It’s early morning on the outskirts of Perth. A blue bonneted Kenworth with a Cummins engine is pulled up awkwardly on the side of the road, hazard lights blinking in the dawn light.
The driver’s frustrated. This isn’t the first time the truck has shut down out of nowhere during warm-up. It always seems to happen in the morning, and once it’s restarted and warm — it drives fine. Intermittent engine light on the dash. No puddles underneath. Just random shutdowns that keep messing with the day before it even begins.
He gets it to us at Webbie’s Mechanical, hoping for answers — and a permanent fix.
First step? Hook up the diagnostic gear. The fault code history tells us what we suspected — low coolant. But with no obvious signs of a leak, it’s time for a pressure test to track down what the eye can’t see.
We hook up the pressure tester to the radiator. We presurise the system to 1 KPA and it starts dropping instantly. Not good. That confirms it: the system’s not holding pressure and we go looking for a leak.
A little closer inspection and there it is — a fine stream of red coolant spraying from the top radiator hose. Not a full-blown rupture, just a small, consistent leak that only shows up when the system’s hot or under pressure.
And when it leaks just enough to drop coolant overnight. The engine’s built-in safety kicks in the next morning and shuts it down to avoid damage.
We replaced the hose, retested the system, and watched the gauge climb and hold strong. Coolant topped up, pressure steady, and no more mystery shutdowns.
The Kenworth rolled out of the workshop cool, clean, and finally sorted.
The Takeaway?
Not all breakdowns come with constant warning lights and big puddles. Some sneak up on you quietly — a bit of pressure lost here, a few drops of coolant there — until the engine says, “Nope.”
If your truck’s throwing up a mystery issue or behaving differently than usual, bring it in. We’ll find the problem, fix it properly, and get you back on the road without the guesswork.
