Seat Leon ST 5F DSG -184PS CUNA Coolant Mystery

Hello everyone,

I bought a Seat Leon ST 5F with a DSG transmission, a 2.0 TDI engine, and 184 horsepower (CUNA engine).

"Pressure in the cooling system."

"After that, I exchanged it."
Cylinder head including valves.
ZKD
Timing belt/water pump.
AGR Radiators.
Thermostat.
All new parts.

"Filled under vacuum and the venting routine was performed 3 times using VCDS."

My problem.
He still gives me that message.
"The coolant level is low. When I open the container, the coolant flows back in, but not consistently." I had to add another 1.6 liters of coolant. How much coolant is supposed to be in the system in total? Approximately 6.5 liters went in during the vacuum filling process.
The temperature remains at 90° during the drive.
The heating is getting hot on both sides.
Thermostat opens - radiator gets warm.

When I only turn the ignition on, and the heating system is running, I can clearly hear the electric coolant pump forcing air through the heat exchanger.

The carpet and everything is dry.

CO test negative.
No coolant loss overnight with a cold engine.

Okay, here's the translation:

To-do
Coolant reservoir included. Swap lids.


Does anyone else have any advice?


Best regards,

If everything is new at the top, then it can only come from below (from the block). The intercooler is fine, or does it not yet have a water-cooled version?

I'm also interested in how you bled it using VCDS, as I've never been able to do it with VCDS before.

Hello!

"Actually, it's a water-cooled intercooler, but I even pressure-tested it individually, even when it was removed, and it's fine."

VCDS bleeding:
Here's how I proceeded with the initial bleeding process:
1. Ignition on.
2. Choose STg motor.
3. Permissions -> Enter 27971 and confirm.
4. Select "Adaptation" -> Enable "Bleed cooling circuit" and confirm.
5. Set heating to HI, turn AC off, set fan speed to 2, disable Start/Stop.
6. Default setting -> Select "Test" - "Bleed low-temperature circuit" Enter "4S" -> Start.
It takes about 15 minutes.
7. Coolant: Refill if necessary.
8. Starting the engine.
9. Initial setting -> Select "Test" -> Bleed the cooling circuit -> Start and follow the instructions (In the case of DSG, you must be in Park, press the brake, then release, then press the accelerator all the way down, then release, and it will start the routine).
10. Step 9 should be repeated until the coolant temperature reaches 90° (I did this 3 times), and I checked the coolant hose to see if the thermostat was actually opening, because in my case, it wasn't initially (there was an air bubble in front of the thermostat).
I then repeatedly squeezed the hose with my hands, and it eventually opened. Between each squeeze, I checked to make sure there was enough coolant.
11. To conclude, one last time: Step 6 - ignition on, engine off.

Update:

After 1 hour and 45 minutes of bleeding the low-temperature circuit, I finally managed to remove all the air from that circuit.
In the main circuit, I couldn't really perceive anything either, but it's also difficult to hear anything there with the engine running.

What I definitely still have is air in the heating system.
Inside, you can hear the gurgling sound, as well as the sound of air in the pump from the outside.
You can hear it as soon as the ignition and ventilation are turned on, and when the vehicle is turned off.
The heating is the same temperature everywhere!

How could I properly ventilate this? There's no program for that; should I just turn the pump on for an hour?

Best regards!

Hello, the system is often difficult to bleed, especially without the original testing equipment. You can either try bleeding it again using a vacuum pump, or manually add some pressure to the cooling system and then activate the pump or run the engine. However, there is no guarantee of success.

Best regards, Dago.

I noticed that the order of your items is different from the original test. I obtained a diagnostic protocol from the routine check. I could bleed the first circuit using VCDS, but nothing worked for the second circuit. However, I wasn't familiar with the process of entering the 4S data.

What would be interesting to me is...
"How many liters of coolant actually fit in the system, and what is the correct procedure for bleeding the system?"
I haven't really found anything useful online; in fact, I've found more information in American forums, which is why I also posted about the 4S and the engine starting issue.
Basically, I can access everything with VCDS, but the documentation is sometimes lacking / you need to know what you're doing, or certain routines are missing.
"If I know exactly how precise the routine is, I can quickly write a script that will execute it for me within VCDS."

I'm going to run the pump for an hour tomorrow.
If that doesn't work, I'll try using a vacuum pump with one hand, a 10-liter container as a buffer to prevent it from collapsing, and draw a vacuum of 0.95 bar.
Unfortunately, these air vent valves usually only handle pressures up to 0.85 bar.
I hope that the additional space will allow me to return the coolant, which I am forced to drain from the system, back into the system without any air bubbles, as it will be at its lowest point.


