Hydraulics 101

It's time to make sure your technicians know their hydraulics

Like most problems in a shop, it starts small, but will your technicians be able to diagnose and fix it before it becomes a major problem?

A seal is leaking on a bucket truck's hydraulic pump--probably one of dozens of small jobs that could be done throughout the day. The question is, will your technicians handle the situation with some preventative maintenance, or will they let it slide until it ends up costing you much more?

Spotting something minor like this is what proactive PM scheduling is all about, and in this case, simply changing out the seal--keeping oil losses to a minimum--can save a fleet hundreds of dollars. Let it go, and soon the leaky seal could burn up from a lack of oil, forcing you to spend $600-plus on a new pump and more oil, not to mention associated costs of keeping a needed truck out of service.


Many fleets end up wasting precious dollars on their hydraulic systems because of a lack of proper education, says Joel Barnes, technical trainer manager for Heil Environmental.

"When you are charged with finding mechanics, the first person you look at is a highly qualified diesel mechanic, (but) that guy may not be well-schooled on the hydraulic side of it," he says. "Over the years, he's just seen what he's seen and done what he's done, he's never really been to any classes or schools on hydraulics. I find, everywhere I go, a guy who's a 20-year diesel technician, but knows nothing about hydraulics because he's never had to deal with it. And so it really gets left out a lot of the time."

And it all starts with the basics. As he travels across the country, training technicians on proper hydraulic maintenance, Barnes sees a startling lack of understanding about simple schematic diagrams.

"I'll go somewhere and the first thing I'll tell them is to get out a schematic and look at the entire system; that way you can see what's involved," he says. "Everywhere I go, they don't know how to read the schematic, and they sit there looking at it, (saying), 'I can look at that all day long and I don't know what these little symbols mean.' If you can't read a schematic, the first thing you ought to do is learn how, because that's the key."

Technicians who cannot understand schematics generally end up unnecessarily replacing parts, driving up shop costs.

"(They'll) replace the valve 20 times and not know why," Barnes says. "If they would look at the schematic, they would see it was another valve before that one that was causing the failure."

Effectively troubleshooting and maintaining hydraulic systems means identifying and correcting potential problem areas before they become major issues, says Bob Johnson, director of fleet relations for the National Truck Equipment Association (NTEA).

"It's pretty darn basic, but at the same time it can be complex," he says. "Inspect all the components; look at the hoses and seals--any locations where hoses can be subject to abrasion or they cross over, support or rub on each other--look for signs of hose damage or wear, re-position them or put a protective wrap on them if necessary. Look for signs of leakage in any fittings, and if any fittings are leaking, check them--if they're loose, tighten them.

"Then make a note where you found loose fittings," Johnson says. "If you find the hoses binding, try to relieve that. Look at your cylinder seals, look for leakage there; make sure that the wipers are in good condition. Make sure all your fittings are tight; all your mounting pins and bolts are snug, because if anything works loose it can cause problems down the road. Make sure the rod wipers are in good condition, make sure your motor seals aren't leaking."


Joe Sullivan, fleet supervisor for Long Island, NY-based Norsic and Sons refuse haulers has worked with Heil Retriever Class-5 trucks for more than a decade. He says setting the correct hydraulic pressure and making sure the system is going through its proper auto cycle correctly are two important factors in properly maintaining hydraulics.

This content continues onto the next page...

We Recommend