White smoke from a snowblower is usually caused by one of three common problems, they include:
- Excessive engine oil
- Leaking carburetor float valve
- Snowblower incorrectly turned over
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, and replacing a leaking float valve.
Diagnosing Snowblower White Smoke
Smoke from the muffler of your snowblower means the engine is burning oil. The 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. Overfilling 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 excess oil out of its 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.
1 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 the oil level: Checking the oil is easy, but there is a set procedure. Follow these simple steps:
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.
Locate 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.
Threaded Dipsticks – Reseat the dipstick (do not seat threaded type dipsticks).
Remove the dipstick and read the level.
Dipstick Flavors – Sticks employ an upper mark to signify full and a lower mark to signify low; the area between may be hatched, which indicates an acceptable oil level.
Read – 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, which makes oil and fuel handling mess-free. You can check out the model I use here on the “Snowblower tools page.”
Siphon – Easiest and mess-free way to remove excessive oil.
The other way is to drain off the excess oil through the oil drain; you’ll need a wrench, container, and some rags for the cleanup. 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.
Drain Oil – 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.
2 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 its 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, or at least not dumped on their side, allowing them to tilt the carburetor side down, allowing oil to enter the carburetor. On startup, the oil is sucked into the motor together with the gas. The gas burns clean, but the oil produces white smoke.
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. The best way to work on the machine is to tilt it up onto the bin, as per the picture above.
How to fix the smoke: In this case, no real action is needed. Do, however, check and adjust the 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 the smoke will clear.
3 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 is 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 valve’s job to ensure enough gas in the bowl.
The float is exactly what its name suggests; it’s a plastic float that rises and falls with the gas level 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.
Carburetor Bowl – 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 easiest tests; remove the dipstick; if it’s overfull and stinks of gas, your float needle needs to be replaced.
Replacing Float Valve
This is a simple job, and replacing the float needle won’t take more than thirty minutes. This post covers it pretty well, but if you need a video, you’ll find it here; it’s a lawnmower, but the carburetors are identical. If, however, your carburetor is old, it might be best just to swap it out altogether; a new carb isn’t expensive. Check out the Amazon link below.Amazon Snowblower Carburetors
Follow these steps to nail it like a pro:
Gas Tap – Shut off the gas or clamp the fuel line.
Access Carburetor -You’ll likely need to remove the plastic air intake housing.
Remove Carb Bowl – You’ll likely need to remove the plastic air intake housing.
Remove – Remove float pin and release float and needle; a needle-nose plier helps a ton.
Replace – Remove float from float and replace it (Replace rubber seat if applicable)
Refit – Fit float, needle, and secure with float pin.
Refit bowl, careful not to overtighten, and finally turn gas “On.”
You’ll need to 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.
Gas Tap – To prevent your snowblower from 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 lawnmower, but it’s identical for a snowblower “Mower fuel tap”.
Most snow blowers are happy to use about 5W30 or 10W30 engine oil.
Top Mechanics Tip
In addition, and this is important, add a fuel stabilizer to your gas tank at the end of the season. Modern gas goes stale in as little as one month, degrading fuel lines and plastic carburetor components.
The stabilizer keeps gas fresh for up to 2 years and protects your fuel system components from damage; in fact, use the stabilizer in all your small engine kit, generators, lawnmowers, dirt bikes, ATVs, and outboard motors. It’s safe to use in two strokes also (not an oil substitute for two strokes), chainsaws, weed eaters, hedge trimmers, etc.
You’ll find a short video here showing how to mix it and use it, together with a link to the stabilizer I use in the workshop.
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 the 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.
- 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.