I have a 2004 Audi A4 and am having coolant system issues. I seem to be fo rever bleeding the system as air keeps getting stuck in the heater matrix ( so we have no heat) and more recently the temp gauge seems to be going up p ast normal for a bit and then goes back again. Also,the computer has start ed randomly saying it is low on coolant. I am assume both these symptoms a re because air happens to have got to the sensors.
There are 2 bleed points on it 1. a hole in one of the hoses which goes to the heater matrix 2. a nut on a metal water pipe on top of the engine which you undo a bit wh ich lets air out.
Based on my central heating experience ( :) ) I have brought the engine up to temp and then with the engine off (in case it sucks in air when bleedin g) I loosen the nut on top of the engine and let the air/ water and air mix come out until it is water only. I then do the same for the heater matrix .
Only other thing to say is that it seems to be losing water (needs topping up in the header tank) about once a week.
I can understand there may well be a leak somewhere but don't understand wh y it keeps getting air in the system.
Anyone have any ideas?