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A4 (B5 Platform) Discussion Discussion forum for the B5 Audi A4 produced from 1995-2001 B5 FAQ

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Old 11-30-2008, 07:41 PM   #1
TristanP
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Default Heater core backflush w/ pics

After being without heat since early spring, I decided it was time to set things right. Using this post as a guide, I went to Home Depot and bought 10' of 3/4" id tubing to make my life easier. As I later discovered, 7/8" would have been much easier to work with.

Remove the rear firewall rubber gasket, cover, and plastic tray/pollen filter and passenger side windshield cover. Get the wiper arms vertical. The engine bay should now look like this:




Wedge the driver side wiper cover up on top of the wipers to get it out of the way. Remove the corrugated hose cover (it's split on the back) to expose the lines running into and out from the heater core. You should now be looking at this:




Slide your tubing over the inlet side and run the other end down to a bucket of some sort. You'll need 4-5'.






Slide a shorter length of tubing over the outlet side (1-2'). I used a brass hose nozzle that increases flow as you twist it because it sealed fairly well against the end of the hose. Turn on the water flow (not too hard as the heater core is a bitch to replace) and watch the gunk come out. Keep flushing until the water coming out is clear.

Reverse the hose and forward flush, again making sure the water coming out is clear. Now is probably a good time to drain, flush, and bleed your whole cooling system. Reverse the removal steps to get things back together. Here's what I was left with:



...oh yeah, and HEAT.
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Old 11-30-2008, 08:31 PM   #2
Roger @ CA
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Default Did the same last week except without all the hoses... just undid one of the hoses on the

client's 2002 A4 and let it flush for 10 minutes on the driveway... now she has heat again as well :-)
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Old 12-01-2008, 04:08 AM   #3
ModifiedA4
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Default nice!

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Old 12-01-2008, 08:12 AM   #4
djdc
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Default I need to do the same, but whats the risk of causing a leak in the heater core?

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Old 12-01-2008, 09:10 AM   #5
Roger @ CA
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Default Heater core is inside the car... 8 hours later you can swap it out, after taking dash out :-)

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Old 12-01-2008, 09:35 AM   #7
ModifiedA4
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Default question...

was the coolant in the resevoir tank the same color as the 'gunk'?
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Old 12-01-2008, 10:43 AM   #8
TristanP
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Default Yes, I still need to replace the radiator

Flushing it out produced more of the same. Maybe I'll get to that this winter in my new garage. For the moment, I can live with it. Gotta stay warm.
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Old 12-01-2008, 11:42 AM   #9
ModifiedA4
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Default ok...

so its safe to assume if your resevoir looks like virgin G12, flushing the heater core might not be needed.
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Old 12-01-2008, 12:34 PM   #10
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Default Thats what I'm thinking as well. I got no heat but my resevoir coolant looks OK.

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Old 12-01-2008, 12:34 PM
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