rum4mo

That is what I'd expect, so that is probably another possible reason dismissed! I see there is a small pocket in the casting that coincides with where that rubber gasket material joining point is, I wonder if some sealant needs to be added to that point only? I wonder what the purpose of that "pocket" in the casting really is for as when you look closely at the previous pump, it also has that pocket in the casting but that rubber gasket seems to have been either made in a single piece or the joint point is invisible - is the "unevenness" in the rubber gasket on the new pump actually where the material is joined or something else that has caused that appearance on that new pump? Edit:- I do understand that any fluid leaking out around the gasket sealing point, should, if it is just a small leak, run down the face of the engine, but if it was a bigger leak it might spray out and get caught by the belt pulley, just a though option for this second pump leaking.

I would hope that the only way that you could cause damage to a new pump would be to over load the shaft bearing by over tightening the auxiliary drive belt - I don't know about that engine, but I'd hope all modern cars have an automatic adjuster to avoid that happening to cars nowadays. I'd be a bit annoyed if that had happened to a new pump that I had only fitted a few months ago!!

I did that to a very small impact damage on a tyre on my daughter's previous car, there had been a comment in the MOT - so I glued it back down before it git ripped off, in that case there was nothing but rubber at the "base" of that crack/tear so after checking and cleaning it properly I glued it with a suitable rubber glue, I've forgotten which type/brand - and applied pressure "somehow" for a few hours, again forgotten how. Next MOT, no comment.

I totally agree with you there, but now that I've looked closely at that picture, there is a seal now sitting inside the water pump assembly, surely if there was pressure you would have expected a seal maybe elsewhere, to get pushed out into the lower pressure zone - ie outside the pump housing - no? Edit:- also the area around the pump<>engine gasket looks clean enough and as no coolant was spotted coming out from within at that joint, the surfaces must be okay.

I would have expected that an assembly with a profiled rubber gasket fitted to it would not need any other additional sealer added, what was the mating surface condition like, ie all around the areas that that gasket engages with, as I'd think that is where your problem lies. These pumps are really just agitators in as much as they are not positive displacement pumps, in other words I'd not expect a pump of that type to be able to develop a high head pressure if ending up being in a "dead head" situation, while the thermostat might be choking the flow, that pump would be able to freewheel without creating enough presure in the system to force a seal out, and the other side of the system would still be open or have "access" to the header tank pressure relief valve in the cap - if that is still okay.

I had that feeling but I was not 100% about reading zero when the system was extremely short of gas charge, so I did what maybe others would have done in that situation and quickly depressed the Lo side port valve core and was rewarded with a "too low" hiss!

To add to the above, that crack is on the edge of the rim protection area, and might just be due to that tyre having "kissed" a vertical surface quite firmly - but only you could judge that from its appearance close up. Edit:-as always, if you are in doubt, use common sense and default to replacing.

Ending up with "accidental" good fuel economy can be almost addictive - my wife got bored/annoyed with me getting excited about passing the 66MPG figure over a 20 mile journey average.

I'd prefer to have a spare like the one in the picture than a skinny space saver, you could drive a lot more miles with that on as a spare though still be limited to a lower speed - though I've forgotten the actual speed limit. Any width bigger than that would raise the carpet, that is what my wife's 2015 Polo came with and the wheel/tyre size her winter wheel/tyres are. Maybe as good as it gets spare wheel wise for Fabia/Polo/Ibiza of that age. Edit:- a very good tip wrt "check that you can remove all the wheels"!

Just to tidy up what I said that I was going to do, Bumax replied to my enquiry and stated that their Ultra versions of all fixings are only manufactured to special order, ie no stock held. What they did suggest was their "88" version which is by tensile strength equivalent to an 8.8 carbon steel item, they also provide a "109" version which is by tensile strength equivalent to 10.9 carbon steel bolts. Their 10.9 Stainless Steel offering is :- 4762A406016109 BUMAX 109 ISO 4762 Socket Head Cap Screw M6 x 16 and comes in boxes of 100 bolts. They have also given me details of my local Bumax distributor who is located in Aberdeen so I will contact them to see if they sell these items in split batches as Bumax can not as every box is sold with traceability, I've found in the past that some times resellers do split boxes to allow individuals to buy in smaller quantities - ie provide a different type of service to the occasional user. So I'll see how this goes, as I said much earlier, I am only planning on replacing this bolts with higher strength bolts in a bid to walk away from this potential problem, so this action is as I said earlier, just me applying a "sticking plaster" and not trying to dig down to the root cause of these bolt failure - that would take a lot more time and effort and I want to move on from this ASAP.

