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Dear Tom and Ray: My local Subaru dealer wants $130 to install a $30 block heater, because it involves draining the coolant. I'd do it myself, but that would mean buying some new tools. Would it be safe for me to simply wrap plumber's heat tape -- the stuff they use for warming copper pipes -- around the engine and cooling hoses? If it doesn't touch the exhaust, is there any danger of fire? The tape comes equipped with its own thermostat, so it turns itself on when the temperature falls below about 25 degrees. It sells for about $35 in the local hardware store. Seems like a natural solution, doesn't it?

-- Seth

Ray: It's a perfect solution, Seth. Except it won't work for beans.

Tom: Plumber's tape provides just enough heat to keep the water inside a 3/4 -inch copper pipe from freezing. But it won't provide enough heat to help you start your car on a frigid morning.

Ray: While the plumber's tape wraps around the outside of a pipe, an automotive block heater actually goes inside the radiator hose. Working from inside, it heats the coolant directly and heats up enough of it to make a real difference in the morning.

Tom: But since it has to be installed inside a sealed system, your mechanic needs to cut the radiator hose, which then requires draining and refilling the entire cooling system, and then bleeding it to purge it of air.

Ray: That's going to take at least an hour of labor. And when you add in the cost of the heater itself, the hardware for the hose and the fresh coolant, it comes to about $130.

Tom: Alternatively, if you use the plumber's tape, it'll only cost you $35. But remember that you'll also be paying a hefty electricity bill every night just to heat up the outsides of your hoses. That might not be of much benefit to you, but I'm sure the local squirrels that nest in your engine compartment will appreciate it.

The "Car Talk" radio show can be heard locally on WBFO-FM 88.7 on Saturday mornings at 6 and 10 a.m.

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