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Old 22-01-19, 12:46 PM   #1
Peacedub
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Default Audi A6 C5 2.7 biturbo

Hey all,

Sorry but I didn't know which category to put it into so I've placed it here first.

I've recently purchased the titled vehicle and all is good in the world

Its not so much of a problem but the heaters blow cold when at idle and warm up again when the revs pick up then cold on low etc, its more annoying than anything especially in these cold mornings. I've done a full coolant flush and replaced as I usually do with new cars. Its just had in the last 12 months a cambelt with water pump etc. Is this an issue with the matrix/heater flaps?

Thanks in advance
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Old 22-01-19, 12:51 PM   #2
Mellis46
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Thermostat?
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Old 22-01-19, 02:09 PM   #3
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not sure if it's the same as the 2.6 but is there an air bleed screw in one of the rubber pipes just before they go through the bulkhead?
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Old 22-01-19, 03:20 PM   #4
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Originally Posted by Mellis46 View Post
Thermostat?
Yeah this was my first thought, it gets up to temp pretty quick, stuck open? it was a mission to do the coolant swap (bumper off job), is the thermostat a bastard on these engines? I'm more used to cars with loads of space under the bonnet. These are literally shoe horned in!

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Originally Posted by V6Rob View Post
not sure if it's the same as the 2.6 but is there an air bleed screw in one of the rubber pipes just before they go through the bulkhead?
Not sure, I too have a 2.6 v6 avant as well so will compare.
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Old 22-01-19, 09:19 PM   #5
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Quote:
Originally Posted by Peacedub View Post
Yeah this was my first thought, it gets up to temp pretty quick, stuck open? it was a mission to do the coolant swap (bumper off job), is the thermostat a bastard on these engines? I'm more used to cars with loads of space under the bonnet. These are literally shoe horned in!

There isn’t a lot of room no! It’s been a while but I remember us getting one in and it being part of the timing belt / water pump service, it’s next to the water pump itself. Sure someone who knows better will correct me if I am wrong!

If the engine itself comes up to temp but the heater doesn’t it probably isn’t the stat tbh, more like air in the system or duff heater matrix...
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Last edited by Mellis46; 22-01-19 at 09:25 PM.
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Old 22-01-19, 09:48 PM   #6
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Yes, the thermostat is the water pump / timing belt job on these. In the middle at the front of the engine block.
The quickest way is to remove bumper, front panel with rads on one side (so You don't need to disconnect aircon rad) and it's a pretty simple job. Just timing tool for camshafts recommended.

If the engine gets up to ~90C them it will be air in the pipes or matrix. I would bet on air
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Old 23-01-19, 12:05 AM   #7
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BMW V8's have this issue; it's almost certainly air in the system somewhere. The trick with Beemers is to make sure the heater valves are open / set at the hottest temperature (my 740 has two as it has dual climate control) when you fill the system, rev the engine a bit to pump the coolant round the heater matrix and then top up. It also helps to raise the front of the car somehow to make sure the filling point is as high as possible.
You may have to repeat the process a couple of times as I did after an alternator swap. DON'T ASK!!!
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Old 23-01-19, 08:48 AM   #8
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Thanks to everyone for your rapid responses. I too am thinking its air in the system, I did give it a vigorous bleed and repeated a couple of times. The cambelt and water pump were replaced a year ago (less than 2000 miles) so I'm thinking its not the thermostat, well hoping! its gets up to 90c within 5 min and maintains it. This would indicate the thermostat is working correctly? it has dual climate and I've noticed the passenger is slightly warmer through the vents but not by much when set to max temp. Aircon on off doesn't change anything. i'll try give it another bleed and see how I go. The main reason I carried out a coolant change was because this was happening before and still doing it after.
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Old 23-01-19, 10:50 AM   #9
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i'll try give it another bleed and see how I go.
Don't forget to set the aircon temperatures at their highest before bleeding, otherwise you won't get a proper flow of water through the matrix. The fact that one side is warmer than the other lends weight to the air theory.

Most dual circuit aircon systems control the temperature of the water in the matrix, not by changing the blend of warmed / cool air.
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Old 24-01-19, 02:06 PM   #10
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Quote:
Originally Posted by SwallownAmazon View Post
Don't forget to set the aircon temperatures at their highest before bleeding, otherwise you won't get a proper flow of water through the matrix. The fact that one side is warmer than the other lends weight to the air theory.

Most dual circuit aircon systems control the temperature of the water in the matrix, not by changing the blend of warmed / cool air.
Nice 1. I did bleed with aircon off but heaters whacked on high and blasting on full fans through all heaters so I will carry out another bleed tonight while switched on. Fingers crossed it will sort it cos im bloody freezing sat in traffic!!

Last edited by Peacedub; 24-01-19 at 02:08 PM.
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