Signs & Symptoms of a Defective Crankcase Breather on a Lawnmower Engine

The crankcase breather, also known as the PVC valve, traps emissions from your lawnmower's gas combustion engine and redirects them away from the engine. This protects the engine from corrosion and reduces pressure in the engine system. If the breather fails to work properly, the lawnmower will emit excess exhaust and the engine will eventually fail. Catch breather problems before they become serious so you can save your engine.

Spilling Oil

If your lawnmower leaks oil, it could be a sign of a defective crankcase breather. Spilled oil points to a number of problems; one problem might be that the breather is simply dirty, although the breather could also be cracked or otherwise defective. Oil leaks might suggest that you overfilled the breather with oil or that there's a problem with the oil fill cap or gasket or with the piston rings in the engine.

Excessive Exhaust

When the crankcase breather gets clogged, your lawnmower starts releasing white or blue smoke from the exhaust pipe. This smoke is caused by pressure building up in the engine, which forces oil through the cylinder, where it burns and releases smoke out the exhaust. If you see this type of smoke, check your breather to ensure it is free of clogs. Cleaning the breather can sometimes help it begin working again.

Seal and Piston Damage

Seal and piston damage be symptoms of a defective crankcase breather. The breather helps reduce pressure within the engine; if it isn't working properly, pressure builds up and may damage other parts of the engine. If you continually have to replace your seals or your pistons are worn out and you can't figure out the cause, the breather may be defective. Extra pressure inside the engine can lead to these types of problems.

Decline of Engine Performance

If your engine is slow or sluggish, you may want to check the breather. Engine problems may occur due to a breakdown of breather functionality. If the breather isn't working properly, excess residue builds in the engine and eventually turns to corrosive acid, which can severely damage your engine. If the engine loses power altogether, it can be due to defective seals -- a symptom of a problem in the breather.