Subaru Justy Thermostat Issues Need Expert Solutions

Had the exact same symptoms on my 2004 Subaru Legacy Diesel. The engine overheating issues started gradually, inconsistent temperature readings and slow warm-up times were the first signs. The coolant system appeared fine at first inspection, but the real problem was indeed a defective map thermostat in the thermostat housing. The faulty thermostat was not regulating coolant flow properly, causing temperature fluctuations. Sometimes the engine would run too hot, other times it would take ages to reach operating temperature. This turned into a serious issue when left unaddressed. The constant temperature swings started affecting engine performance and fuel efficiency. The repair involved replacing the entire thermostat housing assembly since the map sensor was integrated into the unit. The fix completely resolved the temperature control problems. Worth noting that while the coolant level and pressure tested fine, the thermostat was the actual culprit. Would strongly recommend getting the thermostat checked specifically, as general coolant system inspections might miss this particular fault.

Thanks for sharing your experience. I recently faced nearly identical symptoms with my Subaru Justy, the erratic cooling system behavior was quite concerning. After replacing the thermostat housing assembly, the temperature issues disappeared completely. Has the cooling fan behavior remained normal since your repair? Also, would you mind sharing the total cost for fixing it? I want to compare if repair prices have changed much since then, as I am keeping track for future reference.

After getting the defective map thermostat fixed by the mechanic, the cooling system has been working flawlessly. The temperature control is now completely stable, and the cooling fan operates exactly as it should, activating only when needed at higher temperatures or during idle. The total repair cost was 350€, which included both parts and labor. Based on the thorough diagnosis, the mechanic confirmed that faulty map thermostats are a common issue causing engine overheating problems in these models. The coolant system now maintains proper operating temperatures without any fluctuations. From my experience, addressing this issue promptly was crucial to prevent any potential long-term engine damage from inconsistent temperature regulation. The repair has proven to be a reliable fix, with no cooling-related issues appearing in the months since the work was completed.

Thanks everyone for the helpful replies. After reading about your experiences, I took my car to a local mechanic who specialized in cooling system repairs. The diagnosis confirmed a faulty thermostat in the thermostat housing, just as suspected. The repair cost came to 380€ total, slightly higher than expected but worth every cent. They replaced the entire housing assembly since the temperature sensor was integrated. The engine now warms up normally and maintains consistent temperature even in heavy traffic. The mechanic showed me the old thermostat, it was clearly stuck and not regulating coolant flow properly. No wonder the engine was having such erratic temperature swings. Since the fix, the cooling fan cycles normally and engine overheating is no longer an issue. Really glad I got this sorted before it could cause any serious engine damage.