How to Flush Your Car Radiator

Clear Coolant Sludge from your Engine

Like any part of a car’s engine, regular (probably daily) use will mean that the radiator will begin to rust and build up deposits of coolant sludge inside it. This means it needs to be flushed every couple of years to prevent that process occurring and subsequently affecting the performance of the radiator and the engine as a whole.

Flushing the radiator is a simple task to perform yourself – you don’t have to take the car to the garage, but make sure you wear protective gloves or other appropriate clothing while you work, as coolant can be hazardous to the touch.

Step-by-Step Guide

  1. Ensure the engine is completely cool so you don’t burn yourself while you work – wait at least two hours after turning it off to be on the safe side.
  2. Clean the radiator with soapy water and a brush.
  3. Position the drainage pan underneath the radiator drain valve (or petcock). Pull the petcock handle to release the coolant.
  4. Double-check the radiator cap and the two hoses that take the heated coolant out of the system and flush the system with cold coolant for wear and tear, and take the opportunity to replace them if necessary.
  5. Rinse the radiator by filling it with water and pulling the petcock again to let it run out.
  6. Add new coolant via the radiator cap in the same way (but don’t pull the petcock out).
  7. Bleed the radiator by leaving the radiator cap off and running the engine with the car remaining stationary for fifteen minutes. This allows air voids to exit and should subsequently mean that more coolant can be added.

It’s a relatively straightforward task that might be made more complicated if the hoses or radiator cap had to be replaced, but there isn’t much work involved in performing either of those tasks.

If in doubt, please consult a qualified mechanic.

How much does it cost to repair a radiator?

The cost of repairing a radiator varies depending on both the car make and model and the specific job, in terms of securing replacement parts and labour.

  1. A new radiator hose will cost around £60–£70 to replace.
  2. A new water pump will cost around £250–£300 to replace.
  3. A new radiator fan will cost around £150 to replace.
  4. A new heater core will cost up to £600 depending on the make and model of car – most of this is labour costs.
  5. Sealing a hole or crack will cost around £20–£30 for a bottle of sealant.

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