VW Caddy Erratic Temperature Points to Faulty Thermostat

Had almost the exact same issue with my VW Touran 2019 gasoline model. As someone with moderate car repair experience, I can tell you these temperature control problems can be tricky to diagnose. The engine overheating symptoms and inconsistent temperature readings you describe match what I experienced. My car would sometimes take forever to reach operating temperature, while other times the temperature gauge would spike unexpectedly. After noticing coolant leaks and erratic temperature behavior, I took it to my regular workshop. They diagnosed a defective map thermostat, which was causing the temperature sensor to receive incorrect readings. The repair, including parts and labor, cost me 350€. The main warning signs to watch for: Inconsistent temperature gauge readings, Engine taking longer than usual to warm up, Potential coolant leaks, Check engine light possibly illuminating To better assist with your specific case, could you share: Current mileage on your Caddy, Any check engine lights or error codes, Whether you notice any coolant loss, If the heating system is working normally These thermostat issues are fairly common in VW models from that era, and its best to address them promptly to prevent more serious engine overheating problems.

Last service was at 85000km and Im seeing the exact symptoms you described. No check engine light yet, but Ive noticed small coolant loss recently. The heating works fine though. The temperature sensor readings are all over the place, especially during morning commutes. After reading about faulty thermostat housings in these models, I checked for any visible leaks around the thermostat area and found slight dampness. Going to have the water pump checked too since its probably due for replacement at this mileage. Really hoping its just the thermostat and not a bigger cooling system issue. Has anyone had success with aftermarket thermostat parts, or should I stick with OEM for this repair?

Thanks for the additional details about your Caddy. Based on my experience with my Touran, I strongly recommend going with OEM parts for the thermostat replacement. After dealing with similar cooling system issues, I initially tried an aftermarket thermostat to save money. It worked for about 3 months before the temperature control problems returned. Ended up spending more by having to do the job twice with the OEM part. The coolant loss and damp area you found near the thermostat housing are classic signs of a failing unit. Since your car is at 85000km, its smart to consider the water pump too. The timing is right, and its more cost effective to replace both while the cooling system is already opened up. The inconsistent temperature readings during cold starts were exactly what I experienced. Its a clear indicator of a failing thermostat that isnt regulating coolant flow properly. If you notice the cooling fan running more frequently than usual, thats another common symptom of the system trying to compensate for poor temperature regulation. My total repair costs with OEM parts: Thermostat assembly: 180€, Water pump: 220€, Labor and coolant: 280€ The complete job resolved all the engine overheating issues and erratic temperature behavior. Just make sure whoever does the work properly bleeds the cooling system after installation.

Thanks for the comprehensive feedback about your experience. Your Touran repair costs really help set my expectations for the upcoming work. My local shop quoted similar prices for OEM parts, so that validates their estimate. The temperature sensor readings on my Caddy have gotten worse this week, and the coolant loss is becoming more noticeable. After hearing about your experience with aftermarket parts failing, I will definitely go with OEM for both the thermostat and water pump. No point risking further cooling system issues by trying to save a bit on parts. Just booked the car in for next week. They will do a complete cooling system inspection, replace the thermostat housing, temperature control unit, and water pump. The total quote is around 750€ which seems reasonable given the parts and labor involved. Really glad I caught these warning signs before any serious engine overheating damage occurred. Will update the forum once the work is done in case others run into similar temperature control problems with their VWs.