Strange goings on in the coolant header tank

I wonder if any of you kind chaps could throw any light on this.

Okey doke. Background information first.

The car is a 2.0TFSI 190, just - just - three years old and with a measly 14,000 miles on the clock. It had a service yesterday. The coolant was tested and its level checked as part of this service. It has never needed any adding, and until some time in the last four or five days has been that nice pink G13 colour.

This morning I happened to have a look at something unrelated under the bonnet and noticed out of the corner of my eye that not only had the coolant in the header changed to the colour of weak tea (with no milk), but something had deposited itself on the inside of the tank. Although it's not as clear as it once was, the level is between the marks, and there are no leaks.

Here are some pics:

Header tank.jpg
Header 2.jpg
Tank insides.jpg
Brown stuff.jpg
Coolant dip.jpg

The first picture is a little bit yellower than it is in real life, and the second one rather more so. This is pretty obviously the result of the torchlight - a bright LED - shining through the coolant. The staining on the inside of the tank is much more marked below its equator, as it were.

The light patches in the bottom half are whiter than they appear on these two pictures, and are much closer in colour to the natural translucent white of the top of the tank.

Photo 3 shows the inside. You can see the staining on the internal components.

I'm sorry about the rather graphic nature of pictures 4 and 5, and I can only apologise to anyone in the middle of their lunch.

No 4 is the result of wiping my finger on the side of that little tab visible on No 3. It looks oily, but it isn't. If you look closely at this and No 5 (which is a bit of rolled up kitchen towel used as a dipstick) you can little particles of this sediment.

You can also see on the kitchen towel pic how much of the G13's normal pink colour has disappeared.

As I said, this stuff is not oily. There is nothing floating on top of the coolant in the tank. Stick your hooter in the neck of the header and it doesn't smell of oil.

There is absolutely no sign of water in the oil either.

The effect is very much like the staining you get on the inside of a mug when you make a brew with a teabag then get distracted and wander off for an hour without having put any milk in it.

Anyone seen anything similar?

Cheers

Pete
 
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AlS3BE

Registered User
These cars have a silica bag inside the expansion tank. There’s a thread about it on here somewhere.
they are prone to popping around the 3-4 year mark.
You need to flush the coolant system to get the crap out now.
 
These cars have a silica bag inside the expansion tank. There’s a thread about it on here somewhere.
they are prone to popping around the 3-4 year mark.
You need to flush the coolant system to get the **** out now.
I did think about that. Why would it discolour the coolant (and leave a brown deposit) when it's designed to leach gradually into the system anyway?
 

AlS3BE

Registered User
I did think about that. Why would it discolour the coolant (and leave a brown deposit) when it's designed to leach gradually into the system anyway?

could be the silica is so fine it mixing with the coolant so it looks discoloured.
Kinda like sand in water, you give it a shake/stir the water is not clear. Let it settle and it all sinks to the bottom leaving clear water on top. that’s what it looks like in the bottom of your expansion tank. Some crap has settled there.
 

sportback A3

Registered User
ive got a golf gtd, mk7. im on a facebook group and so many members have advised to remove the silic bag, carefully with long nosed pliers. if and when the silica bag bursts, its renowned for blocking the heater matrix with the beads, its an expensive replacement job. as it blocks the matrix.. 90% of people remove these bags, Hopefully yours is ok
 
Thanks markie.

I'm getting another opinion from the breakdown dude tomorrow. It's free, and I can't do anything else because it's Sunday anyway.

The car hasn't been driven for more than a dozen miles since the coolant was nail varnish pink so hopefully if the silica bag has bust, the contents won't have had chance to bung up the heater matrix yet.

Hopefully...

Your theory as to where the brown particles have come from is food for thought, though.
 

sportback A3

Registered User
Im no mechanic when i mention the corrosion etc, it maybe that the silica reacts with oxygen and the coolant, when the bag is submerged, its not in air. Have you tried looking for the bag, and if it has burst.
 

AJB

Registered User
Could it have been topped up with the wrong kind of coolant during the service? I know that mixing the blue/green G11 with pink G12 forms brown sludge. I don't know if the newer G13 also forms sludge if mixed with G11. I think G13 and G12 are safe to mix.

