Find & Fix Lawn Mower Deck Problems


Too often lawn mower owners wait for their deck to start making noise or smell like burnt rubber before they consider looking at their deck. Not taking time to look at the mower deck before this happens can result in a very costly repair. Don’t make this mistake with your lawn mower deck.

The way your lawn looks a day or two after it is mowed can indicate it’s time to look at your lawn mower deck for repair.

Observing your lawn after you have mowed it can give you some indications of mower deck problems:

  • The tips of your grass turn brown a couple days after you mow.
  • You have an uneven cut where the lawn may have a step-type cut or your yard is scalped
  • An uncut strip of grass can indicate you have a problem with your blades
Find and fix lawn mower deck problems

7 Things to Look at When Trying to Find Deck Problems

It is always best to start with the easy items and work your way to the more difficult deck problems. These problems can exist in all versions of mower deck including those on walk-behind, zero turn, and riding lawn mowers.

Remove Spark Plug Boot and Key From Your Lawn Mower for Safety.

Safety is key when working on your mower deck. It is important to remove the spark plug boot and the ignition key from your lawn mower. I like to stick the key in my pocket so no one picks it up and tries to start the mower not knowing I’m working on it.

Wear heavy work gloves when working with your mower blades as they can be sharp. Follow additional safety tips as shown in your operators manual.

Check the Condition of Your Lawn Mower Blades

Like mentioned earlier, the tops of your grass can become brown a couple days after you mow. The reason this happens is worn mower blades will beat the grass instead of precisely cutting it. The ends of the grass are beat up and will slowly turn brown. Dull blades must be sharped or replaced. I go into more detail on sharpening, replacing and balancing blades in “Inspecting Your Lawn Mower Blades Saves You Time & Money“.

Bent mower blades can also affect the cut of your lawn. Sometimes a bent blade is very noticeable and other times it is hard to tell. You can easily check for a bent blade by parking your mower on a flat surface.

You will need to measure one end of the mower blade from the ground to the blade tip. Then rotate the blade and measure the opposite end of the blade from the ground to the blade tip. If there is over and 1/8″ variance, replace with a new blade.

Repeat this step with the other mower blades if your mower deck utilizes more than one blade. Never attempt to straighten a mower blade as a straightened blade will be weakened and compromised. You don’t want a weak blade rotating at high speeds.

Check Your Lawn Mower for Low Tire Pressures

Did you know something as simple as the wrong air pressure in the tires can cause you to end up with a bad mower cut? Check your tire pressure. When you have a low tire, the mower deck no longer sits parallel to the ground which causes uneven cutting.

Make Sure Your Deck Height is Level

You need your deck to sit level for a good cut. The check this, you need to measure the deck at all four corners from the ground to the bottom of the deck. If you have a variance in your deck, refer to your owner’s manual for proper instructions to level the deck. This step varies with the manufacturer and model of the mower.

Check the Bearing in Spindle Housing

Next, move you should check the bearings in the spindle housings. With a good pair of work gloves, grab a hold of each end of the mower blade and rock it up and down. If you feel any movement or noise, chances are you have a bad bearing in the spindle housing that must be replaced.

The bearing can be replaced in some manufacturers spindle housings. Other manufacturers will only allow you to buy the whole assembly.

Check the Condition of Your Mower Deck Belts

Your mower belt must be in good condition without any cracking, wearing or glazed appearance to it. Replace the belt if needed.

Check Mower Deck Pulleys & Idler Pulley Brackets

Your next step is to check your mower deck pulleys and idler brackets. With the deck belt removed from your mower, spin the pulleys to make sure they are moving smoothly and not making noise. If you do hear a noise or there is any restriction in movement, you need to replace the pulley.

Check the idler pulley bracket to make sure there isn’t any play where it mounts to the deck. The idler bracket must be kept greased so it doesn’t seize up. To prevent the belt from breaking, the idler pulley bracket is designed to move and spring back to put tension back on the belt.

If the bracket is unable to move, the belt can slip and cause the blades to also slip in heavy or deep grass so our cut looks bad the next day.

A Clogged Lawn Mower Deck Can Affect Quality of Cut

Grass can affect your quality of cut. Keeping your mower deck clean of grass buildup is essential. Besides scraping your deck during regular service maintenance, there are other steps you can take to avoid grass buildup.

  • Avoid cutting wet grass .
  • Always run your mower at full throttle when the mower deck is engaged.
  • Cut your grass regularly so you don’t have clumping of grass.
  • Coating your mower deck with silicone deck spray can help minimize the amount of grass collecting under your mower deck.

It is necessary to the performance of your mower to keep your mower and mower deck clean.

How Often Should You Perform Maintenance on You Lawn Mower Deck?

The lawn mower deck is the main component of your lawn mower, but I think it is often the most neglected. For the average homeowner, lawn mower deck maintenance should be performed at least twice per mowing season. If your yard is heavily watered or fertilized you need to perform maintenance more often.

Grass is full of moisture and fertilizers, if you use them, that can create erosion of the deck so you may not get the life you expected out of your lawn mower deck. Scrape and clean out the undersides of your decks more than once a year.

While you are under the deck, use the steps above to identify all mower decks parts are functioning as needed and are in good condition. Performing these routine checks will help you prevent more costly repairs.

Lawn Mower Decks Are Not the Same

Mower decks look pretty similar. Is there really a difference? There are significant differences to consider in a lawn mower deck when making a purchase. These are important items that will affect the quality and durability of your lawn mower deck:

  • Whether the lawn mower deck is a stamp deck or fabricated deck
  • The thickness of steel used for the lawn mower deck shell for durability
  • Lawn mower deck depth affects the quality of cut
  • Quality and durability of lawn mower parts
  • The use of greaseable parts for easy maintenance resulting in less failures
  • How easy is it to find and buy parts for the mower deck to keep your lawn mower deck in good condition

What is Causing My Mower Deck to Vibrate?

Mower deck vibration can be caused by bad bearings in the cutter housing, unbalanced blades, or debris wrapped around the blade shaft or lodged in the components of the mower deck.

Other parts of your mower may also be causing your lawn mower to vibrate. Check out our article “How to Stop Your Lawn Mower from Shaking and Vibrating”.

My top items to keep on hand to service & troubleshoot your lawn mower

Socket & Allen Wrench SetOpens in a new tab. – Tool set needed to service & troubleshoot your mower problemsCarburetor CleanerOpens in a new tab. – Clean clogs & buildup in fuel system
MultimeterOpens in a new tab. – To check voltage, continuity & current to identify electrical problemsFuel StabilizerOpens in a new tab. – Stabilize & clean your fuel to minimize fuel system buildup
12-Volt Battery ChargerOpens in a new tab. – Battery/trickle charger to start your mower & slowly charge your batteryFilter WrenchOpens in a new tab. – Helps loosen your filter
Oil Drain PanOpens in a new tab. – To collect oil with spout to place in containers for disposalBattery Powered InflatorOpens in a new tab. – Keep your lawn mower tires inflated to prevent uneven cutting or steering issues

Powered Equipment Team

We're just a guy and a girl obsessed with outdoor power equipment! We are excited to share the knowledge and tips we have learned over our combined 55 years in the power equipment industry. We have both ran equipment dealerships and took pleasure in helping our customers everyday providing equipment repair, parts, purchasing, and business tips to our residential and commercial clients. We hope our blog will help you with your next purchase, repair, or project.

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