🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Thermostat stuck open — engine never reaches temperature
💰 Estimated Repair Cost
$15 – $30 USD
Parts and labour estimate
🔧 Tools Required
Basic tools, drain pan
📋 Overview
A thermostat stuck open or removed prevents the engine from reaching operating temperature. Common on cars where thermostats were removed by a previous owner attempting to cure overheating.
🩺 Symptoms
- Temperature gauge stays low
- poor heater output
- poor fuel economy
- white smoke persisting
🔍 Possible Causes
- Thermostat removed or stuck open
- incorrect temperature rating
🛠️ Diagnosis Steps
Run engine from cold. Temperature gauge should reach normal by 5-10 minutes. If it never reaches normal, thermostat is open or absent.
✅ Most Confirmed Fix
Fit correct 80 degree thermostat.
92% of users confirm this fix worked (51 reports)
🏷️ Parts Needed
Wahler 80 degree thermostat for M115
🔗 Other Mercedes-Benz W115 Faults
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