A visit to the Polo underworld

[veteran]

As hinted at toward the end of my thread about removing the headlights and other front lighting assemblies, I put my 2017 6C Match Edition 1.2 up on ramps this morning and got underneath, to suss things out as regards the exterior of floorpan.

The box-section hole I'd talked about turned out not to be a hole at all. Instead, it was a small, deep depression in an expansive plastic covering that ran along just about the entire length of the middle section of the car's underside, either side of the exhaust pipe, as it were. That said, the large cover had, here and there, quite a number of holes and slits in it.

The cover is functional, just that; a cover that protects wires, cables, and plastic tubings that pass underneath the vehicle, from roughly the front to the back. So the fact that the cover had all kinds of holes and purpose-made slits in it did not affect, as far as I could tell, the basic weathertightness of the floorpan or would have had any appreciable effect on roadnoise. The cover doesn't form part of what I'd term a 'box-section'. I could see that underneath the cover, the usual floorpan underseal had been used. Although I spotted some installed blanking grommets just inboard of the sills, at their ends, I couldn't see any obviously-missing grommets.

One thing that didn't look quite right to me, however, was that this large cover had two 'tongues' near to its forward end (situated just forward of the left-to-right steel crossbrace) and these tongues looked as though they were designed to tuck in to the underbelly of the tunnel. But they'd both been left out, drooping down a bit. It doesn't look quite right, but perhaps this has been intentional, to allow the maximum airflow toward, and waterflow away from, the floorpan. On the other hand, these tongues, which each measure about 15cm x 15cm, will act as water scoops in the event that the car is ever driven through deep water, eg. through a ford, or just along a flooded road. The plastic wasn't totally rigid and I wondered if it'd be possible for me to retrospectively tuck them in, but I could see that various intricate fasteners would need to be undone in order to flex the tongues sufficiently to do that. So I left them as they were.

With the car reversed on to the ramps, I could take a look at the rear section of the underside. There, it was not a pretty sight. It appeared that someone on the production line had started to apply a pinkish-brown underseal to the boot underside (essentially, the exterior of the wheel-well) but had abandoned it some way through, leaving most of it untreated. Furthermore, something had clearly gone wrong with the applicator, with the result that a diluted residue of the pinkish underseal had got sprayed (that's to say, mis-sprayed) over virtually the whole of the rear underside - so, over the exhaust boxes and pipes, over the rear axle/subframe, over exposed parts of plastic fuel lines, exposed brake lines, the coilsprings, the dampers, and so forth. It'd all dried on as thousands of powdery, pink spots.

Now, I didn't want to take any remote chance of this residual stuff having any detrimental effects on any of the paintwork of those aforementioned components, either in the medium term or long term, so I spent half an hour or so with a rag, cleaning it all off. It now looks much better. It'd gone all over the part of the bumper that tucks under the rear of the car too. Actually there, I found a small, broken, plastic fastener, whose function was probably to stop the bumper vibrating against the underside. I've had to fix that temporarily with a standard rubber grommet.

Turning my attention to the rearward parts of the sills, it was obvious that the sills had been wax-treated internally. Although a couple of the bigger holes in and around the sills had been stoppered with blanking grommets, there was still one hole, about 1cm diam, on both sides, that'd been left unstoppered. These two holes were probably where the tubes for the wax had been fed in, while the car was on the production line. Again, whether these were intentionally left open is impossible to say, but certainly if you were to drive the car through 6 inches or so of water, quite a lot of water would get into the sills. This all begs the question as to whether it's best for sills and box-sections to always be left vented, or whether they should be fully stoppered. On my old Golf, I made sure that all such holes were plugged, and that car's bodywork is still fine after some 23 years! If anyone's got any special thoughts on this, I'm all ears.

As regards those pinkish spots or splashes of what I presume to have been dilute wheel-well underseal, I'd noticed a couple of weeks ago when I was underneath the car emptying out some excess engine oil, that a good deal of the front subframe had acquired these spots. At the time, I couldn't figure out what they were. At one point, I presumed they were just mud splashes. But of course now I know.

It rather looks as though, in hopefully an isolated instance, the standard of production-line workmanship had slipped, and that my Polo kinda ended up as a less-desirable B grade. I've nonetheless managed to clean 85% of the 'splashwork' off. Come the Spring, I'll get underneath again and treat the bare areas, and the subframes in particular, to some good old waxoyl.

