Snowblower White Smoke

Smoke billowing from your snowblower is an alarming look, but no need to panic, white smoke is a common problem and usually easy to fix.

White smoke from a snowblower is usually caused by one of three common problems, they include:

  • Excessive engine oil
  • Snowblower incorrectly turned over
  • Leaking carburetor float valve

In this post you’ll learn how to diagnose the root cause of white smoke and how to fix it. We’ll cover: Checking and removing excessive engine oil; Turning over a snowblower correctly; Replacing a leaking float valve.

Mower gas cap

Vented Gas Cap

Diagnosing Snowblower White Smoke

Smoke from the muffler of your snowblower means the engine is burning oil. Question is why? It is commonly caused by oil entering the cylinder and the engine burns off the oil along with the gas, the difference is when oil is burnt it produces a ton of dramatic white smoke.

The root cause of the problem is usually self inflicted – adding too much engine oil. Most operators believe too much oil can’t hurt, or too much oil is better than too little. Well they are partly correct. But too much oil can definitely hurt.

Snowblower engines that don’t employ an oil filter, use what’s known as splash lubrication. Paddles attached to the crankshaft slap the surface of the oil on every rotation of the crankshaft.

The slap of the paddle splashes oil to every corner of the engine.

Over filling the oil means the paddles remain submerged below the oil level, no splashing means much of the engine isn’t getting lube.

When the crankcase is over full the retracting piston has no choice but to force the excessive oil out of it’s way. The oil is forced into the cylinder and often the carburetor too. This of course is burnt in the normal cycle and produces white smoke.

Next we’ll look at diagnosing and fixing each of the top causes of white smoke.

Mower gas tank

Winged & Threaded caps

Excessive Engine Oil

Diagnosing excessive oil is easy right? If you recently topped up the oil level and it coincides with the white smoke, chances are it’s got too much oil. The next move is to dip the oil level to confirm your suspicions.

How to check oil level: Checking the oil is easy, but there is a set procedure, follow these simple steps:

Vented mower gas caps

Vented gas caps

  • Park snowblower is on level ground and the engine is off for at least 5 minutes. This ensures an accurate measurement of oil on the dipstick
  • Go ahead and locate the dipstick, often it’s marked with an oil symbol or the word “OIL”, in addition the dipstick cap may be a contrasting color
  • Remove the stick and clean it with a lint free rag
  • Reseat the dipstick (do not seat threaded type dipsticks)
  • Remove the dipstick and read the level
  • Sticks employ an upper mark to signify full and a lower mark to signify low, the area between may be hatched, this indicates an acceptable oil level

If the oil reads above the upper mark on the stick (often marked “Full” or “F”), you found the problem – Excessive oil level.

How to remove excessive oil

We have two choices here, use an oil extraction tool or drain the oil through the drain plug.

By far the easiest way to remove oil from an engine is using an oil extraction tool, I use one in the shop and it makes oil and fuel handling mess free. You can check out the model I use here on the “Snowblower tools page”.

The other way is to drain off the excess oil. Maybe your snowblower needs an oil change anyway, well now’s the time. If however your oil is good, you may use a clean container to catch the oil.

But use caution, clean grit from around the engine drain bung, as grit dropping into the oil is not good for the motor.

Before draining the oil, warm the engine. This ensures a fast and complete drain. Locate the oil drain bung, if it has a spigot, great! If not have some rags ready for a clean up.

Tilt the engine towards the oil drain and release the bung.

After drain, refit the bung and clean thoroughly and check for leaks after oil fill.

Snowblower Incorrectly Turned Over

Diagnosing is simple, right? Did the smoke coincide with tilting your snowblower over? It’s very tempting to just tilt the snowblower over on it’s side to run some maintenance or clear snow. However doing so risks oil entering the cylinder through the carburetor.

These engines are designed to remain upright, allowing them to tilt, carburetor side down, allowing oil to enter the carburetor. On start up the oil is sucked into the motor together with the gas. The gas burns clean but the oil produces white smoke.

How to correctly turn snowblower over: A snowblower shouldn’t be tilted on its side, however if it must be tilted, the carburetor side should remain upwards at all times.

