Diagnosing And Repairing A Smoking Diesel Tractor Engine

The diesel engines used to power tractors and other agricultural vehicles are incredibly robust and reliable and can be expected to last for many years of service with minimal maintenance. However, even these formidable engines are vulnerable to the same mechanical problems as all combustion engines, and one of the most common signs of trouble with a tractor's diesel engine is excessive exhaust smoke.

Large plumes of smoke billowing from your tractor's exhaust can be caused by a wide variety of engine issues, some of which can be far more serious than others. In many cases, you can go some way towards determining the cause of the problem by observing the colour of the smoke, but you should always call in professional diesel mechanics to conclusively diagnose and repair the underlying problem(s).

Why is my tractor's diesel engine producing too much smoke?

White smoke

Most diesel engines tend to produce a few puffs of white smoke when they first start up — this is caused by incomplete fuel combustion and will cease quickly once the engine has come up to optimal running temperature. However, if white smoke continues to emanate from your tractor exhaust after the engine has warmed up, more serious mechanical issues may be to blame.

In many cases, white smoke from a tractor's diesel engine is caused by misfiring engine cylinders, which are not receiving the right amounts of fuel and/or oxygen to complete the combustion process. This is usually caused by malfunctioning or mistimed fuel injectors, but it can also be caused by wear around the cylinder heads, which allows too much air into the cylinder chambers. Clogged crankcase breathers and contaminated fuel supplies can also cause excessive white smoke.

Black or dark grey smoke

Dark grey or black smoke is caused by excessive diesel fuel within your tractor's cylinders, which inhibits the combustion process and leaves unburned diesel fuel in the exhaust fumes. If your tractor is currently pulling a plough or other heavy load, occasional puffs of black smoke are nothing to worry about, but constant black or grey smoke is a cause for concern.

The most common cause of excessive black or grey exhaust smoke is dirty or clogged air filters, which prevent sufficient oxygen from reaching the engine cylinders and cause some of the diesel fuel to remain unburned. Cleaning and or replacing these filters is often sufficient to fix the problem, but you should call in professional assistance if the dark smoke persists.

Blue smoke

If your tractor is producing thick exhaust smoke with a distinct blue tinge, this is a classic sign that the engine is burning excessive engine oil. This problem is usually caused by wear and is particularly common in older diesel tractors. Worn piston rings, malfunctioning oil valves and glazed cylinder liners are just some of the mechanical problems that can cause excessive oil consumption, and conclusively diagnosing the cause of the problem usually requires professional expertise.

Blue exhaust smoke tends to be a particularly common problem in turbocharged diesel tractor engines. If the turbo's oil feed lines or drain lines become clogged, oil can back up into the turbocharger itself and combust within. This can be very hard on a turbocharger, and the line(s) must be unclogged and flushed as soon as possible to prevent permanent damage.