Mysterious Coolant Loss

[TDI190]

I have a MY2018 190TDI L&K 4x4 Mk3 Superb that has a mysterious coolant loss. I need the help from the forum to figure out any potential cause of the coolant loss.

 

For the fourth time in almost three years the expansion tank has dried up. Each time this happened I sent the car to the dealer, and each time they couldn't find the cause. The dealer has pressure tested the system every time and visually checked for leaks and not found anything. They just refilled the expansion tank and returned the car to me. The car has about 55' km now and and the factory warranty is about to expire. Between each fillup I have monitored the level in the expansion tank and it is quite obvious that the level drops steadily (but slowly) over time.

 

I tried to search the forum but could only find threads pointing towards for example the water pump. If the water pump is the culprit there should be visible signs, shouldn't it? I talked to a independent Skoda mechanic today and he mentioned that he had seen several cars with coolant leak from the EGR valve.

 

Wherever the leak is located it is a quite slow leak. Hence it is no surprise that it cannot be detected by pressurizing the coolant system at the dealer. 

 

What are your ideas? Has anyone experienced the same?

 

 

 

 

[k.young]

EGR would be my guess as well..........

[Sheriff]

Water pump failed on mine. Losing water but no visible leaks. Garage said when they took it off and span it, the bearings were knackered and rough as hell. New pump and cam belt sorted it and no problems since.

Edited 14 November, 2020 by Sheriff

[LordTyrion]

I get a warning every so often and top it up. The recent one was a more substantial drop than previous ones so this thread is an interesting one for me. I'm pleased the warning exists as otherwise I'd have been oblivious. 

[therams]

I had coolant loss problem with no visible leak, had the cambelt  and pump changed early (would of needed doing march 2021 latest), the car used to make a  whining noise on start up,this has has resolved the  coolant loss and noise but have still have  some debris in expansion tank

[TDI190]

Unfortunately the dealer just isn't interested in performing a more thorough inspection.

[TDI190]

Yesterday the dealer told me that it is perfectly normal that the car consumes some amount of coolant. The explanation was that it gets so hot in the EGR valve and DPF that coolant is consumed. However, on follow up question from me, they couldn't explain this process at all. Also when I mentioned that my friends Superb (exact same MY and specifications) had not used any coolant whatsoever even though it is driven under the same conditions and has more miles. The dealer said that different cars can be different and have different software coding etc. and that also was perfectly normal.

 

To me all of this sounds like complete nonsense. Does any of the above dealer statements have any validity in the real world?

 

I double checked the owners manual, and no surprise, it does not mention anywhere that consumption of coolant is normal. However it does mention specifically "Loss of coolant indicates cooling system leakage - risk for engine damage"

[Ootohere]

@TDI190   Who at the dealership told you that, was it some drug dealer in getting their car serviced?

 

If it was the Master Tech i would have them put that in writing with their name and sign it.

[TDI190]

2 minutes ago, e-Roottoot said:

Who at the dealership told you that

It was a mechanic. Supposedly a qualified and experienced one as well. 

 

I am baffled that they would make a statement like this. 

[SuperbTWM]

35 minutes ago, TDI190 said:

 The explanation was that it gets so hot in the EGR valve and DPF that coolant is consumed.

 

I questioned somebody that said that on here, as it sounded like rubbish to me, and while the DPF cannot ever consume coolant itselfs in the literal sence, it can infact cause coolant to be boiled off locally in the EGR cooler and overpressurise the system momentarily causing a small loss of water.

 

I cant remember if this is a symptom of the silica bag in the header tank rupturing and blocking some of the cooling passages in the egr cooler or heater matrix (which is downstream of the egr cooler)

 

There is a thread documenting this on here somewhere

[TDI190]

6 minutes ago, TDI190 said:

It was a mechanic

I just checked the dealers website, and the person saying this is actually the workshop manager.

[TDI190]

4 minutes ago, SuperbTWM said:

I cant remember if this is a symptom of the silica bag in the header tank rupturing and blocking some of the cooling passages in the egr cooler or heater matrix (which is downstream of the egr cooler)

So if I understand you correctly this by itself is actually a malfunction in the system?

