Front subframe fixing bolt failure!

RUM4MO

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Jun 4, 2008
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Not an Ibiza, but a same age VW Polo, the bolt nearest the front on the near side, ie the one roughly behind the ARB mounting clamp area, failed due to what I consider to be corrosion caused by road spray and winter salt spray getting in from above this bolt and welling up in the over sized hole the bolt passes through and so trashing that fixing bolt, the car is an August 2015 VW Polo 1.2TSI with 38K miles - I had not expected that to happen!

I only discovered this as I left the Polo on the driveway as I was going to wash it, and spotted a bolt head on the garage floor round about where the front near side of the Polo is normally, driving up onto ramps confirmed what I though, ie a front subframe, or support frame fixing bolt!

I'll leave removing that bolt's shank to my local VW Group Indie as they will either be able to weld a nut/bolt onto the remains and unscrew it, or drop the front subframe to access it and that will mean that car needs a 4 wheel re-alignment.

Really just a "heads up" so maybe time to check all the front subframe fixing bolts, especially this one, I'm not sure if the same situation could happen on the off side, though safer to check both sides. Note neither I or my local VW Dealer have ever messed about with that bolt, so I reckon that it is down to trapped water corroding it, ie a slight design over sight.
 

300bhpdaily

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May 26, 2020
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That’s worrying I dare say if you hadn’t seen the head on the floor this might never had got spotted by a garage. I definitely will be paying closer attention to subframe bolts from now on.
 

RUM4MO

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Absolutely, I do try to give our cars a good look over when servicing them, but I can't be 100% confidant that I would have spotted a headless bolt.

That car was not handing out any clues/noises to suggest that there was a problem with how the front subframe was still connected, or not to the body.

I feel that the front directional winter tyres are getting slightly saw toothish and so making a slight bit of road noise since maybe December, so maybe this bolt having failed is causing a slight bit of wheel misalignment, I was going to get that car's 4 wheel alignment checked and adjusted before swopping over to summer tyres, if the front subframe need dropping as I'm going to get my local VW Group Indie to replace ALL the bolts that fixing the subframe to the car and any other bolts that fix to the 2 rear flanges and the dogleg mounting, a set of bolts are on order from my VW dealer's parts department.

Edit:- we have in the past run a 2002 VW Polo 1.4 from new until 13 years and 105K miles, and also a late 2009 SEAT Ibiza for 10 years and 65K miles and never had this failure - but I can't say that I have 100% checked these bolts on both cars every years.
 

RUM4MO

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out of curiosity do you have a picture of the bolt?

And here it is:- this bolt is an M12, so you can see were the 12mm diameter was, then it looks like it has been corroded down to maybe 8mm before it started to shear, though the shearing looks like it happened a long time ago! The grey/silver mark in the centre(almost) is where the bolt head finally had contact with the bolt shank. You can see by the silver ring of uncorroded area on the bolt head that this bolt head had successfully sealed that lower face of the subframe from the road below, and so, it seems, trapped/contained any water/salty water that ended up getting into the space above, and so immersed that area of that bolt probably to a continuous supply of nasty stuff which is ideal for corrosion to get going.

Edit:- as a family, we have run a 2002 VW Polo 1.4 16V for 13 years 105K miles and a late 2009 SEAT Ibiza 1.4 16V for 10 years and 65K miles, and not noticed that this could be an issue, so that happening to this car at this age, is a bit alarming.
Hopefully today, after the Easter holidays, my local VW Group Indie will be back working so I can pay them a visit and book this car in as I am not using it now that I know this has happened. This might explain the slight saw-toothing on the front winter tyres that started back in November - well on certain road surfaces there was and still is a slight bit of new road noise.
 

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Crossthreaded

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And here it is:- this bolt is an M12, so you can see were the 12mm diameter was, then it looks like it has been corroded down to maybe 8mm before it started to shear, though the shearing looks like it happened a long time ago! The grey/silver mark in the centre(almost) is where the bolt head finally had contact with the bolt shank. You can see by the silver ring of uncorroded area on the bolt head that this bolt head had successfully sealed that lower face of the subframe from the road below, and so, it seems, trapped/contained any water/salty water that ended up getting into the space above, and so immersed that area of that bolt probably to a continuous supply of nasty stuff which is ideal for corrosion to get going.

