Concrete Mixer Truck Inspection Guide: What to Check Before You Buy

This guide walks through every system to check, in order. Bring it with you and work through it item by item. Most of what goes wrong on a cement truck lives inside the drum or the drum drive, so a quick walk-around will not find it.

If you have not read our used concrete mixer truck buying guide yet, start there. It covers sizing, pricing, and history. This article goes deeper on the inspection step.

Before Your Concrete Mixer Truck Inspection

A few ground rules.

System 1: Drum Shell and Interior

Start with the drum. It is the most expensive part to replace, and the part most buyers check the least.

Here is how a concrete mixer truck works. The drum holds the load and turns slowly the whole way to the job. Spiral steel blades inside, called fins or flights, fold the concrete as the drum turns one way. Reverse the drum and those same fins push the concrete up and out the back. If the shell or fins are worn, the truck mixes poorly and unloads slowly.

Machine off

• Walk the full length of the drum and look for welded patches, pinholes, gray slurry stains, or rust lines. Each one points to a thin spot or a past repair.
• Pay close attention to the belly, the low part where the load rides, and the head, the closed end near the cab. The steel wears thin in these areas first.
• Ask whether the drum has ever had thickness readings taken with an ultrasonic gauge. A shop can do this from the outside in under an hour. It is the only real way to know how much steel is left.
• Shine a light through the rear opening and any inspection hatch. Look for built-up hardened concrete on the fins and walls. Heavy buildup adds dead weight, cuts how much you can haul, and hides fin wear.
• Check the fins. The New Jersey Department of Transportation’s concrete truck inspection procedure (opens in a new tab) treats blades as excessively worn when they drop below 90 percent of their original height. That height is measured at the widest part of the drum, nearest the head. Ask the seller for the original fin height so you have something to compare against.
• Look for cracked, bent, or broken fin sections near the rear opening.

Machine running

• Turn the drum in the charge direction and watch the shell for wobble or a visible dip as it rotates. A bent or out-of-round drum loads the rollers unevenly.
• Pour in some water and run the drum in discharge. Water should move out steadily. Weak flow can mean worn fins or heavy buildup.

System 2: Drum Drive

The drum drive is what turns the drum. On most trucks, an engine-driven hydraulic pump sends oil to a hydraulic motor. The motor spins a planetary gearbox, a compact set of reduction gears bolted to the front pedestal. The gearbox turns the drum. At the back, the drum rides on a steel roller track, also called the drum ring, that sits on two rollers.

Machine off

• Check the gearbox oil level and look at the oil. Metal flakes, a burnt smell, or a milky color all point to internal wear.
• Look for oil around the gearbox seals, the hydraulic motor, the pump, and every hose between them.
• Check the front pedestal and rear roller stand for cracked welds or loose mounting bolts.
• Look at the rear rollers and the roller track. Flat spots, chipped edges, or a groove worn into the track mean wear. Check that both rollers touch the track evenly.
• Find the drum speed plate and the revolution counter. The New Jersey DOT procedure calls for a metal plate that shows the maker’s mixing and agitating speeds, plus a counter in working condition that tracks drum turns.

Machine running

• Run the drum through its full speed range in both directions. Speed should change smoothly when you move the control.
• Switch from charge to discharge and back. The drum should slow, stop, and reverse without a clunk or a jerk.
• Listen at the gearbox and the pump. A steady whine, grinding, or knocking means trouble.
• Rev the engine up and down. The drum speed should stay steady once it is set.
• Watch the rear rollers as the drum turns. They should roll quietly with no bounce, squeal, or side-to-side drift.
• Check every hose and fitting again once the system is under pressure. Some leaks only show up then.

System 3: Water System, Chutes, and Controls

The water system washes out the drum and adds water to the mix. The chutes carry concrete to the pour. Both get used every day and both take a beating.

Machine off

• Check the water tank for rust, dents, and leaks at the welds. Look at the mounting straps.
• Check the sight glass, also called the sight gauge. It should be clean and easy to read. The New Jersey DOT procedure expects the water reading to be accurate within 1 gallon, or 1 percent of the tank’s mixing water capacity, whichever is greater.
• Look at the main chute, the fold-over section, and the chute pivot. Check for cracked welds, worn liners, and a worn pivot pin or bushing.
• Count the extension chutes. Most trucks carry several, and missing ones cost money to replace.
• Look at the charge hopper and fins near the rear opening for heavy wear and buildup.

