Heater Hose

Heater hose is flexible rubber hose that carries hot engine coolant to and from the heater matrix and around the cooling system. This guide explains what it is for and how to choose the right size.

What it is for — Heater hose handles hot coolant under the temperatures and pressure of an engine cooling and heating system, so it is made from rubber that resists heat, coolant and ageing where a general-purpose hose would perish. Use it to replace perished heater and coolant hoses and to plumb heater matrix, bypass and coolant runs.

Choosing the bore — Heater hose is sized by internal bore, which must match the pipe stubs and connections it slides onto. Measure the outside diameter of the stub, or the old hose bore, and choose hose to match so it seals under a clip without being forced or too loose. Fitting the wrong bore is the main cause of leaks and blow-offs.

Fitting — Cut the hose to length, ease it fully onto the stub, and secure each end with a suitable hose clip. Route it clear of hot and moving parts so it is not chafed or scorched in service.

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