Hydraulic System

[Skippydiesel]

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???

 

[ILENGINE]

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.

 

[Skippydiesel]

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?

 

[ILENGINE]

@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.

 

[Skippydiesel]

@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.

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 %.