How to Repair the Rusted Under Carriage of a Car

Written by jenny carver
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The undercarriage of a car is prone to rusting. Rust does not usually accumulate or cause rotten floor pans after a few years, but over a period of decades. To repair a rusted undercarriage, not only does the rust need to be stopped, it must be prevented from reoccurring. Otherwise, the repair will need to be repeated in a few years.

Skill level:

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Things you need

  • Wire brush
  • Jack
  • Jack stands
  • Paint brush
  • Rust doctor

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  1. 1

    Park the car on a flat surface, and raise it with a jack. Place a jack stand near each front tire under the frame of the car. Lower the jack so the car sits on the jack stands.

  2. 2

    Lay down, and crawl underneath the car, looking up at the undercarriage. Use a wire brush to brush away and remove all loose rust from the surface of the undercarriage.

  3. 3

    Brush on the Rust Doctor product with a paint brush. Cover all of the surface of the undercarriage so the metal is no longer visible. A second coat may be necessary. The liquid will begin turning black once painted on the metal. This is the result of the liquid and the rust reacting to create a barrier against moisture.

  4. 4

    Wait a full day before driving the car, allowing the undercarriage to dry without chipping or cracking.

Tips and warnings

  • Always wear protective safety goggles when removing rust from a vehicle. Rust Doctor is the only automotive rust product designed to be applied directly on top of rust without previous deep cleaning. It forms a bond to seal out moisture. It is also available in gallon and five-gallon size containers for large jobs, such as undercarriage repair.

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