Your car radiator is a key part of the cooling system, responsible for keeping your engine at a safe operating temperature. When coolant can’t circulate properly due to dirt, corrosion, or leaks, your car risks overheating — one of the most damaging issues an engine can face.
Knowing how to flush a radiator and how to fix a radiator leak can prevent breakdowns, extend engine life, and save on costly repairs.
What Is a Radiator?
A radiator is a heat exchanger located at the front of your vehicle. It cools down the hot coolant coming from the engine block before sending it back to absorb more heat.
Key radiator components include:
- Core: The main cooling section with metal fins.
- Inlet and Outlet Tanks: Hold and circulate coolant.
- Radiator Cap: Regulates pressure and prevents boiling.
- Hoses: Carry coolant between the radiator, water pump, and engine.
Coolant (antifreeze and water mixture) flows through these parts, absorbing heat and releasing it via the radiator fins as air passes through — thanks to the fan belt and cooling fan.
How Does the Radiator Work?
When the engine heats up:
- The thermostat opens to allow coolant circulation.
- Hot coolant flows through the radiator core.
- Air from the grille or cooling fan removes heat.
- Cooled fluid returns to the engine to absorb more heat.
If this process is interrupted — by clogs, rust, or leaks — the engine can overheat, leading to blown head gaskets, warped cylinder heads, or engine failure.
Common Symptoms or Signs of Radiator Problems
You may need to flush or repair your radiator if you notice:
- Overheating or High Temperature Gauge: Poor coolant flow.
- Coolant Leaks Under the Car: Usually from radiator seals or hoses.
- Rusty or Sludgy Coolant: Indicates corrosion or contamination.
- Sweet Smell or Steam from the Bonnet: Coolant escaping under pressure.
- Low Coolant Warning Light: Persistent fluid loss.
Ignoring these symptoms can lead to serious engine damage or costly repairs.
How to Flush a Radiator
Flushing your radiator removes old coolant, debris, and rust. It’s a simple maintenance task you can do at home.
Tools & Materials Needed
- Radiator flush solution
- Antifreeze/coolant (check your car manual)
- Drain pan
- Funnel and hosepipe
- Gloves and rags
1. Let the Engine Cool
Never open the radiator cap on a hot engine — it’s under pressure. Wait at least 30 minutes after turning off the car.
2. Drain the Old Coolant
- Place a drain pan under the radiator.
- Open the drain plug or remove the lower radiator hose.
- Allow the old coolant to drain completely.
Dispose of used coolant properly — it’s toxic to pets and the environment.
3. Add Radiator Flush Solution
- Close the drain and fill the radiator with radiator flush and clean water.
- Start the engine and let it run for 10–15 minutes with the heater on.
- Turn off, cool down, then drain again.
This process removes internal rust and sediment.
4. Refill with Fresh Coolant
- Mix new antifreeze and distilled water (usually 50/50 ratio).
- Pour through the radiator cap using a funnel until full.
- Start the engine and let it idle to remove trapped air.
Top up as needed until coolant level remains stable.
How to Fix a Radiator Leak
A leaking radiator must be repaired immediately to avoid engine damage. Here’s how to handle small leaks safely:
1. Locate the Leak
- Check hoses, radiator seams, and the core for wet spots or dried coolant residue.
- Use a flashlight to inspect under pressure.
2. Temporary Fix (Small Leaks)
For minor leaks or pinholes:
- Use a radiator stop-leak product as a temporary solution.
- Follow the instructions on the bottle — usually, it’s poured directly into the radiator.
This can seal small leaks in the core or tank but isn’t a long-term fix.
3. Permanent Repair
For serious leaks:
- Replace damaged hoses, clamps, or radiator caps.
- If the radiator core is cracked, it must be professionally repaired or replaced.
- Aluminium radiators can sometimes be welded; plastic tanks often require full replacement.
4. Refill and Test
After any repair, refill the system with coolant and run the engine.
Check for new leaks or drips once the engine reaches operating temperature.
Radiator Flush or Replacement Cost in South Africa
Typical pricing for radiator services:
- Radiator flush (DIY): R250 – R450
- Professional flush service: R600 – R1,200
- Small leak repair: R500 – R1,000
- Radiator replacement: R1,500 – R4,000 (depending on vehicle type)
Related Car Parts and Maintenance Tips
For complete cooling system care, also inspect:
- Thermostat: Replace if sticking or slow to open.
- Water pump: Essential for coolant circulation.
- Fan belt: Drives the cooling fan.
- Oil cooler: Helps maintain engine temperature balance.
- Cylinder head gasket: Prevents coolant leaks into engine oil.
- 5w30 engine oil: Helps regulate temperature and lubrication.
Related guides:
Conclusion: Why Radiator Maintenance Matters
A clean and leak-free radiator keeps your engine running at the right temperature, improves fuel efficiency, and prevents costly overheating damage.
Flushing your radiator every 40,000–60,000 km and checking for leaks regularly ensures long-term reliability and engine performance.
Need radiator parts, coolant, or hoses?
Find high-quality, affordable auto spares online at car-parts.co.za today.