By: Author John Cunningham. Published: 2020/12/02 at 5:15 pm
Mower decks frequently wear out long before the engines, which makes me a little sad, truthfully. Deck protection is a chore every mower owner could easily do with just a little knowledge and some elbow grease. I’ve been a mechanic for over twenty years; I’ll show you how to take care of your mower deck.
Protect a lawn mower deck from corrosion in five steps:
- Turn mower over, (air filter side up)
- Clean deck underside thoroughly with stiff brush
- Remove loose corrosion using a wire brush
- Cover drive belt with old cloth
- Apply thick coat of auto body undercoating
In this post, you’ll learn how to safely work on your mower, and you’ll also learn how to avoid common mower repair mistakes that can render your mower a no-start.
Mower Repair Safety
Accidental starting while working on your mower, while rare, is possible. To eliminate even the slightest chance, we’ll remove the plug wire and tuck it out of the way. We’ll also turn gas off and seal the gas tank to prevent spills; we’ll cover all of this a little later.
The mower blade is sharp, so a pair of stout work gloves is advised. A premium mask like 3m is advised; corrosion dust will hang in the air when cleaning. A mask is also required when painting your deck. Quality safety glasses are always advised; I can’t count the number of times they saved me from a trip to the ER.
When applying the undercoating, do so in a ventilated area. You’ll find all the safety kit I use here on the “Safety gear page.”
Tools you’ll Need
You can, of course, power wash your deck underside; I don’t generally advise pressure washing as power washer pressure is strong enough to penetrate oil seals and remove critical bearing grease. Water on the electrics and in the carburetor causes a ton of problems, too.
In addition, you can’t paint the underside until the deck thoroughly dries out. That said, power washing is a ton faster than elbow grease; just be mindful of the risks.
If you don’t have a power washer or prefer not to use one, then you’ll require a stiff-bristled brush and a few paintbrushes for the nooks & crannies. When it comes time to remove loose rust, you’ll need a wire brush; alternatively, use a cordless drill and a wire brush adapter; it works great and saves your energy and time.
You’ll find all the tools I use here on the “Mower cleaning tools page.”
1 Turning Mower Over
Turning your mower over is a simple enough task; what could go wrong? Well, there is an incorrect way to turn or tilt your mower. Turning it over incorrectly is a common cause of white smoke or a no-start. Tilting it to the wrong side causes oil to enter the combustion chamber.
Remove Plug Wire – Your mower plug wire lives right out front of the engine; give it a twist and a pull to remove it.
Gas Tap Off – If you have a gas tap, now’s a great time to use it; turning the gas off prevents gas from flowing from the gas tank to the carburetor.
Plastic Sheet – In addition, place a sheet of plastic under the gas cap and refit the cap, preventing gas from leaking from the gas tank.
Turn Mower Over – A mower should always be turned over with the air filter side facing skyward. Your mower air filter lives on the opposite side of the muffler.
2 Cleaning Deck
If you are using a power washer, try and avoid directing water at the engine crankshaft seal, drive axle, drive belt, wheels, carburetor, air filter, and armature pull assembly area. Pressure washers may force water into bearings, washing away grease and promoting corrosion.
Water on the electrics may cause misfiring, no start, or premature armature failure. If the electrics do get wet, allow them to dry out completely before running the engine.
Wash Port – Not many owners know about the deck wash port. Simply attach a garden hose and run the mower. The spinning blades force the water to wash the deck, but be warned it leaves quite a mess on the ground.
Wd40 helps prevent damp ingress, and spraying electrical components before washing may help prevent issues. If you are cleaning by hand, use a mask; old, dry grass may be dusty. Cleaning by hand is a touch tedious, but the end result will be worth it.
Using the stiff brush on the open areas of the deck, it’s okay to move the blade around out of your way. Smaller paintbrushes are great for the tighter areas. An airline works great to remove debris.
3 Remove Loose Rust
You’ll definitely need a mask for this bit when using the wire brush, fine rust particulars will hang in the air, and you don’t want that crap in your lungs. My top tip is to use a cordless drill with a wire brush adapter, a fantastic labor-saving device that makes the chore almost pleasurable.
If you don’t have power tools, no problem, we’ll do this old school. Use a wire brush to remove loose surface rust and loose paint flakes.
We are not trying to clean down to the metal here; just so long as the loose debris is removed, we’re good. When complete, clean up the work zone. Otherwise, we’ll get loose debris sticking to fresh undercoating.
4 Cover Drive Belt & Pulley
Prevent Overspray – When painting the deck underside, we’ll need to avoid painting a few areas. No need to be too particular, I just use some cardboard or shop rag.
We’ll need to avoid getting undercoating on the drive belt, pulleys, and drive axle. Thick undercoating on the belt or pulleys may cause self-drive issues. If you do overspray, just clean it off, and you’ll be set.
5 Apply Undercoating
I use auto-body undercoating, which protects the deck from corrosion and helps prevent grass sticking and the chute clogging. The undercoating remains flexible, which prevents cracking; although your deck is metal, it does flex.
Undercoating is only as good as the surface it’s applied to. If there’s loose material oil or the surface is damp, the undercoating won’t remain on the deck.
Undercoating products are available for air tools or in DIY-style rattle cans. One can be enough to get the job done. 3M makes great products; you’ll find a link here on the “Mower cleaning tools page.”
One Thick Heavy Coat – With all prep work done and mask on, apply one thick coat; you may need to contort yourself to nail the areas concealed by the position of the mower.
The sides and the chute are the most important areas to coat; use up the whole can as the product goes off after a few hours.
If you’re using a spray gun, clean it immediately after use. Allow 24 hours for the undercoating to dry completely. Nice work! Your deck is now protected for years to come. Don’t forget to turn the gas on, remove the gas cap plastic, and refit the plug wire.
- About the Author
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John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s fluff-free How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.