Marcus Reid

Diesel Technician & Senior Contributor

Marcus spent two decades in independent diesel shops before moving into writing, working mostly on Power Stroke, Cummins and Duramax pickups along with the RVs and farm equipment that came through the same bays. At USA Diesel Finder he covers diagnostics, DPF and emissions systems, and the practical side of choosing a shop — what a fair estimate looks like, which symptoms can wait, and which ones can't. His goal is to give owners enough context to have a confident conversation with their mechanic.

Articles by Marcus Reid

Diesel mechanic testing crankcase pressure to diagnose blow-by on a heavy-duty truck engine
Diagnostics & Repair
7 min read

What Is Blow-By on a Diesel? Causes, Symptoms & Fixes

Blow-by happens when combustion gases leak past the piston rings into the crankcase. Learn what causes it, how shops test for it, and when it means an engine rebuild is coming.

Diesel mechanic using fuel injector cleaner equipment during injector service on a heavy-duty truck engine
Diagnostics & Repair
8 min read

How to Service a Diesel Injector: A Practical Guide

Learn how to use fuel injector cleaner correctly, when a bottle additive is enough, and when your diesel needs professional cleaning, testing, or replacement. Includes 2026 pricing and a clear decision framework for owner-operators and fleet managers.

Mechanic testing whether diesel injector cleaner works on a common rail fuel injector at a repair bench
Diagnostics & Repair
7 min read

Does Diesel Injector Cleaner Work (and How to Use It)?

Diesel injector cleaner can clear light varnish and restore lost power on mild fouling, but it won't fix a failing injector, a stuck code, or CP4 pump contamination. Here's what it actually does, how to use it right, and when to book a shop instead.

Mechanic checking air brake antifreeze evaporator on a diesel truck's compressed air line in winter
Diagnostics & Repair
8 min read

Air Brake Antifreeze: Keeping Air Lines from Freezing

Air brake antifreeze (alcohol evaporator fluid) keeps moisture in your air brake system from freezing in winter. Learn how it works, how much to use, and what happens when air lines freeze solid.

Diesel mechanic testing a glow plug with a multimeter during cold-start diagnostic repair
Diagnostics & Repair
7 min read

Diesel Glow Plugs: What They Do and When to Replace Them

Glow plugs heat a diesel engine's cylinders for cold starts, since diesels have no spark plugs. Learn how they work, the warning signs of failure, and what replacement costs in 2026.

Mechanic inspecting a diesel engine valve train assembly related to jake brake compression braking system
Diagnostics & Repair
7 min read

Jake Brakes Explained: How Engine Compression Braking Works

A jake brake turns a diesel engine into an air compressor to slow the truck without the wheel brakes. Learn how compression braking works, why it's loud, when to use it, and how to fix one that's acting up.

Mechanic testing a diesel fuel injector on a workbench during a common rail diagnostic inspection
Diagnostics & Repair
6 min read

Diesel Fuel Injectors: How They Work, Fail and Get Replaced

A diesel fuel injector sprays precisely metered fuel into the cylinder at pressures over 20,000 psi. Learn how common rail and unit injectors work, the warning signs of failure, what a shop checks first, and what replacement really costs in 2026.

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Diagnostics & Repair
7 min read

Repair Turbo Charger: How Diesel Turbos Work and What Kills Them

Turbo whine, boost loss, and blue smoke usually trace back to oil starvation, contamination, or worn bearings. This guide breaks down how a diesel turbocharger works, what actually kills it, and what it costs to repair a turbo charger versus replace one in 2026.

What Does EGR Stand For? Diesel Emissions System Explained
Emissions & DPF
6 min read

What Does EGR Stand For? Diesel Emissions System Explained

EGR stands for Exhaust Gas Recirculation — a diesel emissions system that cuts NOx by recycling exhaust back into the engine. Learn how it works, common failure signs, repair costs, and why deleting it is illegal under the Clean Air Act.