Or oil getting into the coolant is another possibility - perhaps via the oil/water oil cooler? (If the oil is at a higher pressure than the coolant in that, then if there's a leak it'll go oil into coolant, and it won't go coolant into oil).

I know the silica bag thing is talked about on forums, but I'm not sure how often it actually fails in real life, and I hadn't heard of it forming layer of deposit like that - I'd understood that the possible issue was the granules or whatever they are getting into the heater matrix and blocking it.
 
This looks disappointingly familiar. The photo looking into the tank could have been mine.

Time to organise a trip to the dealer. With a bit of luck they might smile favourably on a hapless soul whose car is three years and five days old.

Hey ho.

.
 

AJB

Registered User
This looks disappointingly familiar. The photo looking into the tank could have been mine.

Time to organise a trip to the dealer. With a bit of luck they might smile favourably on a hapless soul whose car is three years and five days old.

Hey ho.
.
Interesting if the silicate bag can cause deposits like that. I've learnt something.

I really hope the dealer does play ball and smile on you favourably. If it's got FSH then there's not much more of a case for goodwill than something that can't be operator error, and that's failed only 5 days after the warranty ran out. In fact, not even that - has failed less than 5 days after the warranty ran out and been noticed 5 days after.
 
Could it have been topped up with the wrong kind of coolant during the service? I know that mixing the blue/green G11 with pink G12 forms brown sludge. I don't know if the newer G13 also forms sludge if mixed with G11. I think G13 and G12 are safe to mix.

Or oil getting into the coolant is another possibility - perhaps via the oil/water oil cooler? (If the oil is at a higher pressure than the coolant in that, then if there's a leak it'll go oil into coolant, and it won't go coolant into oil).

I know the silica bag thing is talked about on forums, but I'm not sure how often it actually fails in real life, and I hadn't heard of it forming layer of deposit like that - I'd understood that the possible issue was the granules or whatever they are getting into the heater matrix and blocking it.
I know that the coolant hasn't been topped up - it's never needed it.

I'm one of those sad gits who gets some kind of perverse pleasure from having my head under the bonnet whenever there's nothing on telly, so I'd have noticed.

It's all my dad's fault, God bless him.

And there is no evidence at all of oil getting into the coolant. Not a sausage.

I did find some examples other than the one in the Skoda forum above. The colour change to a browny-orange is a recurring theme.

Incidentally, the breakdown bloke who came out this morning wasn't a lot of help. As I mentioned previously it was a chance to get a free second opinion from someone who knew more about it than I do.

That's what I was hoping, anyway. It soon became apparent that I knew more about it than he did. I don't say that to make me out to be a clever clogs or him a dimwit, mind - it was just that he'd never come across it before. His advice was pragmatic, as you'd like to think it would be; don't drive it any more than necessary.

I'm taking a crumb of comfort that some of the people affected by this and who have had it resolved with just a flush, a refill and new header tank (which is only about thirty quid in my case) have driven for far, far longer with a split bag in the tank.

Months, in some cases.

.

.
 
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AJB

Registered User
You sound similar to me!! I blame my dad too...!!

One other thought-you say the coolant was tested, so I guess they’ve either stuck a probe in or stuck a pipe in to suck some out to test. Could they have damaged the bag doing that? As in is it somewhere accessible and below the filler?

Obviously could just be coincidence, but I was thinking about the “just serviced” thing, plus I’ve got from my dad a general assumption that whoever was in there might well have got something wrong.

(And yes, I was sad enough to check my undertray for missing screws after mine was serviced and then to go back to ask to have the one they’d left out back...!!)
 
One other thought-you say the coolant was tested, so I guess they’ve either stuck a probe in or stuck a pipe in to suck some out to test. Could they have damaged the bag doing that? As in is it somewhere accessible and below the filler?

Obviously could just be coincidence, but I was thinking about the “just serviced” thing, plus I’ve got from my dad a general assumption that whoever was in there might well have got something wrong.

