Often leaks and rattles are the only things looked for in an exhaust system. The exhaust system should also be tested for blockage and restrictions. Collapsed pipes or clogged converters and/of mufflers can cause these blockages.
There are many ways to check for a restricted exhaust. The most common of these is the use of a vacuum gauge.
- Connect a vacuum gauge to an intake manifold vacuum source. Bring the engine to a moderate speed and hold it there.
- Watch the vacuum gauge.
- It should indicate a vacuum of 16-20 in. of mercury.
- Increase the engine's speed to 2000 rpm and observe the vacuum gauge. Vacuum will decrease when the speed is increased rapidly, but it should stabilize at 16-21 in. of mercury and remain constant.
- If the vacuum does not build up to at least the idle reading, the exhaust system is restircted or blocked.