I think that you are slighted confused about this, there are quite a few places on these cars where fixings that are made from a metallic material or alloy that does not rust/corrode are used, most people would just call these items stainless steel - which is what the fixings supply industries are also calling them collectively - nothing more like tensile strength can be taken from that description in the same way as for any other metal/steel fixings are used elsewhere - but no one, apart from you need to be sticking strength or lack of strength labels to different versions in a bid to keep everyone safe. What else would you expect anyone else to do when illogical challenges were being made about what they had written, do you really expect that you can jump in and make a statement and expect others to "behave"? Life does not need to be like this, stop digging.

Honestly I really don't understand where you are coming from here, and I'm being truthful, I've read through all my postings and at no point that I can find did I suggest that any old stainless steel is just the job - which is what you effectively wrote in an earlier posting when you suggested that I was handing out dangerous advice. I own and run a car with this potential dangerous issue, I am very concerned about this and not just dipping in with dangerous suggestions, I think that you have mis read something some where in this thread and are now trying to duck out, not clever.

@Wino, if you re meaning me suggesting that people attempt to source stainless steel bolts from the Swedish company I quoted, you will find that they are no ordinary stainless steel fixings, and so strength will not end up being an issue - cost will be though I'd think, oh and they list them as stainless steel fixings.

Honestly (back) I'd never ever suggest anyone go out and grab a correct size stainless steel bolt to replace anything, I've used SS bolts for years at work and I know exactly the trade that comes with most of them, I'll need to look back, but I can't think that I've suggested that anyone does that. The point remains that these bolts are a stainless steel and picked to be that for a very good reason as having any non stainless bolts in that location would work fine - until they needed to get removed at a later date, now if they snapped their heads off then due to having been bolted into aluminium alloy, then that could require a bit of expensive machine shop work to get the bits out of a cylinder head. I would have thought that VW Group design might have considered just using the old "green coated" bolts for that and deliberately walked away from doing so. Now, if I was deliberately suggesting that people should get their charge intercoolers off and swop these bolts for high strength Umbrako ones - then I'd expect to get a tanking, but I have not and will not as that would probably remove one issue and cause another.

There are many ferritic stainless steels out there - but when talking in general in engineering, the phrase "stainless steel" is the generic description to differentiate from normal high carbon steels which are like Unbrako seriously strong. What else are you looking for in this thread if only to nit pic on a fixing material that most people that are likely to be working on their cars or any other mechanical product, would call it? If they rust/corrode in normal use on a car then they are not stainless, if they do not rust/corrode in normal use on a car then I'd call that stainless steel without drilling down to the exact version of stainless steel, I've already made it perfectly clear that my plan is to attempt to source a stainless steel fixing that is of a higher strength than that currently used by VW Group in this application - where is the error in doing that?

As you may, I was more indicating what I'd be planning to do, so there is nothing wrong with that, so what steels do you know about that are used for bolts, that look like stainless steel and are not?

I've checked these new bolts again and they are slightly ferromagnetic so I was wrong in that sense, but there are magnetic stainless around.

Well, what else could these bolts be, they are zinc plated steel, they are not whatever the plating is that replaced cadmium, they do not seem to be HSS covered in a coating, they are not the old green coated ones - which you might expect as they are screwing into aluminium, ie the steel ones with a barrier coating/dip and they are not super strong Unbrako ones. The new ones that I have are exactly the same to look at as the broken one in the pictures in this thread. With time they have not tarnished are started to rust - so these are properties of stainless steel, are they not.

Correct, but there are some manufacturers providing stainless steel fixings that meet the 8.8 tensile strength numbers, so some of them list them as being that grade, as it seems in this case. Edit:- Making out the marking on the head of at least the new bolts that I bought, is not too conclusive, if I did not know better the markings could be 8.8 or 8.0 or 0.0, so after finding that some manufacturers do declare that their stainless steel fixings meet the 8.8 grade, I'm assuming that that is what is on the heads of these bolts.

Well, they look like stainless steel, they are not magnetic I know this because I have bought a replacement set of 4 from VW - and I've used many stainless steel screws and bolts in my life time. The tightening torque for them is extremely low even for an M6 8.8 grade bolt/screw, I'd think that the "anti slacken" element here is the cushioning effect of the injectors top seals. Something is causing some of these bolts to fail and the only thing that I can think of is the "pumping" action of the injectors switching being amplified by the unsupported end section of the rail including the extra load having the pressure switch stuffed onto the end of that overhanging section of rail.

