Finding and Eliminating Interior and Chassis Noises
[A/H] The first thing to do is get a service manual with an exploded view of the dash, then read on. The following is something I wrote for dealer technicians to help with body noise:
Body and chassis noises are often difficult to duplicate. Get as much information from the customer as you can. When does the noise happen? Cold or hot? When the car is changing gears, starting, stopping, or turning? Over bumps or driveways? This will help you to duplicate the noise. Some interior noises are especially noticeable when the car is cold, others when the interior is hot.
- Road test the car, preferably with the customer to identify where and when the noise occurs. Identify the location of the noise: Inside or outside, front or rear, left or right. (For interior noises go to Step 2. For body noises go to Step 4.)
- For interior noise it is best to have one technician drive and another listen. By holding parts firmly, i.e.: glove box door, dashboard, or interior trim, noises can be isolated. Sometimes it is necessary to remove trim parts and continue road testing to isolate plastic noises. Sometimes pounding on the dash, seat or trim will reproduce the symptoms.
- When the general area of the creak is found and the interior panels are firmly held, if the creak is still not isolated it may be necessary to remove interior plastic parts to identify the source of the noise. Once found, insulate the friction area, or area of contact with EPT or felt. Use wire ties to secure loose components or foam to eliminate rattles.
- Unibody noise that is only apparent when the car is being driven must be reproduced, and the location identified. If it is twisting that is causing the noise (pulling into a driveway and the body pops or creaks as one tire is low in the gutter and the other is high on the sidewalk) it may be useful to find a parking lot with steep drainage gutters or a loading ramp that will allow one tire of the car to be driven on a high area. Is it the right side or left side, front or rear, high or low? Once it is reproduced on a road test and identified as a Unibody noise then attempt to reproduce the noise with the car not moving.
- With the car in a quiet area of the shop have one technician sitting in the car (drivers seat?) where the noise can be heard best, have another technician use a floor jack and lift one corner of the car to simulate twist or stress similar to what was affecting the car during the read test. First jack up slowly and lower the car slowly, then jack up fast and lower the car fast to reproduce the noise. If the noise is not heard, try another corner of the car. It may be necessary to jack on all 4 corners before duplicating the noise. Once the noise is reproduced go to Step 7.
- Sometimes the initial torque of the engine when the clutch is engaged (5 spd.) or a quick throttle blip with the park brakes applied (AT) is enough to twist the body to reproduce a creak. Other times a quick throttle application then hard braking at less than 5 mph is enough to flex the body and reproduce a noise. Reproducing this type of noise in a parking lot next to a block wall or the side of a building will make the noise echo off the wall and be heard easier. Once the noise is reproduced go to step 7
- When the creak is reproduced and the general area of the creak is located, reproduce the noise while a technician places his hands on the panels near where the creak was heard. If the creak can not be felt keep moving the hands in different positions until the noise is felt. Once the creak is felt, it can be eliminated.
- The panel where the creak is felt will have spot welds on the edges and sometimes a second panel will be spot welded to the middle of the first panel. The seam where there is two or more pieces of sheet metal may be isolating unibody stress and may allow one of the panels to move and create popping or creaking in the middle of the panel. This movement is not visible but can be located by touch.
- After feeling the creak, massaging the area with a block of wood and a dead blow hammer. The ideal piece of wood is about 1 inch by 1 inch about 6 to 10 inches long. Sometimes a thin piece of wood similar to a hammer handle is needed to get between wires, hoses, etc.
- Place the end of the wood along the spot weld seam and hit the wood with a dead blow hammer. When hammering along the seam it is only necessary to move the metal 1/2mm to 1mm. This will relieve stresses, or strengthen a panel against movement to eliminate a noise. It is not necessary to move any sheet metal more than 1mm.
- If after massaging the metal in a specific area, the noise is still there, reproduce the noise and feel it again. Continue massaging on other panels, on the reverse side of the panel, etc. until the noise is gone.
- Do not use metal punches or long screwdrivers to move the metal, perforating the metal is very easy and removing the paint will contribute to rust in the future. The block of wood will give a larger surface area for the hammer and move the aluminum just a little over a large area. I have fixed several of these and the only thing you will
notice (if the dealer does it right) from removing the quarter panel is that the bolts just under the trunk lid will need to be touched up with paint. Usually it isn't movement between sheets of aluminum but more of an "oil canning" of one sheet held in a stressed position by spot welds. By moving the aluminum a little the stress is repositioned.
- After massaging the area, attempt to reproduce the noise in the stall and on a road test to confirm the repair successful.