CAT257B. Does not want to turn when it warms up. lift arm cylinders leaking down while running.

[trkirkendall]

I have a 2005 CAT257B. The lift arm cylinders will leak down fast while running the machine. You have to hold back on the joystick to keep it up. If you turn the machine off it does not leak down. I have repacked the cylinders and it still does it.
Also, when the machine warms up it does not want to turn. When you first crank it it turns great. It tracks straight, does not pull to one side. Just put a new radiator/hydraulic cooler on it. & new hydraulic filter. I have owned the machine for 6 years. It has had these issues since I bought it.
S/N - CAT0257BVSLK03751

 

[Nige]

The lift arm cylinders will leak down fast while running the machine. You have to hold back on the joystick to keep it up.

It's pilot operated, so when there is no pilot pressure (engine off in other words) nothing will move. The problem is quite likely to be tired springs, worn seals, etc, in here ............

 

[trkirkendall]

Thank you for your reply. Just ordered a spring seal kit. What are your thoughts on the machine not wanting to turn once the machine heats up?

 

[Nige]

What are your thoughts on the machine not wanting to turn once the machine heats up?

My first suggestion would be a complete test of the hydrostatic drive system and see what numbers it throws up compared to the specification. Out of interest what oil are you using in the hyudraulic system.?

 

[trkirkendall]

I run cat hydraulic fluid. I put a pressure test gauge on all the ports. I think it calls for 3200 PSI. The lowest pressure I saw was 3000psi

 

[Nige]

I put a pressure test gauge on all the ports. I think it calls for 3200 PSI. The lowest pressure I saw was 3000psi

All I can suggest is do all the tests mentioned in the attachment above in the order that they are specified and then post all the results.
The document is a total of 21 pages and covers far more than what you have apparently tested so far.

 

[trkirkendall]

It's pilot operated, so when there is no pilot pressure (engine off in other words) nothing will move. The problem is quite likely to be tired springs, worn seals, etc, in here ............

View attachment 302117

I replaced the springs (# 11) under the joystick. That fixed my lift arm cylinder drop. I have been dealing with that issue for 6 years! Thank you. I am going to try and test the hydraulic system sometime this weekend hopefully.

 

[Nige]

I am going to try and test the hydraulic system sometime this weekend hopefully.

You're going to need a fair amount in the way of pressure gauges and tooling.

MHO - Don't skimp on the tests, especially when it comes to tooling. Do each one using the test equipment specified in the order that they are listed in the document. Don't try to "make do" with pressure gauges that are not the specified range for the test in question. Use the correct range of gauge for each test or you might end up missing something subtle that could be the key to all the problems.

 

[trkirkendall]

My MB1 & MB2 ports are supposed to be at 5555psi. I am only getting 4200psi from both ports. I’m going to try to adjust the relief valves to get the right pressure. Someone put this pump on the machine right before I brought it.

 

[Nige]

Someone put this pump on the machine right before I brought it.

It is a Cat pump (as opposed to a "will fit") I hope.?

 

[trkirkendall]

Yes. The tag says CAT 236-5106, 06/05, 13680Z

 

[Nige]

Yes. The tag says CAT 236-5106, 06/05, 13680Z

236-5106 is only the Part Number for the Work Tool (implement hydraulics) pump, not the hydrostatic drive pump. The hystat pump should have a tag with either 229-8216 or 289-6340 on it.

 

[trkirkendall]

I have been adjusting the MB1 & MB2 relief valves. I can not get more than 4500psi out of it.

 

[Nige]

Have you replaced the hydraulic filter recently.?
If not then I suggest that you should do that, then cut open the old one and look for "sparklies" in the filter media. See this helpful VIDEO that will give you an idea how to do it. Yes, I know it's an engine filter but the principle is the same, especially the part about squeezing the filter media in a vice. Post photos of what you find.

 

[trkirkendall]

I just put a brand new one on today before I started doing all the checks. I saved the old filter so I could cut it open. I will post pics when I cut it open.

 

[Nige]

I just put a brand new one on today before I started doing all the checks. I saved the old filter so I could cut it open. I will post pics when I cut it open.

That'll work.

 

[trkirkendall]

I ordered a filter cutting tool. It will be here Monday. I worked the machine today. It feels like it has less power now. Could I have tightened the spring tension on the relief valve to much? Is there another relief valve that I need to look at. Like a main one for the pump?

 

[Howie8812]

I'm having similar issues with my machine. Did you find a fix for yours?

 

[trkirkendall]

I finally got around to do all the checks. I found that my charge pressure was about 100psi to low. I took the relief valve out. I know this was not the correct thing to do but I did not have any of the washers to put in to adjust the pressure. I decided to stretch the spring a little bit just to see what would happen. I stretched it and put it back together, luckily when I checked it the change pressure was within the tolerance of what it should be. Then I checked the crossover relief valves and it brought the pressure up from 4500psi to 5200psi. Still lower than what it should be but it was an improvement. I tested the machine out this weekend. I did notice a slight improvement but still pretty weak turning when it warms up. I also added some hydraulic fluid booster to see if that would help. (See picture of what hydraulic booster I used)
I did finally cut my used hydraulic filter open and I did not find any metal in the filter.

 

[Nige]

Good write-up. Sounds like in your case that a replacement spring in that relief valve is called for as a long-term fix. It might get the pressures even better aligned to specification.