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Silica Bag - Coolant MQB Engines

Boydie Dec 16, 2018

  1. Boydie

    Boydie S3 8V DSG VCDS Map User

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    This may have been brought up before but after a quick search I couldn't find anything.

    I recently heard about these bags which are located inside the MQB engines (may be others) within the coolant tanks. They are small bags of silica which are designed to preserve the life of coolant but over time it has been known for these to burst and cause mega problems within the coolant system. Not a good thing for cars out side of warranty!

    Anyway, here is a short video (not me) of how to remove it, I will be doing this today hopefully if the weather isn't too bad!

     
    CraigM and TomBlueS3 like this.
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  3. Marky79

    Marky79 Registered User

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    Somebody must have done mine, never even hear of that before.
     
  4. TomBlueS3

    TomBlueS3 Registered User Bronze Supporter VCDS Map User

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    I have never heard of this before!!! Very interesting...I’ll have to have a look to see if mine is there (15 plate S3)
     
  5. AlS3BE

    AlS3BE Registered User

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    This is probably one of those things like the suspension block that’s gets forgotten about during the PDI. I just cant see what a little bag of silicon is gonna do In What is essentially water circulating round and round
     
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  6. Sean6211

    Sean6211 Registered User

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    The silicate bag is there for a reason, and VAG isn't the only manufacturer who does it apparently. Mercedes does it as well.

    From one of VW's Self Study Program 514 page 31:

    Coolant Expansion Tank with Silicate Repository

    The coolant expansion tank contains a silicate repository. Silicate is used to protect the aluminum components in the coolant
    system from corrosion. There are silicates in the G13 coolant, but they are used up over time if the engine is subject to high
    thermal loads.

    To compensate for the silicate consumption, silicate is taken from the repository and added to the coolant. The silicate
    repository provides additional protection against corrosion for the aluminum components in the coolant system over the entire
    lifespan of the engine.
     
    TomBlueS3 and Phutters like this.
  7. Boydie

    Boydie S3 8V DSG VCDS Map User

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    I would rather top the car up with G13 than have a bag in the tank which is basically a ticking time bomb
     
    AlS3BE and TYb like this.
  8. Rideen

    Rideen Registered User

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    I'd rather risk it bursting than risk aluminium parts of the cooling system rusting because silica from coolant has been used up without me knowing it.
     
  9. Phutters

    Phutters .

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    My inclination, for what it's worth, is to assume that the blokes who design the engines know rather more about all this than I do.

    I'm not going to start removing components just because there's a possibility they might go wrong.

    .
     
  10. AlS3BE

    AlS3BE Registered User

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    Agree to this to a point but the blokes who design these thing also just need it to last the warranty period. Temporarily stopping corrosion in the coolant system is just that , temporary. That bag of silicon isn’t gonna last forever. In my head if it isn’t designed to last then should be changed like a service item especially if there’s reports of it bursting and running a muck
     
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  11. cuke2u

    cuke2u Well-Known Member

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    Have you one inside the coolent tank of your car, has anyone here in this forum actually reported having one? Your assumption that parts in a car, aside from renewable ones, are only designed to last the length of a warranty is a tad cynical...
     
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  13. MikeParkin

    MikeParkin Registered User

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    Just got mine out took 5 mins, car wasn’t worth having warranty after a few month from new anyway so....
     
  14. Sean6211

    Sean6211 Registered User

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    Yes, I have one in my 2014 A3. Visible when using a bright torch shining through the purple G13 coolant.

    Per the Self Study Program, VAG designed the silicate bag to continue supplementing the coolant for the lifespan of the engine. Regularly extracting old coolant and topping up with fresh coolant may be beneficial, but how many people actually do that? Most people don't even check their oil level regularly, let alone top up their coolant tanks.
     
  15. Boydie

    Boydie S3 8V DSG VCDS Map User

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    Can you just replace it with a new one? Mine is now 4 years old and I do not plan to keep the car another 4 years so just replace it with a fresh one?
     
  16. Sean6211

    Sean6211 Registered User

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    I doubt it is available as a replacement from Audi, if it is designed to last the life of the engine. Your best option is to renew the entire coolant expansion tank if you want a new bag.

    There has been no evidence of widespread failure of the silicate bag on the MQB platform. In fact, it is found in both VWs and Audis for the past 10+ years, and if this is the first time many are even hearing of a silicate bag in the expansion tank, then it is clear that failure rates are extremely low.
     
    Boydie, AlS3BE, cuke2u and 1 other person like this.
  17. RS3 S.

    RS3 S. Registered User

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    ...........as above first time i've heard of this?.
     
  18. scobie140

    scobie140 Registered User

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    Every day is a school day
     
    N88 RBN likes this.
  19. Mikeso51

    Mikeso51 Registered User

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    Googling around, it seems that several VAG cars, and some others, have silicate reservoir cartridges in the radiator header tanks. Not seen any mention of problems, and they have been in use for more than 10 years, so leakage can’t be a major issue. Should anyone want replacements, there are several listings on eBay.
     
