Dear Car Talk:
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. Will bypassing the heater core cause drivability issues? — Ronald
No. Driving a ‘99 Pontiac is what will cause your drivability issues, Ronald.
I’m not sure why you want to bypass the heater core in the summer if it’s not putting out any heat. But if you do, bypassing it will have no effect on the cooling system — positive or negative.
The heater core is, essentially, a second, small radiator that’s under the dashboard in the passenger compartment. It’s attached to your car’s cooling system via two hoses — one that sends coolant in, and one that sends it back. And when you turn on the heat, that’s where the heat comes from.
Bypassing it is a piece of cake: You simply pull off the two hoses that connect it to the cooling system. Then shunt them together with a connector, clamp it up tight, and you’re done. It’s a 5-minute job. But if you live in a place where you need heat in the winter, you’ll eventually want to fix it, Ronald.
I’d suggest you start by flushing it. It may have built up so much corrosion over the last 25 years that the small passages are blocked, and coolant can’t flow through it. You can start by trying compressed air. Blow it in the opposite direction of the coolant flow and see if you can blow some gunk out of there. You can also run water from a garden hose through the system backward.
Your mechanic may also be able to run some oxalic acid through it. And, perhaps, through one or all of those methods, you can remove enough gunk to get some heat out of the thing.
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. Or you can continue to bypass it and wait for an early fall sale on hot water bottles, Ronald.
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