Golf VII GTI - Drain the cooling system using VCDS

Hello, dear forum community!

I have a Golf VII GTI Performance where the water pump leaked - a well-known problem with the 2.0 TSI engines.

Now I have vacuumed the system, but I was unable to - as specified in the Rep. Guide - bleed the cooling system using the basic settings.

The engine doesn't overheat when stationary; the coolant temperature in the engine rises to around 98°C when the engine is revved, and the radiator inlet temperature remains around 30°C – resulting in a high temperature difference.

I believe I read that this engine series is operated at very "high" temperatures, meaning that high cooling and oil temperatures are expected here...

But I don't want to operate the car on the street like this...

It seems that the desired default setting should only be found after logging into the MSTG. Is this correct?

If so, could someone provide instructions or code assistance?

Thank you and best regards,
Alex

In a forum, I found a guide on that.
Start the engine
Connect VCDS
Disable Start/Stop
For vehicles with auxiliary heaters, please turn them on for approximately 30 seconds.
Turn off the air conditioner (the AC button should not be lit).
VCDS -> Select Engine Electronics
16 Select access permission 27971 and confirm
10 Adjustments to select -> Activate cooling system
Select default settings -> Select cooling system bleed -> Start -> Follow instructions
No guarantees regarding the accuracy of the information provided. Perhaps a VCDS specialist could offer further clarification.

Hi,
I'm also linking this topic to the following post: /viewtopic.php?t=30892
I tried using VCDS to bleed the brakes on our Golf VII 1.6 TDI, meaning I started by accessing the Engine Electronics (STG001), performing the basic settings, and selecting the function. This corresponds to the RLF procedure. The process takes approximately 10 minutes and involves a specific RPM profile with stages. Switching valves, etc. is (while sitting at the steering wheel) not directly observable. Whether pumps and valves are activated during this process, I cannot say, but that would be necessary for bleeding the brakes. The coolant temperature does not play a role. After RLF, a warm engine is also not required, but in my opinion, this would also be necessary.
Further down, under "Adaption," you'll find a channel for switching between active and passive modes, which I haven't tried yet.
I believe the venting method according to RLF is worth discussing. Also, the prescribed filling under vacuum.
hg
Herbert

Herbert wrote:

I believe the venting method according to RLF is worth discussing.

Hi Herbert,

Okay, let's go

You are saying that you need a warm engine. I suspect you are referring to the thermostat, which you believe should be open. Normally (TM), the thermostat has a small hole at the top, so that air can escape, or water can flow through. An open thermostat accelerates the process safely, but should not be a mandatory requirement for venting.

Herbert wrote:

Similarly, the prescribed filling with vacuum.

Under vacuum, any existing air bubbles will further expand and become more easily removed.

I hypothesize that, even without the venting procedure, all the air will be completely removed. However, it will simply take longer, and coolant may need to be refilled multiple times. Also, the engine should not be subjected to excessive thermal stress during this time. This may be acceptable for the DIY enthusiast. However, for a workshop, this could potentially lead to additional customer complaints, which should be avoided. Furthermore, the car should be "roadworthy" immediately after the service, as it must always be assumed that the customer is inexperienced.

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

Greetings
Guste

My friend (VW service specialist) informed me that the workshop estimated 1 1/2 hours for the filling (with vacuum) and subsequent venting using tester 1 1/2. My 7 GTD is scheduled for the new filling and venting next weekend. I have arranged for the vacuum filling device, and then VCDS will be used. I will report.

Hi,
reheated the discussion about filling and bleeding the cooling system.
From the connection diagram for the cooling system and the observation on the engine, it is not possible to obtain a clear impression of possible residual amounts after draining and possible air bubbles during filling. With the branched circuits and 5 check valves, the possibility of pockets cannot be definitively ruled out. Depending on the perspective, the air-charge cooler, the cylinder head, and the heat exchanger actually have a bypass. It is important to determine whether the thermostat actually has a venting hole. Previously, I would always encounter a surge of residual liquid when expanding.
When replacing the coolant, I would therefore flush (as the manufacturer also recommends). When filling with vacuum assistance, I would expect to see air bubbles. The vacuum should not be too strong, otherwise the remaining residues in the cooling system will evaporate, and the alloy will form deposits. Pure water boils at approximately 30 mbar at room temperature. Water/glycol boils at a slightly lower pressure.
The question is whether filling without vacuum makes sense, and whether one should vent at certain points. Initially, the circulation runs almost completely from the thermostat to the radiator on its own.
hg
Herbert

Herbert wrote:

When replacing the coolant, I would therefore flush (as the manufacturer also recommends).

Wash with what? With a special cleaner or distilled water?

With aqua dest. (as stated by the manufacturer).

Herbert

Herbert, you should only apply a maximum of 0.8 bar of vacuum pressure, otherwise nothing will happen. I'm just finishing up the engine swap, tomorrow I'll just need to install the front and then I'll get it done.

Where did you get that number from? It might be reasonable, but the RLF, for example, shows with the electric vacuum pump "green zone or better", which is 50 mbar or less. I'm concerned that a supposed expert isn't providing adequate information.

Herbert

According to Instructions for the vacuum filling device: This device uses a special nozzle that can only create a vacuum of up to 0.8 bar. VW uses an electric vacuum pump that can create a much higher vacuum.

I have an additional note regarding rinsing with distilled water:

One doesn't nearly drain out the entire contents of the cooling system after rinsing. Therefore, it is also advisable to have the G12evo concentrate available to restore the necessary antifreeze. Because, with a high probability, this will not work with the pre-mixed solution, which is set at -25°C.

Must the refilling be done exclusively with a vacuum filling machine? Unfortunately, we don't have that.

VCDS is definitely required for the bleeding process.

Can't the cooling system simply be "filled" through the coolant reservoir and then bled using VCDS? Afterwards, refill the coolant and then bleed again. Continue the entire process until the liquid level no longer drops.

Would this also work or must it be filled under vacuum?

dennis91 wrote:

Would this also work, or must it be filled under vacuum?

See above...

guste100 wrote:

Under vacuum, any existing air bubbles will further expand and become more easily removed. I hypothesize that, even without the venting procedure, all the air will be completely removed. However, it will simply take longer, and coolant may need to be refilled multiple times. Also, the engine should not be subjected to excessive thermal stress during this time. This may be acceptable for the DIY enthusiast. However, for a workshop, this could potentially lead to additional customer complaints, which should be avoided. Furthermore, the car should be "roadworthy" immediately after the service, as it must always be assumed that the customer is inexperienced. As far as my purely subjective opinion is concerned, which is also open for discussion.