Most vintage car owners remember to change their oil, but many forget about the other half of the equation — the cooling system. While fresh oil protects moving parts, a neglected cooling system invites rust, scale, corrosion, and even electrolysis. These issues don’t just reduce performance — they slowly destroy your engine from the inside out.
Understanding Electrolysis
Older vehicles combine multiple metals — copper, brass, aluminum, iron, and steel — in a single cooling circuit. This creates a low-level electrical charge in the coolant, especially as antifreeze inhibitors degrade. That charge encourages metallic deposits to form inside the radiator, heater core, and water jackets, gradually clogging coolant passages with crusty white or gray buildup.
You can check for this by placing a voltmeter probe into the coolant with the engine idling. Even a slight voltage reading indicates active electrolysis.
Flush Every 3 Years
To avoid cooling system failure, flush and refill the entire system at least once every three years. Use a proper ethylene glycol mix (typically 50/50 to 65/35), or the factory-specified fill. In early vehicles before antifreeze, owners used water in summer and kerosene in winter. Modern antifreeze does far more — it raises the boiling point, prevents freezing, and protects internal metals from corrosion.
Drain Cocks and Heater Cores
Many antique vehicles have drain cocks on the engine block — use them during flushing until the water runs clear. Don’t forget the heater core. Turn the heater on during flushing to keep coolant from becoming stagnant inside that loop.
Why Water Alone is a Mistake
Never use plain water as coolant. It encourages rust throughout the system and has a lower boiling point. Antifreeze contains corrosion inhibitors that protect internal parts and raise thermal performance.
Air in the System = Accelerated Corrosion
If there’s a leak — a loose hose clamp, failing head gasket, or pinhole in the radiator — air gets pulled into the system. Oxygen combines with heat and moisture to create acids that break down metal. Even a minor leak should be fixed immediately to avoid catastrophic damage.
Real-World Example: The Van with No Impeller
We once serviced a 150 series van with severe overheating. It had already blown a head gasket. After replacing the gasket, hoses, thermostat, and flushing the system, the van still overheated. We pulled the water pump — and found only one impeller blade left. The rest had rusted away entirely. That pump wasn’t circulating anything. Regular inspections could have prevented it.
Another Cautionary Tale
Back in 1973, a customer arrived on a flatbed. His engine was seized and the wiring had melted. He’d driven 30 miles at full overheat, ignoring the pegged temperature gauge. The repair cost was more than the car’s value. He sold it for scrap. A working cooling system could’ve saved the car — and the wallet.
Tips for External Radiator Care
On the East Coast, winter salt can corrode the outside of your radiator and coolers. Gently pressure wash the fins with soapy water at a local car wash to remove salt buildup during winter driving.
Quick Maintenance Checklist
– Hoses: Check for cracking or internal separation. Pieces can break off and block coolant flow.
– Thermostat: Test in water to ensure it opens at the rated temperature (160–180°F for older cars). Replace if sticking.
– Radiator Cap: Check gasket and spring. A bad cap won’t hold pressure, leading to overheating.
– Fan Blades: Inspect for cracks or loose rivets. A thrown blade can destroy a rare radiator core.
– Water Pump: Rock the fan gently — any bearing play means replacement is due.
Radiator = The Heart of Your Cooling System
If your vehicle still overheats at idle or under load, odds are the radiator is to blame. Periodic visual checks for leaks and debris buildup help. Severe rust may take several flushes to clean completely. A radiator shop can clean, rod-out, or re-core your unit to original specs.
In vintage vehicles, cooling system care isn’t optional — it’s essential. Proper maintenance means fewer breakdowns, better performance, and a far longer life for your engine.