It started like many breakdown calls do — a driver stuck on the side of the highway, steam rising from his Kenworth, frustrated and confused. The engine had shut down again from overheating, despite the coolant being topped right up.
No obvious leaks. No pressure warnings. Just heat and shutdowns.
The truck got towed into Webbie’s Mechanical, and once we tilted the cab, the culprit revealed itself pretty quickly: the fuel/water separator was full of coolant.
That’s not something you ever want to see.
Just to be sure, we cracked open the radiator cap — and the smell hit instantly. Coolant mixed with diesel. If you’ve ever smelt it, you’ll never forget it. If you haven’t — consider yourself lucky.
The issue? The injector tubes inside the cylinder head had failed. Coolant was pushing through into the fuel system and vice versa. It’s a dangerous mix that can destroy injectors, foul filters, overheat the engine and leave you stranded — just like it did here.
We got to work:
- Pulled the head
- Replaced the injector tubes
- Flushed the radiator
- Drained the contaminated fuel from both tanks
- Refilled and bled the systems
Once it was all sealed back up and running, the Kenworth fired beautifully — no heat issues, no engine codes, and most importantly, no more cross-contaminated chaos.
The Takeaway?
If your truck’s overheating and everything looks fine — it might be what’s happening behind the scenes (or under the rocker cover) that’s to blame.
And if you ever smell coolant and diesel mixed together?
Pull over. Call us.
Because it doesn’t fix itself — and it definitely doesn’t smell better with time.
