Hydraulic oil smells

The last two times I've changed my hyd oil, it stunk. I'm using the oil the Manufacture recommends. Changing the filter and oil every 300 hours like recommended. This time I changed it at 250 hrs, still stinks.

Part of my problem is the hyd holds 5 gallons. About 1 gallon can't be drained. It's in the pump, hoses, 11 cylinders, and hydrostatic motor.

So, I've been wondering what is the best way to flush out the old stinky 1 gallon without taking everything apart? 44 hose fittings, some can only be gotten to by removing the cylinder form backhoe. NO WAY, NO HOW, DON'T EVEN THINK ABOUT IT. I just had a battle removing the leaky stabilizer cylinder.

Options I've been pondering:
Only put 1 gallon in hyd, run all the controls up and down, put the rear wheels up and run them forward and backward. Then when I drain it, half the old gallon of old will remain.

If I did this a second time procedure a second time, then I would be left with a quart of old, then a Pint, then a half pint.

Or do a 2 gallons fill and flush twice? or fill it with 4 and drain it all out?

Either way, I would be using 4 gallons. A 4 gallon fill and flush will leave me with 20% of a gallon remaining. One gallon at a time will leave me with 6.25% of a gallon.

My question is, will adding a gallon at a time be safe to do with out damaging the pump? 2 gallons?

What's the best and safest option to clean up the hyd? I plan to go just 150 hours instead of the full 300 and see what happens. Oil is cheaper than a new pump.

It might sound funny to ask this, but what do you mean by the oil stinks? I ask because I've been into hydraulic systems that are factory fresh, and those that haven't had the oil changed in nearly 10,000 hours. In every case the oil has always smelled "like oil" unless it had been overheated and had a bit of a burnt smell to it.

If yours has that burnt smell to it then there's something wrong with your system that's letting the oil get way too hot. Beyond that I really don't know what else to tell you as I have never encountered hydraulic oil that 'stinks' in more than 25 years of working on equipment of all kinds.

The smell could be a burnt smell. The hyd shop rebuilding the cylinder says the oil is breaking down and I should use an oil the manufacture doesn't recommend.

So how would you flush it out? 1,2 or 4 gallons?

(quoted from post at 12:39:50 01/13/15) The smell could be a burnt smell. The hyd shop rebuilding the cylinder says the oil is breaking down and I should use an oil the manufacture doesn't recommend.

So how would you flush it out? 1,2 or 4 gallons?

Click to expand...

ou can't get it all out anyway unless you dismantle the whole system.

If the oil overheats. Get a bigger tank or install an oil cooler.
I never change hydr fluid unless i have to drain it for a repair.or lose it by a broke hose,..then i just add.
I never smelled a bad odor yet.

You might be right. Mine has both smell and dark
color. I'll ask my hyd shop the best way to cool
the oil.

(quoted from post at 12:53:46 01/13/15) You might be right. Mine has both smell and dark
color. I'll ask my hyd shop the best way to cool
the oil.

Click to expand...

It sounds like the oil is oxidizing(breaking down). If it holds 6 gallons and you drain out 4 gallons, you have changed 66% of the oil. I would do something like get as much oil drained and replaced as I could. I would also change the filter or filters and operate it for 10 hrs or so and change the filters again. That is probably about the best you can do with a closed system. The oil is breaking down from heat, so a cooler might be a good idea. Also it is probably not the case, but there are soy oils out there that are marketed as hydraulics. These have a low resistance to heat. I assume you have a good oil.

It holds 5 gallons, 4 I can drain out.

Not sure where I could safely add a cooler
without the risk of it getting damaged. It has 11
hydraulic cylinders. Some may get warm to the
touch, but not hot like engine temps.

Black absorbs sunlight and Black also is the best
color for radiating heat, black body radiation. I
may paint all cylinders black. What can it hurt?
Does anyone make aluninum cooling fins I could
attach to cyliners?

I think I may do like you say, fill it, use it
for a while then drain it more often. Then try
the hyd fluid my hyd shop recommends.

What is it and how are you using it?

11 cylinders with 5 gallons of hydraulic fluid... Sounds like a compact tractor with a loader (4 cylinders) and a backhoe (7 cylinders).

Either we're looking at a poorly designed system, or you're trying to do more with it than it was designed for. Some of these little tractors just aren't designed to dig trenches all day. If you're putting on 300 hours quick enough to notice a pattern with the oil smell, you're working that little guy HARD.

