How to Find Decay or Rusted out areas on a car frame

Before buying an older car, or if you already have one, it is important to find any weak areas, such as rust and decay which may have created rot in the frame, which supports the car. Many times these areas are hard to spot just by looking for them with your eyes only!

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Pointed awl scratchers or small picks, ideally one with an angle at the end another straight end.
• Ball pein hammer
• Car jack and support stands
• Wheel blocks
• Flood Light and flashlight

1. 
   Small section of a typical car frame.

   Put your emergency brake on. Set your wheel blocks up behind the tires so the car won't roll once it is jacked up on and angle. Jack one corner of the car and get some supports under the frame. You will ultimately be jacking up all 4 corners to gain complete access, unless of course you have a car lift. Before you set up the jack stands I would check, per the next section, that the stands will be set on a solid portion of the frame. Let the car down from your jack so that all support is on the jack stands. I wouldn't suggest just counting on a jack to support the car, especially when you are going to be under it.

2. 
   Pick and ball head hammer to tap frame with.

   With your lighting set up and flashlight nearby, starting at one section of the frame, you should first inspect visually for any evident holes or scaling back of the metal. If you find any areas like these, using your hammer, you would tap-tap-tap on and around this area listening for any dull sounds. Test the sound out along the frame so you know what you are listening for. Ding-ding would represent good metal whereas a dull sound could represent decay.

3. 

   Upon discovering a dull sound or visual damage as mentioned in the previous step, you now want to use your picks and dig in, poke and scratch open the area as best as possible to uncover the real damage. You may also use your hammer to tap the head of the pick if you need more force. The object here is to unveil the damage.
   Many times you will have a thin layer of good metal hiding the rust and decay behind it. Moisture that created the internal rust in the first place may have not worked it's way to the final surface of metal yet and is hidden.

4. Survey and record the damaged areas, if any. If all is well, Good News! If you have encountered damage, it may not be the end of the car. If the damage is limited, you may be able to get a professional welder to weld in new metal plate as needed to regain full support!

Tips & Warnings

• Take your time and don't rush this job. It is easy to miss a section which may hold the decay even though it looks fine.
• Decay would be most prevalent around the lower, sloping sections of the frame, especially around the lower portion of where the frame angles downward near the wheel wells.
• This method is not fool proof in that you may have decay along the top sections of the frame that you cannot get to so easily, but in general the moisture will settle within the inside lower section of the frame first and eat it away.
• Be certain that you have proper support with car stands before you get under the car and that the jack stands are set level under the frame of the car.
• Before you set the jack stands under the frame, check that section first for any decay using your hammer and pick.
• If you uncover serious frame damage it is probably not a good idea to drive the car until repaired.