Tech Help Needed, Hissing sound after coolant tank replacement

[James0013]

Hi guys, I had to replace the coolant tank on my 2000 A6 2.7T (the old one had a crack in it). I got the the tank swopped out OK.

But when I started the car back up there was a hissing from the top right of the engine (that is where one of the return lines comes from on its way back to the tank) it sounds like air is escaping from some place. I am guessing that when I replaced the tank some air got into the system could this just be a self bleed or should I be worried?

Anyone know if there is a bleed valve on the A6 cooling system?

HELP!!
Thanks James

[2.slowT]

Here is a post on this from a different forum.

It might not have been the same model but I dont see why it would not work. This is what they did. Dont try this method untill someone confirms!

I just ordered a coolant reservoir from Shokan 40 bucks new. I will need to know how to do this also. PM me if you find out and its not posted.

The cooling system is not self-bleeding, IME. Start the car cold with the cap off the reservoir, let it warm up/idle till the fan turns on high the first time. It will push coolant out the reservoir and then top it off after the fan turns on. This would not cause a misfire/stumble as you're describing though.

[Daft]

Hi guys, I had to replace the coolant tank on my 2000 A6 2.7T (the old one had a crack in it). I got the the tank swopped out OK.

But when I started the car back up there was a hissing from the top right of the engine (that is where one of the return lines comes from on its way back to the tank) it sounds like air is escaping from some place. I am guessing that when I replaced the tank some air got into the system could this just be a self bleed or should I be worried?

Anyone know if there is a bleed valve on the A6 cooling system?

HELP!!
Thanks James

I'd like to add to the post above that there are two places that you can bleed the cooling system on the 2.7T. One is between the driver's side valve cover and the throttle body (located on a black metal pipe you will find a 4-5mm hex screw), the other is on the heater core pipe under a rubber boot that covers the heater core pipe right before it enters the passenger compartment in the battery well.