A lot of people don’t know what to look for, so I am going to point out a few things that might be overlooked.

We will start with the couplers. Look at the ISO coupler connection for your implement and also look at the drain tubes that come out of the back and down to the bottom of the tractor. You may say there aren’t any leaks from the ISO couplers, but it might be leaking from the drain tubes.

Look around the tractor at hydraulic lines, fittings and cylinders that might be leaking. After that check the lines that go to the pumps and power steering and other hydraulic parts that could leak oil. You want to check inside the cover panels for any lines that may be developing a slow leak.

As you look around the tractor or equipment, you may come on a part that has some dirt and grease caked on it. That’s a sign of possible leakage. You should check hoses and other parts around that collection point to try to find the source. It may not be a large leak and would not be a high-impact item.

If you are worried about it, you should clean it off and run it for awhile to see where the leak may be coming from.


An example of the impact seemingly small leaks comes from when I worked for the Department of Energy. We would test tractors to make sure they were running efficiently. One tractor had a leak on the coupler and the owner thought it wasn’t a big deal, “just a little leak.”

So I put a clear plastic bag on the coupler and had him run the machine for half an hour or so and we calculated it out that he was losing about a gallon of hydraulic oil an hour. It was probably even more when his machine was really revved up and working hard.

Even though he had been putting in oil like crazy, he didn’t think that was where the problem was. Having a way to measure leaks will help you understand how much oil is being lost. Attaching a clear plastic bag to the part that’s leaking is a simple way to do that.

So after you walk around the tractor and make sure you don’t see any leaks or problems, check the oil. The owner’s manual will tell you if you can check it cold or if you need to check it after it’s been running.

If it’s a loader or it has a loader implement attached to it, you need to check the oil when the loader is down and the pressure is released, because when the loader is up, the oil is displaced in the cylinders and the dipstick will show that you have low oil levels.

Some operators pick up a load in the bucket and drive with the bucket all the way up. You need to make sure you have enough oil because with all that oil being displaced, you can mess up equipment drive trains by driving around with low oil levels.

After checking the engine oil levels, coolant levels and hydraulic fluid levels, you need to check the oil cooler, which is usually located in front of the radiator. You also want to check the radiator to make sure there aren’t any restrictions across the front of that radiator; keep the screens clean.

Also make sure the belts are properly adjusted, so you get proper cooling. Sometimes you can get oil leaking on the outside of the radiator and the oil collects dirt and plugs up the radiator fins.

If your cooling system isn’t working properly your oil temperatures will go up (that’s a given), but the hydraulic oil will also go up. Of course dirt, water, aeration and cavitation are problems too, but the heat compounds the problems.

People don’t understand how some of these problems can affect the equipment and how it operates. By having the oil levels down, the radiator plugged and dirt and water getting in the system, it really shortens the life of the equipment.

By taking proper care of your equipment, a lot of these machines will run indefinitely. So by keeping the dirt and water out, changing the oil and filters religiously and keeping it at proper operating temperatures, the machinery will keep running for a long, long time. T

he biggest problem is that we become complacent and don’t run regular checks on the equipment. Keep a detailed record of when maintenance work is done. Keep it accessible and up-to-date. That takes the guesswork out of protecting your investment.  FG

Jim Schlund
Diesel Mechanics Professor
College of Southern Idaho

Jim Schlund graduated from the diesel mechanics program at Idaho State University in 1962 and has been involved in the mechanical industry for almost 50 years. He started his career at International Harvestor Company as the Service Foreman. He then started teaching at the College of Southern Idaho, where he taught for 35 years.

During his years of teaching, he was involved in corporate training for General Motors, training military units on diesel mechanics. He also developed curriculum for John Deere and Case IH training through the college. He was involved in certified training for Freightliner Manufacturing and has been nationally ASC-certified for most of his career.