How to fix the smoke: In this case, no real action is needed. Do however check and adjust oil level if needed, before starting the engine and allowing it to idle until the smoke clears. It may take 5 minutes or so, but it will clear.

Leaking Carburetor Float Valve

The carburetor float valve lives inside the carburetor. It works together with the carburetor float to control gas flow to the carburetor bowl.

Problems arise when the rubber valve tip (some carbs use rubber valve seat instead) wears out. Blended gas is causing them to degrade prematurely. (More on this later)

Diagnosing isn’t difficult and the presence of one or more of the following symptoms are often enough to confirm your snowblower suffers from this problem.

Symptoms of leaking snowblower carburetor float valve include:

  • Smell of gas in the garage
  • Excessive oil level
  • Smell of gas from the oil
  • Leaking gas from carburetor
  • Engine flooded with gas
  • Engine sputters when running
  • Engine hydro-locked
  • Air filter gas soaked
  • Gas tanks drains overnight

How The Float Valve  Works

The carburetor gas bowl is a reservoir of gas that stands ready to feed the snowblower engine.

As your snowblower works hard it demands more gas, it’s the float and float valves job to make sure there’s enough gas in the bowl.

The float is exactly what its name suggests, it’s a plastic float that rises and falls with the level of gas inside the bowl. The float is attached to the float and when the bowl is full, the float tip is forced into the fuel port, blocking fuel flow.

As the snowblower uses some gas the float falls and the float opens allowing gas to fill the bowl once again. This is a continuous cycle of gas flow control proportional to usage.

However when the float wears it can’t seal the port completely. Gas continues to fill the bowl, this doesn’t present a problem when the snowblower is operating, the problem only becomes apparent after the machine is parked for several hours.

Checking for gas in the oil is one of the easies tests, remove the dipstick, if it’s over full and stinks of gas, your float float needs to be replaced.

How The Float Valve  Works

This is a simple job, and won’t take more than thirty minutes. Follow these steps to nail it like  pro:

  • Shut off gas or clamp fuel line
  • Remove carb bowl
  • Remove float pin and release float and float
  • Remove float from float and replace it (Replace rubber seat if applicable)
  • Refit float and float
  • Refit float pin
  • Refit bowl
  • Turn gas on
  • Change the oil and oil filter (if fitted) contaminated oil will damage the engine. The gas in the oil washes the cylinder and exposes internal components to excessive friction

Most snowblowers are happy to use about 5W30 or 10W30 engine oil.

To prevent your snowblower developing a float valve leak, turn your fuel tap off when not in use. If you don’t have a valve fitted, go ahead and fit one. It’s a simple inexpensive procedure.

Check out this post, it covers the process for a lawn mower but it’s identical for a snowblower “Mower fuel tap”.

Top Mechanics Tip

In addition, and this is important, add fuel stabilizer to your gas tank at the end of the season. Modern gas goes stale in as little as one month and it degrades fuel lines and plastic carburetor components.

Stabilizer keeps gas fresh for up to 2 years and protects your fuel system components from damage; in fact, use stabilizer in all your small engine kit, generators, lawnmowers, dirtbikes, ATV’s, outboard motors. It’s safe to use in two strokes also (not an oil substitute for two strokes), chainsaws, weed eaters, hedge trimmers etc.

Other Possible Causes Of White Smoke

There are other possible causes of white smoke and they include the following:

  • Head gasket fault – Worn gasket may allow oil to enter the cylinder. The fix – Replace the gasket.
  • Contaminated gas (oil mix) – Using mixed gas may cause the engine to smoke. The fix – clean fuel system.
  • Engine oil rings worn – Engine worn out or damaged oil rings. The fix – replace engine.
  • Drive system or Auger jammed – Often causes the belt to smoke. The fix – release the jammed component.
  • Breather valve blocked – Faulty crankcase breather allowing oil to enter the engine. The fix – replace the breather.


Auto Technician and Writer at Lawnmowerfixed | Website

John Cunningham is an Automotive Technician and writer on I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.