Edit:- as a family, we have run a 2002 VW Polo 1.4 16V for 13 years 105K miles and a late 2009 SEAT Ibiza 1.4 16V for 10 years and 65K miles, and not noticed that this could be an issue, so that happening to this car at this age, is a bit alarming.
Hopefully today, after the Easter holidays, my local VW Group Indie will be back working so I can pay them a visit and book this car in as I am not using it now that I know this has happened. This might explain the slight saw-toothing on the front winter tyres that started back in November - well on certain road surfaces there was and still is a slight bit of new road noise.
So I presume that's going to be the same as my 2016 Ibiza RUM? I'll be having a very close look at this when I do the annual service in the next month or so. Are you handing it over to our local VAG indy? - The one opposite the Aldi supermarket. If so I'd be interested to get their take on it.
 

RUM4MO

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Yes it will be the same set up on your Ibiza, and yes booked in yesterday for work to be started on 28th April.

I suppose as always, when a customer wanders in and explains what has happened etc, there is only so much credibility they will give the "self diagnosis" but he guy did take on the fact that I had already set the wheels in motion in as much as I have placed an order with Western VW at Newbridge for a complete set of bolts that fix that subframe to the body, and bolts that fix the support brackets to the subframe and dog leg mount to the gearbox and the subframe.

I hope that the parts turn up in time as they always have done in the past, I prefer to use Western VW Newbridge for parts as the parts department there is still allowed to operate as a true parts department, I've been dealing with the guys there since they were Sloans in Gorgie Road, no fancy counter or seating area, just a back door or the "Tradesman" entrance!

Edit:- I find it quite shocking that that ever managed to happen to a modern car over the period of 6.5 years and 34K miles, I'd not had that issue - that I knew about, with a previous 2002 Polo kept for 13 years and 105K miles, or a late 2009 Ibiza kept for 10 years 65K miles, though in all fairness I never checked these bolts - and that is the thing, these bolts will still look okay from below even when the bolt shank has corroded. You can't tell the condition of the shank from the condition of the bolt head.
The main reason why I have just handed this car over for proper mechanics to sort out is, they can get the car far enough in the air to safely apply heat and/or drill to extract that sheared bolt and any others that shear when being removed. Also I requested a complete 4 wheel re-alignment to be carried out after replacing ALL the bolts securing that subframe to the body.
 
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Crossthreaded

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Yes it will be the same set up on your Ibiza, and yes booked in yesterday for work to be started on 28th April.

I suppose as always, when a customer wanders in and explains what has happened etc, there is only so much credibility they will give the "self diagnosis" but he guy did take on the fact that I had already set the wheels in motion in as much as I have placed an order with Western VW at Newbridge for a complete set of bolts that fix that subframe to the body, and bolts that fix the support brackets to the subframe and dog leg mount to the gearbox and the subframe.

I hope that the parts turn up in time as they always have done in the past, I prefer to use Western VW Newbridge for parts as the parts department there is still allowed to operate as a true parts department, I've been dealing with the guys there since they were Sloans in Gorgie Road, no fancy counter or seating area, just a back door or the "Tradesman" entrance!

Edit:- I find it quite shocking that that ever managed to happen to a modern car over the period of 6.5 years and 34K miles, I'd not had that issue - that I knew about, with a previous 2002 Polo kept for 13 years and 105K miles, or a late 2009 Ibiza kept for 10 years 65K miles, though in all fairness I never checked these bolts - and that is the thing, these bolts will still look okay from below even when the bolt shank has corroded. You can't tell the condition of the shank from the condition of the bolt head.
The main reason why I have just handed this car over for proper mechanics to sort out is, they can get the car far enough in the air to safely apply heat and/or drill to extract that sheared bolt and any others that shear when being removed. Also I requested a complete 4 wheel re-alignment to be carried out after replacing ALL the bolts securing that subframe to the body.
Yes I remember Sloans very well. You went down the left hand side of the building to the car park at the side/rear. I never needed to use them for much so have no particular memories of them or their service but it's useful to know that Western at Newbridge are helpful people. I'm definitely going to be having a very close look at those subframe bolts when I get home and trying to avoid potholes etc on the drive back north!

