T-Cross Engine Temps Swing From Cold to Hot, Fix Needed

Had the exact same symptoms on my 2016 VW Polo GTI last winter. The inconsistent temperature control was a clear sign of a failing map thermostat, which controls coolant flow through the engine. The symptoms match perfectly, irregular engine temperature behavior where the engine overheating alternates with slow warm-up cycles. This puts extra strain on the entire coolant system and can potentially damage the water pump if left unchecked. The temperature sensor readings were erratic in my case, jumping between normal and high without any pattern. A full diagnostic revealed the map thermostat was stuck, preventing proper coolant circulation. The repair involved replacing the thermostat unit and performing a complete cooling system flush. This was a serious issue requiring immediate attention, as continued operation could have led to severe engine damage. The fix brought the temperature control back to normal, with consistent warm-up times and stable operating temperatures. Based on your mileage and model year, this is a common wear point for these components. Would recommend getting the temperature sensor readings verified and having the thermostat checked by a specialized workshop.

Thanks for sharing your experience with the map thermostat issue. My cooling system problems turned out very similar. Recently got it fixed and have put about 5000km on it since with no temperature problems at all. The cooling fan now kicks in normally and the thermostat regulates temperature like it should. The engine warms up consistently and maintains proper operating temperature, which is a huge relief. Curious, what did the repair end up costing you? In my case the parts and labor came to around 380€ for replacing the thermostat and flushing the coolant system. Have you noticed any other issues come up since getting it fixed?

Now can finally confirm the repair cost on my Polo GTI, paid 350€ for the complete thermostat replacement including labor. The temperature control has been perfect since fixing the defective map thermostat over 8 months ago. The coolant system is working exactly as it should now, no more erratic temperature readings or overheating concerns. The engine warms up normally and maintains steady operating temperature even on longer drives. Making sure the thermostat cooling circuit motor was properly diagnosed and replaced was key. These temperature sensor and thermostat issues are quite common at higher mileage. Getting it fixed before any major engine damage was definitely worth the investment. The cooling system flush they did during the repair also helped ensure everything is running optimally. No other related problems have emerged since the fix. The engine temperature stays firmly in the normal range now, which gives great peace of mind.

Had to share my repair story update! Finally got everything sorted with the thermostat housing replacement and cooling system service. The new mechanic I found did excellent work, diagnosed the problem right away when I described the temperature fluctuations. Total bill was 380€ which included replacing the thermostat, flushing the entire coolant system, and testing the cooling fan operation. Money well spent considering the risks of engine damage from overheating. The water pump thankfully showed no signs of wear, so that saved some cost. The mechanic mentioned these thermostat failures are pretty common once cars hit higher mileage like mine. Been driving about 5000km since the repair and the engine temperature now stays perfectly steady. No more cold start issues or overheating, the cooling system is working exactly as designed. Such a relief to have this sorted before any serious problems developed. Thanks again for sharing your similar experience. Really helped confirm I was on the right track with the diagnosis. These temperature control issues are definitely not something to ignore.