What Is the Limit on Rust Hole Size to Pass a Pennsylvania Auto Inspection?

Car Diagnostic Technician
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In Pennsylvania, an automotive vehicle must undergo a regular safety inspection to ensure that the vehicle is not dangerous to drive. There is no specific limit on rust hole size to pass the inspection. The vehicle’s floor pan is the large sheet metal stamping that forms the floor of a motor vehicle.

Pennsylvania statutes require that a vehicle’s floor pan cannot be rusted through to cause a danger to occupants or permit emissions like exhaust gasses to enter the passenger compartment.

After passing the inspection for vehicle safety, most passenger cars and light trucks will receive an inspection sticker. This sticker is valid for one year from the month of inspection or one year from the expiration of the current inspection sticker on the vehicle.

How Much Rust Is Acceptable?

It is OK to buy a car with rust or corrosion on other parts, like the bumpers, undercarriage or converter. There is no set acceptable amount of rust, but the operator must be able to safely drive the vehicle.

An owner should not worry about rust under the car that does not affect the floor. An owner should also not worry about a rust issue that does not cause other parts of the car to be inoperable.

PennDOT’s Rules on Floor Pans

The Pennsylvania Department of Transportation (PennDOT) identifies concerns regarding rust and rust holes in four subchapters of its safety inspection regulations.

The four sections cover:

  • Passenger cars and light trucks.
  • Medium and heavy trucks, buses and school buses.
  • Recreational, semi trailers and utility trailers.
  • Motorcycles.

As to passenger cars, light trucks, medium and heavy trucks, buses and school buses, and motorcycles, the inspector should check the flooring and floor beds. The inspector should not pass the vehicle if the floor pan is rusted through in a way that could cause a hazard to occupants or permit exhaust gasses to enter the passenger compartment.

As to recreational, semi trailers and utility trailers, the inspector should reject passenger-carrying trailers if the floor pan is rusted through so as to cause these dangers.

Some Observable Exterior Rust Is Allowed

A vehicle will not fail inspection just because some rust is observable on its exterior. There is no specific “reject if” criteria for rust on the exterior of the vehicle. The term "rust" does not appear in regulations related to protruding metal.

Exterior Car Rust Raises Concerns

If a vehicle has a substantial amount of rust on its exterior, this is an indicator for a safety inspector to look more closely at other areas of the vehicle, like the frame and flooring. The exterior rust suggests other spots in the car may be compromised. A bumper that is rusted so that it is not firmly attached makes a vehicle unsafe to drive.

Rust on Brake Rotors

If there is rust or pitting on the brake rotors, this does not mean the vehicle fails the inspection. A brake rotor is a circular metal disc connected to the wheel. There are four brake rotors in a car, one for each wheel. The inspector must determine if the rust is temporary, meaning it is merely surface rust. Surface rust can result from the vehicle being parked for a period of time.

To reject a vehicle for rusted or pitted rotors, the inspector must find that the rust or pitting causes diminished braking performance. This issue must prevent the vehicle from stopping within the prescribed distances.

If the rotors are above the minimum thickness allowed by the statutes, and there is no rejectable scoring, the inspector can note the rust or pitting on the customer’s work order.

Vehicle Rejection on PennDOT Vehicle Inspection

PennDOT’s procedure for inspecting a vehicle frame provides that a vehicle is to be rejected if one or more of these conditions are found:

  • Frame is not in solid condition.
  • Repairs are made with tape, tar paper or cloth or in another temporary manner.
  • Frame components are missing, cracked, rotted or broken, or are in a deteriorated or dangerous condition.
  • Body mounts do not hold as required.
  • Body mount is broken, cracked, deteriorated or missing.

A body mount is a device that insulates or secures the vehicle floor from and to the vehicle frame. Rust can be a reason that a vehicle frame is broken, a frame component is missing, or a body mount performs insufficiently.

Methods of Addressing Rust

Rust occurs when steel corrodes. This process takes place when the iron particles in steel are exposed to oxygen and moisture. There is more of a risk of rust in areas where local governments or private road owners use road salts in winter.

Entities that maintain roads employ a range of substances, including sodium chloride, calcium chloride and magnesium chloride, to melt snow, sleet and ice.

Effects of Road Salt

Road salts speed up the corrosion process because they absorb water from the air. This allows corrosion to take place at lower levels of humidity and for longer periods of time than if no salts were present. Road salts can particularly corrode the undercarriage and electronics of buses and fleet vehicles.

Stopping the Spread of Rust

Methods to stop the spread of rust include:

  • Washing a vehicle on a regular schedule.
  • Washing, sanding and painting rusted areas if rust hole in the body of the vehicle.
  • Spraying undercoating on floor pan, wheel wells and other exposed areas of the car.

Ways to Fix Rust Holes

A mechanic or body shop can fix a rust hole in a floor pan by following this basic procedure:

  • Remove the carpeting around the rust hole
  • Clean up the dust.
  • Have a patch panel ready and trim panel to correct size, if necessary.
  • Cut around the rust repair to be done keeping as much of the original metal as possible.
  • Sand edges of remaining floor.
  • Trim and fit new panel.
  • Weld new panel into place.
  • Replace the carpeting.

If a vehicle has multiple rust holes, the owner should consider replacing the entire floor pan.

Fraud in Concealing Rust in Vehicles

A consumer purchasing a used car should get an inspection to determine whether the seller is concealing rust. This is especially true for cars driven under cold weather conditions or near water, such as lakes, rivers and coasts. Putting a car on a lift is a good way to view the undercarriage.

A seller may spray paint over rust on the bottom of a car as a method of concealing it. Such measures may hide the rust on the vehicle’s frame and brakes. When a buyer test-drives a car, they should particularly test the brakes to see how well they perform.

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