2 hours ago, Somniax said:

Hi all!

 

I recently joined team vag after years with MB.

I found out about this issue with the silicate bags and immediately took a glance to my expansion tank. No problems in the heating and the liquid is clean and pink.

The tank is "two wall" design and even with a strong torch/flashlight shining through the tank I was not able to locate any bag or capsules. Tank has no label for "mit silikat".

 

The car is Superb 2020 facelift 2.0tdi dsg 4x4 and part nubmer for the expansion tank ends with AA, yes two A letters. It seems that this model of expansion tank is also used in the latest Octavia mark 4. I found this out by looking parts online from crashed cars here in Finland. I was not able to find any additional information about this version of the tank.

Is there anyone who can verify, whether this expansion tank has silicates or not? Thank you!

Hello Somniax, welcome to the fold. It is possible that your tank is one without the silicate additive fitted - AFAIK, VAG stopped fitting these at some point, hopefully some one will be along to confirm when the change was made. I believe that there are three versions of expansion tank -

1; The original type with a silicate 'tea bag' fitted - it seems that this is the one guilty of most issues with coolant discolouring and blockages:

2; Updated version incorporating a plastic 'tube' in the tank - AFAIK, this type was OK as it is unlikely to split:

3; No silicate dispenser included:

The silicate granules are intended to extend the service life by leaching slowly out into the coolant - and AFAIK, would be OK left in place - provided they stayed where it was intended.

I've just replaced my coolant reservoir, as it had 'Mit Silikat' on it.

I bought a Febi-Bilstein branded reservoir from Parts in Motion for £20 including postage.

https://www.partsinmotion.co.uk/febi-coolant-expansion-tank-103446-detail

I could have bought one from Aliexpress for about £8, but I thought PIM would be a safer bet if I had a problem.

I would hazard a guess that the Aliexpress part is probably the same item.

My original reservoir was the double-walled version, part number 5Q0121407A, which was made in January 2015, the same as my car. It didn’t look like there was room for the tea bag in the inner chamber, so I’m guessing the ‘silickat’ is in the outer chamber.

The coolant was replaced recently when I had the water pump and timing belt replaced, so it should be good for some time.

Yesterday I have replaced my 5Q0 121 407 F with 5Q0 121 407 AA. I haven't found any information about the F version in this thread so I will share my findings.

The "mit silikat" marking wasn't there, but the G13 marking was, so I just replaced it to be sure.

Today I cut the tank open and it was completely empty. The only difference I found between the tanks is that the F version has the G13 marking and the AA version has no marking at all.

Maybe this information will help someone and they won't have to change the tank unnecessarily like I did.

Now I plan to replace G13 with G12evo.

BTW, I have Skoda Octavia Mk3 1.0 TSI MY2017.