Whether the VW dealer who acquired and sold me the car knew about the state of the underside is unknown. I have to say that I've always been quite cynical about car dealers and their so-called pre-delivery checks. I just don't think they do them at all thoroughly enough; I think they probably just glance at a few things under the bonnet, ensure the washer fluid's topped up, kick the tyres, and that's about it. The dealer probably assumes that if there's anything amiss underneath the car, the customer's never going to bother to look there, in any event.

But there's obviously a lesson here, not to assume that everything on handover is, in fact, 100% okay. Alright, you might say that, in this particular case, the degradation was primarily aesthetic. Certainly, topside, everything looked immaculate. Nevertheless, finding out what the true state of your vehicle is, both top and bottom, could have some longterm implications in terms of safety and longevity. My adage has always been, "know your car".

[joe6]

Interesting dialogue. I am a bit like you. First thing when I get the new car home is up on ramps/jack, wheels off, clean them and alloy seal them inside and out. Paint brake callipers if the car does not come with them already treated (like the GTI) as they stay much cleaner if painted. Check for any noticeable issues underside as the bodywork has already been checked for damage/uneven body panel joins before signing for the car. Not had any issues with my Polo but did notice that under the rear of the front plastic inner wing there is a gap that can accumulate mud. (Worth a quick hose down from time to time.) Muck can also get from here to the front car doors as the plastic panel sealing the rear of the front wing is not a good fit. Going to try a pair of short mudflaps to see if that helps.

[RUM4MO]

Well, I'd go further with respect to the long plastic side under covers, they really should be removed every 2 or 3 years and the mud/grit removed and something like WaxOyl applied where necessary and especially on the ribbed/threaded studs that the these covers retainers get fitted to, one thing though, these current versions of Polo/Ibiza/Fabia have all now got plastic retainers - back in 9N and probably 9N3 days, they had thin lightly galvanised plate retainers, and they rotted out, and in some cases the these side covers fell down and got ripped off if you did not examine them annually and replace retainers when necessary.

Edit:- also, I have checked yet, but back in the 9N and probably 9N3 days, the exhaust heat shields were retained using these lightly galvanised steel retainers - but the exhaust heat shields were aluminium, so it should not be a surprise to many technically competent people to hear that they aluminium heat shields ended up with holes in them above these steel retainers, and so they fell down over the retainers!

Another Edit:- yes, I see what you mean about these tongues, though they will force air under part of these covers, which works for me in the wild and wet North!

[SRGTD]

Very interesting and detailed.

With the car reversed on to the ramps, I could take a look at the rear section of the underside. There, it was not a pretty sight. It appeared that someone on the production line had started to apply a pinkish-brown underseal to the boot underside (essentially, the exterior of the wheel-well) but had abandoned it some way through, leaving most of it untreated. Furthermore, something had clearly gone wrong with the applicator, with the result that a diluted residue of the pinkish underseal had got sprayed (that's to say, mis-sprayed) over virtually the whole of the rear underside - so, over the exhaust boxes and pipes, over the rear axle/subframe, over exposed parts of plastic fuel lines, exposed brake lines, the coilsprings, the dampers, and so forth. It'd all dried on as thousands of powdery, pink spots.

I always thought that the underbody factory anti-corrosion process took place before any suspension / brake line / exhaust components were fitted to the car’s underbody. If so, then for whatever reason, the underseal overspray onto various components would appear to have happened after your car left the production line?

[veteran]

SRGTD,

I did wonder, at one point, whether all that pinkish-brown 'gunge' on some areas of the wheel-well and the colour-matching spray-spots over the subframes, the long plastic undercover, and many other components under the car had come from elsewhere, eg. perhaps the car having been driven along or through a muddy, unmetalled road. Perhaps some of these docksides have pinkish-brown clay soils and aren't as neat and tidy as we imagine? But, really, if you'd seen it - I've cleaned off almost all of it now - you'd had to have concluded that this had probably happened somewhere on the production line. The wheel-well - and we're talking here of course about its external appearance, underneath the car - has been left with only a small smattering here and there of underseal (oddly, this pinkish stuff) to protect it. Yes, it could have happened post-production, possibly even after it reached the UK, but I can only imagine some pretty outlandish scenarios.

[derkie54]

Mine looked like this when I collected it.

[derkie54]

Just found out what Photobucket are doing............what photo sharing sites do other members use ?

[SRGTD]

Just found out what Photobucket are doing............what photo sharing sites do other members use ?

I use Postimage; http://postimages.org

[derkie54]

Thanks SRGTD

[veteran]

Rum4mo and SRGTD,

Before this thread gets overtaken by something different, I thought I'd report further on the mystery underbody splashes.

