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Chasing a hydraulic leak on STC48A (see other thread) and did some more investigation and diagnosis after reoccurring hyd. leak after replacing the seals at the cap and charge pump. It appears that the bypass/dump valve is the culprit. I removed both left and right ones and inspected and the...

I still have a hydraulic leak after replacing the o-rings. Very disappointing.

This morning I turned that 5/8” hex head bolt that you suggested counter clockwise 180 degrees and I could then push the mower around. IOW, you’re right, those are the dump valves. However, even after loosening that dump valve even further never relieved the pressure enough when the pumps were...

As StarTech says this can be done in place, which is what I did. The key to keeping the master cylinder in place is to not get in a hurry as you lift the cap off the body after the retaining bolts have been removed. The piston springs will push the cap up off the body after the bolts are removed...

The only place I found the multi-shouldered “push on type” fittings during this ring replace that job was on the return lines on left hand pump (top right side of left pump) I used a box knife and was careful to try and not damage the fitting, and even then I put some small nicks in the...

Here’s what my owner manual shows. Absolutely no help.

I tried that this afternoon unsuccessfully. IOW, no bypass. It was 5/8” and I loosened it several revolutions. (It wasn’t a 90 or 180 turn to a stop like I was expecting) I was afraid to continue unscrew it in case it came all the way out. My wheels continued to turn when the steering handles...

I have replaced the hydraulic pump housing o-ring and charge pump o-ring on both pumps on my mower. I read a lot about hydro-gear “air-purge procedure” at various places while studying up on this job. The procedure references bypass valve, but I’m not sure my pumps are equipped with them. My...

I’m not sure, can’t quite figure out the system yet, first time I’ve done hydraulic repair on this mower. The 3/8 flexible hose starts at the top of the oil reservoir and proceed to a tee fitting (shown in picture) on the right side ( as you sit on mower) of the left pump and then continues to...

Putting a new oring/seal under the cap on my hydraulic pumps on STC-48A. I was disconnecting the hoses and could not get the small 3/8” line pulled off this fitting without cutting/slicing the hose. Is that the intent of this type of fitting and cutting and replacing the hoses is expected when...

I left the pumps mounted to the frame i.e., did not pull the pump. In order to do this job, you need to drain all the hydraulic fluid. Even then, there is a lot of extra oil running around the engine compartment after you disconnect the lines. Have a full roll of paper towels standing by.

Thanks for the replies. Should I do a system drain even if I leave the pump mounted on the frame? Is the drive shaft pulley difficult to remove?

(Sorry for the orientation, can’t figure out how to rotate it) Looks like the cap seam is leaking and a new seal would fix it. However, I have read elsewhere that in some cases a new cap was required to stop the leak. Further, whether I replace just the seal or the cap, can it be done with the...