Help, cat 928g

hey guys i am having an issue with a cat 926g serial num 6xr02074 where the implement controls slow when the machines warm up, the first few min after startup it works fine but after it gets very slow, changed the hyd oil to cat 10w and all filters changed .
im thinking from past experiences that the hydraulic pumps are worn, thing is im not sure which pump controls the bucket and lift functions . im not sure if its the pilot or main pump that is going bad, im seeing the piot pump is coupled with the cooling fan and the temps are normal showing me its more of the main pump
can anyone help with which pump contros the main function?

Here's the SysOp for the Hydraulic System. Hopefully that will help you.

thanks nige , im in mia this week and gonna buy the rebuild parts for pump 20 and 21so when i do tear into it i wont be waiting for parts.

I would recommend checking the pilot pressure first. There is a pressure reducing valve that supply’s the pilot pressure and I have seen them have erratic pressure causing slow hydraulics.
I think it’s number 1 in the systems op diagram.

Mobiltech said:

I would recommend checking the pilot pressure first. There is a pressure reducing valve that supply’s the pilot pressure and I have seen them have erratic pressure causing slow hydraulics.
I think it’s number 1 in the systems op diagram.

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Thanks for the input , what exactly would I be looking for ? Low pressure caused by a blocked valve ? Can it be repaired or needs to be changed?

Shivan Dookeran said:

Thanks for the input , what exactly would I be looking for ? Low pressure caused by a blocked valve ? Can it be repaired or needs to be changed?

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Pull the valve apart and take a look.?
There are not many serviceable parts inside, just a few O-Rings & backup rings.

Ok from what I gathered ,I should be looking for pilot pressures of 450psi and 3600psi at the main relief, should be test ports at the pump and main control valve body? Not seeing test port locations

The pressure test point for the pilot system is on the PRV itself under the cab floor on the right side of the machine - Ref #3. Spec is 375 ± 25 psi.

According to the procedure the low pressure standby value for the steering system should be tested before testing the pilot pressure. It uses the same test point as the pilot pressure.

Hey guys update time , tested all the points and decided to start from scratch as it was being worked on by someone before , drained the hydr oil and changed all filters again , worked it all day with no problems .

Now I'm having another problem, seems the brakes disc's are worn as it's a high hour machine , what's should I know if I'm gonna get it changed ? What should I change ? Seals ,bearings and bushings ?