If you're driving a diesel truck (2007+ model with DPF system), you've probably seen smoke coming out of the exhaust at some point. While a small amount of white smoke on a cold start is normal, persistent black, white, or blue smoke can indicate serious issues. Here’s a breakdown of what each color smoke means and how to address it.

Black Smoke

Cause: Black smoke typically occurs when fuel doesn’t burn completely during combustion. This can be due to issues like:

• Sticking fuel injectors
• Poor turbo performance
• EGR valve or cooler problems
• Dirty air filters causing restriction

What to Check: Black smoke means soot is bypassing the Diesel Particulate Filter (DPF), which is responsible for trapping it. This could cause damage to your DPF or SCR system. Inspect your fuel injectors, turbo, EGR, and air filters to find the source of the problem.

Tailpipe Residue: If you notice black residue on your exhaust tailpipe, it indicates that soot is being pushed past the DPF due to a failed component, such as the 7th injector, turbo, or EGR. Run a forced DPF regen to clear the system and ensure normal exhaust flow.

White Smoke

Cause: White smoke often signals unburnt diesel or coolant entering the exhaust system. Common causes include:

• Defective fuel injectors
• Poor cylinder compression
• Issues with injection timing
• Coolant leaking into the combustion chamber

Specific Case (Volvo D12): If you drive a 2004-2007 Volvo truck with a D12 engine and experience rough idle, revving, and white smoke, check the EGR valves. A stuck open EGR valve could let hot exhaust gases into the intake, causing this issue.

What to Check: If coolant is entering the cylinders, it can damage your engine and aftertreatment components. Replace any faulty EGR components and perform an inspection to avoid long-term engine damage.

Blue Smoke

Cause: Blue smoke indicates oil is burning in the combustion chamber. This can be caused by:

• Worn valve seals or guides
• Broken piston rings or cylinder seals
• Changes in oil type/grade
• Fuel contamination in oil

What to Check: Blue smoke is an oil-related issue that could lead to engine wear. It's important to perform an engine compression or dyno test to assess engine performance. Also, make sure to inspect and clean the DOC, DPF, and SCR systems if oil or fuel contamination is present.