Hydrostatic Newbie-System Flush

Fritzhaus · Oct 26, 2012

I just picked up a Lite-Foot (Pistenbully Scout) snowcat. It has the following components.

Sauer series 90 pump
Volvo F11 final drive
Auburn Gear hubs

The previous owner used it for cabin access and put a whopping 30 hours on it over 8-9 year. The fluid in it has 30 hours on it, but it's old. Current fluid is Chevron AW-32. Because it's so old, I'd like to flush and replace with ATF type F.

I'm not a mechanical retard (lots of experience rebuilding motos), but I've never worked on hydrostatic systems, so I'm looking for insight.

Here's what I think one would do to flush the system.

Drain reservoir
Drain pump
Drain hoses at final drives

Refill process.

Keep everything clean!
Replace both filters
Fill pump at upper access
Fill reservoir
Turn motor over with coil removed (30 sec)
Repeat above step and check reservoir level
Keep pressure gauge attached to M3 port, repeat above steps until spec'd pressure is obtained.
Check reservoir level, fill as needed.
Start engine, slowly cycle drives forward/backward for several minutes to remove air.
Recheck reservoir level.

Thanks for any and all advice.

300 H and H · Oct 26, 2012

To me oil doesn't get old. It's already old. I would have a lab do a analysis of a sample before going to all the trouble. I realize what your thinking, as oil is cheap...I started a diesel engine with 14 year old fuel in it not so long ago and still haven't changed the more than 14 year old oil in the hydro stat for the ground drive. It was stored inside BTW...

If the fiters are doing the job, and there is no water in the system, I would be temped to let it go until the regular service interval. JMHO...

Regards, Kirk

Fritzhaus · Oct 26, 2012

300 H and H said:
To me oil doesn't get old. It's already old. I would have a lab do a analysis of a sample before going to all the trouble. I realize what your thinking, as oil is cheap...I started a diesel engine with 14 year old fuel in it not so long ago and still haven't changed the more than 14 year old oil in the hydro stat for the ground drive. It was stored inside BTW...

If the fiters are adiquite, and there is no water in the system, I would be temped to let it go until the regular service interval. JMHO...

Regards, Kirk

Other stuff I've read says the same. Pay for the analysis first.

I'm neurotic when it comes to maintenance on my other vehicles, and if I screw this one up, it's pretty damn expensive.

300 H and H · Oct 26, 2012

Fritzhaus said:
Other stuff I've read says the same. Pay for the analysis first.

I'm neurotic when it comes to maintenance on my other vehicles, and if I screw this one up, it's pretty damn expensive.

Yea especially toys that could not only leave you stranded but also embarrassed in a major way as well.... :sad:

Run it a good bit to warm and stir the oil and take a sample of the tank and get it tested. Caterpillar dealers do this at about $25 per. My bet is that it's just fine.

Hope we all get some good snow, :clap:

Kirk

Fritzhaus · Oct 26, 2012

300 H and H said:
Yea especially toys that could not only leave you stranded but also embarrassed in a major way as well....

Run it a good bit to warm and stir the oil and take a sample of the tank and get it tested. Caterpillar dealers do this at about $25 per. My bet is that it's just fine.

Hope we all get some good snow,

Kirk

Well, being stranded isn't a concern. I always have my backcountry skis with me, so no biggie. Plus, the cat is so damn big, it's like an small hut!

Anyway, thanks again, I'll do the test first.

Snowtrac Nome · Oct 27, 2012

if i were to change the oil it wouldn't be to atf i would use a synthetic oil like chevron clarity we run that in all of our equipment up here and it works good in the cold. as for the need to change i second kirks advice with juce drive tehre is a lot of oil it will be expensive and you would be well suited to have a sample anylized and change it when the lab tells you to.

Fritzhaus · Oct 27, 2012

Thanks for the replies.

Right now it has Chevron AW 32 in it.

I've called Pistenbully and Prinoth, and both have given me multiple different suggestions for fluids. Then on the other snowcat forum, a guy with 30 years experience highly suggests ATF-F.

Snowtrac Nome · Oct 27, 2012

the lubritcity of atf is lacking also if has a wet disc additive package atf belongs no place but in a transmission and not in engines or hydraulics you may also run into problems with seal compatibility with the detergents that are added

Fritzhaus · Oct 27, 2012

dds said:
if i were to change the oil it wouldn't be to atf i would use a synthetic oil like chevron clarity we run that in all of our equipment up here and it works good in the cold. as for the need to change i second kirks advice with juce drive tehre is a lot of oil it will be expensive and you would be well suited to have a sample anylized and change it when the lab tells you to.

I checked the specs on the Chevron AW 32 and the Clarity. The pour point, viscosity, etc, are all very similar.

Fritzhaus · Oct 27, 2012

This is from Sauer-Danfoss.

Snowtrac Nome · Oct 27, 2012

another synthetic fluid i have been using from another compaany i work for is amzoil both fluids have worked much better than conventional oils in extreem cold

dieseldr · Dec 31, 2012

I would be inclined to use ATF type A, since type F is tough to find in my area. Maybe you have a stockpile of type F, so use it. Looks like the oil spec sheet is acceptable to it so go ahead.

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