Firstly, please let me apologize for starting an oil thread. I never thought I'd see the day. I've only been bending wrenches for 30 years, so apparently I have lots to learn. I'm working on an old Bobcat 632, and I just changed the hydraulic oil, and the machine doesn't like what I give it. I have tried AW46, and most recently 15w40 conventional. Both caused lots of hydraulic whine where there was no whine before (or not much anyway), even after letting the machine sit for awhile, and running it blocked up so the machine can run no-load and supposedly get the air out. By the way, the manual calls for 10w30 or 10w40 SE oil. I've been down the API classification rabbit hole, and wow that stuff gets dizzying quickly. Detergent levels are climbing, zinc levels are dropping, and everybody says their oil is the right one to use. Gads. I now have a bucket of 10w30 conventional SM oil coming. Hopefully that will do it. I am ok putting some zinc additive in there to bring it closer to 1970's levels, but the detergent thing has me concerned. I ran into a thread where a heavy equipment mechanic said to never use detergent oil in hydraulic systems, that they cause cavitation, which seems to be what I just experienced. But there's no such thing as a multi-vis non-detergent engine oil. Plus, I beliebe Furthermore, I have always had a problem believing that these machine manufacturers like Bobcat, Komatzu, JD all engineer their own oil. They say they do, but I have to say I think that's just marketing gimmick. I got nothing to back that up though. Anyway, curious to hear your thoughts. Lets not turn this into a "my oil is better then yours" thing ok?
A friend that manufactured pea, bean and grape harvesters used either 10x30 or 10x40. worked fine and harvesters are still operating some 35 years later.
If the manual states a requirement for 10W30 oil then there is a possibility that both the AW46 and the 15W/40 were a tad on the heavy side and that was what caused the whine/cavitation issue.? Is there a screen on the suction side that has not been cleaned recently.?
There's no inlet screen. Well, to be clear, there is a screen on the filler neck on the tank, and that's the closest thing to an inlet screen that machine has. The manual gives a bobcat number, which supersedes to another number that is just AW32. I also see elsewhere on this forum, that this exact subject has been covered fairly thoroughly, so in the interests of not beating this apparently dead cow any further, that we should consider this thread resolved. Thanks all!
if you were worried about zinc content for a hydraulic system you could simply throw a "standard" (not zinc-free aka "ashless" in other words) SAE 10W hydraulic oil in it and call that it......... viscosity-wise SAE10W is somewhere between ISO AW22 and AW3232 IIRC.
Most tractor fluid is 10W-30 and some say it is a good oil to run in skid steers. On an older machine like a 632 I wouldn't think the type of oil would be that critical. Curious how much of a whine and when? I had an older skid steer that had a lot more whine than my 94 model. Even the 94 will have more hyd. noise when doing heavy pushing. 10W-30 was pretty much the standard oil for skid steers in the 70's, 80's, 90's and even longer on some brands and the whine used to be quite common (and louder) on older hydrostatic transmissions. The whine might be inherent and nothing to do with the oil.
What did the oil look like that you drained out? Filthy? Did you grab a sample? Probably had Tractor Supply J20C in it lol.
D Definitely valid on older machines and some whine. This one I’ve had for a few months and while it had some whine with the old oil, it wasn’t much. All I did was put new oil in and change out the filter that still said “Clark” on it and had rust all over it, and now I got whine under even the slightest movement. Once I put the new fluid in, I’ll check pressures again and see where I’m at.
The oil was water contaminated, but it worked just fine I replaced the filter too, and that thing looked like it hadn’t been changed in years, if at all. So who knows what was in there. I got a Japanese grey market tractor in the shop too, that has a painted oil filter on it, ya know like they do at the factory? You can tell it’s been painted to match the engine. That thing is from the ‘70s too, and I bet that filter is original!
I worked for the Case dealer in the late 90's. I remember the skid steers required an anti aeration additive added to the hydraulic oil. Even if you used the Case hydraulic oil the additive was required.
The water kept it quiet. Add a half-gallon of distilled water to it. Should keep corrosion at bay**********
A lot of times the oil chart will have a mono grade for non colder weather. Maybe a non detergent sae 20?