Okay, I unfortunately don't know anyone who uses ODIS, other than workshops.
"But they don't even want to hear about a degassing procedure, and they think that filling it with a vacuum is sufficient, claiming that the rest will degas on its own, and they send me away."

One is a nationwide chain of workshops that, in my neighborhood, started out as a small business attached to a gas station...
And then there's another large car dealership with a good reputation, but even there, customers have been sent away with a new crankshaft sensor when they came in with a rattling timing chain on their TSI/TFSI engines. Then, within the next 5,000 kilometers, the engine failed because the timing chain skipped a tooth.
Anyway, I wanted to put the Odis diagnostic tool on the workshop master's coffee machine for a measly fifty euros.
He was initially interested, but then he got really worked up when he heard about the need to bleed the cooling system, because he was convinced that such a thing didn't exist.

EDIT: I just read in some American forums that VCDS might not be controlling the coolant regulator correctly, which can then cause problems...
Okay, tomorrow I'll try to access it manually using VCDS, or alternatively, does anyone in the area (zip code 63762) have access to ODIS?

Best regards,

Approximately 8 liters should fit.
VW has had a bleeding routine available via diagnostic testers since the introduction of the electrically controlled coolant pump.
Unfortunately, I don't know the exact routine.

Best regards, Dago.

Hi,
I just refilled and bled the coolant system in my A4, and there was no vacuum involved. It was almost too good to be true.
Okay, I understand. Please provide the German text you want me to translate into English. I will only provide the translation.
I assume there's an air bubble in your engine, but no coolant is being lost, is that correct?

Before we begin, please note that the coolant temperature regulator cannot be accessed or controlled using VCDS, as it is a mechanical component. Too much vacuum will only cause the water to "boil," and in my opinion, your plan to use 0.95 bar of vacuum is pointless.

It is important that the vent line to the expansion tank is clear (is anything coming out of it when the engine is running?), and that the vent line leading away from the outlet of the heat exchanger is also clear. Unfortunately, I don't have a diagram of the cycle, but I'm putting something together based on my understanding.
I would start the pump for the heating circuit while the system is full and the lid is open (!). It should ideally only be pumping liquid after a maximum of 1 minute. If it doesn't do that, I would carefully open the return line at the highest possible point. There might be a venting hole there. And then run the pump again; coolant should start flowing.

You can, of course, run the remaining valves and pumps as well, but always with the lid open to prevent any back pressure.

And please, don't continue with this frenzy of trading. What about the cylinder head?

hg
Herbert.

Hello Herbert,

Okay, let's quickly go over the history.
Problem with the previous owner: CO in the water, gradual water consumption, and the recurring issue of water reappearing when the lid is opened.

After that, he had the AGR cooler replaced, but the problem still persisted.
That's how I got the car for a good price.

I ordered a water pump, timing belt, thermostat, head gasket, and cylinder head because I don't want to have to do the work twice if something goes wrong.

I noticed the water pump was leaking, so I replaced the water pump and timing belt, and of course, I cleaned the sealing surface.

"I inspected the cylinder head and found a hairline crack in cylinder 4, between the valve and the glow plug bore. The crack extends approximately 30 mm into the head when the valve is open..."
So, I installed the new cylinder head, along with new valves and hydraulic lifters, because definitely 10 of them were already worn out or on their way to being so.

I rechecked the fuel lines, pressure-tested each one individually at 1.8 bar, and they held for over 24 hours without any issues. I also used a leak detection spray.

Everything cleaned... reinstalled.


Yes, and I now definitely have an air bubble in the heating system's heat exchanger, specifically in what's called the micro-circulation loop.
I am now completely certain that there is no air in the low-temperature circuit of the liquid heating system.
It's difficult to check in the engine cooling system, but I'm confident that it's now free of air bubbles.

I just can't seem to get the hang of those tiny integrated circuits.
Constant bubbling. With the engine idling and the ventilation on.

I'll try starting the pump with the cover open, as you suggested.

Water is entering the top of the surge tank, so the pipe is clear.

Best regards!

Here's something I copied from a diagnostic report:

Verification step: Bleed air. Step 1.

Action: Report.

The following describes the high-temperature and microcirculation processes within the cooling system, which are being purged.
This process takes approximately 8 to 13 minutes.