I've explored this matter a little further. This time, it meant just kneeling by the rear bumper and peering underneath at the exterior of the spare-wheel-well with a torch.

Looking in the boot, at the wheel-well, the interior of the well has a number of large grommeted holes covered over with some black bituminous pads. Only one grommeted hole is left uncovered in this way, presumably so that water can, if necessary, be allowed to drain out of the well. The thin black bituminous pads might possibly serve as vibration dampeners, as well as seals to the outside. They're each not of regular shapes.

On the exterior of the wheel-well these same positions are covered with the aforementioned pinkish-brown (beige) material. Looking more closely, the pinkish areas are in fact oddly-shaped but quite well-defined pads that have clearly been applied at some stage during the car's manufacture. So, instead of the external pads being bituminous they appear to be made of something else. I've summised that they might be made of a material which has been deemed both fireproof and unlikely to become unbonded from the metal once applied. As I say, they're not of regular shapes but of very irregular ones. I'd say that about a third of the underside of the wheel-well is covered in these pinkish 'pads'. The uncovered areas of the well appear to have the usual grey-green Hammerite-like appearance.

My theory is that the pinkish pads - whatever their prime purpose - may be partially water-soluble and that, at some stage, there was some residue of them to the sides of the 'pads' (say, a paste). Possibly, what has then happened, somewhere between the production line in SA and me, is that someone or some thing has played a strong jet of water on to the underside of the car, including on to the wheel-well, and consequently some of the pads' residue became splashed all over the rear underside of the car, including over parts of the exhaust, brakes and suspension. I've cleaned off most of these dried-off splashes but even halfway down the underside of the car, where I can't quite get to at present, there are still prominent pink splashes showing, and even looking right up at the front of the car, there are a few pink splashes visible around the lower, back of the engine. So, it must have been a pretty powerful jet to have done that.

I don't think this is the way VW normally do things. Perhaps those pinkish pads hadn't been fully finished off at the factory? Perhaps the residue was meant to be removed in some other, more-controlled way? Perhaps the pink pads normally have some sort of hard, waterproof coating applied to them and that's missing on mine?

Have a look at the exterior of the wheel-wells on your cars, to see if you've got something similar there. As I say, you don't need to get under the car, just kneeling at the back and using a torch will suffice.

[joe6]

No pink pads (or pink elephants!) on mine on the underside of the spare-wheel-well. Just galvanised metal with the forward edge and sides of the well covered in underseal to prevent stone chips which is yellowish in colour. This underseal also covers any floor panel joints. There are three rubber/plastic 'grommets' on the underside of the well which presumably cover/fill the holes in the well - one has a tube protruding from it that I think must be the 'breather' tube for the battery. Wondered how they vented that! Not checked the inside of the well as in the GTI the battery is in the boot under the spare wheel.

[veteran]

That's interesting.

Maybe, come the Spring, I should apply a suitable underseal to the whole of the exterior of the wheel-well? But brush-on underseal (eg. Finnegan's) wouldn't seem appropriate, as in my experience it never dries to the required 'skin' (remains runny), and also it's the wrong colour. Most of the underseal on my Polo is grey.

I've also been wondering whether this is another one of those VW 'innovations'. That's to say, maybe they figured that any underseal of the normal kind put on to the wheel-well would be too near the exhaust system, so they've used something else instead.

[derkie54]

I have the same pink pads as you Veteran and I'll post a picture later.

[derkie54]

[RUM4MO]

Derkie54, as your car is a 5 door and not a GTI, I'm quite sure that your car, veteran's and mine are all built in South Africa - so should all share any/same regional "touches"!

Edit:- I've just had a look at my wife's August 2015 Polo 1.2TSI 110PS SEL 5 Door, and it is exactly the same as the picture above, I looked under my February 2011 Audi S4 and it has the same type of grommets but the complete wheel well has been heavily undersealed etc, I looked under the November 2009 Ibiza SC and it has different grommets - or they are inserted the other way round though I doubt that, and it has the light wax coating everywhere else on the wheel well.

I can't explain the "interesting" shapes that VW have left exposed when spraying that thicker sealant on.

Another Edit:- the rear box in that picture does not good too good - same as the rear box on wife's 2015 Polo, does not look like VW managed to add in much SS into that metal alloy that was used there, prepare for that outer skin splitting open in a few years, but remember that outer skin is just that so the inner box will not leak - yet. My wife's October 2002 Polo 1.4 16v 75PS managed to keep its original back box for the 13 years 105K miles we kept it for, so maybe these exhausts will last long enough.