Hydro static fluid / drive problems

[jd4310man]

I have an older Swinger 220 Wheel loader that has a Sundstrand / Saurer/Danfoss hydrostatic variable displacement piston pump, and a fixed displacement piston motor. The previous owner or owners must have dumped automatic trans oil in the hydro oil tank, and now the system is full of a oil that resembles pepto-bismal. I drained the tank, drained the hydro cooler and filters, and got all the fluid i could get out of the cylinders. I added 5 gallons of new aw46 oil. The oil still looks reddish and now the pump/ motor doesn't want to drive the machine at all. Will move but no power. It may have fine air bubbles in the oil. What is the best way to purge the system of all the old nasty oil? And what is a good oil specifically for these hydrostatic transmissions? And should I be running an anti foaming agent? Thanks for any input.

 

[davesl708]

As to the fine bubbles letting it sit overnight should let the bubbles rise and collect. Bleeding should get rid of the remaining air.
Any chance of getting a manual on the unit? I would go with the OEM oil recommended.

 

[MHarryE]

Red comes from the dye companies use to spot leaks. It's not specific to ATF. We have a red dye in products out of our plants in America and fluorescent green in our European plants. So just because you see red oil does not mean it's bad. My Cat mini-excavator, built in the UK, came with red oil and still looks the same red despite my using non-dyed oil for replacement.

It really sounds like you have a component problem.

 

[jd4310man]

Well the oil is still milky looking a little less red. I let it sit overnight and run it around today and the performance is still lousy. I think your right MHarryE, the pump and motor need to be rebuilt. The warmer the oil gets the less it wants to go. Hopefully they still carry parts for it. Does anyone have any ideas about how much a rebuild would cost? I will be removing the components myself, just not sure what to expect.

 

[oldnslo]

Some older Sundstrand products recommend ATF as the fluid of choice. Sunstrand became Sauer Danfoss and is now just Danfoss. They should have rebuild options on most of there equipment. Cost depends on size of components and what is required to get them back operational. I would budget a minimum of $2500 - $3000. This estimate could be high or it could be low.

 

[MHarryE]

At Gleaner in the mid to late 80s we switched to Sauer-Sundstrand from Dennison and New York Air Brake/Hydreco. We continued to use ATF like we had used in the others but Sauer-Danfoss didn't like it. They denied most of our warranty. ATF was cheap, however, so we continued to use it and negotiated a lower part cost from Sauer-Sundstrand with no warranty except in the case of a major production problem by Sauer-Sundstrand. As the engineering manager responsible I wanted to switch to the hydraulic fluid they recommended but purchasing and bean counters won. The thing is I can't remember what Sauer-Sundstrand's recommended fluid was. When I moved to Cat our facility used Mobil DTE-20 AW46 despite Parent Cat saying we shouldn't a hadda outta done that, but we had a low failure rate. Sauer-Danfoss at that time had no complaint with our oil selection. Eventually our plant did buckle in and switched to Cat Hydo Advanced 10 for normal fill, 15W-40 engine oil for hot climates. Sauer-Danfoss had no problem with those, and we did recover warranty from Sauer-Danfoss when I was at Caterpillar.

 

[jd4310man]

I run the machine yesterday and when the oil is cold and thick it will drive a whole lot better. Im sure the pump and motor are a bit worn, but could it be possible that the oil is the wrong viscosity? Im sure the old oil was contaminated and thin. Not sure if i want to keep dumping oil at it?

 

[Xfaxman]

I run the machine yesterday and when the oil is cold and thick it will drive a whole lot better. Im sure the pump and motor are a bit worn, but could it be possible that the oil is the wrong viscosity? Im sure the old oil was contaminated and thin. Not sure if i want to keep dumping oil at it?

Yes, your symptoms are exactly what happens when hydraulic fluid is used in a system designed for motor oil.

 

[jd4310man]

If its supposed to be motor oil, Then then what type should I run? And should there be a anti foaming agent added to it?

 

[J_J]

Try 10W-30 motor oil, and it can be found just about anywhere. . We don't seem to have a problem with foaming, even though it is a detergent oil.

This is what we use in out Power-Tracs.

You can use synthetic if you want.

 

[jd4310man]

Is the Power-Trac a piston pump, piston motor type system? I just confermed today that the pump on the swinger is an old saurer sundstrand hydrostatic pump. I only used John Deere Hy-Guard in my Deere compacts and just a tractor hydraulic fluid in the Magnatrac. It has a simple gear pump that isnt too picky on what oil is used.

 

[J_J]

The pump on my PT is an Eaton piston pump, but others use a Sauer-Danfoss.

Eaton® 70360 Variable Displacement Closed Circuit Piston Pumps

 

[jd4310man]

Well, yesterday i drained the system again and this time i undid all of the lines i could and worked all the cylinders back and forth manually to get all the fluid out i could, and i loosened the lines to the hydrostatic pump. I know its virtually impossible to get all the old fluid out of all the nooks and crannies. I refilled the system with ISO 46. I called NMC and thats what they recommended. Now with draining all the lines and components, and filling with new oil and running for the first time, the oil looked foamy. Is that normal since there is a lot of air in the system? The oil still looked a bit pink but not as bad. Hydraulics are a major pain to mess with when theirs contamination involved.

 

[J_J]

If you have foamy fluid, then you are introducing air into the hyd system.

 

[Xfaxman]

Who or what is NMC?

 

[jd4310man]

They are the company that bought out the swinger loaders back in 92. They renamed them NMC last year. Hear is a link to their site. NMC-Wollard

 

[Xfaxman]

If it worked before you drained the hydraulic system the first time, that would lead me to think it runs on motor oil, not hydraulic fluid.

First step is get a manual for it.

 

[jd4310man]

xfaxman: The Oil that was in it was so badly contaminated with water, that I dont think it was working right. Like I said before I called and spoke with someone at NMC-Wollard about what kind of oil to use and they told me ISO 46. I also ordered the manuals for it, but they haven't come in yet. Im pretty sure the pump and motor are wore and could use a rebuild. Is there a reputable place to order parts for Sauer / Sundstrand?

 

[oldnslo]

Im pretty sure the pump and motor are wore and could use a rebuild. Is there a reputable place to order parts for Sauer / Sundstrand?

Sauer Sunstrand became Sauer Danfoss and is now just Danfoss. There should be reputable rebuilders for this product in your area. If this is the older 20 series products they are semi-obsolete but I believe the majority parts are still available for rebuilds.

 

[Hamco]

I solved my foaming problem by replacing the oil seal on the Aux. oil pump. It was sucking air in. Was a cheap fix thankfully. Still using dextron oil just fine