Does Hydraulic System need purged on STC-48A with PG-1KCC-DY1X-XXXX pumps

[Threejack]

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 owners manual only references “dump valves” and indicates they are on the back of the pump somewhere and are used to move the mower without running the engine. However, I don’t see anything that looks like it would be a “quarter or half turn valve” of any nature. Additionally, there isn’t any direction of purging air after say a hydraulic fluid and filter change In the OM.

So do I have a dump valve and where is it? And do I need to do some sort of air purge?

I’ve attached a couple of pictures of my pumps if that will help.

 

[ILENGINE]

Take a look at the top right corner of the pump in your first picture next to the hose fitting. That looks about right. That style of valve on a Cub Cadet that I am working on excepts a 5/8 wrench. Some even have a hole drilled through the hex to except a bolt or slide pin.

 

[Threejack]

Take a look at the top right corner of the pump in your first picture next to the hose fitting. That looks about right. That style of valve on a Cub Cadet that I am working on excepts a 5/8 wrench. Some even have a hole drilled through the hex to except a bolt or slide pin.

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 were pushed forward ( with rear wheels off the ground) So I gave up before I did something stupid and thought I’d seek some knowledge.

 

[Threejack]

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

 

[StarTech]

Yes the system has to be purged of air. I done two of these pumps so far this year. Basically you fill the reserve tank, jack up the rear as for wheels not touching the ground, and operate that lap bars with the engine running. You may need to refill the reserve tank a time or two. Depends if the wheel motor were drained or not.

 

[Threejack]

Take a look at the top right corner of the pump in your first picture next to the hose fitting. That looks about right. That style of valve on a Cub Cadet that I am working on excepts a 5/8 wrench. Some even have a hole drilled through the hex to except a bolt or slide pin.

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 operating (engine running) to NOT have the wheels turn if the steering handles were advanced. IOW, no bypass.

 

[ILENGINE]

If you could roll it most likely they hare in bypass. Sometimes you will get some movement of the wheels even in bypass.