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  1. #1
    Registered Member One Ring
    Join Date
    Jan 12 2018
    AZ Member #
    412365
    Location
    Tulsa/Oklahoma

    Why do I keep having to bleed the system for heat to work?

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    I have a 04 A4 Quattro 1.8T that recently had the radiator and thermostat replaced as well as having the coolant system flushed 3 times due to an issue with the heater. After the system was bled the heater was working well for a couple of days, but then began blowing lukewarm air again. I have bled the system multiple times on a few different occasions now and the heater blows super hot air each time I bleed the system but then returns to lukewarm in a day or so. I am not losing coolant in the system and the engine is getting to proper running temp and staying in place. Are there any ideas as to why air keeps getting into the system and how can I fix it? Thanks for your help

  2. #2
    Established Member Two Rings
    Join Date
    Nov 03 2010
    AZ Member #
    66528
    Location
    Yorba Linda, CA

    First be sure that you are doing the air-bleeding correctly. The engine has to be shut OFF, not running. Disconnect the sensor connector under the coolant reservoir, then raise the reservoir as high as the hoses allow and keep it there. The reservoir should be kept full and the blue cap off, then pull back the heater hose with the small hole in it until just past the end of the heater pipe. When you have a constant little stream of coolant, push the hose back on and re-clamp. Put the reservoir back and you are done.

  3. #3
    Senior Member Three Rings
    Join Date
    Mar 21 2016
    AZ Member #
    370603
    My Garage
    69 Nova
    Location
    California

    For all the hate the 3.0 gets, it was pretty easy to bleed the system. I literally just put a couple liters of G12, couple more of distilled water, until it came out of the bleed screw. Tightened it up, and that's basically it.

    I didn't even lift the reservoir. I *might* have jacked the car up, but I don't remember.

    No problems, hot heat whenever I have heat on.

    3.0 ftw, apparently, lol.
    04 A4 3.0 Quattro 6 Speed
    69 Nova with a bunch of stuffs

  4. #4
    Senior Member Three Rings a4lownslow's Avatar
    Join Date
    Feb 12 2014
    AZ Member #
    144887
    My Garage
    2007 Audi A4 2.0T
    Location
    Hudson WI

    Quote Originally Posted by DarkoNova View Post
    For all the hate the 3.0 gets, it was pretty easy to bleed the system. I literally just put a couple liters of G12, couple more of distilled water, until it came out of the bleed screw. Tightened it up, and that's basically it.

    I didn't even lift the reservoir. I *might* have jacked the car up, but I don't remember.

    No problems, hot heat whenever I have heat on.

    3.0 ftw, apparently, lol.
    It’s not 3.0 specific lol. I do a lot of work with the b6/b7/b8 and the reason you had no issues is because when the cooling system is working properly that’s all you should have to do! It will self bleed any air.

    Nowadays i use a vacuum refill tool, but never had issues with simply adding coolant to reservoir.


    Sent from my iPhone using Audizine

  5. #5
    Registered Member One Ring
    Join Date
    Jan 12 2018
    AZ Member #
    412365
    Location
    Tulsa/Oklahoma

    Thanks for the reply. I've only done it with the engine running because that's what I've been reading in my own research. I will definitely try this process and hope for the best. Thanks again

  6. #6
    Veteran Member Four Rings old guy's Avatar
    Join Date
    Dec 28 2006
    AZ Member #
    14483
    My Garage
    '03 A4, '13 A5, '18 MB-GLA
    Location
    Western Maryland
    Items for Sale

    Bleeding info in here: Clicky click®
    A4 Motoza tuned Frankenturbo F21L mixed flow turbo / Bosch 550's / 3" MAF / TyrolSport SMIC / 034 HFC / TT 2.5" DP / Borla Exhaust / Eibach ProKit Springs / Koni Yellows / H-Sport Sway Bars / TyrolSport Brake Stiffeners / HyperShift Short Shifter / Podi
    A5 Mods to come: Little stuff so far. 20/25mm spacers / H&R OE Sport springs / 35% tint / Neuspeed Power Module / black window trim / RS grille.

