You can feel summer creeping in and harvest in full swing, and lately we’ve seen a surge of trucks coming in with problems that have been put off just a little too long. Everyone’s busy. Everyone’s running hard. And trucks are feeling it.
One of those trucks was a Volvo that rolled in with a split brand-new header tank.
Brand new — and already split.
Not something you ever want to see.
When that happens, our first thought is always the same:
Over-pressurising.
But now we needed to find out why.
There were a few possibilities. A hit to the tank. A failing compressor. A head gasket starting to go. Even a cracked head can cause it. So we started testing — properly and step by step.
We ran a combustion gas test through the cooling system:
No combustion gases.
Good news — not a head gasket.
Next, we pulled the coolant lines off the air compressor and bypassed it.
And instantly?
The bubbling stopped.
There was our answer.
The compressor was pushing air into the cooling system, over-pressurising it, and that pressure is what split the brand-new header tank.
Once we found the cause, the fix was straightforward:
Replace the air compressor.
Refill and bleed the cooling system.
Run final checks.
And just like that, the Volvo was back to work — no pressure issues, no leaks, no surprises.
Another truck saved from unnecessary downtime.
Another customer back earning, not waiting.
📍 Webbie’s Mechanical — finding the real problem is what keeps your truck on the road.