I also think it very wise of you to hand it over to them for rectification. We all know what an absolute pain tackling well rusted in bolts is and so much easier if access is good - as when up on a lift. I'll be keeping my fingers crossed for you that the cost turns out to be reasonable.
 
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RUM4MO

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Ah, you are away from home, I'm heading down to Londonshire early next month with the S4, I really just did not need this faffing about trying to get the Polo sorted out round about the Easter holiday period to increase my worries, my poor S4, normally a garage queen has ended up spending a lot of its time doing the Polo type of work, which is okay as it will run out its tank full of winter grade petrol that it was loaded with near the end of February, but it does like to drink a lot of fuel when stuck in town in traffic holdups, 25MPG, Polo would have made it to 50MPG when suffering that use. Collecting/returning people to Waverley station - horrible, or even worse than normal!

Safe motoring!
 
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Crossthreaded

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Ah, you are away from home, I'm heading down to Londonshire early next month with the S4, I really just did not need this faffing about trying to get the Polo sorted out round about the Easter holiday period to increase my worries, my poor S4, normally a garage queen has ended up spending a lot of its time doing the Polo type of work, which is okay as it will run out its tank full of winter grade petrol that it was loaded with near the end of February, but it does like to drink a lot of fuel when stuck in town in traffic holdups, 25MPG, Polo would have made it to 50MPG when suffering that use. Collecting/returning people to Waverley station - horrible, or even worse than normal!

Safe motoring!
Yes RUM away from home till the weekend way down in the West Country. Slightly nervous about what we may be returning to as my older boy had some holiday to use up so moved himself and family into our house while we are away so they could experience some life in the "big city". I'm actually quite glad to have them there as it means I don't have the worry of the house being unoccupied but my Mrs is wondering what sort of state the house may be in on our return. I'm not though - worried that is - He's a canny lad and his wife and boy are sensible types too. I keep telling her it'll all be fine.

Do you remember we'd been having conversations about how I could code in a non BEM battery for the Ibiza as I was experiencing stop start problems and suspected the original battery was "dodgy". Well, having behaved absolutely fine and got us down to, first my daughter's house in southern England, and then across to my better half's sister down here in Devon, It's suddenly decided it's had enough. Luckily I took my CTEK with me and I can get it to start if I leave it on charge overnight, which I've been doing for the last couple of days, but I dare not stop it if we are away from base which is making things very difficult. The local SEAT main agent down here is fitting a new battery for me first thing tomorrow morning. He gave me the choice of a "cheapie" or "best quality" - both approved by SEAT (apparently when the vehicle is more than 5 years old they are allowed to give this choice?) Anyway, I chose the best quality option having had poor experiences with "cheap" batteries in the past. He's quoted me £250 all in including the coding and DTC read following installation with a guarantee valid at any SEAT agent nationwide. This aligns with what I was quoted at the 3 indys near us, give or take a tenner. (quotes between £130 to £165) so I'm not feeling too hard done by - but it's a pretty ridiculous price to renew a battery isn't it!

Interestingly, perhaps? I noticed tonight, as I was connecting up the CTEK, that the end of the battery nearest the centre line of the car is bulging slightly. You've got to look carefully to see it but it's definitely there. In my book that's positive confirmation of plates swelling due to sulphation and further confirmation that I've had as much out of this battery as it can give me. I'm hoping to be able to take some pictures tomorrow showing this - if successful I'll try to post them on here for your delectation!
 

RUM4MO

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That battery issue is very annoying, I have/had planned to fit the new battery to my 2011 S4 before we go down to London, or at least Bromley, having the Polo laid up waiting to get sorted out has driven me to thinking that I'll just leave the original battery in it, as it is not showing any signs of aging - it is just me considering that at 11 years old, it would be wise to replace it - it is an AGM so typically they live longer than EFB, I will also take a CTEK, a 5 amp extension lead and probably my smallish jump pack!

I've just had a look at the EFB on the 2015 Polo and it still looks very flat ie not bulging at all - that car has a thermal insulator blanket all round the battery - does your car not have that? I managed to force each of the 4 sides out far enough to shine a torch in to check for bulging.