(And yes, I was sad enough to check my undertray for missing screws after mine was serviced and then to go back to ask to have the one they’d left out back...!!)
I'd be fibbing if I said that hadn't occurred to me as well.

My initial thought was to give them the benefit of the doubt and lean towards a coincidence, but that may well not be sensible.

The 'them' is an independent outfit I've been using for about fifteen years, and I've been using them for that long because they're very good.

You could argue (with some justification) that I've made this whole thing - or the resolution of it - more difficult than it needed to be by taking the car outside the dealer network for this particular service, but we are where we are.

My intention is to go down there tomorrow morning and see what they say. I don't have any problem in asking them if there is a possibility that the bag of silica might have been damaged by mistake when the coolant was tested.

There's little point trying to second guess how they'll respond.

On the other hand, if. they damaged the bag accidentally, they would in all probability not know they had damaged it before closing the bonnet, especially if the coolant check was one of the last things they did.

The contamination would only become apparent the next time the bonnet was opened, which was by me on Saturday morning. I collected the car at half three the day before. Needless to say I didn't open the bonnet there and then to check that they had done it all correctly.

You just don't do that. Nobody does.

Given how thorough they are - and they are .thorough - I'm confident that had there been any visible contamination in the expansion tank when they popped the lid to make a start, they would have made a note to that effect, and in all probability given me a bell to let me know while the car was still there.

They know what an expansion tank half full of clean three year-old G13 looks like.

I won't walk in there and put a box of insinuations and accusations on the counter. Once defences go up, you've made the job ten times as hard.

We'll have to see what happens.

P.S. There is one thing that's as sure as eggs, and that's if the bag has been punctured (accidentally, of course) rather than just split, there's no point going to the dealership harbouring even the tiniest shred of hope that there would be any goodwill, because there won't be.

They'd show me the door I just walked in through.

.
 
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AlS3BE

Registered User
I'd be fibbing if I said that hadn't occurred to me as well.

My initial thought was to give them the benefit of the doubt.

The 'them' is an independent outfit I've been using for about fifteen years, and I've been using them for that long because they're very good.

You could argue (with some justification) that I've made this whole thing - or the resolution of it - more difficult than it needed to be by taking the car outside the dealer network for this particular service, but we are where we are.

My intention is to go down there tomorrow morning and see what they say. I don't have any problem in asking them if there is a possibility that the bag of silica might have been damaged by mistake when the coolant was tested.

There's little point trying to second guess how they'll respond.

On the other hand, if. they damaged the bag accidentally, they would in all probability not know they had damaged it before closing the bonnet, especially if the coolant check was one of the last things they did.

The contamination would only become apparent the next time the bonnet was opened, which was by me on Saturday morning. I collected the car at half three the day before. Needless to say I didn't open the bonnet there and then to check that they had done it all correctly.

You just don't do that.

Given how thorough they are - and they are .thorough - I'm confident that had there been any visible contamination in the expansion tank when they popped the lid to make a start, they would have made a note to that effect, and in all probability given me a bell to let me know while the car was still there.

They know what an expansion tank half full of clean three year-old G13 looks like.

I won't walk in there and put a box of insinuations and accusations on the counter. Once defences go up, you've made the job ten times as hard.

We'll have to see what happens.

P.S. There is one thing that's as sure as eggs, and that's if the bag has been punctured (accidentally, of course) rather than just split, there's no point going to the dealership with even the tiniest shred of hope that there would be any goodwill, because there won't.

They'd show me the door I just walked in through.

.

to be fair if it’s someone you have used for ages and trust it’s not worth arguing about. realistically the expansion tank can be cleaned and the flush will be just water then refill £10-20 worth of coolant. More labour than parts. Different if they blew a gearbox or engine.
I would probably think twice about a new expansion tank. The new one will have a silica bag in there so might be better just clean out the old one so it doesn’t happen again.
 
to be fair if it’s someone you have used for ages and trust it’s not worth arguing about. realistically the expansion tank can be cleaned and the flush will be just water then refill £10-20 worth of coolant. More labour than parts. Different if they blew a gearbox or engine.
I would probably think twice about a new expansion tank. The new one will have a silica bag in there so might be better just clean out the old one so it doesn’t happen again.
I take the point.