  20. MartinVW

    MartinVW Registered User

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    Hey guys.
    I too had never heard this, but I have just had my Passat in for a service and they told me that the bag had burst and would contaminate the coolant system and eventually block the coolant heater matrix.
    The coolant expansion tank needs replacement at a cost of £650.
    The car is 6 weeks out of warranty :frown new:
     
  21. Gazwould

    Gazwould Registered User

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    Yep Mercedes do it and claim a 15 year coolant life !
     
  22. MikeParkin

    MikeParkin Registered User

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    Get them took out ! Never used to have them.
     
  23. ZipZap01

    ZipZap01 Registered User

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    Modern coolants like G13 contain only the minimum amount of silicate needed to protect the water pump from corrosion. Older formulations used loads of silicate, so would never deplete - but had the opposite problem, the high levels of silicate could congeal into a sludge after a few years.

    Silicates degrade with time. The problem with low silicate coolants, is that because they only have the minimum dose from the factory, they have a limited lifetime before they stop working. To get around this some manufacturers put silica beads in the coolant which gradually leach silicate into the coolant to counteract the depletion.

    Removing the silica beads will shorten the life of the coolant, and you should think about draining and replacing the coolant every couple of years if you want the water pump to last.
     
    AlS3BE likes this.
  24. MikeParkin

    MikeParkin Registered User

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    I have changed my coolant and will change it again.
     
  25. AlS3BE

    AlS3BE Registered User

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    Very informative post :icon thumright:
    Didn’t know any of that till now.
     
  26. 3dit0r

    3dit0r Registered User

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    I had this on my A3 1.8TFSI Quattro at 3-years/35K miles. Fortunately it was still under factory extended warranty, I wouldn’t have wanted the bill.

    Dunno, feels like an unnecessary cludge to me, why not just design a more appropriate coolant than have something floating around which can burst and clog everything up?

    Quite apart from the main rad, I would not want to have the DSG (S-Tronic) coolant valve blocked and have a £10,000 gearbox overheat and go South because some numpty designer stuffed a silicone teabag in the expansion tank instead of speccing a service life for the coolant.
     
  27. Beags

    Beags Registered User

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    Just had this happen on my '16 2.0tdi Octavia Scout - Coolant level suddenly dropped and the reservoir looked v murky. Driver's side fans 8degrees cooler than the left.

    Car 7 months out of 3-year warranty.

    Garage presented a quote for a 'discounted' £1030 (discount due to TPI) for flush and new heater matrix. I complained heavily and was referred to Skoda CS. Within 2 days I had a 55% contribution from Skoda!

    Took the sting out a little but still an avoidable headache - the garage told me they don't inspect the silica bag at all when checking coolant during service!!!

    - They also informed me it was the second case they'd had that week and they'd had 9 others in as many weeks. :blink:
     
    Last edited: Nov 10, 2019
  28. 3dit0r

    3dit0r Registered User

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    In the US they would have had a class action lawsuit by now if there were that kind of failure rate, and VAG would be footing the bills or recalling the vehicles. Here, though...

    Anyone know if we owners can simply replace the silicone bag every year just as a service precaution? How much could a silicone bag possibly cost?
     
  29. MikeParkin

    MikeParkin Registered User

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    Take the bag out and replace the coolant.
     
  30. Sparks43

    Sparks43 3rd Gear

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    I was told that Audi's don't have them but VW Golf's do and they are a pain as they get stuck in the heater rad
     
  31. MikeParkin

    MikeParkin Registered User

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    I’ve taken mine out.
     
  32. 3dit0r

    3dit0r Registered User

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    What's the procedure on these cars? I wouldn't hesitate to do this on my older Audis and Golfs, but I know Audi now use a pressurised cooling system filler which automatically purges air from the system. On some cars there was a VCDS procedure for activating the Aux heater also, so it's possibly not a trivial thing?

    I'll call my friendly local parts dept shortly and see if the bag can be had as a service part.

    It's true they clog the heater rads when they go, seem to be more reports on the VW forums, but they're possibly just more active forums? It's not true that Audis don't have them, though, several confirmations on this thread alone and I've had one go and been replaced/flushed by Audi under extended warranty.
     
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  34. 3dit0r

    3dit0r Registered User

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    Right just spoken to parts. Doesn't seem like the bag is available separately, comes with the expansion tank. £27 inc VAT genuine from Audi. Considering how much easier/cheaper this is than a complete coolant flush, I'll be doing this as a 2-yearly service item. At 1/3 price of the oil at an oil change interval, I'd say it's a no-brainer.

    If the worst does happen, you're looking at £79 just for the specialist flush kit Audi have to use when these go south. Plus possibly the cost of a heater matrix and a lot of labour, although looking back at the job on mine, it seems they got away with a proper flush and didn't have to do the heater matrix, so maybe that £79 was worth it after all...
     
  35. MikeParkin

    MikeParkin Registered User

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    I changed my radiator when I put my Wagner intercooler on. I did exactly as you normally carry out a drain and change.

    It has been spot on since then and that was over 2 and a half years ago.
     
  36. 3dit0r

    3dit0r Registered User

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    Good to know it's just a normal drain/fill procedure.

    Yeah, it's certainly an option to just change the coolant out every so often - do we know the age/mileage interval that the coolant is supposed to have depleted its silicate supply without a bag in the system, or is it dependent on driving conditions/style, etc.?
     

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