Air lock in coolant system!!! Please Help!!

[Nad*s3]

:sadlike, Yesterday i topped up my coolant level and stupidly drove around for about an hour without replacing the cap, i realised this after parking up and seeing water gush out from under the bonnet, i topped up the bottle, replaced the cap and carried on as normal. I let the car cool down for about an hour after driving it again, i now have a temp problem.
If i run the car without the cap the temp will stay at 90, as soon as i replace the cap the car starts overheating, im only getting cold air from the heaters and only half of the pipes are getting hot, ive been told its a number of things can any1 help???!!! Does anyone know the correct procedure for bleeding the system??

 

[Jamesh]

Give the bottom hose a good squeeze to try and expel any air, when you dont have anymore bubble in the expansion bottle, top up to the max, replace cap and run car making sure the fan cuts in and doesn't overheat.

 

[Nad*s3]

i'll give it a try!!, 'the bottom hose stays cold and fans r not cutting in at the moment even if the temp goes over 90c

 

[A3-frankie]

My dad had air in his system some time ago. We got the car up to temp on a drive then with engine still running took the cap off the coolant resevoir tank and left the car running,the water should bubble and show signs of air coming out. We then took for another short drive, then the same again. I i remember rightly we let the fan cut in a couple of times whilst sitting. All the air just worked its way out.

I bet if you read a haynes manual for any car it would give you tips.

 

[A13X-A3]

I know that this is an old thread but Ive got the same problem on my '97 1.6 sport. Ive changed the thermostat for a unipart version this morning, that didnt help. So i took it out completely, the car drove fine for a round trip of 40ish miles to my audi dealer, where i bought a genuine thermostat. Fitted that, same problem. Dont know what it is, but the car runs fine, doesnt overheat, even with motorway driving without the thermostat, but once its back in, the car overheats again.
Any help will be appreciated.
Alex:icon_thumright:

 

[S3 Jock]

its an air-lock by the sounds of things. Not sure of yrou engine layout exactly, but look for a bleed-screw at teh back of the engine (usually where on one of the hoses going to the heater matrix)

You need to unscrew this and run the engine until no air/bibbles burp out and you get a steady flow of water when you blip the throttle.

Get the thermostat back in and bleed it properly

 

[madvw]

lifting up the front of the car high on a trolley jack and running the engine can sometimes work.

 

[A13X-A3]

ive sorted mine. Was my worst fear, water pump had gone. took me a day to save the cash of garage doing it, changed the timing belt and tensioner too.
Cheers for all the advice though.
Alex

 

[dummi]

not sure but i think the temp guage has something in built so when its not covered in water it will stay bang on 90C. i suggest you fill the system up squeezing the hoses etc and pray you have not weakened the head gaskets etc