  7. #7
    Registered Member One Ring
    Join Date
    Jan 12 2018
    AZ Member #
    412365
    Location
    Tulsa/Oklahoma

    Quote Originally Posted by Turbo510 View Post
    First be sure that you are doing the air-bleeding correctly. The engine has to be shut OFF, not running. Disconnect the sensor connector under the coolant reservoir, then raise the reservoir as high as the hoses allow and keep it there. The reservoir should be kept full and the blue cap off, then pull back the heater hose with the small hole in it until just past the end of the heater pipe. When you have a constant little stream of coolant, push the hose back on and re-clamp. Put the reservoir back and you are done.
    So I did this today and I ended up with pretty similar results. The heat got hot but slowly died off throughout the day except when I push the gas pedal it will get really hot. I'm thinking the next step is to replace the heater core. It doesn't seem to be as difficult to replace in this vehicle as some dealerships and mechanics make it out to be so I figured I'm going to give it a shot on Saturday. Any other suggestions to try before then? Thanks for your help

  8. #8
    Veteran Member Four Rings EuroxS4's Avatar
    Join Date
    Jan 24 2010
    AZ Member #
    53856
    My Garage
    2003 Atlas Grey A4 Avant 1.8T 6speed manual quattro,2002 GSXR 600
    Location
    Paramus,NJ USA

    Its called a blocked heater core.Your better off replacing it.Should only take about an hour or so.
    VW/Audi Immobilizer removal and immobilizer adapting solutions for any and all VAG Vehicles,Odometer matching, SKC/Pin retrieval services.Located in Northern NJ.For inquries pm for details.

  9. #9
    Senior Member Three Rings
    Join Date
    May 24 2008
    AZ Member #
    29149
    Location
    cornish,me

    I would think that if the heater core was blocked you would not get any heat at all. I think that it is more likely that some how air is getting into the cooling system somehow. These cooling systems don't appear to be able to circulate the coolant when there is air in the system. I would drain the coolant and draw a vacuum on the system to see if it can hold the vacuum. This will tell you if there are any air leaks into the cooling system. It won't tell you where the leak is but you will know whether or not you have a cooling system integrity problem.

  10. #10
    Registered Member Two Rings
    Join Date
    Feb 10 2015
    AZ Member #
    314531
    Location
    seattle

    Quote Originally Posted by redrubberband88 View Post
    So I did this today and I ended up with pretty similar results. The heat got hot but slowly died off throughout the day except when I push the gas pedal it will get really hot. I'm thinking the next step is to replace the heater core. It doesn't seem to be as difficult to replace in this vehicle as some dealerships and mechanics make it out to be so I figured I'm going to give it a shot on Saturday. Any other suggestions to try before then? Thanks for your help
    check your j-plug

  11. #11
    Veteran Member Four Rings EuroxS4's Avatar
    Join Date
    Jan 24 2010
    AZ Member #
    53856
    My Garage
    2003 Atlas Grey A4 Avant 1.8T 6speed manual quattro,2002 GSXR 600
    Location
    Paramus,NJ USA

    Quote Originally Posted by refueler View Post
    I would think that if the heater core was blocked you would not get any heat at all. I think that it is more likely that some how air is getting into the cooling system somehow. These cooling systems don't appear to be able to circulate the coolant when there is air in the system. I would drain the coolant and draw a vacuum on the system to see if it can hold the vacuum. This will tell you if there are any air leaks into the cooling system. It won't tell you where the leak is but you will know whether or not you have a cooling system integrity problem.
    Not true.If you have a blocked or partially blocked heater core thats restricted it will blow luke warm at idle and warm under load due to the pressure being built up inside the cooling system.you could try flushing the heater core back and forth.Or run the car with clr in the cooling system for 8 hours and see what happens.However sometimes they are too far gone to save.I recommend a replacement.
    VW/Audi Immobilizer removal and immobilizer adapting solutions for any and all VAG Vehicles,Odometer matching, SKC/Pin retrieval services.Located in Northern NJ.For inquries pm for details.



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