Machine running

• Run the water pump or air-pressure system and spray the wash hose. Pressure should build quickly and hold.
• Add water to the drum and watch the sight glass drop. It should match what went in.
• Raise, lower, and swing the chute through its full range. Do this with power if the truck has a powered chute. Stand clear of the chute the whole time.
• Test the rear drum controls. Speed and direction should respond at once. If the truck has an emergency stop at the rear, test it.

System 4: Engine, Transmission, and PTO

A mixer truck engine works hard even when the truck sits still, because it is turning the drum at the job. That is why engine hours often tell you more than miles on a cement truck.

Machine off

• Pull the dipstick. Milky or burnt oil is a problem.
• Check the coolant level and look for leaks at the radiator, hoses, and water pump.
• Compare engine hours, miles, and service records. Ask for oil analysis reports if the fleet kept them.
• On newer trucks, ask about the emissions system service history. Diesel particulate filter and DEF system repairs add up fast.
• Look at the power take-off, or PTO, that drives the drum pump. Check for oil leaks and loose mounts.

Machine running

• Start the engine cold. Listen for knocking, and watch the exhaust for heavy smoke.
• Check for blow-by at the oil fill cap. Heavy smoke puffing out means worn rings.
• Engage the PTO and run the drum. The engine should hold a steady idle without bogging down.
• Take a test drive. Shifts should be smooth with no slipping, flaring, or hard clunks.
• Watch the warning lights after startup. Any light that stays on needs an answer.

System 5: Chassis, Axles, Suspension, Brakes, and Tires

A mixer truck carries a full load on every trip, often on rough job site ground. The chassis takes that weight day after day.

Machine off

• Walk both frame rails. Look for cracks, welded repairs, and rust, especially under the front pedestal and the rear roller stand.
• Look at the lift axles. Many mixers run one or more pusher axles ahead of the drive axles, and some add a tag axle behind them. Some also carry a booster axle that folds down behind the truck. Check the air bags, lift arms, pivot points, and tires on each one.
• Check the suspension for broken springs, cracked hangers, worn bushings, and leaking air bags.
• Look at the brake chambers, slack adjusters, drums or rotors, and air lines for wear or damage.
• Check every tire for tread depth, sidewall cuts, and uneven wear. Uneven wear on one axle points to an alignment or suspension problem.

Machine running

• Build air pressure and listen for leaks. Pressure should build at a normal rate and hold with the engine off.
• Raise and lower every lift axle and the booster axle from the cab controls. Each one should move smoothly and hold its position.
• Test the brakes on your drive. The truck should stop straight with no pull.

System 6: Cab, Electrical, Lights, and DOT Documentation

Machine off

• Test every gauge, switch, and warning light. Include the in-cab drum controls and the lift axle controls.
• Check the seat, seatbelt, mirrors, horn, wipers, and backup alarm.
• Walk around and check every light, reflector, and the rear camera if the truck has one.
• Ask for the most recent annual inspection report. Under the federal periodic inspection rule, 49 CFR 396.17 (opens in a new tab), a motor carrier cannot run a commercial truck unless it has passed an inspection within the past 12 months and proof of that inspection is on the vehicle. A recent report shows you what an inspector found. An old or missing one tells you something too.
• Ask for the ownership documentation and confirm there are no outstanding liens.

Machine running

• Confirm the gauges read normally and no warning lights stay on.
• Run the drum controls from the cab and confirm they match what the rear controls do.

When to Bring a Professional

Hire a third-party inspector or a heavy truck technician if you are not sure how to judge the drum drive, the drum shell, or the brakes. For any truck priced above $75,000, a professional inspection is worth the cost. The fee usually runs $500 to $1,500. Ask the inspector to take ultrasonic thickness readings on the drum. That one step can tell you whether you are buying a drum with years left or one that needs replacing soon.

Red Flags That Should Stop the Deal

Walk away unless the price clearly reflects the problem:

Once you are happy with what you found, you know what to look for. Financing options are available through Equify Financial. If you still need it, our used concrete mixer truck buying guide covers sizing, budget, history, and financing in more depth.