Coolant flush

[EMN1.8]

I'm doing a coolant flush on my 2004 A4. I drained everything from the radiator, and BELIEVE I got everything out of the block. I filled the reservoir with Prestone coolant flush and water, but was only able to get 4 and a half to 5 quarts into the system. I drove the car today, and the reservoir is still full, and i didnt get a coolant light. So I'm thinking maybe I didn't drain everything from the block? Could anyone tell me where to properly block from, and if there's any technique to bleed the system? Thanks

[fallingreason]

Keep draining from the rad coolant sensor, filling with water, idling with heater on high, flushing, repeat until clear. Then fill and idle with g12 until full.

[old guy]

Disconnect the lines to the oil cooler and you will get more out of the lower block.

[texasboy21]

I'm doing a coolant flush on my 2004 A4. I drained everything from the radiator, and BELIEVE I got everything out of the block. I filled the reservoir with Prestone coolant flush and water, but was only able to get 4 and a half to 5 quarts into the system. I drove the car today, and the reservoir is still full, and i didnt get a coolant light. So I'm thinking maybe I didn't drain everything from the block? Could anyone tell me where to properly block from, and if there's any technique to bleed the system? Thanks

When you drain the system from the lower temp sensor/drain plug only about half of the coolant will come out. Typically to flush the system you drain, refill with distilled water - run until you reach operating temp - drain, and repeat until the water you are draining is clear. Once its clear, top off with G13 (not diluted).

Half of the coolant will be the undrained distilled water, and the other half will be the G13 - a perfect mix.

[maurizio]

Depends how Thorough you want to be. I do it from the rad sensor, oil cooler and the heater core. You will have to use air to get it out of the heater core though.

[jacobsen]

I'm doing a coolant flush on my 2004 A4. I drained everything from the radiator, and BELIEVE I got everything out of the block. I filled the reservoir with Prestone coolant flush and water, but was only able to get 4 and a half to 5 quarts into the system. I drove the car today, and the reservoir is still full, and i didnt get a coolant light. So I'm thinking maybe I didn't drain everything from the block? Could anyone tell me where to properly block from, and if there's any technique to bleed the system? Thanks

It may take a week or two before you trust that you cleared the system of large debris. If you want to remove scale and crust that is coating the inside of your cooling system you will need something pretty heavy-duty to burn it off. Something like liquid plumber or diluted muriatic acid. The heater cores on this car have a tendency to collect a lot of sediment and it takes out the heating capacity of the core. I think that's where your Flushing should be concentrated.


To bleed this car properly you never want to try and bleed with the motor running or with the motor warm.

With the motor off and the motor cold. Fill the expansion tank and open the hard pipe bleeder screw until it stops burping and a steady stream of coolant comes out. Do the same thing to the top heater core hose, there is a hole in it designed for you to bleed it from. Do the same thing, pull the hose back a little bit until the hole is exposed to atmosphere and wait for it to stop burping and a steady stream of coolant to come out. You should do this a couple of times over the course of a week I think just to be positive you got all the air out. And to be certain that you do not have a leak or a bad head gasket spitting exhaust into the coolant system.

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[old guy]

A thorough flush really isn't that difficult and takes less than an hour. All you need is a hose nozzle and a 12" section of hose. Your flush points will be the upper heater core hose, the oil cooler supply hose, the lower CTS, coolant reservoir return line and the upper radiator supply hose. You can reverse your flush pattern back and forth depending upon where you place the hose section.

First remove the lower CTS and oil cooler supply hose and let everything drain out. Remove the upper heater core hose. Then you can use any combination you want to flush everything in both directions. For example you can plug everything back in except the heater core and flush the heater core from the core side and then use the nozzle to flush from the block side which will push through the heater core in the opposite direction.

Then you can disconnect the oil cooler hose and and CTS and do the same thing from either side. Then with the lower CTS out flush the radiator from the upper hose. Then put the CTS back in and flush the radiator from bottom to top using the large hose connected to the coolant reservoir and the upper radiator hose disconnected. Hopefully you get the idea. Flush back and forth through the various openings and you will have removed everything in one operation.

Slowly add two 1.5L bottles of the proper coolant and slowly top off with de-ionized water.

Done.