Rob.S4

I own a 01 Audi s4 and maintenance for the most part has been taken care of religiously...from the first owner to me..

I am new to the Audi world and have basic mechanical skills such as oil changes and brakes and so forth

My issue occurred today while letting it sit after a ride to the mall and back and after shutting it off a pop noise occurred and didn't think much of it...then I realized smoke was arising from the hood and then I open it and see G12 draining out fast...

Further inspection showed two things..
1st there seems to be a hole that's there and a cap that should be there...but also there's a wire(harness) hanging from there and not sure where it disconnected from...I want to believe what ever covers the hole also had some kinda sensor which connects to the wire sensor harness looking thing...but there's nothing found to put back..

The hole is probably connect to the bottom of the radiator


So I was wondering what the part is?
Why did this happen?..
(Background info ...the g12 was never flushed out and when I recently opened the cap it look like a water down orange color and had a lot of minerals/crap around the rim of the cap and container..pics below)

Any info explaining why and how to repair and prevent this from happening would be great..

Rob.S4

anything?

donromani

1st pic - yup, there should be a sensor there. Hard to imagine how that thing popped out with the clip (that black plastic thing) still on there, and how the sensor then came off of the harness....
I believe the sensor would be the coolant temp. sensor, or the the thermal switch for the after run system, someone else here will have to clarify that for you since I'm not 100% sure.

The Second pic - it could be that someone added normal coolant to your g12, or that the g12 was just really old. My money is on the first one as this looks exactly like the gunk that built up in my parents B5 Passat after the dealership topped off the g12 with normal antifreeze.

Flush the system with a cleaning solution (available at autozone etc.) and refill with Pentosin g12 diluted with distilled water according to the label.

The sensor will cost about $50 to replace I think...

Rob.S4

great info and point in direction..
but yea honestly i don't know why out of all places it popped off like that and while the car was shut off after a 2minute idle.. and the engine wasn't overheating or anything..

the its a hose at the bottom left of where the radiator is so im hoping i can find what i need..

yea and the g12 looked reall old but whats the cause of all the gunk?..

is something getting into there...should i check anything else?

donromani

The sensor popping out like that is really strange - it must have been connected incorrectly or something. Once you have the replacement it will take 2 minutes to replace, no problem.

No, there's probably nothing getting in to the coolant. The VW and Audi engines have a bunch of sensors, gaskets and other components that react chemically with regular coolant mixes. The g12 is a special formula that is designed to be inert so it doesn't react with the engine components. If regular coolant is used you'll get a build-up (essentially rust particles) that bind together and form the gunk you see.

Don't worry about it - there is no critical damage to your engine. Just flush and refill and make sure no moron mechanic ever puts any regular antifreeze in your coolant tank.

complacentsee

Old G12 looks exactly like that aswell. Mine looked like that after about 70K miles The original take makes it look worse.

Rob.S4

just got back from work and ready to jack it up and remove the belly pan...

i cant even think to where the hell the sensor went..

im gonna try and flush it out ..

can i use a hose to flush it out ..any proper way to do it..

i got 2 containers of g12
how much do i need..

and what part do i need exactly..ima go take some more snap shots of this mystery and will be back in an hr...

thanks again guys...truly a community of Audi owners i appreciate a million

complacentsee

the owners manual should say how much it takes. There are 2 varities of G12. Pre mixed and unmixed. Usually dealers sell premixed 50/50 and you need alot then. If it is unmixed, pick up some distilled water for the mix. make sure there is nothing added after. Otherwise de-ionized water will work fine aswell, and sometimes is sugjested, however distilled water is also deionized and will by definition be more pure than the deionized. (At leasted based on my knowledge)

Rob.S4

after looking over some service records ..its seems they topped off all the fluids but from some generic mechanic shop..im sure they improperly added the coolant type...

i also came upon the sensor in which i mistaken to see at night still connected to the harness after pulling it out from between the belt..

im assuming this is the coolant temp sensor as stated from above by donromani...

now im hoping the sensor is still good ..

all i have to do is put the rubber gasket around the sensor and plug it back in and put the clip back in? is this correct?

i haven't flushed the system out yet but was wondering the best way to do so...

the following pictures if what ive seen and will probably take the sensor back off to flush the system out..

Rob.S4

this is the sensor seated back in there..

i don't feel so confident from the clip but this is how i think it sitts in there..



and here the bottle of g12 ive picked up by a bridge auto parts store near home...