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Bleeding Cooling system

Discussion in 'A4/S4 forum(B5 Chassis)' started by hardhitter, Dec 6, 2009.

  1. hardhitter
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    hardhitter Member

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    I've just bought an A4 1.8 TQS and it's not getting up to temp on the gauge (very low or somethimes not registering). As it's low on coolant I need to top it up and make sure theres no air in the system. Hopefully it's just an air lock or something. Otherwise I'll have to start looking at the thermostat and water pump.

    Can anyone tell me the procedure for bleeding the cooling system ?

    Cheers
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  2. DEEJAY TQS
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    DEEJAY TQS Member

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    yep mines exactly the same, except the person before me replaced the sender unit, so mines probably the thermostat, mine losses a small amount of water, if i top it up to max,by the end of the month its down to minimum, not sure where the water goes,as theres no leaks i can see, my cam belt is due in the next couple of months so ill get a new water pump in there and see if its that
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Its more likely to be the stat or the CTS than an airlock tbh.

    I'd just throw a stat at it first off, they're not dear and easy to change, and if that doesnt sort it do the CTS. (Or just do them both)

    To bleed the system you partly remove one of the heater hoses and fill until water comes out the little hole.
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  4. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Also, ours does the water loss thing.

    Fill it up and within a few weeks or a month its back down to minimum. But once it gets to minimum it stays there and doesnt go any lower, so i just leave it there.

    Ours has crust around one of the rad hoses and i suspect that when the expension tank is at maximum the system pressure is higher, forcing water past the jubilee clip at the rad. When the tank drops to minimum the greater volume of air means the pressure is lower and it doesnt leak.
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  5. hardhitter
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    hardhitter Member

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    I have no idea if it's actually leaking or loosing water (due to only just buying it and getting it home). Drove it about 50 miles home and it looks to be at the same (or similar) level to when I set off.

    Is the CTS the one to the rear of the engine, looking from the front ? It was the only CTS sensor i could see without taking covers off etc. Where abouts is the thermostat housing ?

    Thanks
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Stat housing is underneath the water pump. Follow the bottom rad hose and you'll see it.

    CTS is located in the metal coolant gallery on the rear of the cylinder head.
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