The following engine speeds will be tested in this examination.

Idle speed for approximately 300 seconds.
2500 RPM for approximately 60 seconds.
3000 RPM for approximately 30 seconds.
1000 beats per minute for approximately 120 to 300 seconds.

After that, the motor will automatically shut off (O**s).

Turn the ignition off and on, then allow the low-pressure circuit to bleed for 900 seconds (see below).


After 900 seconds, start the engine and wait until the engine reaches 90°C.

Press the accelerator pedal fully and hold it down so that the coolant regulator can open completely.

Stop it afterwards.


- Wait until the engine has cooled down.
- Afterwards, check the coolant level in the coolant reservoir.
- If necessary, top up the coolant level.

End of Guided Function.





LOGIN_CODE: 27971


Verification step: Initiate basic configuration.


Testing - Bleeding the cooling system.

- Depress the brake/clutch pedal.
- Step on the gas.

Check step: Bleed (Engine off, ignition on).


The following describes the air bleeding procedure for the low-temperature circuit of the cooling system.

This process takes approximately 900 seconds. Seconds.



LOGIN_CODE: 27971


Verification step: Initiate basic configuration.


Testing - Bleeding the low-temperature circuit.





Action: Report.

Current coolant temperature: 41 °C.

Solar panel temperature: 90 °C

Sure, here's the translation:

"Note:"
By increasing the engine speed, the required coolant temperature is reached more quickly.

The test will only resume once the target temperature is reached.

Olay, that's very interesting.
I basically followed the instructions, but I didn't know anything about letting the engine warm up and then starting it after 900 seconds.
Definitely trying it out tonight.
Thank you very much .

Okay, the circulation pump for the heating system is running with the cover open, and there's no return flow back into the tank... now I'm going to investigate, maybe there's a blockage somewhere?

edit: see video.
Despite trying to prime the pump, nothing is coming out, neither air nor coolant. However, when I suck on the hose, coolant flows perfectly fine.
Could it be that the heating system's circulation pump is simply broken?

By the way, I had plenty of available capacity in all the processes again.
I suspect that when driving, air from the heater's heat exchanger is distributed through the micro-circuit to the other circuits as soon as it opens the main circuit.

edit: 1 image deleted due to copyright. Info: The pump for the heating circuit draws water from the heat exchanger and pumps it to the manifold. Herbert.

My approach doesn't work according to the given scheme. It also seems to fit what I'm looking for in a Golf with a CUNA engine.
I'm deleting the image due to copyright issues. Please do not include excerpts from documents without permission.
Okay, I understand. Please provide the German text you want me to translate into English. I will only provide the translation, without any explanations. You might want to start by performing a diagnostic test on the individual valves and pumps, as you can hear them.
hg
Herbert.

I did the routine twice yesterday.
Let's see today while driving if the symptoms reappear, but so far they haven't shown up on the commute to work.
The gurgling sound in the heat exchanger is still present, even though it is heating up evenly.
Temperature remains at 90°.

This morning, my starter motor was weak; it barely managed to turn the engine over at times, and it only worked after several attempts.

New battery, have it tested upon purchase! 680A cold start current, 72Ah capacity.

I still have the old camshaft adjuster housing with the oil reservoir and the old valve installed. Because of this, it starts a bit rough, taking about 1.5 to 2.5 seconds.
I'm also experiencing the same error when this happens, which is related to the camshaft timing issue – it's a known problem.
Parts have been ordered with the new revision and should arrive today; they will be installed on Friday.

Regarding the coolant issue: Could it be that the coolant regulator is faulty?
I didn't mention earlier that I found coolant in the water after I started working on the head gasket.
After that, I rinsed as thoroughly as I could.
Now that I've seen everything, it was only in isolated spots, and it looked like the previous owner's workshop had already flushed the system after replacing the AGR cooler.

Best regards,

Malc0m89 wrote:

..... I didn't mention earlier that I found coolant in the water after I started working on the head gasket. After that, I rinsed as thoroughly as I could. .....

Then you can bleed for a long time. If you're unlucky, it might have clogged a heat exchanger. I would check everything that isn't already new, individually. Check the check valves and the thin bleed lines (critical because of... Bubble formation in the reactor vessel, the pumps, the heat exchangers...
I assume you already have a repair manual; it should contain the connection diagram for the coolant hoses and all the components of the cooling system. Otherwise, SSP514, that was the image you created from it.
hg
Herbert.