VW Up Thermostat Failure Causes Wild Temp Swings

Had the exact same problem with my 2021 VW Polo last winter. With some experience working on VWs, I can tell this sounds very familiar, especially the temperature control issues you described. The engine overheating symptoms and irregular temperature gauge behavior pointed to a defective map thermostat in my case. After noticing coolant leaks and inconsistent engine temperature readings, I took it to a specialized workshop. The mechanic confirmed the thermostat was not regulating coolant flow properly, causing the engine to alternate between overheating and running too cold. They replaced the map thermostat unit for 350€ including parts and labor. This completely resolved the temperature control problems. Before committing to repairs, could you share: Any warning lights on the dashboard? Are you noticing any coolant leaks? Does the temperature behavior change in city vs highway driving? Have you checked the coolant level recently? Best to address this quickly since engine overheating can lead to more serious damage. The water pump and temperature sensor are worth checking too, but based on the symptoms you described, the map thermostat is the likely culprit. Would be helpful to know these details to better compare with my experience and provide more specific guidance.

The thermostat replacement completely resolved my temperature control issues. After 128946km and regular maintenance, this was the first cooling system problem I encountered. The coolant system now maintains steady temperature and the engine warms up normally. Total repair cost was 350€ for parts and labor. The mechanic also checked the temperature sensor and cooling fan operation while diagnosing the issue. The thermostat housing showed visible wear when removed, confirming it was the root cause rather than the water pump or other components. Getting it fixed prevented potential engine damage from continued overheating. Regular coolant system maintenance at scheduled services helped catch this before more serious problems developed.

Thanks for the update, glad to hear the thermostat replacement solved your temperature control issues. This matches my experience exactly with my VW Polo. The coolant system really does need that thermostat working properly to maintain consistent engine temps. When my thermostat housing failed at around 125000km, I also noticed the worn components during replacement. One tip from my experience: since having the repair done, I make sure to watch the temperature sensor readings more closely during routine maintenance checks. While the water pump and other cooling components were fine in both our cases, catching any future thermostat issues early helps prevent more extensive engine repairs. The 350€ repair cost seems to be the standard rate for this job. Like you mentioned, its worth every cent to protect against potential engine damage from overheating. Good call getting it checked out when you first noticed the symptoms. Normal temperature regulation is critical for engine longevity, so its great that your coolant system is now functioning as designed. Regular maintenance definitely helps spot these issues before they become major problems.

Thanks for providing those details about your successful thermostat repair. The temperature control issues I was experiencing matched your description exactly, and getting it fixed for 350€ was money well spent. The coolant system is now working perfectly, maintaining steady temperature and proper warm-up cycles. The mechanic confirmed the temperature sensor readings are normal and the cooling fan operates correctly. When they removed the old thermostat housing, the wear was clearly visible, validating that replacing it was the right call. Having the thermostat replaced at 128946km makes sense given the typical lifespan of these components. Regular maintenance of the cooling system helped catch this before any engine damage occurred from the overheating cycles. For anyone reading this thread with similar symptoms, erratic temperature gauge behavior and inconsistent engine temps, checking the thermostat should be a priority. Getting it diagnosed and repaired promptly can prevent more costly issues down the road. Best update I could share is that the engine now maintains proper operating temperature in all driving conditions. Thanks again for the helpful comparison to your experience.