Diesel Truck Cooling System Repair

Overheating diagnosed properly

Heat is what kills diesel engines: warped heads, cracked liners, scored cylinders, and cooked head gaskets all start with a cooling system that quit doing its job. The trouble is that a dozen different faults produce the same temperature gauge reading, so we test the system instead of replacing parts in order of price.

What we repair

• Radiators — leaks, external blockage, and internal scaling that kills flow
• Water pumps — weeping seals, worn bearings, and impeller failure
• Thermostats and housings — stuck closed, stuck open, and the leaks around them
• EGR coolers — the classic coolant-into-exhaust failure, especially on 6.0L Power Strokes
• Oil coolers — oil and coolant mixing where they never should
• Fan clutches and shrouds — a fan that never locks up will overheat a truck under load
• Hoses, belts, and coolant leaks — including the ones that never reach the ground
• Head gaskets — when combustion pressure is what is pushing coolant out

Signs your cooling system needs attention

• Temperature climbing under load, on a grade, or while towing
• Coolant loss with no visible puddle
• White smoke and a sweet smell from the exhaust
• Milky oil, or coolant that looks like chocolate milk
• Heater blowing cold, or a fan that never seems to engage
• Repeatedly topping off the overflow tank

Do not keep driving an overheating diesel to "get it home." The repair bill for a cooling system is a fraction of what a warped head or a cracked liner costs. If it is running hot, shut it down and call us.

Trucks and equipment we cover

Light-, medium-, and heavy-duty diesel — Power Stroke, Cummins, and Duramax pickups, medium-duty box and service trucks, semis, plus Sprinter vans, import diesels, and diesel equipment that overheats working in the Texas summer.

Related services

• Diesel engine repair — when overheating has already done damage
• Heavy-duty parts & repair
• Oil change and preventive maintenance
• Fleet maintenance & management — catch cooling problems on a schedule

Why Modern Diesel

A Christian, veteran-owned shop serving the Greater Austin Area (Travis, Bastrop, Williamson, Hays) from 2900 N FM 973, Austin, TX 78725. We pressure-test, we show you what we found, and we tell you what it actually needs. Call 512-717-2777 if your truck is running hot.

Common questions

Why does my diesel truck keep overheating?

Overheating usually traces back to one of a handful of causes: a failing water pump, a stuck thermostat, a radiator packed with debris or scaled internally, a bad fan clutch, or a head gasket letting combustion gases into the coolant. On some engines a failed EGR or oil cooler will do it too. We pressure-test the system and check the actual coolant temperature against what the ECM reports before recommending any repair.

Do you repair EGR coolers and oil coolers?

Yes, and on some platforms they are the usual suspect. A leaking EGR cooler pushes coolant into the exhaust — white smoke and steady coolant loss with no puddle underneath — and a failed oil cooler mixes oil and coolant. Both are common enough on 6.0L Power Strokes that we check them early.

Can you find a coolant leak I cannot see?

Usually. Not every leak drips on the ground — coolant can go out the exhaust through an EGR cooler, into the oil through an oil cooler, or into a cylinder through a head gasket. We pressure-test the cooling system and, where it helps, run a block test to check for combustion gases in the coolant.

How often should coolant be serviced on a diesel?

It depends on the coolant type and how the truck is worked, but coolant does not last forever — additives deplete, and depleted coolant lets liners and radiators corrode from the inside. We test coolant condition during service and tell you where yours stands rather than flushing it on a fixed schedule you may not need.