1991 Lexus LS400 Exhaust Manifold Gasket Replacement Cost

As the engine pumps hot exhaust gases out of the cylinder head, the exhaust manifold receives it, and pressure builds inside the manifold. The metal gasket expands with the cylinder head and manifold, to fill the tiny gap between them, so back pressure may build without the gas escaping the exhaust system,

When the exhaust manifold gasket becomes corroded to the point of failure, it no longer muffles engine exhaust noise, and the result will be a tapping noise from the exhaust manifold. If the muffler bracket has broken, or the rubber hanger is worn, the muffler and exhaust pipe may hang down, placing additional strain on the hot manifold, and cause the exhaust manifold gasket to leak. Lastly, the manifold gasket leaking could register as lean fuel conditions at the oxygen sensors, causing black smoke from the exhaust under heavy acceleration, check engine light illumination, and OBD trouble codes for exhaust and emissions, fuel delivery, and lean running conditions. More exhaust manifold gasket symptoms

Driving a vehicle with a leak in the exhaust manifold gasket is generally not recommended for very long. It can ruin fuel mileage, fail a smog inspection, and cause damage to exhaust valves. Frequency

Normally, the exhaust manifold gasket can go thousands of heat cycles before failure, but engine condition, and driving style may play a significant role in the longevity of the gasket, except for corrosion, and collisions. Most exhaust manifold gaskets last until they are removed to perform another service. In any event, the rate of decay is dependent on the operating environment, and the likelihood of replacement is based on age, rather than mileage.

Identifying an exhaust manifold gasket leak can be very easy if ticking is present, and plenty of exhaust gas is making a stink at the engine, but minor leaks can be tricky. Ordinarily, the vehicle will be raised, and the intake manifold will be inspected for signs of leakage, such as black marks, and burned non-metallic components around the exhaust manifold. If there are no signs, the exhaust may be smoke tested, or plugged to make leaks more apparent.

Exhaust manifold gasket replacement only requires the manifold retaining hardware to be removed, the old gasket removed, and all mating surfaces cleaned thoroughly. If the manufacturer specifies sealant, it is applied to the gasket, otherwise the gasket is placed on the exhaust studs. The exhaust manifold will slide in place on the gasket, and the technician will torque new exhaust manifold retaining fasteners to factory specification.

As manufacturers spend millions of dollars designing the perfect exhaust system for their engines, we recommend using at least OEM quality parts, if not parts from the OEM.

The exhaust system operates at extreme temperatures, so metal becomes brittle after a long service life. Fasteners need to be replaced when an exhaust manifold gasket is replaced as the old bolts are unreliable, and the fasteners may be destroyed during removal.

Replacing an exhaust manifold gasket is only a DIY capable project if the leak can be positively diagnosed at home, and when caught early. If caught late, the exhaust valves must be inspected by a trained professional technician. If any welding is required, a professional exhaust welder should complete the repair.