Alright, I own a 2003 A4 1.8t quattro automatic. A few days ago while driving on the interstate, I noticed my coolant gauge going from half way down to the quarter way mark and giong back to half way mark, and I also noticed that my gas gauge has gone down a quarter way already and i've only driven 70 miles!!...usually on a full tank of gas, it won't go down to the quarter way mark until i've hit 100 miles, and that's crusing at 75mph on cruise control! yeah it's gotten a lot colder out, it's around 16 degrees today, before it was 32 degrees out! okay so going back to my problem I replaced the COOLANT TEMP sensor yesterday, the only problem is, i bought it at AUTOZONE for 7 bucks, the stealership wanted 56 bucks for it! I did noticed a few differences with the old CTS and New CTS.

NEW CTS:
my temp gauge will go up to halfway after letting the car warm up for 20mins, but the heat would be blowing out cold air, unless i m giving it gas, or driving around the city then it will blow out hot air, but once the car is at a stop, it continues to blow out cold air again. the temp gauge will remain in the middle where it should be unless i m driving on the interstate, then i would noticed it flucuating every 20mins? from the middle mark down to the quarter mark and then back up to the middle mark again...still getting bad gas mileage,..18-20mpg going 75 at 16 degree weather..


OLD CTS:

my temp gauge will be only at the Quarter Mark when the car is warmed up for 20mins, but I will be blowing in WaRM air regardless if the car is stationed or moving. THe temp gauge willl remain at the middle when i m doing city driving, but once I hit the interstate, it starts flucuating..and i m getting poor gas mileage..not sure if that's due to the temp..but if i calculate it right its' around 18-20mpg on cruise control going 75 at 16 degree weather..

So what do you guys think is wrong? could it be a defective CTS that I got from Autozone or could it be a different issue..termostate, water pump, etc...

thanks! hope you all can help..

 

hmm, maybe it wasn't your CTS to begin with, thermostat could be an issue, don't think water pump...