UK-POLOS.NET - THE VW Polo Forum

Just a "heads up", I found a rusty bolt head on the garage floor today, near where the front near side of my wife's August 2015 VW Polo 1.2TSI 38K miles rests in the garage.
As it looked very much like a front subframe or support frame fixing bolt, I drove the car up onto ramps and sure enough the near side near the front of the front subframe had an empty hole where a bolt head should be, the bolt that is near the ARB mounting clamp - road spray and/or salty winter water seems to have got in from above and got contained down at the head of that bolt leading to it corroding to the extent that it lost strength and failed.

Fixing this looks to be a bit tricky, so I'll be leaving it to my local VW Group Indie to sort out either by tacking a bolt or nut to the end of that sheared bolt or dropping the support frame, in which case a 4 wheel realignment will be required.

Did the bolt fall out or did it just lose its head?

It lost its head, salty water seems to be able to "well up" further up the front subframe and so keeps that area around the bolt "neck" wetted with water and salty water, so ending up in that situation is always a possibility I think.

weld a nut and unbolt

Blimey that's a slightly odd one. At least you had the good fortune for it to fall off in the garage, so noticed it. What sort of condition do the remaining bolts look like? If it's a subframe drop to get the failed one out I'd replace the lot with new.(would be surprised if that what is recommended anyway) Not sure if they are stretch versions or normal??

wolfie wrote: Fri Apr 15, 2022 7:21 pm Blimey that's a slightly odd one. At least you had the good fortune for it to fall off in the garage, so noticed it. What sort of condition do the remaining bolts look like? If it's a subframe drop to get the failed one out I'd replace the lot with new.(would be surprised if that what is recommended anyway) Not sure if they are stretch versions or normal??

I've ordered up a full set of bolts for the subframe, so they should arrive probably Wednesday/Thursday seeing as this is Easter weekend.

I don't know how long it would take for the subframe to start to rattle/knock as that bolt looks like it weakened and finally failed a long time ago, as it was only probably the bolt's collared head being tighten up against the newly painted new subframe in the South African factory that allowed, with some time, for that bolt head to bond to the painted surface of the subframe, and so when that bolt finally finished off shearing, it was retained for some time still bonded to the surface of the subframe.

The way things looks, it seems like that the bolt head with its collared head effectively seals the over sized hole that it passes through in the subframe, as there is a continuous shiny area all round the collar of that bolt head, inside that shiny rust free zone there is heavy corrosion, outside that shiny rust free zone there is moderate corrosion. So at the area of that bolt where the head meets the shank, I think that there has been an almost continuous depth of water/salty water "bath"!

Edit:- we as a family have run from new, a 2002 VW Polo 1.4 for 13 years and 105K miles, with the subframe adjusted by a main dealer and a VW Group Indie twice during its 5th and 6th years, and a late 2009 SEAT Ibiza 1,4 SC for 10 years roughly 65K miles with no subframe adjustment being done, and neither of them, as far as I know ended up losing the head of any of its subframe bolts, so yes a bit strange - but I'm lucky in that sort of way!!

RUM4MO,

I can't think, for the life of me, what 'ARB' stands for right now, but from your general description of the issue I'll go and look through my EasyManual drawings to see if I can identify the bolt(s) in question, as in all probability it'll be the same arrangement on my Polo. That's to say, I'll want to avoid the same problem ultimately.

Into what exactly does the bolt screw? (The bolt itself just passes through a hole in the subframe, right?). And is the mating thread - in whatever - still good? Was it possible to see? Is this a part of the front subframe that's a box section, or is it instead on a flat, plain spot on the front subframe?

I must say that, almost from Day One of ownership of my Polo (and other cars I've had before that) I've always treated any normally tricky-to-get-to parts of the subframes on the vehicle with a dose of Waxoyl, spraying especially into crevices and through holes in box sections (but carefully avoiding any box sections that might carry wiring looms). Although the VW factory will have already treated those areas, they're not always as fully done by the factory as might be desirable. Rainwater can sometimes still find its way in and although holes are deliberately left in the subframe box sections for drainage, water/moisture can still lurk around inside, ultimately causing corrosion. So, an extra bit of waxoyling here and there tends to be worthwhile.

veteran wrote: Sat Apr 16, 2022 11:18 am RUM4MO,

I can't think, for the life of me, what 'ARB' stands for right now,

Pretty sure RUM4MO, is referring to the Anti Roll Bar... AKA Sway Bar.

wolfie wrote: Sat Apr 16, 2022 11:55 am

veteran wrote: Sat Apr 16, 2022 11:18 am RUM4MO,

I can't think, for the life of me, what 'ARB' stands for right now,

Pretty sure RUM4MO, is referring to the Anti Roll Bar... AKA Sway Bar.

You are correct.

Veteran, I have yet to give this area of the car a full examination, so far all I've confirmed is where that bolt head came from, and checked the heads of all the other subframe to body fixings, I think that there is only 1 other same size and area as the one that failed, there are also 2 elsewhere and 2 M10X35 bolts that maybe connect 2 flanges to the subframe and 4 M8X20 bolts that secure the other ends of these flanges to the body.

The M12X1.5X75 bolt that failed has a washer built into its head and passes through an over sized hole on the subframe (over sized to allow for moving the subframe around), then maybe through another oversized hole on the over face of the subframe and then bolting into, I'm guessing, a threaded plate that is welded to the car body.

So, waxoyl'ng I don't think would have stopped this happening unless you were very aware of how this area of the car was constructed and so flood that area included this "sump/box" that gets formed by this bolt head plugging the lower face of that hole and so stop any water "welling up" in the bottom of that over sized bolt hole.

I've now had a look at the exploded diagrams of the front subframe and suspension parts in my EasyManual and can understand now why I was so perplexed by your account of this. Whereas I thought you were describing something right at the very front of the vehicle (but just to the side), it transpires that you were talking about the anti-rollbar/droplink position much further back, or at least it seems so. There appear to be a number of long, large bolts used in that vicinity; the main subframe has several.

veteran wrote: Sat Apr 16, 2022 9:18 pm I've now had a look at the exploded diagrams of the front subframe and suspension parts in my EasyManual and can understand now why I was so perplexed by your account of this. Whereas I thought you were describing something right at the very front of the vehicle (but just to the side), it transpires that you were talking about the anti-rollbar/droplink position much further back, or at least it seems so. There appear to be a number of long, large bolts used in that vicinity; the main subframe has several.

I'll need to take up the challenge of finding where that section is in my EasyManual!