

Thank you 3CW. I will definitely read the post from Willie. A few days back, I put extra effort in cleaning the radiator fins to assure good air flow and cooling of the hydraulic oil. I ran the Cat a couple of hours yesterday. It worked well at first but, after 1/2 hour, left track began to stutter again. The leak around the joystick plungers is tiny but, I'm wondering if that could be enough leak to cause the problem? As you can tell, I'm not familiar enough with hydraulics to diagnose this but, I am having a ball trying and you guys help is extremely appreciated.

 

[dmitry_bulldozerman]

Thank you Nige. I will follow your suggestions. I respect your knowledge.

Thank you 3CW. I will definitely read the post from Willie. A few days back, I put extra effort in cleaning the radiator fins to assure good air flow and cooling of the hydraulic oil. I ran the Cat a couple of hours yesterday. It worked well at first but, after 1/2 hour, left track began to stutter again. The leak around the joystick plungers is tiny but, I'm wondering if that could be enough leak to cause the problem? As you can tell, I'm not familiar enough with hydraulics to diagnose this but, I am having a ball trying and you guys help is extremely appreciated.

Hello. This problem cannot be caused by a tiny leak in the joystick. But this problem can be caused by a tiny break in the seal on the brake piston of the hydraulic motor. I wrote to you about this above and attached a diagram of the hydraulic motor.

 

[Gregory A White]

Hello. This problem cannot be caused by a tiny leak in the joystick. But this problem can be caused by a tiny break in the seal on the brake piston of the hydraulic motor. I wrote to you about this above and attached a diagram of the hydraulic motor.

I’m beginning to accept that it is probably the motor. Is rebuilding the motor something a pretty good DIYer could do?

 

[Gregory A White]

I printed the diagram.

 

[92U 3406]

Have you at least ran some test to determine the motor is NFG? Tossing parts at something gets costly quickly. A failing drive pump will give you similar symptoms.

I'd at least run a case drain flow check on the motor before condeming it. Get the hydraulic oil warmed up, then remove and plug the case drain hose at the motor you are testing. ONLY plug the machine side - leave the motor side open. Connect a hose to the case drain fitting on the motor and put it into a bucket. Stall out the motor and give it full travel pressure. I don't believe CAT has a spec on case drain volume per minute but one of their tech guys once told me that a good motor will trickle out a pencil lead sized stream at operating temperature. If the motor is shot then oil will be pouring out of the case drain.

 

[92U 3406]

I've torn apart a couple CAT skid steer travel motors to confirm failures. I don't know your level of mechanical ability but I would say it'd test the abilities of the average DIYer.

 

[Gregory A White]

So, I put the skid steer up on blocks with tracks off the ground. Tracks operated as they should. I put a 10,000 lb strap on the problem track to simulate the force of moving the machine on the ground. It did not pulsate at all. Added engine rpm’s and thought it was going to tear thru the track. Still no pulsating. When back on the ground, put it against a tree and pushed. The right track spun on the dirt but the left would not. Could I have a bad relief valve for the left track? If so, which would it be on the main valve? It did the same in reverse

 

[92U 3406]

Did you measure the case drain volume when you did this? If not you wasted your time and didn't learn anything new.

 

[Gregory A White]

The case drain test produced a steady stream the size of a pencil or more. If I did it correctly, it drained approx 9 gallons in about an hour. I went ahead and pulled the motor out. I have the motor part # as 280-7862. Is that correct for
2004 Cat 257B
SLK00398?

 

[92U 3406]

I'd be checking the pump next before throwing a motor at it. Case drain leakage from the motor doesn't seem to be too terrible.

 

[Gregory A White]

Thanx for the advice. This is exhausting.
Am I looking for pressure or volume when checking the pump? Or both? Point me in the right direction.

 

[92U 3406]

@Nige would be the fellow to ask for specifics. I unfortunately lost access to SIS when I got laid off from the dealer a few years ago. Everything I've mentioned so far was going off my memory the best I could.

 

[Nige]

Attached are the Test & Adjust and Troubleshooting procedures for the hydrostatic drive system.

 

[Gregory A White]

Hello. This problem cannot be caused by a tiny leak in the joystick. But this problem can be caused by a tiny break in the seal on the brake piston of the hydraulic motor. I wrote to you about this above and attached a diagram of the hydraulic motor.

Dmitry, can you give me the part # for the brake piston seal (#7) you mentioned earlier. If you have a parts diagram for the entire motor, i would appreciate that. I am rebuilding the drive motor and that seal #7 looks pretty worn.