You cool oil with an oil cooler. It looks like a radiator but instead of water, the hydraulic fluid runs through it. Depending on your tractor it may not be feasible to put an oil cooler in the system.

If the backhoe is detachable the best place to put an oil cooler would be in the return line from the backhoe.

Another option would be additional fluid capacity. Again, you could install this in the return line from the backhoe. The backhoe would push oil into the auxiliary tank, and the auxiliary tank would push oil into the tractor. Another 5 gallons would probably be enough.

One challenge will be finding a place out of the way for a 5 gallon tank or the oil cooler, where it won't stick out but will still work.

Then again you may just be working the machine too hard.

Are there any wet clutches or brakes on the tractor? If so is the smell and contamination from slipping or dragging clutches?

All hydrostatic, no clutches or brakes.

Yes, it is a compact. Terramite t5c.

No real good place for an extra tank or cooler.
There is a rubber hose, radiator like hose, with
radiator hose clamps, from the tank to the pump.
If I could find about 1 inch diameter soft copper
I could make a small coil heat exchanger, put a
fan on it. That might cool the oil before it gets
to the pump. It wouldn't be under any pressue
putting it on the suction side of the pump.

Next time I'm using it hard, I'll get my IR
therometer out and see how hot the oil is in
different locations, especially where it comes
off the pump. The pump has 1600 hours on it. Hope
it's not the pump.

if the machine is still factory.
I'd check for a sticking valve, a replaced hose that is a smaller size, etc.
Something that might be putting the pump into relief, which will superheat the fluid quickly.

As far as smell...on the Kubotas I've owned, which I work very hard, when I smell hot hydraulic fluid, I know it's time to take a break. The vent is under the seat.
On little machines with lots of hydraulics, they just can't design in a big enough reservoir in my opinion. Should be tripled at least.

Stink? well everybody's nose is different.
Shop and barn smells....ahhh
walk into a house with air fresheners, carpetfresh stuff, eveybody wearing perfume and hairspray...get me [i:e11f7d67cc]out[/i:e11f7d67cc] of here..it [i:e11f7d67cc]stinks[/i:e11f7d67cc] in here.LOL

Based on what your saying, I've got to agree that it definitely sounds like the oil is overheating. That said, what oil are you running in it, as the parts manual is calling for a 15w40 engine oil for outside temps above 40 degrees. Running the wrong weight of an oil can cause problems so I'd check that. The typical temp you'll want to see on a hydraulic system is below 210, but the very maximum you'll want to see is 250 degrees. Once you get that hot, your burning and breaking down the oil, so the cooler the better.

Looking at the manual ((the link below)) it recommends changing the oil every 250 hours, or every month and a half, if using it 8 hours a day. Like I said, I've seen hydraulic systems with thousands of hours on them, with no problems, so this quick of an oil change schedule on a system tells me that there is something not right, and they are trying to compensate for it by changing the oil -vs- fixing the problem.

That said, in my opinion, your best bet would be to install a small hydraulic cooler in the return line, and drive the cooling air with an 12v DC fan. Ditchwitch uses this design on many of their smaller pieces of equipment, like cable plows, that have a small hydraulic system, but use a lot of flow to both drive the machine as well as operate the various functions. If you could find the cooler off of a 255 cable plow, or something similar, and get it tied in, I think you'd see a world of difference. Good luck.
Parts manual

I found something I didn't know. On the back of my hoe, it says change hyd oil every 300 hrs with 10w40, engine every 100 hrs. The manual you posted on page 7 says change hyd every 250 hours and use 15w40. IN BIG BOLD PRINT, IT SAYS DO NOT USE HYDRAULIC OIL. I've been using what is printed on the back plate of terramite, 10w40.

Terramite has changed hours and oil a little. That said, I plan to change my oil and filter more often. Really think my problem is oil breaking down which then may cause temps to go up. Now I may be looking at pump damage, which in turn may be the reason the oil smell burnt and is turning black.

Same with engine. I can go 60 hours, oil looks clean on dipstick, hasn't used a drop. At 75 hours oil is breaking down, turned black and is down a tick on stick. That's when I change engine oil.

I think I may change hyd oil every other engine oil change and see what happens.

Hope motor oil comes down in price. I watch for sales, buy a good brand when price drops below $2.

My hyd shop on recommends I use ISO 40 hyd oil. So, who do I believe, hyd shop or Terramite?

I will be talking to the owner of the hyd repair shop and pick his brain about a cooler.