Ever had that moment where you want to work, but the machine is dead? You have a whole pile of sand, gravel and cement waiting. Every minute that your concrete mixer sits silent, money is lost.

Broken equipment is one huge headache. Do you know that one of the top reasons construction projects lose profit is because of machine failure? Various studies indicate that unplanned downtime alone can raise project costs by nearly 15%. That’s one problem nobody wants to face.

But don’t panic. You don’t always have to call in a mechanic or run out for a cement mixer rental. Most mixer problems are relatively simple. The good news is, you can usually fix these yourself with just a few basic tools. 

This guide will show you exactly what is wrong and how to handle it. Here are the top 10 problems and the easy ways to get your drum spinning again.

Key Points

• Always check the easy stuff like power cords first because they usually cause the problem.
• Clean your mixer immediately after use because dried concrete is the number one thing that breaks machines.
• If your machine starts emitting strange squeals or grinding sounds, stop work immediately.
• Spending just five minutes on its care today saves it from costly repairs tomorrow.

1. The Motor Hums but Won’t Start

You flip the switch. You hear a buzzing sound, but the drum does not move. This is a common case of a concrete mixer not starting.

The Fix

This usually occurs for two reasons with electric mixers:

• Check the Capacitor: This small part gives the motor a “kick” to start. If you have to spin the drum by hand to get it going, the capacitor is likely dead. It is inexpensive and not hard to replace.
• Check Your Power Cord: Are you using a long, thin extension cord? If the cord is too long, by the time electricity gets to the motor, it is weak. Use a shorter cord made for heavy-duty service to supply adequate power to the motor.

2. The Gas Engine Sputters or Dies

Your portable concrete mixer engine tries to start, but does not. Alternatively, it runs for two seconds and dies.

The Fix

Gas engines are particular about fuel and oil.

• Low Oil: Newer engines have a sensor that protects the engine in case the oil is low; it simply will not start. Check the dipstick and fill it up.
• Bad Gas: Did the mixer sit all winter with gas in it? Old gas turns to gum and clogs up the engine. Drain the old gas and add fresh fuel.

• Dirty Spark Plug: If the spark plug is black and dirty, it is not going to fire. It needs to be cleaned using a wire brush or replaced with another one.

3. The Mixer Drum Won’t Turn

The motor sounds great and runs fast, but the drum is just sitting there and not turning.

The Fix

The connection between the motor and the drum is severed.

• Broken Belt: Remove the motor cover. Inspect the rubber belt for any signs of snapping or loosening. This is usually the most frequent cause. Replace it if it is broken.
• Broken Keyway: The “key” is a small piece of metal, locking the pulley wheel to the motor shaft. If it breaks, the shaft will spin, but the wheel doesn’t. You’ll need a new key.

4. Mixer Stops When Full

The machine spins fine, but when you add wet concrete, it groans and stops.

The Fix

This issue can be solved by doing the following two things:

• Tighten the Belt: A loose belt will slip under a heavy load. You must loosen the motor bolts, then pull the motor back to tighten the belt and then lock it down.
• Worn Clutch: A clutch on a gas model acts like a brake pad. If it is worn out, it won’t grip the drum to turn a heavy load. You need to replace it.

5. Noises Coming from the Concrete Mixer

Sounds awful. You’re hearing grinding, screeching, or loud clanking.

The Fix

This is a common problem, but can be fixed by:

• Grinding: This points to gear problems and solutions. Look at the big ring gear around the drum. Is gravel stuck in the teeth? Clean it out. If teeth are missing, you need a new gear.
• Squealing: This is a dry bearing. Locate the grease fittings on the drum shaft and add grease immediately until the noise stops.

6. The Drum Wobbles Too Much

The mixer vibrates heavily. It appears that it may tip over.

The Fix

No need to panic. This can be fixed in two simple ways:

• Bad Bearings: Turn the machine off. Take hold of the edge of the drum and rock it up and down. If it moves or “clunks,” the main bearing is ruined.
• Bent Frame: The metal frame holding the drum should be checked. It is unsafe if this is cracked or bent and needs welding or replacement.

7. Concrete Mixer Not Mixing Properly

Concrete is not mixing properly. You encounter pockets of dry sand or clumps of cement.

The Fix

Fix this problem by doing the following:

• Worn Paddles: Look inside the drum. The metal blades or paddles wear down from sand. If they are small or flat, they cannot fold or mix. Install new paddles.
• Loading Order: Never put cement first. It sticks to the back. Always water, then gravel, then cement. This keeps the mix moving.

8. Troubleshoot Electrical Problems

The mixer immediately trips the circuit breaker. Or, you smell burning plastic.

The Fix

Electrical issues need to be resolved as soon as possible.

• Loose Wires: Vibration shakes everything. The machine should be unplugged, the switch box opened and checked for loose wires that may cause a short circuit.
• Dust in Motor: A motor that is full of concrete dust overheats. Use an air compressor to blow the dust out of the vents so that they can cool down.

9. Concrete Mixer Drum Stuck

The drum refuses to tip over and turn. It’s stuck solid.

The Fix

The following points can be of great help in this regard:

• Dried Concrete: If concrete sets in the gears, you have a big job. You must chip it away carefully with a hammer and chisel.
• Rust: If the machine sat in the rain, the pivot points might be rusted. Spray them with penetrating oil, such as WD-40, and work the wheel back and forth.

10. Gearbox Leaking Oil

You observe a puddle of thick oil on the ground under the mixer gearbox.

The Fix

Fixing this issue is not a big problem. Do the following:

• Bad Seals: Dust destroys rubber seals. If the seal on the gearbox shaft breaks, oil leaks out. Replace the seal at once. Running gears without oil will destroy them in minutes.

Maintenance Checklist

To avoid these problems, follow this simple routine. It takes five minutes but saves hours of repair time.

Daily

• Grease the fittings (zerks)
• The drum should be washed before the concrete sets

Weekly 

• Check belt tension. It should be tight but have a little give
• Check the power cord for cuts

Monthly

• Check gearbox oil levels
• All bolts on the frame should be tightened

When To Get A New One?

Sometimes, a machine is too old to save. If the drum metal is paper-thin, gears are stripped and the motor smokes, it is time to take a look at concrete mixers for sale. Attempting to fix a dying machine is unsafe.

If you work on many sites, portable mixer concrete units are an excellent option. If you are going to do bigger jobs, buy from a trusted seller.

Frequently Asked Questions 

1. Should I grease the big ring gear around the drum?

No. Never grease the open ring gear. Grease traps sand and dust creating a gritty paste that grinds the teeth away fast. Keep it dry.

2. Why does the red button on my motor pop out?

That is the thermal overload switch. It pops when the motor gets too hot. You might be overloading the drum or using a bad extension cord. Let it cool down and reset it.

3. Can I leave wet concrete in the mixer overnight if it is covered?

No. Concrete sets through a chemical reaction. It won’t prevent it from becoming rock until morning by covering it.

4. How will I know whether it is tight enough?

Use your thumb to press the belt. It must go down approximately half an inch. If it goes down farther, it is too loose. If it is as taut as a string on a guitar, then it is too tight. 

5. My gas mixer runs rough. Is it the altitude? 

Yes. At high altitudes, the air is thinner. You may need to adjust the carburetor so the engine gets the right mix of air and fuel. 

Conclusion 

All it takes is patience to fix the concrete mixing plants. Checking simple things, like plugs and belts, saves money and time by keeping your job site moving. If you’re tired of breakdowns or require equipment that will work hard, you need a partner you can rely on. 

Need to upgrade your equipment or require expert advice? Look no further than Batchcrete International for all of your mixing requirements and support.