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Is there an easy way of knowing if you've got the revised expansion tank below? From the cut-away picture, it's difficult to work out if the silicate is still a large sack or a pellet of some sort. Does anyone have a part number for this revised tank?
If your tank says MIT Silicat on it then it will either be this design 'container' - or the 'tea bag' design?
If the 'tea bag' design you can see if you look through the top of the filler neck.
If the 'container' design you can't see it from the filler neck.
My tank is 5Q0 121 407 A and it says Mit Silicate and has the 'silicate container' like in the diagram above, and my car is 2014 Leon ST 184 TDI - there is no way to inspect the integrity of the 'container' unless you cut the tank in half!
There are LOTS of OE number supersessions - I believe 5Q0 121 407 M is the latest version.
Even though I have what I would consider a 'safer' design i'm still changing it to a tank with NO silicate.
My car has done 90,000 miles and there are two reasons for blocking the heater matrix - either left over casting sand from the engine production or from the silicat in the header tank.
It seems strange to me that my car would only start to block the header tank after 80k miles if it were the casting sand - why not sooner! So I still think silicat in the header tank may be to blame?
I have the same car as @SuperV8 and changed mine to a tank with no silicate.
I'll just change the the coolant at every inspection service.
This is a list of which tanks will fit my car. Hard to tell which version/design they all are.
I'll just change the the coolant at every inspection service.
This is a list of which tanks will fit my car. Hard to tell which version/design they all are.
I'd guess, but only a guess, that as that diagram shows a raised "bump" on the upper surface, then if you had Mit Silikat and that raised bump, it would not be the "tea bag" version.
On the subject of casting sand, do you not think that it might take differing and maybe random length of time to get enough of the remaining casting sand out and along to the heater matrix? I'd think that what was thought to be adequate clearing out of the sand from castings had been done - but for too many that was not enough to get it all out.
Edit:- my "not industrial" employed Chemical Dr daughter was a bit unsure as to what/why this silicate was in there, in as much as "is it just coated with a slow dissolving coolant additive to keep the PH level towards the alkaline side of things" or "are these granules actually the product that is getting dissolved and so reducing in physical size" - maybe someone out there knows the absolute answer to that, no guessing though!
Another edit:- maybe that bump is on all these tanks as the small returning coolant pipe must connect to the tank somehow!
On the subject of casting sand, do you not think that it might take differing and maybe random length of time to get enough of the remaining casting sand out and along to the heater matrix? I'd think that what was thought to be adequate clearing out of the sand from castings had been done - but for too many that was not enough to get it all out.
Edit:- my "not industrial" employed Chemical Dr daughter was a bit unsure as to what/why this silicate was in there, in as much as "is it just coated with a slow dissolving coolant additive to keep the PH level towards the alkaline side of things" or "are these granules actually the product that is getting dissolved and so reducing in physical size" - maybe someone out there knows the absolute answer to that, no guessing though!
Another edit:- maybe that bump is on all these tanks as the small returning coolant pipe must connect to the tank somehow!
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Yes, they ALL have this raised bump - it is just the flow return connection.
One visible difference though is earlier versions (like mine) have an internal path for overflow coolant - via a hole at the bottom, and the later ones G and M have an external pathway for expelled coolant to the side, I guess so it is more obvious if your tank has been leaking - like your overflow on your boiler at home must be visible.
There is absolutely an allowed 'tolerance' for the amount of casting sand remaining in the block/heads from production - they will/should have tested this, so the vehicle remains reliable with a certain amount of sand in the cooling system, and with these modern complicated internal shapes i'm sure it will be more difficult to remove the sand. This will be a balance of time spent cleaning the internal passage ways vs money cost in warranty/failure/blockage, i'm sure this tolerance will have been tightened on newer cars.
this is what I collected out of my heater matrix on the last flush I did in March:
Anyone know if this is Silicate from the header tank - or remains of casting sand from engine production?
edited as the picture had changed a bit dark!
Zoomed in but a bit blurry
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In your photos it does look more like fine grit which possibly is as you say casting sand ?
To be honest you're always going to get some kind of fine abrasive particles from any engine that's water cooled, antifreeze can help against corrosion but it can't fully prevent it, small particles from inside the engine block or cylinder head are going to wear away or partly dissolve making the coolant semi abrasive, including other bits wearing away from inside the radiator core tubes or heater matrix, and thermostat possibly even water pump.
Looking on Etka at Audi, SEAT, Skoda and VW, they all share the same part numbers, it's only I think the first 3 digits that are different between the 4 VAG manufacturers. I've read through this whole thread and done some research on like I say Etka and online elsewhere, below is what I managed to find out regarding the expansion bottle for SEAT Leon 2012 onwards.
Part number 5Q0 121 407A
1.2 and 1.4 1.6 2.0 litre engines
From 2012 onwards.
This can have silicate bag.
Part number 5Q0 121 407D
1.2 and 1.6 litre diesel engines late 2012 onwards
This has silicate bag.
Part number 5Q0 121 407A
1.8 litre engine up to mid 2014
This has silicate bag.
Part number 5Q0 121 407G
1.8 litre engine after mid 2014 up until roughly early/mid 2019 I think.
This can have I think the semi sealed inner chamber containing the silicate, possibly unable to remove ?
