Boommar. Find Mechanics
Claim shop
BOOMMAR / ON / St. Thomas / Diesel Truck Mechanic

Diesel Truck Mechanic Shops in St. Thomas, ON

Find trusted diesel truck mechanic services in St. Thomas. Compare prices, read reviews, and book online.

✓ Verified Shops ✓ Online Booking ✓ Real Reviews
Diesels Cycle & Small Engine Repair
St. Thomas • ≈ 3 km
DI
Diesels Cycle & Small Engine Repair
9720 Tower Rd, St Thomas, ON N5P 3S7, Canada, St. Thomas
★ 5.0
20 Google reviews
Response ≈ 27 min • $$$ • Quotes free
Diesel Truck Mechanic Fuel System
📞 (519) 636-3596 • Free quote • Verified
View Profile
Ma diesel works ltd
St. Thomas • ≈ 2 km
MA
Ma diesel works ltd
230 Edward St, St Thomas, ON N5P 1Z5, Canada, St. Thomas
★ 5.0
5 Google reviews
Response ≈ 40 min • $ • Quotes free
Diesel Truck Mechanic Truck Mechanic
📞 (647) 378-9686 • Free quote • Verified
View Profile
TruMechanic Truck Services Ltd
St. Thomas • ≈ 7 km
TR
TruMechanic Truck Services Ltd
66 Progress Dr, St Thomas, ON N5P 4G5, Canada, St. Thomas
★ 5.0
60 Google reviews
Response ≈ 47 min • $ • Quotes free
Diesel Truck Mechanic Truck MechanicBrake Services
📞 (647) 674-1777 • Free quote • Verified
View Profile
Wise Line Truck & Auto
St. Thomas • ≈ 7 km
WI
Wise Line Truck & Auto
43718 John Wise Line, Central Elgin, ON N0L, St Thomas, ON N5P 3S9, Canada, St. Thomas
★ 5.0
37 Google reviews
Response ≈ 32 min • $$$ • Quotes free
Diesel Truck Mechanic Truck Mechanic
📞 (519) 631-8228 • Free quote • Verified
View Profile
Gurr Auto
St. Thomas • ≈ 6 km
GU
Gurr Auto
845 Talbot St, St Thomas, ON N5P 1E5, Canada, St. Thomas
★ 4.8
315 Google reviews
Response ≈ 48 min • $$ • Quotes free
Diesel Truck Mechanic Auto MechanicBrake Services
📞 (519) 637-9861 • Free quote • Verified
View Profile
Rob Gillies Truck & Auto
St. Thomas • ≈ 5 km
RO
Rob Gillies Truck & Auto
21 Laing Blvd, St Thomas, ON N5P 3Z4, Canada, St. Thomas
★ 4.7
48 Google reviews
Response ≈ 53 min • $$$ • Quotes free
Diesel Truck Mechanic Truck MechanicFuel System
📞 (519) 633-6384 • Free quote • Verified
View Profile
Showing 6 mechanics • Load more
Online booking workflow

St. Thomas bookings,
zero phone tag.

STEP 01
Search

Filter St. Thomas shops by service, rating, distance, open now.

6 results • verified
STEP 02
Request Booking

Send vehicle + service details. Get a firm quote or pick a slot.

Avg reply 42m
STEP 03
Shop Approves

Owner confirms time, price, and bay availability. One tap.

Calendar & SMS sync
STEP 04
Appointment Confirmed

You get confirm + reminders + live status tracking.

Stripe receipts
St. Thomas customer reviews

Real bookings, real reviews

Verified Reviews for Diesel Truck Mechanic
★ ★ ★ ★ ★

“Very good service and great truck service”

Omar Baroud • Diesel Truck Mechanic at Ma diesel works ltd, St. Thomas
★ ★ ★ ★ ★

“Very impressed with John's services over at Diesel Cycle, very fair pricing, no bullshit and quick turn around. Definitely recommend.”

Nick D • Diesel Truck Mechanic at Diesels Cycle & Small Engine Repair, St. Thomas
★ ★ ★ ★ ★

“Great place for all your auto repaire...friendly staff...Amanda is amazing..will still be a customer in the future”

Carole Riddell • Diesel Truck Mechanic at Wise Line Truck & Auto, St. Thomas
★ ★ ★ ★ ★

“I was driving home from college when I got a nail in my tire. Unfortunately, all the repair shops were closed, so I contacted this company for help. They were incredibly responsive and professional from the start. They asked me to send pictures of the tire and stayed on the phone with me while arranging assistance.
They arrived promptly, repaired the tire, and provided helpful advice to prevent similar issues in the future. Their customer service was outstanding, and they went above and beyond to make sure I was safe and back on the road.
I highly recommend this company to anyone in need of roadside assistance. They were extremely helpful, professional, and reliable. Thank you for the excellent service!”

