The Canuck Mechanic

The Canuck Mechanic Real world diagnostics, repairs, and shop logic from the Fraser Valley.

🔎 Non-invasive testing.One of the nice things about modern diagnostics is that we can often learn a lot before removing ...
07/22/2026

🔎 Non-invasive testing.

One of the nice things about modern diagnostics is that we can often learn a lot before removing a single part.

This is a quick relative compression test from a six-cylinder engine with just 120,000 km / 75,000 miles.

Each red arrow marks the same cylinder during cranking. Notice how every sixth peak is lower? That's the starter not having to work as hard to turn that cylinder through compression... an early clue that one cylinder has a mechanical issue.

It doesn't tell me why yet, but it tells me where to focus next.

Every engine needs three things:
⚡ Spark
⛽ Fuel
💨 Compression

A scan tool might point us toward a misfire, but it can't tell us which of those three is missing. That's where testing comes in.

There's an old saying in medicine:
*"When you hear hoofbeats, think horses, not zebras."*

Most of the time, that's the right approach... but every once in a while, it really is a zebra. That's why we test instead of assume.

This engine came in with an overheating concern and was nearly 3 litres low on coolant.A cooling system pressure test co...
07/17/2026

This engine came in with an overheating concern and was nearly 3 litres low on coolant.

A cooling system pressure test confirmed the system was losing pressure, but there wasn't a single external leak to be found.

So... out came the spark plugs, and in went the borescope.

These two photos immediately changed the direction of the diagnosis.

❓What do you see?
❓What do you think happened here?
❓What would your next step be?

🍁 Sometimes the answer isn't in a scan tool... it's in the process.One of the biggest misconceptions about modern vehicl...
06/18/2026

🍁 Sometimes the answer isn't in a scan tool... it's in the process.

One of the biggest misconceptions about modern vehicle diagnostics is that we simply plug in a scan tool, the computer tells us what's wrong, and we replace a part.

If only it were that simple.

This screenshot is from an oscilloscope connected to a vehicle with a gradual coolant loss concern. Along with scan data, we've performed cooling system pressure testing, a combustion gas (block) test, borescope inspections, reviewed service information, and even consulted with technicians who have extensive experience with this particular engine platform.

Every test gives us another piece of the puzzle.

Sometimes a test rules something out.
Sometimes it points us toward the next question.
Sometimes it completely changes the direction of the diagnosis.

The goal isn't to replace parts until the problem disappears. The goal is to understand why the problem exists before recommending a repair.

This particular vehicle still isn't conclusively diagnosed, and that's okay. Good diagnostics means being honest about what you know, what you don't know, and continuing to follow the evidence instead of making assumptions.

Testing over guessing isn't always the fastest path, but it's the path that gives our customers the best chance of getting the right repair the first time.

🍁 The Canuck Mechanic
Testing over guessing.

F-150 boots: because every truck owner needs a backup transportation plan 😉
06/12/2026

F-150 boots: because every truck owner needs a backup transportation plan 😉

06/09/2026

🔥 One coolant leak turned into more than one finding on this 2018 Jeep.

The vehicle came in overheating and venting coolant under the hood. A cracked plastic coolant pipe was the primary failure, but a closer inspection also revealed another leak beginning at a hose connection.

🌡️ Cooling systems live a hard life. Heat cycles, pressure, vibration, and time eventually take their toll on plastic components. Sometimes the first leak you find isn't the only leak that's there.

🔍 This one was a good reminder that slowing down and looking at the whole system can save a lot of headaches later.

🍁

06/08/2026

How do you test an A/C clutch circuit when there isn't a relay in the system?

This 2004 Volkswagen came in with an inoperative A/C clutch. Instead of a traditional relay, the clutch is controlled through a fan control module.

Back probing the control circuit showed voltage spikes, but no sustained square wave output. At first glance, it would be easy to assume the module wasn't doing its job.

The clutch coil turned out to be open.

To verify the module, I substituted an H7 bulb as a load. The moment the module saw a valid load on the circuit, the waveform changed completely and produced a proper square wave signal.

The module wasn't seeing a clutch.

It was seeing an open circuit.

Sometimes the most valuable part of diagnostics isn't finding the failed component. It's understanding why the system behaves the way it does.

🍁 The Canuck Mechanic















🍁 One thing Canadian mechanics learn pretty quickly..Sometimes the most important part of an inspection isn’t what you h...
06/05/2026

🍁 One thing Canadian mechanics learn pretty quickly..

Sometimes the most important part of an inspection isn’t what you hear on the road test.. it’s what you find underneath afterward 😬

This vehicle came in for a routine inspection and we found some pretty severe structural rust around a suspension mounting area.

The wild part? From the outside, the vehicle still looked fairly normal.

Road salt and moisture are absolutely relentless on some vehicles here in Canada 🍁

And yes.. this is usually the moment where mechanics go strangely quiet while trying to figure out how to explain the situation without ruining someone’s afternoon 😅

Have you ever had hidden rust surprise you on a vehicle?

If you enjoy honest shop finds and real-world diagnostics from a small Canadian shop.. feel free to like and follow The Canuck Mechanic 👍



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Chilliwack, BC

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