When Lack of Maintenance Creates a Much Bigger Problem: Skyjack SJ3219 Steering Failure

That was the case with a Skyjack SJ3219 DC electric scissor lift we worked on in Trenton, North Dakota.

The customer's complaint was unusual:

The machine would steer when it wasn't driving, but it wouldn't steer properly when it was driving.

At first, that could point a technician in several different directions.

Could it be an electrical problem?

A hydraulic problem?

A steering control issue?

A problem with the drive system?

The actual problem turned out to be much more mechanical, and much more preventable.

The steer cylinder rods were bent.

But even that wasn't the root cause.

The real problem was the steering pivot pins that the wheels ride and turn on.

Those pins had become so badly seized that the steering cylinders were trying to turn wheels that couldn't properly pivot.

And eventually, the cylinders lost the fight.

An Electric Scissor Lift Still Needs Plenty of Maintenance

For anyone who isn't familiar with the Skyjack SJ3219, it's a DC electric scissor lift.

Because it doesn't have a diesel engine, it's easy to think of an electric scissor lift as being relatively maintenance-free.

It isn't.

An electric scissor lift still has steering cylinders, wheel pivot pins, bushings, steering linkages, drive motors, brakes, hydraulic components, bearings, structural components, electrical systems, batteries, safety systems and numerous mechanical joints that have to move properly.

This particular machine also gets moved from jobsite to jobsite.

It isn't sitting inside a clean shop every night.

It's exposed to rain, dirt, dust, mud, moisture, road grime and the elements.

That makes proper lubrication and inspections even more important.

The Complaint: It Steers Sitting Still, But Not While Driving

The first clue was the strange steering complaint.

When the machine wasn't driving, the steering would work.

But once the machine was being driven, the steering wouldn't work properly.

That difference turned out to be extremely important.

The steering circuit doesn't have the same hydraulic pressure available under both conditions.

When the machine isn't driving, the steering receives the full available hydraulic pressure.

When the machine is driving, only approximately 400 PSI is diverted to the steering circuit.

That meant the machine could produce substantially more steering force while sitting still than it could while driving.

With a properly maintained steering system, that's not a problem.

The wheels should pivot freely, so the available steering pressure is enough to turn them.

But these wheels weren't moving freely.

The steering pivot pins were severely seized.

That created the strange symptom the customer was experiencing.

When the machine was sitting still, the steering system had enough pressure to overcome some of that resistance.

Once the machine was driving, the steering circuit only had about 400 PSI available, and that wasn't enough to overcome the resistance created by the seized steering pivots.

Suddenly, the complaint made sense.

The pressure difference wasn't the cause of the problem. It exposed the mechanical problem.

The Real Problem Was at the Wheels

Once we started working through the steering system, we found the steer cylinder rods were bent.

That was obviously a failure that needed to be addressed.

But we didn't want to simply replace the damaged cylinders and send the machine back to work.

We wanted to know:

Why did the cylinder rods bend?

That's where the steering wheel pivot pins came into the picture.

The pins that allow the steer wheels to pivot had essentially seized solid.

They had not been properly lubricated, and exposure to the elements had taken its toll.

The steering cylinder was still doing its job.

It was trying to turn the wheels.

The problem was that the wheels couldn't pivot.

The cylinder kept pushing.

The mechanical resistance kept increasing.

Eventually, the force was transferred into the cylinder rods.

The rods bent.

A Hydraulic Cylinder Was Trying to Move a Seized Mechanical Joint

Normally, the steering system works something like this:

Steer cylinder moves → steering linkage moves → wheel assembly pivots.

But when the wheel pivot is seized, it becomes:

Steer cylinder moves → linkage loads up → wheel won't pivot → cylinder continues applying force → cylinder rod bends.

The hydraulic system can generate tremendous force.

That's one of the reasons hydraulic equipment is so powerful.

But that power can also create damage when a mechanical component is seized.

The cylinder wasn't designed to act like a giant press to force a completely seized wheel pivot loose.

Yet that's effectively what was happening.

And eventually, the cylinder rods couldn't take the load.

Then We Tried the Grease

Once we started working on the seized wheel pivots, we got an even better indication of how bad the problem was.

We put grease into the pivot points.

Instead of clean grease immediately working through the joint, rust started coming out the opposite end.

That was a pretty good indication that there was significant corrosion and contamination inside the pivot.