Yes, the West Country is a long trek from Scotland, even Southern Scotland, as we are both retired, we will be planning to stop off on the way down South and probably same on the way back. When younger and with 2 daughters, we used to just leave very early to get to Somerset/Cornwall/Devon/Dorset houses for round about 16:00, but quite a trek as I was doing all the driving, it is even quite a long drive across from the Eastern South coast.
 
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Crossthreaded

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That battery issue is very annoying, I have/had planned to fit the new battery to my 2011 S4 before we go down to London, or at least Bromley, having the Polo laid up waiting to get sorted out has driven me to thinking that I'll just leave the original battery in it, as it is not showing any signs of aging - it is just me considering that at 11 years old, it would be wise to replace it - it is an AGM so typically they live longer than EFB, I will also take a CTEK, a 5 amp extension lead and probably my smallish jump pack!

I've just had a look at the EFB on the 2015 Polo and it still looks very flat ie not bulging at all - that car has a thermal insulator blanket all round the battery - does your car not have that? I managed to force each of the 4 sides out far enough to shine a torch in to check for bulging.

Yes, the West Country is a long trek from Scotland, even Southern Scotland, as we are both retired, we will be planning to stop off on the way down South and probably same on the way back. When younger and with 2 daughters, we used to just leave very early to get to Somerset/Cornwall/Devon/Dorset houses for round about 16:00, but quite a trek as I was doing all the driving, it is even quite a long drive across from the Eastern South coast.
I'm a bit disappointed with the old battery. It's just going into it's 7th year of life but has had quite a bit of dormant time during covid. I've tried to remember to connect up the CTEK when I know I'm not going to be using it for a few days - but I don't always do it so probably my own fault? Did I say it's an EFB? The Ibiza definitely doesn't have a thermal blanket/case/whatever - Completely open to the engine bay.

Yes, I took a 13 amp extension reel too! but I don't have a jump pack. At home I have an old, large (ex Cordoba 1.9tdi) battery which I use to jump family vehicles if needed but it's not a practical solution to take on long trips. I'm still playing with the idea of a supercapacitor type jump starter - Note to self: Must sort one out when I get home.

We had intended to book an overnight on the way down but both thought the "other one" had booked it and only found out neither of us had as we were driving away from the house - Doh! In the event we had an unusually good journey down to my daughters, just on 8 hours with no hold ups or stressful incidents, and that including 4 toilet stops to keep my old bladder happy! I think we may well stop "on spec" on the return journey from Devon as that is usually significantly longer and rather more stressful. If we get into the northern end of the midlands and I'm feeling tired (Her indoors doesn't like motorway driving so I do it all) then we'll just stop at the nearest suitable establishment. I've been doing this trip - Edinburgh area to south of England - at least twice a year since I was in college in London back in the late '60s but I must admit, as I'm aging, it's getting more difficult to do it all in one go - easier in today's cars though compared with my old 850 Mini or 997cc Anglia!
 

RUM4MO

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Quote "I'm still playing with the idea of a supercapacitor type jump starter - Note to self: Must sort one out when I get home." - yes I'm playing a similar game, and haven't even left home yet!!

Yes I knew/assumed that your battery would be an EFB, strange that SEAT don't bother to fit a thermal blanket round it, off course it could be that VW at that point in production didn't bother either, saving pennies maybe, SEAT know a lot about that, which sometimes is a bit annoying!

Ah, "997 Anglia", my first car/van was a a late build Anglia van ex Royal Mail, it had a "huge" 1200 engine, but low compression, so probably a lot less grunt than your 997cc, we did have a 997cc Anglia van at home when I was young thing. Furthest we ever drove in that van was to Dinnet and English Lakes, that was far enough!

The thing about driving back North, you know the roads better and the traffic sort of vanishes after Blackpool or so, less stress to put up with while getting tired, our first journey break from a trip down to Canterbury has after Christmas visit one year, it should have been a 6 or 7 hour journey up to "half way" but it turned into an 11hour drag with snow thrown in near the end, not good, I had my first pit stop at the side of the motorway down a banking as the traffic was backed up frequently for many silly reasons, took us 4 hours to get to the other side of the Thames, a nightmare - but we have had many fast easy trips though.