No, normally nothing to do with slackening off, it is the head of the one nearest the RHS end that gets snapped off, if anything, these bolts need to be fitted into the alloy head with a bit of antigalling paste on them. Without any recognition of this issue from VW Group, all people can do is replace with the correct 8.8 grade stainless steel bolt, or if I get any where with trying to source higher strength stainless steel bolts, replace with 10.9 or even higher special stainless steel bolts and hope to stay lucky.

Having a Haynes workshop manual would help you in all areas I'd think, very handy to fall back on if/when needed. 4376 is the one to look out for.

Remember all I am trying to achieve, with my wife's car, is to improve its safety as I don't want this failure to happen to us, especially as I now know that it might - as it has happened to at least 7 others with this engine, also remember that Skoda build or did build all these 1.2TSI 16V petrol engines for all the VW Group marques, I'm sure if I talked to my VW dealership about this issue with my wife's 2015 VW Polo, my concerns would get dismissed as it is only (mainly) happening to Skoda cars and VW cars have VW built engines - that is not true, but that is what I'd expect to be told by VW dealership and VW UK! Maybe to understand this a bit more, these engines feed their injectors from a common fuel rail and that fuel rail gets supplied from a cam shaft driven high pressure fuel pump. The fuel rail is a steel tube that is rigidly fitted to the high pressure fuel pump at the LHS of engine, and then it attached to the cylinder head by 4 M6 stainless steel 8.8 strength along its length, 2 above the rail and 2 below the rail but all 4 spaced out along the rail's length. After the fuel rail passes the injector for cylinder number 1, it extends maybe 75mm and that length has no other support , that end of the fuel rail is open and a fuel pressure switch assembly is mounted or screwed into the end of the rail. So, when you consider everything, the bolt that is nearest the RHS of the car is the one that will always fail first as it carries more load than any of the others, ie the most LHS bolt is closest to the high pressure fuel pump which must be stopping any tendency for that end of the fuel rail to move about due to injector pulsing etc. Just my thoughts as far as I've worked things out! Note:- I'm not trying to sort things out completely, I'm just trying to apply a "sticking plaster", I think that the design of the fuel rail is wrong, and the only way to fix this issue properly, is to provide an extra "anchor" fixing at the "free" end of the fuel rail. ie brace it to the cylinder head and so remove the extra load that the bolt that snaps its head off is experiencing.

What really annoys me about this failure is, this is a fixing failure, and not an assembly or other component failure, that should not be happening anywhere if that part has not been disturbed by a workshop or owner, also the fact that petrol under pressure then sprays out and down the front of a hot engine - okay the exhaust is on the rear of the engine, but with the car moving through air, the fuel will end up passing over the hot exhaust parts. The VW Group part number for these bolts is :- N 105 464 03 and there are 4 of them, they are M6 X1.0 X 16mm and have a cap head, the original ones have a spline or Torx female for tool fitting, but I'm trying to source cap head bolts with any type of tool insert, probably hex, when one fails, they all should all get replaced and fuel rail injector seals will also need to be replaced. Edit:- just stuff Bumax into Google and you should find them . https://www.bumax-fasteners.com/bumax-grades/bumax-ultra/#:~:text=The strongest fastener on the market – and it is stainless&text=BUMAX® ULTRA also has,C with retained mechanical properties.

@Eric-DK, have you ever considered reporting this fault to the motoring watchdog or road transport watchdog in your country, also any motoring organisation - for example we have RAC and AA in UK, just to see if they are interested in this problem. I am currently trying to source "super strong stainless steel" bolts to replace the bolts holding the fuel rail on in my wife's August 2015 VW Polo, really trying to get in there and "improve" things before we have this dangerous failure occur with that car. The bolts used by VW Group are stainless steel with a strength rating of 8.8,what I am trying to do is to replace them with stainless steel that is 10.9 strength, there is a company, I think they are Swedish called Bumax or at least one of their fixings ranges are called Bumax and the bolts that I would like to get hold of are from the Bumax Ultra range, the only issue that I have is that I do not yet know is if this material while being stronger in tensile strength is also more or less suitable for use in this application, I have contacted their UK agents/seller but so far no reply!