Most truck owners associate thermostat failures with overheating.
But sometimes the problem is the opposite.
Recently we had a truck come in where the engine wasn’t reaching proper operating temperature. On inspection, we found one thermostat stuck open.
While the truck wasn’t overheating, it was running too cool — and that created a different issue.
The DPF system relies on heat to complete a regeneration cycle. Without reaching the required temperature, the DPF kept attempting to burn off soot but couldn’t complete the process.
Over time, this leads to blocked DPFs, increased fuel consumption, and potential downtime.
Once we replaced the faulty thermostat, the engine returned to proper operating temperature and the DPF system began functioning correctly again.
The key takeaway is simple:
Thermostat issues don’t always show up as overheating. Running too cold can be just as damaging in the long run.
📍 Webbie’s Mechanical
Keeping your truck running at the temperature it’s meant to.
