1991 Mercedes-Benz 420SEL Engine Oil Light Diagnosis Cost

When diagnosing an engine oil pressure warning light the technician will check the oil level , then the engine will be inspected for engine oil leaks. Running low on oil can cause oil starvation, and oil pressure loss issues. If the oil is full and there are no leaks, the technician will use a computerized scanner to read sensor data, and compare that to actual conditions. Before the technician can suspect any mechanical failure, or start the engine, the engine oil pressure sensor must be proven to function properly. The technician will test the oil pressure sensor and associated electrical circuit, and determine if the sensor should be replaced. If the sensor is reporting correctly, the technician will suspect a mechanical failure within the engine's bottom end, which necessitates removal of the oil pan for physical inspection.

If the diagnosis finds the oil pressure sensor to be faulty, a new one will be installed. If the engine oil pump is suspected, the engine oil pan must be removed for further inspection. The oil will be drained, and the pan removed. Once all necessary components have been set aside, the oil pump will be physically inspected. If confirmed faulty, additional inspection of the bottom end bearings and the oil that was drained will be done to make sure there was no other damaged caused by running with low oil pressure. Assuming there is no other damage, a new oil pump will be installed, the pan re-installed, and the oil and filter replaced. The oil pressure will be checked while the engine is cranking (without starting the engine). If the pressure builds to manufacturer specification, the engine will be started, and final checks will be performed to ensure a complete repair.

If the oil pressure indicator light comes on, we do not recommend starting the engine until the engine has been inspected. Continued use of the vehicle after the warning has come on may result in a seized engine due to oil starvation.

There are many types, grades, and certifications of engine oil. Before adding oil to your engine, be sure to check the manufacturer's recommendations. Consulting your owner's manual is the best way to ensure you are using the correct fluids for your vehicle. Modern engines are especially sensitive to the kind of lubricants used. If there is any uncertainty of what to top off with, contact your local certified shop.

Oil pressure warning light diagnosis should be left to a professional. There is always the possibility that the oil pressure sensor went bad. But without proper testing, starting the vehicle becomes a gamble. Professional technicians have the tools and experience necessary to perform diagnostics and repair without causing further damage.