Hi, If its stuck in opened or closed position its not very difficult to diagnose it yourself, you should not have changed any sensors unless you are 100% sure about their fault In the morning when your touareg is cold start up the Engine and open the hood, there are upper and lower rubber pipes coming from the engine to the radiator, upper one normally is getting warm faster as it's part of the short cycle and lower one is remaining cold until the thermostat will open long cycle, so to diagnose the problem you need to start the engine and put your hand on upper pipe, once the temperature will rise and reach 200 the thermostat MUST open and then lower pipe also must get warm, but if the temperature will start to go over 200 and the lower pipe will stay cold it means your thermostat have stuck in closed position and it needs replacing, do not use any other coolant other thhn OEM G12 or newer G13, and use only distilled water 50/50 with coolant to have best mixture. Hope this helps, kind regards, nikolozHi all,
Need some help. 2006 Treg V8, 140k miles. Love the car, but she has been "difficult". Latest issue: Driving her yesterday about 25 miles all highway, then local roads, at the very end of the trip, Overheating warning came on the LCD. Immediately pulled over Looked for steam, none, fans running, engine did not feel hot. Limped home and did some thinking and searching. I pulled the cap and put in a little less than a quart of coolant. I decided since the car did not feel hot, I would replace the Temp sensor on the back of the motor. It made sense and felt right. After replace, let the car idle in my driveway. She went right to 200 degrees and just sat there, no fans, no problem. I thought we were good. So went for a drive. She was great for about a mile. On the way back, temperature started climbing again. Got home and decided to replace the other sensor in the loser radiator hose. We drove her about 15 minutes ago, but I as anxious to get it done. So I pulled the overflow tank cap to let the pressure off, there was barely any, then put it back on to help hold the coolant in while I pulled the 2nd sensor. When I got the sensor out, the coolant was clean and cold. I knew the sensor was not the problem at that point, but replaced it anyway and went for the same ride with the same results; fine for a mile then climbs. The thing worth mentioning is, that the engine never feels hot! While the upper rad hose is hot, it's not so hot that I cannot hold it in my hand. And it does not feel like high pressure. If the motor was really 220-240 degrees, I would never be able to hold the hose with my bear hand. What do you guys think?
Thank you for your help.