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swandrie
04-20-2010, 09:18 AM
Hello

I notice my bobcat 61 zero turn is wining when making right turns!!! I was wondering if its the pump or motor?? how can one tell which one is the problem?? I have no leaks, also is sin hyd fluid better then regular 20w 50w motor oil??
I would hate to change either one as they are very costly!! thanks for time and help....Sam

piston slapper
04-20-2010, 10:08 AM
Probably the pump. Put a magnet into the hydro tank and see if there is any metal.

Synthetic fluids in hydros are a great improvement. The reason is that regular motor oil starts breaking down at around 220 degrees.(It gets thinner when it gets hot giving you less power) Synthetics start breaking down around 325 Degrees . Hydros generally operate between 250 to 300 degrees meaning you wont lose power when it gets hot and the metal parts will be properly lubricated at all times.

webman418
04-29-2010, 10:41 PM
Hydraulic whine can be caused by a plugged filter. When was the last time you change the Hydraulic Oil and Filter? That would be the first thing to check. It also could be caused by air in the oil. That is easy to tell though as it makes the oil in the hydraulic reservoir look almost milky white. If you look at your oil and is foamy or milky looking, check the low pressure hoses that feed the pump. You could have a fitting loose, but usually you would see an oil leak when it is not running. Still should check. You will know which ones because the hose goes from the hydraulic tank and T's to both pumps. I would bet on a plugged filter. If you changed oil and filter lately you might have the wrong micron filter, especially if it is an after market filter. Just not worth it. A couple of extra bucks for the BOB-CAT filter isn't worth $500 - $800 pump repair. Now as far as Oil goes, you are much better using the 20W 50 Motor oil. BOB-CAT puts a hydraulic cooler on there Z's so heat isn't an issue. They only run temps from 160 to 180 degrees. And, Motor Oil is better for the wheel motors because it has better shear quality. It has to do with the copper, magnesium and zinc that is in motor oil naturally. Although these sound like metals which they are they are such small particals that they actually provide great lubrication in high load, high pressure components with very tight tollerances like the wheel motors. Most pump failures come from debris generated by the wheel motors from wear, so by reducing the wear it makes the whole system last longer. That being said it makes your motors last longer, so stick with the motor oil. It is one of the best hydraulic fluids out there and it is about the 1/4 the cost of synthetics.