As I said, I don't intend to take a confrontational approach. I know how easy it is to demolish a relationship which was built up over fifteen years.

On the other hand, if I keep schtum and cough for a flush and refill there's a possibility it might happen to somebody else.

Now that's not my problem, but it isn't very public spirited either.

And just supposing that we (them and me) come to a no-admission of liability compromise which involves a free flush and refill, I'm perfectly happy to stump for a new tank. It's about £25 - less than the price of a Saturday night Ruby Murray - and I can always take the silica teabag out and get the G13 renewed again in a couple of years.

I don't want some grotty expansion tank in my car - no matter how vigorously they power-wash the existing one it's still going to be the colour of an old pub ceiling.

.
 
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AJB

Registered User
My intention is to go down there tomorrow morning and see what they say. I don't have any problem in asking them if there is a possibility that the bag of silica might have been damaged by mistake when the coolant was tested.
...
I won't walk in there and put a box of insinuations and accusations on the counter. Once defences go up, you've made the job ten times as hard.
...
We'll have to see what happens.
And just supposing that we (them and me) come to a no-admission of liability compromise which involves a free flush and refill, I'm perfectly happy to stump for a new tank. It's about £25 - less than the price of a Saturday night Ruby Murray - and I can always take the silica teabag out and get the G13 renewed again in a couple of years.
That all sounds very sensible - and if it was me I would at least ask the question (in a non-confrontational way, as you say), especially if the bag is visible below the filler (so in the line of fire).

The contamination would only become apparent the next time the bonnet was opened, which was by me on Saturday morning. I collected the car at half three the day before. Needless to say I didn't open the bonnet there and then to check that they had done it all correctly.

You just don't do that. Nobody does.
Haha! No, you don't. Although I sometimes really want to!! And I have been known to stop around the corner... (and at least twice ended up going straight back (2 different main dealers), so saved myself the full drive home and back!)
 

AlS3BE

Registered User
When you get the new tank can you take a pic of the tea bag? I’ve looked around mine before and couldn’t really see it so would be good to see what it looks like and where it’s stuck to.
 
When you get the new tank can you take a pic of the tea bag? I’ve looked around mine before and couldn’t really see it so would be good to see what it looks like and where it’s stuck to.
Of course. I'll try and get the original one and whatever's left of the gubbins inside it too.

It'd be handy to know if these things are vulnerable by design to accidental damage.

I've got to be very careful not to go accusing anyone of anything. Not even carelessness, if that's what it was.

We'll see what comes out in the wash.

.
 

sportback A3

Registered User
Hi, the brown residue is definatley caused by a burst silika bag, which then coagulates as we said they are put in as corroson inhibitor. I hope your lucky, and a simple flush will rid the system of the silika, So many people have needed a new matrix, as flushing wont budge the coagulated silika., Some people only became aware when they noticed one sided heat from the heater blower, overheating, or a blown head gasket I Hope youre lucky.
I would ask to be present when its inspected, maybe coincidence, but you could do with asking how the coolant was tested, e.g did they dip the header tank etc.
people are quoing that it cost in excess of £900, My Golf still has warrenty, but im going to remove the existing bag, and see if i can purchase a new one

Good luck I hope its a cheap fix for you. id certinly put it to Audi or some goodwill
 
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When you get the new tank can you take a pic of the tea bag?
The workshop ordered a new tank from TPS today. We decided OEM was the best bet, not least because it's only a few coppers more expensive than an aftermarket one.

They made sure it's the correct - and most up to date - part number for this particular vehicle and everything.

Much to everybody's surprise it doesn't have a bag of silica in it, and neither does it say 'mit silikat' on the outside.

The plot has got a bit thicker.

I'll let you know what's occurring when I get the duff one back on Wednesday.

A crack CSI team in an unmarked Transit is on standby just round the corner, complete with a little white tent and blue bootees.

.
 
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Noman

Registered User
Recently had my silica bag burst in my coolant system. First the heater matrix broke and then water pump because the silica and coolant liquid became corrosive. Had to spend £600 on new parts.
 
This is a proper mystery and no mistake.

