Flushing a plugged heater core works in only about 40 percent of cases. But that 40 percent of car owners leave the shop feeling happy, so we think it’s worth a try.

Dear Tom and Ray: Our mechanic states that the heater in our 2000 Ford Focus sedan is clogged. He says there is nothing he can do, since attempts to unclog ...

Plugged Heater Core Heat from the circulating coolant is transferred to the heater core. The blower fan pushes air over the heater core (similar to a small radiator), removing heat from the coolant.

Other causes could be a plugged heater core or a defective water-control valve. Despite its big name, the water-control valve is less costly and easier to replace than the heater core.

But a 25-year-old heater core may be irretrievably plugged up. In which case, you’ll have to replace it, which is a big job.

A clogged heater core is one of the most common reasons behind a malfunctioning car heater. Over time, debris and rust can accumulate in the coolant system, obstructing the heater core.

If the heater core is plugged or clogged, one of these hoses will be significantly hotter than the other. 0:00 / 0:00 ...

My brother has a 2006 Toyota RAV4 with 125,000 miles, which we think has a clogged heater core. The Toyota maintenance schedule calls for changing the coolant every 100,000 miles, which he has ...

Dear Car Talk: My heater core started leaking, so I plugged the hoses going to the heater. I live in Hawaii, so I don’t need the heater. After a few months, I noticed that the plugs I had ...

I have a “no heat” problem on my ’99 Pontiac Grand Prix SE 3.9 liter. It runs fine with no overheating (yet). I suspect a plugged heater core and want to bypass it for the rest of the summer ...

To be honest, we find that flushing a plugged heater core works in only about 40 percent of cases. But that 40 percent of car owners leave the shop feeling happy and “flush” themselves, so we ...