I was looking at the Cutlass someone posted for sale on this Buick site and it made me think of this question. I was also watching Fast N Loud last night and they had a Cadillac that looked decent but then found a lot of rust and bondo. So, can you use something to tell if there is bondo? Is there a tool with some sort of gauge or magnet?
A weak magnet works pretty well. If you use a strong one it will still stick if there is a thin coat of putty. Sometimes tapping on the area with your knuckle will do it but not always. Lou
filler if used correctly isn't anything to be worried about but best way is to look at the edges of the panel its on ie bottom of quarters fenders rockers etc 9 out of 10 times if its been butchered up the edges wont be crisp and clean ie no welds will be visiable "hairy" or rounded of corners etc if it looks wavy that doesn't mean its full of filler you can wave a car up by not knowing how to sand primer, look for sand scratches there again doesn't mean its loaded with filler just means there is some there, if any one says there car has no filler they are lying or have a very wavy car, not saying that there aren't guys that cant work metal straight because there are , I can , but to do a whole car that way is nutz
Any cheap refrigerator magnet. Do your online research according to what car it is. Every car has "problem" areas, and those that own them will know. Check these areas very carefully. Look for any sign of even faint paint cracking, paint usually cracks away once the bondo underneath it comes loose or shifts a little. I also do a careful sighting down every panel of the car. Once you've done it enough, you can almost see everywhere they have used filler - unless they are VERY good with it, and blocked the car correctly.
There is a device called "The Snitch" which is just a weak magnet like the refrigerator magnets, which will fall away on spots with material thick enough for the magnet not to couple with the metal. I personally tap with a finger nail. Tap clean sheet metal and a spot with filler a few times to calibrate your ear and you'll be good to go. It isn't 100% reliable, but then neither is "The Snitch". You'll still have to exercise some judgment.
Most decent body guys can tell by looking through the paint. Prep as most know is what makes the paint, if the plastic was not prepped well you can see sand scratches, some waves and sometimes even a shadow in the paint. But otherwise a weak magnet will work. Even then depending on the repair bondo is often nothing to worry about. I saw a lot of new 0 mile cars leave the dealer lot with bondo and the owner never knew.
True enough. I worked for a Chevy dealer in '70, and was backing a Camaro out of the parking lot for service and side-swiped (grazed) another. I was sick about it. But both cars got repaired, and I'll bet nickels to donut-holes that the owners never knew.
A painters mil gauge work too ,basically a magnet with a mil scale on it it measures the thickness of the coatings.
