Q. Dear Tom and Ray:

I just bought a 1988 Ford Escort wagon for my wife, and I found out the brake lights don't work. The fuse was burned out. When I replaced it, it took just a pump or two on the brakes to blow the fuse again. I did this three or four times (duh!) and finally replaced the rear bulbs. Then I replaced a faulty engine ground strap, but I still have the problem. I think I have a dead short, but I have no idea how to go about finding it.

-- Mark

A. RAY: My first piece of advice is to look at every car problem as an opportunity to buy a new tool. The tool you need this time is a "short tester."

TOM: Whenever I buy a new pair of BVDs, there's a little tag that says "Inspected by No. 19." Wouldn't that make No. 19 a short tester?

RAY: No. The short tester Mark needs is available for about $20 at any good auto parts store. It's a self-resetting circuit breaker, which you insert in place of the fuse. So when you step on the brake pedal the circuit breaker will blow. When it's cool enough, it will reset itself. And it'll do this indefinitely, which will save you from having to tap your 401(k) to pay for fuses.

TOM: The other piece of the short tester is a very sensitive induction ammeter. So you have an assistant plant his or her foot on the brake pedal, and then you move the ammeter slowly around the outside of the car. And when you get to a place where the needle is swinging wildly back and forth, that's where the short is.

RAY: If you don't want to go through this search, you can save time by simply asking the previous owner where the accident was. I'd be willing to bet that somewhere along the line, this car was hit in one of the rear quarter panels, and a brake light wire got pinched, and now it's shorting out.

Dear Tom and Ray:

I recently had the radiator replaced on my '85 GM van. I got 13 years out of it, so I really don't have much reason to complain -- but I will anyway. I regularly had the radiator flushed and the coolant replaced. I'd say I did this once every two years. Did all this flushing do any good at all? Or does it just provide full employment to people in service stations? Is it worth changing the coolant if the radiator is due to rot out from road salt and corrosion anyway?

-- Tad

RAY: I'm sure the coolant flushes did do some good. It's true that in areas where they salt the roads, radiators tend to rot from the outside, but there are other, critical reasons for flushing the coolant.

TOM: Remember, "a radiator does not a cooling system make," as Henry Wadsworth Longfellow was fond of saying.

RAY: You flush out the coolant to prevent corrosion in the coolant from harming the rest of the engine. Every time the engine runs, the coolant travels through passages in the cylinder head and engine block. And if there are rust particles in the coolant deposits can build up on the walls of these passages--kind of like cholesterol builds up in your arteries. And if enough crud builds up, it prevents heat transfer and leads to chronic overheating.

TOM: Which leads to a melted engine.

RAY: And then you really would have something to complain about!

(C) 1999 by Tom and Ray Magliozzi and Doug Berman