I've just got back from having the coolant flushed and replaced and a new expansion tank fitted. The new tank was not 'mit silikat'. Neither a bag nor anything incorporated into its internals.

I've got the old tank here. I winkled the silica bag out and it's completely intact, though I can see how easily the bag's contents could block the internals of the heater matrix if it were to rupture.

I'll put some pictures on a bit later.

What is obvious is that there is no way dipping the coolant with a tester would rupture it. It's a very sturdy little thing.

Something caused the coolant to change colour almost overnight, but I've no idea (and neither does the workshop) as to what might have done it.

The mechanic who did the service confirmed (as did everybody else) that had the coolant been discoloured at any time they were working on the car they'd:

a) have noticed, and

b) rung me up to tell me that they'd found something amiss.

So something poisoned the coolant in the mile and a half between them finishing the service on Friday afternoon and me opening the bonnet at home on Saturday morning, but nobody knows what.

I'll reiterate what I said before; the old tank (and the dregs of old coolant still in it) do not smell of oil contamination at all, and the bit swilling around in the bottom does not feel oily in the slightest.

The strange thing (as if it wasn't strange enough already) is that despite all this, my symptoms were identical to those which affected the Skoda in the Briskoda forum link I put in an earlier post, and the bloke concerned in that episode was told by his dealership that a burst bag was the cause of that particular issue.

Any rate, I've now got a system with a new tank full of nice clean purple coolant and everything is working properly, including the heater. At least at the moment it is.

I'm seventy quid down, but that's obviously nowhere near as much as it could have been.

The workshop have been great. It's nice to know my faith in them isn't misplaced.

.
 
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sportback A3

Registered User
Thats great news for you, obviously the £70 cost is a slight downer, but as you and others have said, its a let off really. On the plus side, a flush with new coolant wont be a bad thing, A good job you opened the bonnet n noticed in the 1st place, perhaps the brown residue is the initial stage before the bag bursts.
Im sure i read that the Silika is added in the bag as a slow release agent, which helps with heat disserpaton, perhaps VAG have decided its doing more harm than good, hence why its no longer used.
 
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Here's the article in question. Definitely not ruptured. You'd need a very sharp knife and no little force to poke a hole in it. A tool like a little turkey baster wouldn't touch it

I can see how the slow release deal is supposed to work, though - it's sitting in a pot of water at the moment, and the trapped air inside it is escaping so infinitesimally slowly that it's almost airtight.

You can squeeze it pretty hard and nothing comes out.

Must be an age thing.

Teabag 1.jpg
Teabag 2.jpg
 
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AlS3BE

Registered User
Here's the article in question. Definitely not ruptured. You'd need a very sharp knife and no little force to poke a hole in it. A tool like a little turkey baster wouldn't touch it

I can see how the slow release deal is supposed to work, though - it's sitting in a pot of water at the moment, and the trapped air inside it is escaping so infinitesimally slowly that it's almost airtight.

You can squeeze it pretty hard and nothing comes out.

Must be an age thing.

View attachment 195129 View attachment 195130

It does look like a tea bag now it’s stained:wink:
Now the curious thing is what caused all that crap in your coolant.
 

pburv

Registered User
It does look like a tea bag now it’s stained:wink:
Now the curious thing is what caused all that **** in your coolant.
Might be worth getting the coolant tested with a gas analyser or chemical analyser. Possibility of combustion gases entering the system. It's possible for gases to get in and still not show any coolant in the oil.
Plenty for sale on ebay cheap enough and at least it will rule out a blown gasket. Just do a search for Combustion Leak Tester.
 
It does look like a tea bag now it’s stained:wink:
Now the curious thing is what caused all that **** in your coolant.
Isn’t it just? And it wasn’t a gradual thing either. It happened in less than five minutes of driving time.

As long as everything’s okay now and assuming it doesn’t do it again, does it really matter what happened?

You bet it does.
 
Might be worth getting the coolant tested with a gas analyser or chemical analyser. Possibility of combustion gases entering the system. It's possible for gases to get in and still not show any coolant in the oil.
Plenty for sale on ebay cheap enough and at least it will rule out a blown gasket. Just do a search for Combustion Leak Tester.
I can see the sense in that, but if it is a blown gasket surely it’s going to happen again, and just as quickly as before.

