Amarok Diesel: Strange Temperature Swings Decoded

Had the exact same symptoms on my 2018 VW Transporter 2.0 TDI. The temperature sensor readings were erratic, showing overheating during highway cruising but staying cold during city drives. Initially suspected a failing water pump, but diagnostic tests revealed a defective map thermostat in the thermostat housing. The thermostat was stuck partially open, preventing proper temperature regulation. This caused the engine to struggle maintaining optimal operating temperature. The repair required replacing the complete thermostat housing assembly since the thermostat is integrated. Not a simple fix, took about 4 hours at the shop. It was serious enough that continuing to drive risked engine damage due to inconsistent operating temperatures. After replacement, the engine temperature stabilized perfectly, warms up normally in about 5-7 minutes and maintains steady temperature even under heavy load. These symptoms are classic signs of thermostat failure in VW TDI engines. Would strongly recommend getting it checked by a VW specialist who can properly diagnose the thermostat control system.

Thanks for sharing your experience. Had the same problem with my Amarok two years ago, the erratic temperature readings and engine overheating were driving me crazy. The thermostat housing replacement fixed it completely. Would you mind sharing what the total repair cost was in your case? Also curious if youve had any cooling system issues since the fix. My temperature sensor started acting up again recently, so Im wondering if these problems tend to come back.

Since the thermostat cooling circuit repair on my VW Transporter, the cooling system has worked flawlessly. The total repair came to 350€, which included replacing the defective map thermostat and labor costs. The mechanic confirmed the thermostat housing was the root cause, exactly as they initially suspected. In two years of driving since the fix, I have not experienced any recurring cooling system problems. The engine temperature now remains perfectly stable, no more erratic readings or overheating issues. The thermostat consistently regulates coolant flow as it should. If your temperature sensor is acting up again, have a technician check the cooling fan operation and entire coolant system. While thermostat failures are common in these engines, sensor issues can sometimes appear similar but are typically less expensive to correct.

Thanks everyone for the helpful replies. Finally got the issue sorted. Took it to a different mechanic who properly diagnosed the problem, turned out to be a faulty thermostat housing just like you mentioned. The repair cost me 410€ total including parts and labor. They had to flush the entire cooling system and replace the thermostat assembly. What a relief to see the temperature gauge working normally again. No more stress about potential overheating. The mechanic said these thermostat failures are pretty common on these engines after about 70000km. The whole job took around 5 hours but was worth every cent. Engine now warms up properly and maintains steady temperature during all driving conditions. Will definitely monitor the cooling system more closely from now on and get regular coolant checks to prevent any future issues.