marosekcmo

I have to say, I've found this board very helpful as a new Audi owner. Thank you to all of you who selflessly contribute your knowledge here.

I recently bought an 04 Audi A8 which honestly has been a bit of a hassle to own. Since I've purchased the vehicle back in April, I've had to replace the Coolant Temperature Sensor (Twice) and Expansion Tank in an attempt to get the low coolant indicator from triggering. I have plenty of coolant in the expansion tank and both the coolant temperature sensor and expansion tank are OEM parts purchased from my local Audi dealership.

Upon replacing those parts, since I don't own a scanner, I have a buddy of mine who works at O'Reilly's that erased the codes after the sensor change and then again after the expansion tank change. The temperature gauge would immediately work afterwards, but within a couple of days it would stop working and I would get the low coolant indicator warning light even with coolant level at the max line. Of course, my radiator fan comes on and makes my car sound like a jet engine.

I've searched throughout this forum and couldn't find an answer, but is there something else that could be causing the low coolant indicator light to keep coming on? Thanks for your help.

mishar

Welcome to the board. Check the sticky tread at the top of the treads list. There are lots of useful information.

First thing you need if you are going to maintain and repair your A8 yourself is VCDS. There is no work around. Next is Bentley Manual with wiring diagrams.

Based just on what you said it looks like you have wiring or contact problem. 2004/05 are more prone to problems like that. Get some DeoxIT and apply it whenever you disconnect any harness or scan tells you that it is wiring problem. Coolant level switch is at the bottom of the expansion tank.

marosekcmo

Thank you kindly for your input.

Could my problem be that simple? I sure hope so. I'll try it after work and follow up. Thanks.

mishar

It could be that simple and it won't hurt, or be expensive to check. Other than that VCDS scan is necessary.

MP4.2+6.0

May be as simple as a still bad coolant bottle (sensor), contact problem at the connector, or broken wire internally near the connector. Since you replaced the bottle/sensor if I understand correctly, I would look next critically at the connector as Misha suggested. Could be oxidation as well as general underhood dust, spilled old coolant, etc.

Mister Bally

Using the wiring diagram, bypass the coolant tank sensor. See if the problem happens again. Since you know yours is full, should be no problem.

marosekcmo

Mishar, thank you for your help with my low coolant issue. I took your advice and bought some DeoxIT, disconnected the harness from the coolant sensor in the back of the engine (I believe it's the G62 sensor) and also disconnected the harness at the expansion tank. I followed the instructions on the DeoxIT can and reconnected everything. The gauge still wasn't working so I headed to my friend who works at O'Reilly to see if he clears the codes will the gauge start and stay working. Well low and behold, as I got about a mile down the road, the temp gauge started working and the low coolant warning went away.

I'll keep an eye on this and report back in about a week. Thanks again for your help!!!!