There are several reasons why your car heater core hoses might suddenly start running cold, resulting in no hot air being produced to warm the cabin while you’re driving the car. These include:
If the thermostat gets stuck in the shut position, it won’t open when the coolant reaches the right temperature for hot air to be blown into the cabin area. When it becomes stuck in either the shut or open position, it will likely need to be replaced. This can be a difficult job depending on where it is located within your car’s engine – it is often advisable to take your vehicle to a mechanic so the job can be completed safely and efficiently.
If the heater core becomes clogged up, coolant cannot flow around the heating matrix, radiator and engine, and can therefore not be used to heat the cabin. If you suspect the heater core to be clogged, a flush of the system will be necessary to restore it to working order.
To dislodge blockages, try flushing the core in the opposite direction to normal flow.
When the heating system develops a leak, this means that coolant will leak out quickly – it therefore cannot be heated in order to produce the hot air that is blown into the cabin. K-Seal can help seal holes and cracks throughout the system simply by being added to coolant or oil when levels are replenished. It will find the crack to be sealed automatically, without closing up any openings which should remain unblocked.
Diagnosing the problem as early as possible will enable you to resolve it before it leads to more significant problems – keep an eye on the heat in your car’s interior and coolant levels decreasing quicker than expected, and have your car checked as soon as you suspect a problem.
Find out how to fix a leaking heater core with our expert guides.