Try warming it up with the brake off and see if the foaming still occurs.......wondering if the brake material is just making contact rather than actually firmly on. [/QUOTE said:
HST creep is at least as interesting as the entrained air...but in a different way. Reviewing the way the HST tranny on these Kubotas works - the speed is controlled by a load sensitive governor on the engine, and the load is set by the operator via the Forward/Neutral/Reverse pedal worked by the driver's right foot. That pedal has a couple of opposing spring sets working to make sure that it returns to the centered neutral position when you take your foot off it. With the pedal in the centered position, there isn't any HST fluid flow trying to move the tractor. So it shouldn't matter if the brake is on or what gear the selector is in. Easy to check out though - and one should. The test is: Does the machine try to "creep away" when it's idling?
ON OIL SAMPLING:
The trick is to find a good lab. Our local JD commercial equipment dealer uses a particular lab and I think the Cat dealer uses the same one. Stop by either one as both dealers will sell you a kit that you take home to get started on that process. This kit is just a few pieces of plastic designed to pull up an absolutely contamination-free oil sample which goes into the provided bottle which you then send to the lab yourself. The lab will be looking for parts per million, so contamination is to be avoided. They also want to know as much as possible about the history of the oil, your machine, and particularly what brand and type of oil it is. Reason for that is lab is add value to the analysis by giving you an idea of the life left in that oil. They compare what metal ions they find with what additives were originally in that particular brand of oil when it was manufactured. Depending on the lab, they will also look for gross contamination, but for that they also need to know what was in there originally.
My own take is that oil analysis needs to be done regularly to tell you much. But why not do it...shucks, it's an interesting process and you may get lucky and learn something on a one shot test.
I'd recommend using the dealer's kit at least the first time; labs tend to be very childish about how they want to see samples come to them. Kinda like two year olds at the dinner table.
And the kit cost is nominal. Expect a week or two to get the results back.
On medium sized TLBs, the total cost of the analysis is about the same as the cost of new filters and new oil. Or maybe slightly less since I'm remembering that our Kubota M59 has three factory filters in the trans/hydraulic system and holds about 11 gallons of oil. But it's close to a wash. The good news comes when the analysis saves you from an afternoon of laying under a tractor wrestling the dented center filter can while warm oil gently drips into one ear. It's on a big machine where they measure oil capacity in barrels that analysis really pays off.
Best of luck,
rScotty - an old time wrench-bender
