CLICK & CLACK : Rust Bust

Dear Tom and Ray:

I have a huge rust spot on my car, a '95 Subaru. It is not really a rust "spot," but rather a missing part of my car that has rust around it. I tried to sand it down and put Bondo on it and repaint the car, and it actually looked pretty good for a while! But the Bondo soon fell off, and now the huge rust hole is back. Is there is any option besides replacing the whole part of the car? -- Shannon

TOM: The first mistake you probably made was not removing the rust completely. Bondo is pretty amazing stuff, and it'll stick to just about anything. But if you left some rust around the edges, the edges would continue to corrode, and the patch job would eventually fail. As it did.

RAY: You have to sand the area surrounding that hole down to bare, shiny metal. Then, what body shops will do is they'll tack-weld a piece of sheet metal over the hole and hammer it in so it's somewhere between flush and concave. Then they'll grind down the welds so nothing's sticking up.

TOM: We should clarify: That's what body shops do for old heaps like yours, Shannon. If this were a 2005 Subaru, they'd just replace the whole panel.

RAY: You don't need it to look perfect -- it's an old car. You just want to keep it from looking decrepit. If you're handy, you can add the sheet metal yourself, then slap the Bondo over that and paint it. That should hold.

TOM: Or you might be able to find a local body shop that'll weld on the metal for you, and then you can do your Bondo art.

RAY: Or you can just take a larger piece of sheet metal and rivet it over the whole area. Then you paint it, and from 500 yards or so, at night, it'll look good as new.

Dear Tom and Ray:

My husband and I changed the oil, spark plugs, wires, cap and rotor on our '92 Chevy Blazer -- something we've done many times with no problem. When trying to restart the car, the engine exploded, flames came out of the throttle body, smoke came out of the valve covers, and seals were broken. What could possibly have gone wrong -- and should we donate or scrap our car? -- Jackie

RAY: You made a simple mistake, but as you now know, it led to some very flammable repercussions. You reattached the spark-plug wires incorrectly.

TOM: The spark plugs fire one at a time. They're all timed precisely, so they fire at exactly the right moment the spark is needed in that cylinder. If you put the wire for, say, spark plug 1 onto the top of spark plug 4, spark plug 4 is going to fire at the wrong time. And if it fires when the intake valve is open, it could set fire to the fuel-and-air mixture that's waiting in the intake manifold and the throttle body. This will lead to a distinctive sound, best described as a "phooomph," followed by a Christmassy yule scene under the hood.

RAY: The explosion continued into the valve covers because you have a faulty PCV valve. That's a check valve that's supposed to prevent flames from a backfire from traveling into the valve-cover area.

TOM: Next time you work on the car, in addition to making sure you carefully label the spark-plug wires, add a PCV valve to the things you need to replace.

RAY: You probably didn't seriously damage the engine. You might need a valve cover gasket or two if you blew out yours.

TOM: Start by hooking up the wires correctly. You'll have to find the proper firing order for your engine so you can get it running again.

Got a question about cars? Write to Click & Clack in care of The Post, or e-mail them by visiting the Car Talk Web site at http://www.cartalk.com.

Copyright 2007 by Tom and Ray Magliozzi and Doug Berman