Logic says it should have happened again already...
 

pburv

Registered User
I can see the sense in that, but if it is a blown gasket surely it’s going to happen again, and just as quickly as before.

Logic says it should have happened again already...
I'm sure you are right. Have you driven it hard yet? That could be a good test to see?
 
I'm sure you are right. Have you driven it hard yet? That could be a good test to see?
No, but I didn’t drive it hard before.

I honestly don’t pretend to know what’s going on - I’m just trying to apply some kind of rudimentary common sense to it.
 
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I can see the sense in that, but if it is a blown gasket surely it’s going to happen again, and just as quickly as before.

Logic says it should have happened again already...
I know it's rank bad form to reply to your own posts, but I gave myself such a bad case of the willies thinking about what I just said that I went out in the p*ssing rain with a torch to check that it actually hadn't gone all discoloured again...










































And it hasn't.

Does that mean we can eliminate an internal leak of combustion gases? A leak isn't going to fix itself, after all, and since I drove further today after collecting it than I did at the end of last week, the motor would have got hotter.

.

.
 

pburv

Registered User
I'm sorry if I have cost you some Z,z,z,z,s mate. Wasn't my intention lol
Buy yourself a combustion testing kit from a parts supplier or ebay. They are relatively cheap. At least then you could put your mind at rest and get some beauty sleep haha.
From what you have said and checked it probably is unlikely the gasket has failed but for peace of mind I would like it ruled out if it was me.:icon thumright:
Good luck buddy and I hope it gets sorted:thumbs up:
 
Strange one this.
If your head gasket is leaking cylinder to coolant, the system/expansion tank will usually hold a slight pressure when stone cold and you can hear the release when removing the cap. Wouldn't expect the coolant to discolour so quickly though.
Silica bag isn't burst so can't see that being the source.
Looking for a logical explanation - happened immediately after service - most likely contamination. I've known an engineer have overheating problems many years ago when he topped up his radiator (in an Allegro) with screen wash instead of antifreeze. Is it possible that an apprentice has topped up your coolant reservoir with an incompatible antifreeze that has reacted with the G13 - or even put some brake fluid in there?
 
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Is it possible that an apprentice has topped up your coolant reservoir with an incompatible antifreeze that has reacted with the G13 - or even put some brake fluid in there?
I don't know, and I suspect I never will.

My gut feeling is that it's unlikely if only because the coolant didn't need topping up before the service, and unless he drew off a pint to taste-test it then I can't see why it would have been topped up at all.

Maybe he'd used the tester to baste his turkey the night before and forgot to wipe the end.

I'm going to stop fretting about it for the time being because everything appears to be fine.

.
 

eribaMotters

Registered User
Maybe he'd used the tester to baste his turkey the night before and forgot to wipe the end.

I'd be thinking you are looking at the most likely answer. The tester he used to draw liquid off was not clean and what was in/on it has contaminated the tank.

Colin
 

AJB

Registered User
Looking for a logical explanation - happened immediately after service - most likely contamination. I've known an engineer have overheating problems many years ago when he topped up his radiator (in an Allegro) with screen wash instead of antifreeze. Is it possible that an apprentice has topped up your coolant reservoir with an incompatible antifreeze that has reacted with the G13
I was going to say this (and the level does vary a bit even just with temperature, so it might have been below the absolute max line without actually being low in any meaningful sense).

Maybe he'd used the tester to baste his turkey the night before and forgot to wipe the end.

I'd be thinking you are looking at the most likely answer. The tester he used to draw liquid off was not clean and what was in/on it has contaminated the tank.
But actually this seems even more likely. Especially if it actually was a baster, so you have to squeeze the bulb (ejecting whatever dregs are in it) before it'll suck up new stuff. I wonder if a few dregs of G11 from whatever car was previously tested is enough to give the tea effect. Or whether they use the same baster for sucking out excess brake fluid after a pad change (hopefully not, but you never know...)

Either way it's looking promising for you being absolutely fine now!
 
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