Golf VII GTI: Bleed Cooling System with VCDS

Hello everyone in the forum!

I have a Golf VII GTI Performance where the water pump was leaking - a known issue with the 2.0 turbo gasoline engines.

Now I have bled the system using a vacuum pump, but I was unable to bleed the cooling system as described in the repair manual.

The engine doesn't overheat when idling, but the coolant temperature rises to around 98°C after a short period. The coolant inlet temperature to the radiator is still around 30°C, indicating a large temperature difference.

I seem to recall reading that this engine series is operated at a very "hot" temperature, meaning that high cooling and oil temperatures are to be expected.

I'm not comfortable putting that car on the road like this...

Man soll wohl die gesuchte Grundeinstellung erst nach Login ins MSTG auffinden sollen? Is that correct?

If so, could someone help with instructions or the code?

Thank you very much, and best regards.
Alex.

I found a tutorial about it in a forum.
Start the engine.
Connect VCDS.
Disable Start/Stop.
For vehicles equipped with a parking heater, please turn it on for approximately 30 seconds.
Turn off the air conditioning (the AC button should not be illuminated).
VCDS -> Select "01 Engine Control".
16. Select access permission. 27971. Enter and confirm.
Select 10 adjustments -> Set the cooling system bleed to "active".
Select basic settings -> Select "Bleed cooling system" -> Start -> Follow the instructions.
"No guarantee is given for the accuracy of the information. Perhaps an expert in VCDS can comment on this."

Hi,
I am also linking this topic to the post here: https://community.dieselschrauber.org/en/viewtopic.php?t=30892
I once tried bleeding the cooling system using VCDS on our Golf VII 1.6 TDI. I started by accessing the "Engine Control Unit (ECU)" via STG001, then selecting "Basic Settings" and the "Bleeding" function. This is equivalent to the RLF (Reset Learning Value) procedure. The routine takes about 10 minutes and involves a speed profile with different stages. It's not possible to observe any switching of valves, etc., while sitting behind the steering wheel. I can't say whether pumps and valves are being activated during the process, but that would be necessary for bleeding. The coolant temperature doesn't seem to play a role. After the RLF procedure, a warm engine is not required, but in my opinion, it would be necessary for proper bleeding.
Below the adaptation settings, there is another channel that allows switching between active and passive modes, which I have not tested.
I find the RLF venting method to be debatable. Similarly, the prescribed filling procedure with a vacuum is questionable.
hg
Herbert.

Herbert wrote:

I find the RLF venting method to be worth discussing.

Hi Herbert,

then let's go

You mention that you believe a warm engine is necessary. I suspect you're referring to the thermostat, which, in your opinion, should be open. Normally, the thermostat has a small hole at the top to allow air to escape or water to flow in. An open thermostat will certainly speed up the process, but it shouldn't be a mandatory requirement for venting the system.

Herbert wrote:

Similarly, the prescribed filling with vacuum pressure.

Under vacuum, any air bubbles present will expand further, making them easier to remove.

I suspect that even without a proper bleeding procedure, all the air will eventually be removed. However, it will take longer, and it may be necessary to top up the coolant several times. Also, the engine should not be subjected to excessive thermal stress during this process. This might be acceptable for a DIY enthusiast, but in a workshop, it could lead to additional customer complaints, which should be avoided. Furthermore, the car should be "ready for full throttle" immediately after leaving the workshop, as we must always assume that the customer may not be aware of any issues.

As far as my purely subjective opinion is concerned, which is also open for discussion.

Regards,
Guste.

My friend (a VW service technician) told me, upon request, that the workshop would estimate 1.5 hours for refilling (with vacuum) and then bleeding the system using a tester. My Golf 7 GTD is scheduled for a refill and bleed next weekend. I've already arranged for a vacuum filling device, and then I'll use VCDS. I'll report back.

Hi,
Let's revisit the discussion about filling and bleeding the cooling system.
The connection diagram for the cooling system and the visual inspection of the engine do not provide a clear indication of potential residual amounts after draining or potential air bubbles during filling. Due to the complex circuits and the presence of 5 check valves, the possibility of trapped air pockets cannot be definitively ruled out. Depending on the perspective, the intercooler, cylinder head, and heat exchanger essentially act as bypasses. It is important to determine whether the thermostat disc actually has a venting hole. In the past, when removing it, I always encountered a surge of residual fluid.
When changing the coolant, I would flush the system (as the manufacturer also recommends). When filling with vacuum assistance, I would expect air bubbles. The vacuum should not be too strong, otherwise any remaining coolant in the system will evaporate, and the alloy will leave deposits. Pure water boils at approximately 30 mbar at room temperature, while a water/glycol mixture boils at a slightly lower pressure.
The question is whether filling without a vacuum is worthwhile, and whether it's necessary to bleed the system at certain points. From a first impression, the cooling system seems to fill itself up to the hose connecting the thermostat to the radiator without any intervention.
hg
Herbert.

Herbert wrote:

When changing the coolant, I would therefore flush the system (which the manufacturer also recommends).

What should I rinse it with? A special cleaning agent or distilled water?

With distilled water (according to the manufacturer).

Herbert.

Herbert, you're only supposed to apply a maximum vacuum of 0.8 bar, nothing will happen if you do. I've finished the engine swap on mine, tomorrow I'll just need to attach the front, and then I'll get started.

Where did you get that number from? It's not that it's unreasonable, but the RLF (likely referring to a piece of equipment) shows, for example, with the electric vacuum pump, "green area or better," which means 50 mbar or less. My concern is that someone who claims to be an expert isn't pumping down the vacuum enough.

Herbert.

According to the instructions for the vacuum filling device, it uses a vacuum nozzle that can only generate a maximum vacuum of 0.8 bar. VW, on the other hand, uses an electric vacuum pump that generates a much higher vacuum.

I have an additional note regarding rinsing with distilled water:

You won't be able to drain almost all of the coolant from the system after flushing. Therefore, you should also have G12evo concentrate on hand to replenish the necessary antifreeze. It's highly likely that you won't be able to achieve the required protection with a pre-mixed solution, which is typically formulated for temperatures down to -25°C.

Is it absolutely necessary to refill the system using a vacuum filling device? Unfortunately, we don't have one.

VCDS is definitely available for bleeding the system.

Can't you simply "top up" the cooling system via the coolant reservoir and then bleed it using VCDS? Then, add more coolant and bleed it again. Repeat the entire process until the fluid level no longer drops.

Would that also work, or does it absolutely have to be filled under vacuum?

dennis91 wrote:

Would that also work, or does it absolutely have to be filled using a vacuum?

Please provide the text you would like me to translate from German to English. I need the text to be able to translate it.

guste100 wrote:

Under vacuum, any air bubbles will expand further and become easier to remove. I suspect that even without a proper bleeding procedure, all the air will eventually be removed. However, it will take longer, and it may be necessary to top up the coolant several times. Also, the engine should not be subjected to excessive thermal stress during this process. This might be acceptable for a DIY enthusiast, but in a workshop, it could lead to additional customer complaints, which should be avoided. Furthermore, the car should be "ready for full throttle" immediately after leaving the workshop, as we must always assume that the customer is not an expert. As far as my purely subjective opinion is concerned, which is also open for discussion.