Enjoy your new battery!
 

RUM4MO

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Well the car has been in (AVW) to get the subframe bolts replaced and the 4 wheel alignment checked and adjusted. The other front subframe securing bolt was also rusty but mainly only surface rust at the point where the bolt head meets the shank, further along (up) the thread had proper "dissolving" material and that bolt was still wet 3 hours after the car had been worked on, so it seems that water/salty water can gather/moat/well in that area, in fact another Indie guy said that most VAG cars hold water in that location, ie water even runs out in some when these bolts get removed, just how helpful that design weakness is is debatable! I'll need to have a good look at this area and try to get a good creeping antirust or rust protection product into around these front bolts, the rear bolts were almost "as good as new" in terms of corrosion - though being already stretched meant that they could not get reused.
 
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RUM4MO

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One other thing, the front subframe bolt that was still intact, when removed showed signs of waisting, ie non recoverable stretch - this was pointed out to me by someone on line that show my pictures, I had considered that what he was suggesting was waisting, was only material loss due to rusting, but after scrubbing that bolt up with a wire brush, I'd have to agree that some or most of the waisting was due to that bolt being stretched. No comparison like that could be made concerning the sheared off bolt shank as it was seriously heavily rusted. Going back to the front bolt that was removed intact, the worst area of rusting was maybe 15mm > 25mm higher up than the bolt head, which sounds a lot like the "resident" water level in there varied from maybe 10mm > 30mm(a guess) and the area/section with most rusting is where air and water were normally present, the area always under water had just surface rusting. On the sheared off bolt shank, the same pattern of rusting intensity though at the sheared off bolt head there was more rusting and much more so on the sheared off bolt shank than on the other front bolt. I think that I was wrong in suggesting that rusting had caused this, it looks to be down to over stretching of these 2 front bolts, final failure aided probably by rusting. The 2 rear bolts in terms of rusting looked almost like new, and when placing a straight edge(steel rule) along them there was no signs of waisting.
So, okay a real issue with the front 2 bolts shanks ending up in that rusty condition after only 6.5 years service due to silly design error by VW Group, but also a blunder/mess up on the car assembly line in ZA leading to the subframe securing bolts not being torqued up correctly.
 
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Crossthreaded

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One other thing, the front subframe bolt that was still intact, when removed showed signs of waisting, ie non recoverable stretch - this was pointed out to me by someone on line that show my pictures, I had considered that what he was suggesting was waisting, was only material loss due to rusting, but after scrubbing that bolt up with a wire brush, I'd have to agree that some or most of the waisting was due to that bolt being stretched. No comparison like that could be made concerning the sheared off bolt shank as it was seriously heavily rusted. Going back to the front bolt that was removed intact, the worst area of rusting was maybe 15mm > 25mm higher up than the bolt head, which sounds a lot like the "resident" water level in there varied from maybe 10mm > 30mm(a guess) and the area/section with most rusting is where air and water were normally present, the area always under water had just surface rusting. On the sheared off bolt shank, the same pattern of rusting intensity though at the sheared off bolt head there was more rusting and much more so on the sheared off bolt shank than on the other front bolt. I think that I was wrong in suggesting that rusting had caused this, it looks to be down to over stretching of these 2 front bolts, final failure aided probably by rusting. The 2 rear bolts in terms of rusting looked almost like new, and when placing a straight edge(steel rule) along them there was no signs of waisting.
So, okay a real issue with the front 2 bolts shanks ending up in that rusty condition after only 6.5 years service due to silly design error by VW Group, but also a blunder/mess up on the car assembly line in ZA leading to the subframe securing bolts not being torqued up correctly.
So "overstretched" stretch bolts? Now that interests me a lot because I guess my Ibiza will have been built on a different assembly line to your Polo. I'm still a wee bit "worried" though because no doubt the tightening machine is likely to be pretty much identical to the one used on yours. I'm hoping this overtightening problem will be a one off involving a malfunction or wrongly set up parameter on the particular machine used on your car? doesn't address the water retention problem around these bolts though so I'm still going to have a very careful look next time I'm under there.
 