We continued trying to get grease into the pivot.

The grease pressure climbed.

And climbed.

Eventually, we were seeing approximately 10,000 PSI of grease pressure.

And the steering still wouldn't break loose.

10,000 PSI.

Still seized.

At that point, this wasn't something that was going to be fixed by simply putting more grease into the fitting.

The pivot needed to come apart.

Sometimes Maintenance Means Taking Things Apart

We had to disassemble the steering components so we could get to the problem properly.

Once everything was apart, we could clean the components, remove the contamination and corrosion, inspect everything and determine what could be reused and what needed attention.

After everything was properly cleaned and inspected, we could reassemble the steering system and get the wheel pivots moving properly again.

This is an important distinction:

Greasing a machine isn't necessarily the same thing as maintaining a machine.

Grease has to actually get where it needs to go.

If a pivot has been neglected long enough to become severely corroded and seized, pumping grease into the fitting doesn't undo the damage that's already occurred.

In this case, we had to physically disassemble the components and clean them before the system could be properly put back together.

How a Maintenance Issue Bent a Cylinder

This is the part of the job that really stands out.

The original problem wasn't a bent cylinder rod.

The original problem was lack of lubrication at the steering wheel pivot points.

That led to corrosion and contamination.

That led to the wheel pivots becoming seized.

That forced the steering cylinders to work against an extreme mechanical resistance.

That eventually bent the cylinder rods.

The failure chain looked like this:

Lack of lubrication
↓
Rust and contamination develop inside the steering pivot
↓
Wheel pivot becomes increasingly difficult to move
↓
Pivot eventually seizes
↓
Steering cylinder tries to turn the wheel
↓
Wheel cannot pivot
↓
Excessive force is transferred into the steering cylinder
↓
Cylinder rod bends
↓
Machine develops a steering problem

A relatively simple maintenance issue eventually became a significant repair.

The Machine's Environment Matters

The customer's machine moves from jobsite to jobsite.

That means it is constantly exposed to conditions that can accelerate wear and corrosion.

It's not a machine that spends its entire life inside a clean warehouse.

It's outside.

It's transported on the road.

It works around dirt and dust.

It gets exposed to rain and moisture.

Those conditions make lubrication and inspections especially important.

A machine working in harsh environments needs to be maintained for the environment it actually operates in, not the environment we wish it operated in.

Why Annual Inspections Matter

This is also why annual inspections are important.

With aerial equipment, don't just think of the annual inspection as paperwork.

A proper inspection is an opportunity to find problems before they become failures.

For a machine like the SJ3219, that means looking closely at the steering system and other critical components.

Things like:

• Steering cylinders
• Cylinder rods
• Steering linkages
• Wheel pivot pins
• Bushings
• Retaining hardware
• Lubrication points
• Structural components
• Hydraulic components
• Electrical systems
• Batteries
• Safety systems
• Drive components
• Brakes

The important question isn't simply:

"Does the machine work?"

The better question is:

"Is everything on the machine working and moving the way it is supposed to?"

A machine can still drive, steer and raise while a serious problem is developing.

An inspection is your opportunity to find that problem before it turns into downtime.

Don't Forget Battery Maintenance

Because the SJ3219 is an electric scissor lift, battery maintenance is another important part of keeping the machine reliable.

Electric equipment has different maintenance requirements than diesel equipment, but it absolutely still requires maintenance.

Battery condition, connections, cables, corrosion, charging practices and other electrical components all need to be checked according to the manufacturer's requirements.

It's easy to think:

"It's electric, so there isn't much to maintain."

That's not the case.

No engine oil doesn't mean no maintenance.

The battery and electrical systems need attention, while the mechanical systems still need lubrication, inspection and service.

Don't Forget the Annual MEWP Inspection

And if you're operating aerial equipment, don't overlook the annual MEWP inspection.

MEWP stands for Mobile Elevating Work Platform.

These inspections are important because aerial equipment has safety-critical components that need to be inspected regularly.

The annual inspection is another opportunity to find worn, damaged, corroded, loose or improperly functioning components before they create a bigger problem.

It's not simply about getting a form signed.

It's about making sure the machine is being properly evaluated.

Maintenance Is Not the Same as Making the Machine Work Today

There's a big difference between:

"The machine works."

and:

"The machine is properly maintained."

A machine can work today while a problem is quietly developing.

