Hydraulic System

S

Skippydiesel

Well-Known Member
I am, trying to resurrect a Hustler Super Z. Taking small steps as I don't want to invest too heavily, before knowing what the outcome will be.

I am nearly ready to test the hydraulic transmission. It had been leaking badly, so oil level is well below specified "1in from the top of the reservoir". There may not be sufficient oil in the reservoir to operate the transmission without cavitating.

I would like to top the reservoir up to the correct level but don't know what oil has been used. My (old) Operator Manual specifies "SAE 10W-40, SG, SF/CC, CD service motor oil". This is a very old specification - almost unavailable in Australia.

My intention is just to test the transmission works okay and then drain all the existing oil, replace the filter and refill with a suitable current oil - Hustler 15W-50 synthetic

Will it be okay to use any 10W - 40 mineral (or semi synthetic) engine oil for a short test run??? :devilish:
 
Skippy you will be fine with modern oils. Oil designation are backward compatible, at least for engine oils. Not so much for gear oils in some cases. Also as long as the main unit is full of oil, the reservoir is just an overflow for efficiency loss. Meaning the hydrostat system operates as a closed loop system, and the only oil that is drawn from the reservoir is to replenish what is lost from the pump during operation.

Or to explain a different way. If a hydrostat system is 90% efficient. If you put 1 ounce of oil into the system that circulated between the pump and drive. It will complete 9 cycles before being lost and returned to the reservoir.
 
Thanks Ilengine -

I understand what you are saying about the reservoir level. I have changed all the hoses (not the big return at base of reservoir) and there was no oil in them. This makes me think that the oil in the reservoir may be used up in "filling" the system, resulting in cavitation/air entering the pumps.

So it's okay to top-up the old oil (of unknown type) with what I have on the shelf (10w-40) for a short test run?

:devilish:
 
@Skippydiesel You will be find with using what you have. Just be aware that you will not be able to remove most of the oil in the system unless you disassembly everything and redrain the system.
 
ILENGINE said:
@Skippydiesel You will be find with using what you have. Just be aware that you will not be able to remove most of the oil in the system unless you disassembly everything and redrain the system.
Click to expand...
True!. That contamination (old/new oil) will exist no matter what I do, short of a complete drain.

Should the hydraulics work, I will endeavour to drain as much of the old fluid as possible, before refilling with Hustler Synthetic Oil. Hopefully the percentage of old/new oil will be small and have no adverse effect on the Hustler Oil - might be an idea to do a second replacement at say 20 hrs to further reduce the %.

:devilish:
 
The hydraulic transmission works!!!!
When I say that, its with the wheels off, hubs rotate, at a good speed, in both forward/reverse.
Is the above test sufficient to determine the condition of the transmission ie could the hubs work, with no load but be weak when asked to move the mower??

This is now the longest time I have run the engine.
All went well for the first 10-15 minutes as a I "purged" the hydraulics but then the battery charge light came on.
Put the meter on the battery - 12.2 Volts
Am correct in thinking this should be more like 14 Volts??

:devilish:
 
Skippydiesel said:
The hydraulic transmission works!!!!
When I say that, its with the wheels off, hubs rotate, at a good speed, in both forward/reverse.
Is the above test sufficient to determine the condition of the transmission ie could the hubs work, with no load but be weak when asked to move the mower??

This is now the longest time I have run the engine.
All went well for the first 10-15 minutes as a I "purged" the hydraulics but then the battery charge light came on.
Put the meter on the battery - 12.2 Volts
Am correct in thinking this should be more like 14 Volts??

:devilish:
Click to expand...
Battery should charge between about 13.5 to 14.5 volts. 12.75 is fully charged battery at rest.

Purging the hydros on jack stands and seeing the wheels move back and forth is how it is done and is good. Putting it on the ground under load is how it is tested.
 
Have to put the mower on jack stands and release the hydros. To release the hydros, find the 5/8 headed bolt heads with holes through them and open about two or so turns. Start the engine Move the controls back and forth 8 to 10 times. Close the release valves lower the mower to the ground and test drive the mower to see how it does.
 
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