Audiholik04

Hi,

I have a 2004 A4 1.8T and a few days ago, my check engine light came on. A few days later, my low coolant warning popped up. After allowing the engine to cool down, i added some coolant to my tank. i looked undeneath the car, no leak. Today i was driving, and once again the warning came on and the temperature gauge jumped from 90-130! Upon getting home, i once again let it cool down and i saw my level of cooland was fine! Does anyone know what the problem could be? is it just a faulty sensor or is my engine really overheating? Help!

Thanks, Mike

mm2214

bad thermostat?

Audiholik04

I should note that both my fans arent working either, im hoping thats the problem

Tim$2

That would probably be a good place to start

veedubb

Since you had low coolant, you may have an air pocket which is essentially steam and can cause havoc with your temp sensors. Assuming your cooling system is not leaking, you may want to do a coolant flush, fill and bleed if it hasn't been done in the last two years. Use OEM G12 coolant only. It's pink in colour and it's not that expensive and can be had in concentrate at your Audi dealer. Mix 50/50 with distilled water obtained from any pharmacy and it's cheap too.

Bleeding may be a PITA but I have done a write up on it here: Luke warm cabin heat & lower radiator hose cold

It may also be the G62 Coolant Temp Sensor (CTS) which are known to fail. I just replaced mine last week because it threw a code and my rad fans run full blast sometimes on a cold start. This sensor has two functions and one of them is to control the fans and to provide the temp gauge with a reading, I think. It's pretty cheap but can be a PITA to replace if you don't have small hands.
See here: :: a4mods.com :: - The Premiere Audi A4 Modification Guide and Pictures Library

I had the exact same code (16502) as the author of this article. Make sure you get the updated (4-pin) green sensor as well as the rubber O-ring and the replacement plastic clip when you buy it.

Good luck.