Coolant pump / Filling and bleeding

Hi,
The slow coolant leak and the traces leading downwards towards the timing belt area suggest that the water pump or the seal to the engine block is leaking (A4 8K, as indicated in my profile).
The pump probably needs to be removed. It shouldn't be a problem from a purely mechanical standpoint.
But: Has anyone ever refilled and bled the cooling system without using a vacuum pump? I'd like to try doing that in my garage.
And - with a mileage of 150,000 km, should the pump be reused? Of course, I will check its operation, as well as the tensioner pulleys for the timing belt.
Thank you!
Herbert.

Good evening, Herbert,

It takes significantly longer to bleed the air out of the system, but it does work.

You absolutely must bleed the cooling system through the coolant hose at the splash shield, leading to the heat exchanger.

If you have a "bleeder" for the cooling system, you can use it while the engine is running to help with the bleeding process.

Best regards,

Michael.

Good morning, Michael,
Okay, thanks! So, bleed the system as usual, at the highest point. The description and diagram of the circulation system in the RLF (presumably a manual or document) are confusing.
hg
Herbert.

Hi.

I would replace everything: the timing belt, the pulleys, and the water pump.

Best regards from Hesse.

Hello Herbert,

The RLF is indeed not entirely user-friendly or self-explanatory.

Bleed as usual. Where possible, pre-fill the hoses to minimize the amount of air in the system.

Best regards,

Michael.

Quote:

The RLF is indeed not entirely user-friendly or self-explanatory.

Okay. According to the RLF (repair manual), you should slightly loosen the bolts on the aggregate carrier on the left side (to lower it). While doing this, you can detach the crossbar for the torque support, but it won't come out because the connection to the radiator is in the way. If you lower it on the right side and disconnect an intercooler hose, it will come out. As I've mentioned before, even an RLF can be wrong.

Quote:

Ich würde alles neu machen, Zahnriemen, Rollen und Wasserpumpe....{

Völlig richtig, Rüdi. Der Aufwand ist derart, daß das Aufsparen wegen 60 Tkm nicht lohnt. Ich habe jetzt unter Garagenbedingungen (Werkzeug ist da, Wagen steht auf 40 cm Bühne, RLF ist da) Stunden zum Ausbau gebraucht. Der Arbeitsbereich vor dem Motor ist sehr eng, und die Anleitung nicht immer hilfreich. Der rückseitige Zahnriemenschutz geht ohne Abnehmen der NW Nabe eindeutig nicht raus und muß hier drinbleiben. DI actually wanted to go there because the broth was flowing.
The leak is coming from the shaft of the water pump; it's wet around the hole at the bottom.
The parts will be ordered tomorrow. I still need to find out the exact amount and type of coolant; it's likely G13, even though the reservoir might say G12, given that the vehicle was manufactured in 2014.
hg
Herbert.

Herbert wrote:

The parts will be ordered tomorrow. I still need to find out the exact amount and type of coolant; it's likely G13, even though the reservoir might say G12, given that the vehicle was manufactured in 2014. hg Herbert

I would use G12evo. Before refilling, try to remove as much of the old coolant as possible.

Hi,
Here's how I did it (the quantities are approximate):
Release:
- 7 liters of fluid are draining from the drain valve at the bottom of the radiator (engine cold).
- 1 liter will be added during the water pump replacement.
Refill.
- Approximately 6 liters can be filled into the buffer tank (which will then be full).
- 1/2 liter goes into the upper return line of the heating system.
- Use VCDS to run the coolant circulation pump until there are no more gurgling sounds (initially, there was some mess because the return line was unintentionally still open );
- Keep the engine running; the remaining air will escape through the two overflow pipes from the radiator and the rear of the engine.
- Add 1 liter to the surge tank;

Drive until the coolant and oil reach 90° (thermostat for the main circuit open). No topping up required, no gurgling sounds.

hg
Herbert.