Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1987 Mercedes Benz 300SDLFACTORY OEM SERVICE PROCEDURE
Coolant Temperature Sensor
- Turn engine off. Connect multimeter and set to ohm scale. Check sensor resistance to ground. Resistance should be 2200-2800 ohms at 68°F (20°C). Resistance should be 290-370 ohms at 176°F (80°C). If resistance is to specification, go to next step. If resistance is not to specification, replace coolant temperature sensor.
- Set multimeter to volt scale. Check voltage on coolant sensor connector. Voltage reading should be 5 volts. If voltage is 5 volts, testing is complete. If voltage is not 5 volts, repair open circuit. If no open circuit is found, replace EDS control unit.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.