Silica bag

[Boatman1]

Had to replace the original matrix on my 2014 Octavia 46,000 miles because it was blocked. I read on a VW forum that this was caused by corrosion within the VW cooling system also that this corrosion leached silica out of the coolant hence the silica bag in the filler reservoir to prolong the life of the coolant. I replaced it with a Nissens matrix which apparently has wider veins . Does anyone know whether the silica bag is still required in the coolant reservoir, was it just the matrix that rusts or are other parts of the cooling system prone to rust?

Apparently this is a problem throughout the VW range from 2013-2017 anyone else encountered this problem?

[Andymod]

Can also be casting sand, which was not fully cleaned off in manufacturing 

[rum4mo]

Aye, yes also that, I have yet to read a full write up from a trusted source that defines the need for the "mit silikat" teabag in the coolant tank or any only some cars/engines and if there is any link with which version of coolant is also associated with it being present, ie G12++ or G13 or G12evo or even it seems G13PLUS+!

 

There are other marques that are also fitting these siliate pouches or more typically a proper porous sealed casing, an idea that maybe VW Group should have thought of using instead of their early "teabags" which too many owners have found to end up with failed welded seams so the silicate granules come out  and get the blame for adding to the risk of blocking the heater matrix.

 

I could be wrong but it seems it is mainly diesel engined cars that are suffering most from this, and it I think, is them that had issues with casting sand being left in the water ways.

 

Even some SEAT Leon Cupras, MK3, have these "mit silikat" coolant tanks, and then some don't - though VW Group have always just fitted "what was in stock" in the factory, many with G12 printed on them had G12+ or G12++ fills at the factory, just all a bit messy - like having default battery details in the CAN-Gateway, just sloppy and cheap.

 

Edit:- don't forget SEATs though, many MK3 Leon owners are going through this expensive repair at the moment - with no sign of any shame or goodwill from their dealer!

Edited 2 September, 2020 by rum4mo