RUM4MO

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Yes, your car will have been built in Europe (Spain), my wife's Polo was built in a RHD country that probably pays lower wages than Spain, ie South Africa.

I'll leave having a good look into where/why water gets in until we have been down South, final fitted the new battery to my 2011 Audi S4 today, I've talked about doing that for too long, but now it has been done. The only annoying bit so far is that the old battery when out of the car tests as "Good 12.9V 870A CCA EN" the new one tested 975A CCA EN out of the car and "Good 12.4V 900A CCA EN" when in the car, after running VCDS to examine that old batteries final stats, re-code the new battery and check the new battery's stats, that final check was mainly a waste of time as most of the stats are still showing the old battery's values - which makes sense. I'll need to swop its Winter wheels/tyres over to Summer wheels/tyres and go for a run and check these stats again before fitting its OBD2 port lock back on.
 
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RUM4MO

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There does remain one possibility for these 2 front subframe bolts being over stretched, I handed that car back into Western Volkswagen at the Fort when it was 2 years old and requested that they sort out suspension bush movement noises, maybe they, in either their incompetence or VW directed "fixing route" checked the "tightness" of the front 2 subframe securing bolts, and added in a good bit extra for luck, that should be an outside possibility for a proper VW main dealer workshop - but stranger things have probably happened!
 
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Crossthreaded

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There does remain one possibility for these 2 front subframe bolts being over stretched, I handed that car back into Western Volkswagen at the Fort when it was 2 years old and requested that they sort out suspension bush movement noises, maybe they, in either their incompetence or VW directed "fixing route" checked the "tightness" of the front 2 subframe securing bolts, and added in a good bit extra for luck, that should be an outside possibility for a proper VW main dealer workshop - but stranger things have probably happened!
Certainly an "interesting" thought RUM. As you say, stranger things have happened.
 

Crossthreaded

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Just an interesting wee addition to the knowledge base above regarding these subframe bolts.

Yesterday I followed my younger boy down to his local garage - we were out in Midlothian at their house looking after grandchildren - to drop off his car and give him a lift back to work. He was to get a new windscreen washer pump fitted and it's not an easy one to get at so I was very glad he hadn't asked me to do it! They - manufacturers - are finding ever increasingly difficult to get at places to put washer bottle reservoirs these days aren't they? Only to be outdone by the brilliant idea that on some cars you now need to remove the front bumper to replace a headlight bulb! I'm getting on very well with this wee garage and when we got there they weren't quite ready to start work on his car so it was parked up just outside the workshop. For some time I've had a spare N/S door mirror for it in my boot complete with the necessary tools to fit it so I asked if they minded if I fitted that before they took the car into the shop. Luckily my boy is self employed so can manage his own day and didn't mind waiting.

Anyway, They were happy enough for me to do that and the removal of the old mirror, which was slowed down by a torx type screw which rounded off, went quite well (steel screw in an Ally casting!) - I just hate all these modern fixing systems. what's wrong with a good old hex or slot headed screw? and the new mirror went on easily enough after I cut a slot across the head of the now ruined torx screw. Probably took about 15 minutes total. The chap who was going to be doing the pump came out to see what I was doing and we got chatting. Somehow the subject of doing Astra Clutches came up - my boy's car is an Astra - and I've never done one of the "newer" ones where the subframe has to be dropped. He then went on to tell me how you can get away with just dropping one side of the subframe and pulling the box back without dropping it right out. All very interesting stuff for a "grease Monkey" like me. I then mentioned your rusty subframe bolts RUM and he said he'd not yet come across that on a Polo or Ibiza, but he wasn't actively looking for them of course as the subframe doesn't need to be dropped on ours to do a clutch, however he had run into exactly the same problem on a Volvo recently where the subframe bolt/s were so badly corroded they had to renew them! His opinion if that a lot of the blame is to be laid at the door of the large washer which sits under the head of the upward facing subframe bolt which turns the fixing hole in the subframe into a very effective well for retaining the water. He wonders why the washers are not either slotted or drilled to allow the water to drain away.

So it looks like this is not a problem restricted only to our Polo/Ibiza models.
 
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