We take many enquiries about "cleaning out" or "flushing" of
car radiators. Some people are surprised at what we tell
them, as many are under the impression that "cleaning" the
radiator is just flushing water through the system and that
this can be done at home. This is not always so.
The following de-mystifies our
terminology of cleaning a radiator:

Reverse Flush – flushing the system in a reverse
direction from normal flow, generally using water
pressure similar to a garden hose, to attempt to
dislodge particles in the radiator. This will only
remove floating particles and dirty water in the
system, not anything lodged within the tubes or the
tank.

Power Flush/Engine Flush – removal of
thermostat and using high volume water and
pressurised air. This also will not necessarily clear
blocked radiator tubes but will ensure all coolant
and loose deposits are removed from the engine
and the radiator. Both of these types of flushing can
be performed with the radiator in-situ or removed.

Radiator Cleanout (some people also call this a
flush-out!) – the radiator needs to be removed from
the vehicle for this exercise. The inlet tank (also
called the "top" tank) is disassembled from the
radiator core and each individual tube in the core is
cleared of blockages to ensure complete flow
across the whole radiator. The inlet tank is then
replaced, and pressure tested for leaks. This
process will bring the radiator back to an optimal
performance level.

Chemical cleaning – this involves running a
chemical cleaner through the cooling system to
break down and remove scale in the block. This is
especially important for aluminium radiators to help
prevent electrolysis problems.

External cleaning – it is also important to ensure
that the external face of the radiator is kept free
from debris (i.e. insects, grass seeds, etc). Due to
compact engine space in modern vehicles, the
radiator is usually required to be removed from the
vehicle and high pressure blasting is used.
Radiator Tank removed from an overheating vehicle; a buildup of
contaminants have caused a solid blockage in the bottom half of
the radiator, which is a very common cause of overheating and
radiator failure.
Typical components of a radiator