[Ootohere]

@TDI190 So a Workshop Manager need not be a Trained or Qualified Motor Engineer / Technician / Mechanic.  

Which has always been an issue with Main Dealerships.

 

VW Group training is what matters.

 

Edited 3 March, 2021 by e-Roottoot

[SuperbTWM]

15 minutes ago, TDI190 said:

So if I understand you correctly this by itself is actually a malfunction in the system?

 

Deffinetly a fault, possibly a fault with the design that has been sorted out, especially in a 2018. 

 

 

BTW i'm not saying this is your issue, by the sounds of it, if it was the issue you would see evidence of coolant being released from the cap on the header tank, so if its all clean and no residue you will be ok I think and you will have to look elsewhere. 

[SuperbTWM]

Also, with a leak this small, I don't think you can rule out a weeping waterpump or a small external leak as it will more than likely not be enough to make its way to the floor but it will leave a residue, a good thorough inspection of the waterpump with the timing cover removed will pretty much tell you for definite. 

[TDI190]

There is no residue around the cap on the header tank.

 

The dealer has performed three inspections. On top of that two more inspections have been done at other workshops. The dealer has consistently refused to discuss inspection methods with me. 

[dieselV6]

On my wife's Roomster, a slow coolant leak located at the water pump bearing after ~2 years eventually grew larger... to the point that the 1.6CR TDI engine used around 3l of coolant on a 1000 mile trip across Europe returning from holidays back to the UK. Timing belt was swimming in coolant by then, but otherwise fine. After the belt and water pump job the leak disappeared.

 

[J.R.]

All it takes to prove the presence of a leak is to do a pressure test, preferably a hydraulic and not a pneumatic one, that is to say fill the overflow tank to the brim and pressurise the system with water and not air, lock off the valve and wait to see if the pressure drops to zero.

 

You can do this by pneumatic pressure but it takes much longer for the pressure to drop although in doing so it will displace a considerable amount of coolant which will be easier to trace.

[Micky 32]

Interestingly my 2017 Passat 2.0 TDI 240bhp has done this since new. It’s very little though, it gradually drops from max to min. I’ve had to top it up a few times over it’s 115k miles. Never got worse. I have just done the timing belt and will see if the new pump stops it.

 

i know someone who owns a car accessory shop and he said he sells quite a lot of coolant. He claims modern cars seem to be using coolant. Maybe engines running hot during a regen could be the issue especially drivers who have heavy right feet?

[Ootohere]

Car accessory shops have always done well selling coolant. (& RadWeld etc) 

But modern cars get coolant changes less often than back in the day.

The Car accessory shop owner will know how much of the coolant suitable sold is to the spec for newer VW Group cars or other manufacturers, and how much is sold as used to topping up or maybe for doing a coolant change where someone is changing a water pump, radiator etc.

That is if they are chatty with customers and trades people.

[VladCor]

Would a new EGR valve stop the coolant loss? I'm having the same problem on the 2.0 TDI 2016, replaced the water pump but still loosing a lot of coolant, especially when I go at high speeds. My mechanic also said it may be from the cylinders, any thoughts?

[SuperbTWM]

The EGR cooler can be a possibility but I wouldn't want to change it without knowing for certain.

[wkobre]

Hello guys, same thing happened to me this morning. In April this year I did regular maintenance, plus major one, using CONTINENTAL CTAM CT1168WP8PRO set (with water pump), rollers and all other stuff. Did you discover what caused you the problem? I had recently 2 trips around 600km each with constant speed 150km/h (if that matter). I forgot to mention that I did coolant flush as well when I did service, using Motul G13 (not premixed one) that mechanic mixed with destiled water. Unfortunately I had to go to work, driving carefully, but temperature was steady at 90c. I'll go after work to mechanic and keep you posted. If anyone resolved this, it would be valuable information to share please.

[wkobre]

Additional information, in case it matters, it's 2.0 TDI 150hp.

[Awesam]

So this could be the potential solutions if the part made out of plastic is leaking!

 

https://www.akstuning.co.uk/shop/home/1996-project-9-mqb-ea888x-billet-water-coolant-fitting.html?fbclid=IwAR0KztFwPqZWYS46RiJfb4qUSMo7VaJRRt2Zp9qYWwsfpxbHYQQBxaVg6U8