air in cooling system help please


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Aug 10, 2009
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i had to fit a new rad to my a3 tdi and cant get the air out the syetem i have now done 80 miles and the heater is still blowing hot then cold think it has air in the heater rad but cant undo the pipes to it is there any other way to bleed the cooling system of air ?
try blasting the heater on full power and at it's hotest with the rad cap off for about 10 minutes.
see does the coolant level drop and top up if needed.
this worked with the last car i had.
worth a go anyway.
heater was on full and hottest setting when i filled the sysetm and yes i have had the car running for 35 mins with the heater on full blast and hottest setting just cant seem to shift air from the heater rad it blows hot when the car reaches 90 on temp gauge but it then blows cold after about 5 mins then may get hot again then cold again any one else had this problem the temp gauge sits on 90 and the main rad gets hot thermostate opens and fan cuts in so only seems to be with the car heater radiator ?
how about parking on a slope, with the front of the car higher than the rear.
Then trying again with the cap off.
did u try it with the air-con off?
havent got aircon i thinking of draining the complete system and refilling it i dont kno what else to try thanx for your reply
update to this problem done 100 miles the other day the car heater blows hot when driving and goes cold when i stop in traffic but my main problem hose to top of the main radiator very hot and pressured and radiator and bottom hose cold has had a new thermostate and radiator the flow and thermostate does open if i leave the car running for about 20 mins and cooling fan kicks in temp gauge reads 90 but car does smell hot any idears what to do its totaly lost me i realy cant work out why the system isent flowing through the rad in normal driving condictions and yes had a new water pump aswell
Empty and start again, try and squeeze the bottom hose as you are filling it, heater on full, start engine with cap off , carefully squeezing the hoses, its a pain sometimes but you will get there...
today i drained the system then flushed the complete system and fitted another new thermostate just incase the other new one was faulty slowley filled the system whilst squeezing all hoses including heater hoses car heater on hot and full power no change ? realy doing my head in
When you said the matrix hoses wouldn't budge, how far did you get with them. Once the clips are off they should be able to be twisted a little and if still solid then a flat blade screwdriver to help prise them back from the housing. I think this is your best bet but you have to be careful not to crack the plastic on the matrix.
will have another go at them and post back with what the result is thanx
now i had enougth of this problem lol i am going to take the thermostat out and remove the middle so i am just putting the outer edge back in to create the seal as it seems to me as if the thermostate is totaly blocking the flow around the cooling system once again top hose piping hot and blown up solid under pressure rad cold botom pipe cold i have 2 new thermostates now so nothing to lose open it up and see if i get a flow around the system wish me luck then i know were to point the finger at but realy cant work out why its doing it will update later today with results of this test
i have exactly the same problem with my a3 i already tried taking the stat out and it flowed round fine but downside was that the engine management light came on and then woulldnt run correct so i bought a 3rd thermostat which now opens as it should but i still have air in cooling system im getting my m8 to pressure test cylinders nxt.
i took the thermostate out and water now flowing around the radiator not been on a long enougth drive yet to see if it still overheats but will test soon and report back car heater still blowing cold beginning to think it may be the head gasket its a 1.9 tdi is there any test i can do to check head gasket i havent noticed any loss of water the oil is fine not milky and its running fine with plenty of power ?
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here goes i took the center of the thermostate out water is now flowing through the complete system and running at 60 on temp gauge i back flushed the system and it was clean my heater in the car is blowing warm but there is still a lot of pressure build up in the cooling system hoses are solid its a 1.9 tdi sport could it be the head gasket i filled the expantion bottle to the top and it was blowing bubbles and the higher the rev the more bubbles the car seems to be running fine no smoke good power smooth running no milky oil ? any idears please
here goes a update i have flushed the system clean filled it up and filled the expantion tank to the top squeezed all pipes to remove any air been running without a thermostate for a week all ok today i got a genuine audi thermostate and will go fit it soon the problem i found is its a 1.9tdi with the expantion tank full it blows bubbles in the water ? i thinking head gasket ? but the car is running fine no loss of water and no milky oil ? any advice please will post results once thermostate is bak in later today will a tdi run ok with head gasket leaking ?
Mine blows bubbles in the expansion tank when reved so do other cars I have owned so don't think its ur head gasket
thats good to here lol is urs a turbo diesel ? if yes could you do me a massive favour after running your car for about 30 mins on a drive can you please check if the hose from the bottom of your radiator up the the thermostate is hot also are they under pressure/pipes very firm my pipes get very firm and the top hose to rad gets hot but bottom hose from rad stays cold is yours the same be nice to compare to see if i chasing a fault or not thank you for your reply
Sorry mate mines 18t however when I did my stat a couple of weeks ago the bottom pipe wasnt warming up at first but even when squeezing it but after a few drives it rectified it. Is ur temp gauge reaching normal running temp wen stat is in
right its all back together and on trial running at 90 pipe to top of rad gets hot rad and bottom pipe cold heater in the car a bit hit and miss hot then cold ?
still working ok and i had enougth of it so took drastic messures and sold it lol