If the oil had water in it the damage is done. If everything still works fine, just put some ear plugs in under the muffs and run it. Gear and vane pumps don't care what oil is used. Piston pumps like clean oil with some pumps being a little fussy about oil composition. Most of the time oil type requirements are just the manufacturer's way of dumping design problems in new machines on the owners to avoid paying warranty claims.
With some manufacturers the 1st thing they check is if the oil meets the recommended ISO cleanliness level. If it doesn't no warranty. It's obvious if the oil is contaminated but if the oil is clean and the filter has been maintained just not meeting the ISO spec. could be a fight for warranty with some shops and/or manufacturers. I would guess before ISO specs. became common warranty may have been easier to get on some components.
Ninety nine point nine percent of new machines from the factory don't meet their own cleanliness spec. Multiple companies in this area require loop system filtering of all the oil in the machine for two cycle times and then sampling to meet the owner's own specs. Second part of that is that the dealers don't test new machine oils on warranty claims, because it doesn't matter at that point. It is design problems causing failures at the end of the warranty periods where the manufacturers start bring it up as an issue.
Not sure what method you used to change the hydraulic oil, but it's possible you simply have air in the system and will take time to work out. Bobcat machines don't use a "return to tank" system, instead they use a loop system return to pump, all the reservoir does is keep the loop filled as you cycle cylinders in and out. Air in the loop takes times to work it's way back to tank on a Bobcat.
I remember reading on a skid steer forum someone complimenting Thomas for having a system that returns oil to the tank and wished other manufacturers did the same thing but most don't. Thomas also used 2 inlet strainers, 1 for the hyd's. and 1 for the hydrostatic pumps. A lot of people bashed Thomas skid steers but I would guess 95%+ of those people have never spent any time in one. Just because Bobcat or Case are more popular, and that's what you own, doesn't mean a less popular machine isn't a good machine and have some better features.
I think every hydrostat system I have encountered recirculates the majority of the oil with the leakage and a certain amount of bleed off oil returning to the tank, usually via the oil cooler. The oil is then replaced by the charge pump. The oil is usually filtered after the charge pump. The return to tank will often have a fine strainer rather than a filter.
I was mistaken on the hydrostatic on a Thomas. I found the post I had read several years ago. The main hydraulic circuit is open loop and oil flows directly back to the reservoir similar to an excavator system which apparently isn't common on skid steers.
That's exactly right, I never thought of that. This system doesn't return to tank, so air bubbles have a hard time getting out. In fact, when that oil is cold, and there might be slight flow FROM the tank, there's no way for em to get out at all. Not until the oil starts to warm up and expand, and start flowing back into the tank. I bet most of the air just goes right back into the pumps. That's a design flaw IMHO. Anyway, I ran it again this morning for about 20-30 minutes and it seemed to be getting a little better. Not only that, after that short run, I saw quite a bit of bubbles / foam at the top of the tank, so that thing is still burping and farting from the fluid change. I'm not going to change it again, until I run it more, a little every day. I still have the 10w30 oil coming, but I'll use it in other ways if I don't need it for the 632. Also, a nice perk, my compressions are coming up, and they're looking better and better each time I check it, and I've noticed my blowby is not as bad as it was when I originally put new rings in this motor. I was going to swap in a Mitsubishi S3L2 I have sitting around but maybe now I won't.
Is there a procedure to follow when changing the hyd. fluid to help eliminate or reduce cavitation and air intrusion? On my skid steer the manual says to turn the engine over several times without starting over a few minutes letting the starter cool between each time. You don't just start it right away after changing fluid.
Yes there is. There is actually 2 different procedures, based on S/N. What i just noticed is, I did the wrong procedure. I may have boogered it up by now, but I'll try the correct procedure tomorrow.
It actually helps purge air from the loop if you cycle your cylinders, raise loader arms fully while fully tipping the bucket, then lower and curl bucket, the displacement difference between rod side of cylinders and piston side causes oil to flow in and out of the reservoir to the loop when you do this. Of course it still takes many cycles and will take some time for all those tiny bubbles to dissipate, but it does help.