CAT 248B won't go full throttle

[Jeepasaurus]

Good Evening!
First things first! Here's the Serial Number: CAT0248BLSCL01125

I've got a 2005 CAT 248B with High Flow XPS that starts and runs beautifully, but it won't go full throttle. When pushing the throttle to full you can hear the engine move up in RPM just a little but it's not going full throttle like it should. When at "full throttle" the travel speed is at a crawl. Now, if I move the arms up and/or dump the bucket the engine speeds up and the travel speed increases. Here's some short videos that demonstrates what I'm describing:

It sounds exactly like the problem described in this post: https://www.heavyequipmentforums.com/threads/cat-268b-hydraulic-throttle-up-problem.65080/ ... I did the testing described in the post above. Here are the results:

Hydraulic Gauge connected to the port on the pump compensator valve

• Signal line connected
  • 0 PSI at idle
    
  • 2200-2400 PSI when moving the arms or bucket
• Signal line disconnected and capped
  • 0 PSI at idle... 0 PSI when operating arms while engine at idle speed
  • 0 PSI at full throttle...
    • raise the arms, still 0 PSI
      
    • when lowering arms it jumps to 500 PSI when control is released

Hydraulic Gauge connected to main work tool pressure tap (on implement distribution block)

• Signal line connected
  • 2600 PSI at idle... rose to that pressure without activating the machine (pushing the parking brake switch to unlock the machine and activate the controls)
• Signal line disconnected and capped
  • Just over 3000 PSI when started at idle
  • Moving lift arms up, pressure drops to 2200 PSI at idle
    
  • Lowering arms pressure drops to 2800 PSI at idle
    
  • Full throttle pressure increases to 4400 PSI.
  • Raise arms and the PSI drops a little then when you stop raising arms it spikes to 5800 PSI before leveling back off to 4400-4500 PSI

Additionally, I talked to the Shop Supervisor at the local CAT dealer, and based on what I described he said, "My thought is the compensator valve on the implement pump is giving you issues."

One final note, I did take the hydraulic filter off and opened it up. It was clean. No debris in the filter.

Is there anything else i should check or test? Or is the implement pump or compensator/control valve my main culprit at this point? I just want to make sure that there isn't anything else I should be testing before disconnecting hydraulic lines and making a 7k pound paperweight in my workshop.

Thanks,
Kyle

 

[ahart]

First off, I have to give you a ton of credit for your first post. You’ve obviously spent some time on HEF and noted the good structure of an initial start of a thread, this one definitely meets all expectations with information. Given the pressures you’ve provided and symptoms you’re describing, it sounds as if the pump is stuck and not being controlled by the compensator.

 

[Jeepasaurus]

Thanks for the kind words, quick reply, and confirmation ahart! Much appreciated. I bought the machine 15 months ago with this existing condition. Life and other projects got in the way of getting this project going, so I've had a lot of time to prepare and research (and my brother-in-law came over earlier this week to help out and that was the kick in the rear i needed to get it done!).

Any tips/tricks for removing the implement pump that I should know about?
Do I have to drain the entire tank/hydraulic system?

 

[heymccall]

My 248b is same, except you can super fast jiggle the boom control to destroke pump, when the pump sticks.
I had a new compensator installed. Zero difference.
I'm gonna have to pull main pump too.

As for draining, the tank is up high, so, yup, it'll need drained.

 

[Nige]

The attached procedure from the manual may give you some guidance.
The gear pump on the back comes off first.

 

[Jeepasaurus]

Nige, thanks for the document!

We got the pump off, and cracked it open. And... Three quarters of the actuator piston seal is missing and there is scoring in the bore. So, definitely found the problem! I've attached photos of the actuator piston and the scored bore wall for the actuator piston for your viewing pleasure.


Looking up the part number, 224-9405, on CAT's parts website it says that it has been replaced with part number 455-7935. Does anyone know the difference between the old and new part number?

I'm going to do some calling around tomorrow to see if I can't source a re-manufactured pump, a new pump with old part number, or a new pump with the new part number. If anyone has any suggestions, I'm all ears!

Thanks again for all the help!

 

[ThreeCW]

Your CAT parts person should be able to tell you the reasons why the 224-9405 pump has updated with the 455-7935.

I had a look on-line and was not able to find any remanufactured options other than from CAT.

 

[Nige]

Your CAT parts person should be able to tell you the reasons why the 224-9405 pump has updated with the 455-7935.

No they won't. There is no documentation covering the change, at least at a level to which the normal Parts guys will have access.

Only by looking at another resource was I able to find some information. See attachment. The highlighted parts on the list are all updated but there are no updated Part Numbers for them because the 455-7935 Pump Gp now contains no serviceable parts. Instead it has to be replaced as a complete unit.

Edit: There are some serviceable parts in the 455-7935, but not the "business end" so to speak as there was for the 224-9405. Also I can find no information regarding whether or not a 224-9405 would be an acceptable Core for the purchase of a 20R-9731, the listed Reman Number for 455-7935.

 

[Jeepasaurus]

Nige is spot on. I contacted CAT support via their online chat. They referred me to my local CAT dealer who responded via email. They stated:

"After doing some research we were unable to find any CAT publications showing changes made to this pump. It is referred to as a “Running Change”, with just the part number being replaced."​

I took the pump to a local hydraulic shop this morning. They are going to take a look at it and get back to me in a couple days. I'll keep ya'll posted on what happens!

 

[Jeepasaurus]

Update

Hydraulic shop had the pump for about 2 months... but they did get it repaired! We got the pump installed and the machine is fully operational! Everything working as it should. Engine runs nicely. Throttles up like it should now. I'm a very happy camper!

Thanks to everyone for their input.