N M • Diesel Truck Mechanic at TruMechanic Truck Services Ltd, St. Thomas
For shop owners

Get More Customers
Through Boommar

St. Thomas drivers searched “auto mechanic” 8,400 times last month. Claim your listing, turn searches into bookings.

• Online Booking
• Lead Tracking
• Review Management
• Listing Analytics
Claim Your Listing View St. Thomas pricing
St. Thomas Pro – last 30 days
+41
booking requests
4.8★
avg rating
31m
median reply
92%
show-up rate
Calendar sync • Stripe • SMS reminders • Review automation

Find a Best Diesel Truck Mechanic in St. Thomas, ON

Boommar lists 6 verified mechanics in St. Thomas. Compare real reviews, response times, pricing bands, and open bays — then book online.

Common Diesel Truck Issues

Contaminated diesel fuel or clogged fuel filters restricting flow
Failing fuel injectors or high-pressure fuel pumps (HPFP) losing rail pressure
Clogged EGR valves and cracked EGR coolers causing overheating and coolant loss
Turbocharger bearing failure, sticking variable-geometry vanes, or boost leaks
Glow plug or intake heater malfunctions preventing cold-weather starting
Diesel Particulate Filter (DPF) clogging from excessive idling or short trips

When to Book a Diesel Mechanic

Hard starting or extended cranking, especially in cold weather
Excessive black smoke (rich running), white smoke (coolant leak), or blue smoke (oil burning) from the exhaust
Distinct metallic "knocking" or "clatter" sound indicating injector or bearing failure
Check Engine light, Water in Fuel warning, or emission system derate mode
Significantly reduced towing power, turbo lag, or sluggish acceleration
Frequent forced DPF regeneration cycles or "Exhaust Filter Full" warnings on the dash

Diesel Truck Mechanic Services Available

Diesel Fuel System Repair

Injector replacement, high-pressure fuel pump rebuilds, and rail pressure testing

Turbocharger Diagnostics & Replacement

Boost leak testing, VGT actuator repair, and full turbo replacement

EGR/DPF/DEF Emission System Service

EGR cooler replacement, DPF cleaning/baking, and DEF injector diagnostics

Glow Plug & Cold Start Service

Testing, extraction of seized glow plugs, and intake heater repair

Diesel Engine Diagnostics

Factory-level scanning for Cummins, Duramax, Power Stroke, and Detroit engines

Diesel Performance Tuning

ECM calibration, exhaust upgrades, and intake system optimization

Diesel Truck Mechanic Tips

Always purchase diesel fuel from high-volume, reputable stations to minimize contamination risk
Drain the water separator at every oil change and immediately if the Water in Fuel light illuminates
Use a high-quality winter anti-gel additive when temperatures consistently drop below -15°C
Avoid excessive idling—it prevents the DPF from reaching regeneration temperature and causes clogging
Let the turbo cool down by idling for 30-60 seconds before shutting off the engine after heavy towing
Follow the severe-duty oil change interval if you tow, haul, or drive in extreme temperatures regularly

Frequently Asked Questions

Are diesel truck repairs more expensive than gas engine repairs in St. Thomas? +
Generally, yes. Diesel engines operate at much higher pressures and tolerances than gasoline engines. Components like fuel injectors ($300-$600 each), high-pressure fuel pumps ($1,500-$3,000), and turbochargers ($1,500-$3,500) are significantly more expensive. Diesel-specific diagnostic tools and specialized labor also contribute to higher repair costs.
How much does a diesel fuel injector replacement cost in St. Thomas? +
A single diesel injector replacement costs $500-$1,000 including parts and labor. Replacing all injectors on a common 6-cylinder diesel (Cummins 6.7L, Duramax 6.6L, or Power Stroke 6.7L) typically runs $3,000-$6,000+. It's often recommended to replace all injectors at once to avoid repeat labor costs.
What does it mean when my diesel truck goes into derate or limp mode? +
Derate mode is the engine's ECM intentionally reducing power to protect itself from further damage, usually triggered by emission system faults (DPF, DEF, EGR), overheating, or low oil pressure. You should drive only to the nearest safe repair facility at reduced speed. Ignoring derate can lead to a complete engine shutdown.
How often should I service my diesel truck's DPF system? +
Most diesel DPF systems require a professional cleaning (ash removal) every 150,000-300,000 km, depending on driving conditions. Trucks driven primarily in city stop-and-go traffic or at idle may need it sooner. A DPF cleaning costs $300-$600 and is far cheaper than a replacement filter ($2,000-$5,000+).

Diesel Truck Mechanic in Nearby Cities

Toronto Ottawa Mississauga Brampton Hamilton London Markham Vaughan

Other Services in St. Thomas

Auto Mechanic Truck Mechanic Oil Change & Lube Brake Services Tires & Wheels Auto Detailing Auto Body & Paint Windshield & Glass

Popular Cities

Toronto Vancouver Calgary Edmonton Ottawa Winnipeg