A pivot can be getting tighter.

A bushing can be wearing.

A pin can be corroding.

A cylinder rod can be taking abnormal side loading.

The machine may continue working until the problem becomes severe enough to cause a failure.

That's why preventive maintenance matters.

You don't want the first indication of a seized steering pivot to be a bent cylinder rod.

You don't want the first indication of a worn bushing to be a steering failure.

And you don't want the first indication of neglected battery maintenance to be an electric machine that won't go to work.

Finding the Root Cause Matters

This is one of the biggest things we focus on at Mondak.

If you only look at the failed component, the answer seems simple:

Bent steer cylinder rods.

Replace them.

Done.

But that's not a complete repair.

The next question has to be:

Why did they bend?

In this case:

What failed?

The steer cylinder rods.

What caused them to fail?

The steering wheel pivot pins had seized.

Why did the pins seize?

They had not received the lubrication they needed, while the machine was regularly exposed to the elements.

Why did the machine have trouble steering while driving?

The steering circuit only had approximately 400 PSI available while driving, compared with full available steering pressure when the machine wasn't driving. That reduced pressure wasn't enough to overcome the resistance created by the seized wheel pivots.

What ultimately happened?

The steering cylinders continued trying to move the wheels against the seized pivots until the cylinder rods bent.

That's the complete diagnosis.

A Preventable Headache

Nobody intentionally decides to skip maintenance because they want to bend a cylinder rod.

That's not how equipment failures happen.

They happen gradually.

A grease point gets missed.

Then it gets missed again.

The machine keeps working.

It gets moved to another jobsite.

It gets exposed to more moisture and contamination.

The pivot gets tighter.

Nobody notices because the machine still operates.

Then one day the operator says:

"The steering isn't working right."

Now you're no longer talking about a grease job.

You're talking about disassembly, cleaning, inspection, cylinder damage, repairs and machine downtime.

That's the difference between preventive maintenance and reactive repair.

What We Do at Mondak Equipment and Hose

At Mondak Equipment and Hose, we don't want to simply replace whatever component happens to be broken.

We want to know why it broke.

That is especially important when we're working with hydraulic systems.

A bent hydraulic cylinder rod may be the visible failure, but there may be another mechanical problem that caused the cylinder to take an abnormal load.

Our capabilities include:

• Preventive maintenance
• MEWP inspections
• Field service
• Equipment inspections
• Hydraulic troubleshooting
• Hydraulic cylinder repair and rebuilding
• Cylinder teardown and inspection
• Cylinder resealing
• Cylinder rod fabrication and replacement
• Cylinder barrel replacement
• Clevis repair and replacement
• Hydraulic hose fabrication and repair
• Hydraulic system troubleshooting
• Heavy equipment repair

We can remove a cylinder in the field when the machine can't reasonably come to the shop.

We can bring the cylinder back to our shop for teardown, inspection and rebuilding.

We can fabricate or replace damaged rods.

We can replace damaged cylinder barrels when necessary.

We can repair or replace clevises and other cylinder components.

And once the cylinder is ready, we can return to the jobsite and put the machine back together.

The goal isn't to sell you a replacement component.

The goal is to diagnose the failure, repair it correctly and get the machine back to work.

The Lesson From This Skyjack SJ3219

This SJ3219 came to us with what sounded like a strange steering problem.

It would steer when sitting still but wouldn't steer properly while driving.

The eventual diagnosis wasn't a mysterious electrical failure.

It wasn't the electric drive system.

It was a mechanical problem caused by neglected maintenance.

The wheel pivot pins had become severely seized.

When we tried to grease them, rust came out the other side.

The grease pressure climbed to approximately 10,000 PSI, and the steering still wouldn't break loose.

We had to disassemble the steering components, clean everything and properly reassemble the system.

The seized pivots had forced the steering cylinders to work against extreme resistance.

The cylinder rods bent.

And what started as a maintenance issue became a significant repair.

That's the lesson.

Electric equipment still needs maintenance.

Outdoor equipment needs maintenance.

Aerial equipment needs inspections.

And when something fails, don't just ask what broke.

Ask why it broke.

Because sometimes the most expensive part of a failure isn't the component that broke.

It's the maintenance that wasn't done before it broke.

Inspect. Maintain. Diagnose. Repair. Get back to work.

That's what Mondak Equipment and Hose is about.