Part number 5Q0 121 407T
From late 2018 or early 2019 to roughly early/mid 2020
Semi sealed inner chamber containing the silicate cartridge, possibly unable to remove.
Part number 5Q0 121 407M
From early/mid 2020 onwards.
This new design has no silicate inside bag or cartridge.
The words Mit Silikat = silicate, don't always appear on the expansion bottle, but they can still contain the silicate with part numbers ending in A, D, G and T
The part number ending in M definitely has no silicate inside, as others have already mentioned in this thread.
Also looking at the cutaway image that's been uploaded in this thread, possibly part number ending in G or T, it looks to me as if the silicate bag/cartridge has to be positioned very close to the return inlet port, so it receives a constant flow of hot coolant once up to temp to flow over or around it, to help stimulate it to filter out more chemical into the coolant so to speak.
Regarding the G13 antifreeze as others have already mentioned in this thread it's made using mostly glycerin, as it's much less harmful to the environment, plus from what I've read they add silicate to G13 to give more safe protection against aluminium, cast iron and magnesium alloys, plus in some later cars if they still had any copper/brass or lead materials in radiator core or heater matrix or thermostat, the extra silicate is ment to aid protection against those also, otherwise with out silicate it possibly can weaken or eat into them, but if these are present copper/brass or lead in any of the cooling system materials, it might have a side effect where it degrades the silicate bag even faster, possibly even turning the coolant colour slightly darker ??
Plus anything made of plastic or nylon that's fully submerged in oil or water, and exposed to extremely high temperatures for long periods, is going to degrade over time, possibly 4 or 5 years, or less ??
Hope this helps
Si
Interesting info - just to add/confirm:
My Leon (2014 184TDI) has header tank 5Q0 121 407A and I can confirm it says Mit silicate and has the inner chamber type silicate which you are unable to remove/inspect.
Agree 5Q0 121 407M is the latest revision and this is without silicate.
I‘m unsure which header tank version my 1.8 TSI currently has but wondering whether it is something that should be replaced 
As local garage fitted a new heater matrix last week when climate control stopped warming the cabin (water pump, thermostat housing and temp sensor were done last summer following a P2681 code) but perhaps the expansion tank is another ticking time-bomb ?
As local garage fitted a new heater matrix last week when climate control stopped warming the cabin (water pump, thermostat housing and temp sensor were done last summer following a P2681 code) but perhaps the expansion tank is another ticking time-bomb ?
I‘m unsure which header tank version my 1.8 TSI currently has but wondering whether it is something that should be replaced
As local garage fitted a new heater matrix last week when climate control stopped warming the cabin (water pump, thermostat housing and temp sensor were done last summer following a P2681 code) but perhaps the expansion tank is another ticking time-bomb ?
View attachment 20264 View attachment 20265
In my opinion, it's worth doing.
If your silicant bag has split and contributed to the failed heater matrix, the expansion tank is effectively compromised and could continue to contaminate the system.
I got mine without a bag for £25 and it was 10 mins to change.
The part number is on the bottom - but it says Mit Silicat - so includes silicate repository.I‘m unsure which header tank version my 1.8 TSI currently has but wondering whether it is something that should be replaced
As local garage fitted a new heater matrix last week when climate control stopped warming the cabin (water pump, thermostat housing and temp sensor were done last summer following a P2681 code) but perhaps the expansion tank is another ticking time-bomb ?
View attachment 20264 View attachment 20265
As above so possibly is one of these part numbers below that I listed in my previous post.
Part number 5Q0 121 407A
1.8 litre engine up to mid 2014
This has silicate bag.
Part number 5Q0 121 407G
1.8 litre engine after mid 2014 up until roughly early/mid 2019 I think.
This can have I think the semi sealed inner chamber containing the silicate, possibly unable to remove ?
Si
Part number 5Q0 121 407A
1.8 litre engine up to mid 2014
This has silicate bag.
Part number 5Q0 121 407G
1.8 litre engine after mid 2014 up until roughly early/mid 2019 I think.
This can have I think the semi sealed inner chamber containing the silicate, possibly unable to remove ?
Si
As posted above my Leon (2014 184TDI) has header tank 5Q0 121 407A and I can confirm it says Mit silicate and has the inner chamber type silicate which you are unable to remove/inspect.
I have a big fat bag of silica which I will remove, would it be an idea to put a new one in though?
17 plate 184
17 plate 184
I just wish lots of good hard facts would appear from somewhere and so answer that question and too many others.
Personally, I would fit a new expansion tank and just change coolant every so often. That's what I'm doing with mine.
The problem is that there are a few of us who do all our own servicing AND have enquiring minds, so really do like to be able to understand why all this happened so as to be able to work out if our cars do need extra coolant changes or something else.
Fair enough there will be some people who have no technical ability and because of that no interest in what caused this or anything else, and are just happy to believe anything that they read as being true/facts - but I'm not one of them.
The latest header tank part number - 5Q0 121 407 'M' which all header tanks supersede to is without silicate.
I wonder if they have changed the coolant service schedule also?
Or/and evolved the coolant so that this silicate boost is not required?
Really that is why I keep enquiring as to the when/why/which version of coolant and maybe which engine types that surrounds this general subject.
Really that is why I keep enquiring as to the when/why/which version of coolant and maybe which engine types that surrounds this general subject.
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