GolfGTIforum.co.uk
Model specific boards => Golf mk2 => Topic started by: Waspy on 02 April 2015, 12:24
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Hey guys. My job over easter is to strip the now failing underseal from the underbody of the car and paint with top notch protective paint.
My question: In some of the box sections under the car there are holes, maybe an inch in diameter. What is their purpose? Just seems like a moisture trap. Can I blank them off?
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They lets the water out
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They lets the water out
If they were blocked, how would water get in? Genuine question haha
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Leaking door membrane or through the heater usually
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I mean the ones under the car, like this (excuse the rust, that's what I am busy sorting out) Or are those the ones we are all talking about? The ones that run parallel to the sills are all blanked off with rubber grommets, but these ones arnt
(http://i1104.photobucket.com/albums/h338/jojomojoe/B919A932-4258-41A1-AD46-C0F69CC35BB0.jpg)
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A body shell is constructed using pressed panels that are spot welded, and at various points MIG welded, this means that right from the start of production, the bare steel must have a passive coating, that allows an electrical current to pass through it, but at the same time, repels moisture, so generally, an oil based coating was applied by the steel manufacturer.
Once the body shell was fully constructed, it would need cleaning thoroughly of this coating, this was done by submerging the shell into huge cleansing tanks, and being completely submerged, holes are needed at every point on the shell to allow fluids to flood into inaccessible areas/box sections, and also to allow to drain properly.
The shell would then go on to be electro primer dipped, prior to painting, evidence of this can still be found on any body shell, by looking inside a closed box section, and finding that its coated with primer.
Holes that stop the elements entering the vehicle are then plugged with either metal or plastic grommets, the underside of the shell is then coated with thick rubberised sealer, and then off to be painted
So the holes are a very important part of the construction process, without them you car would have rusted away years ago!
Thom
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Wow! Knowledge bomb there Thom! Haha thanks! So, they shouldn't/don't need/no benefit to bunging them too?
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Yep, very interesting read that; thanks Thom. :smiley:
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Wow! Knowledge bomb there Thom! Haha thanks! So, they shouldn't/don't need/no benefit to bunging them too?
No, don't block them off, air circulation is better than no air circulation! You can however give the box sections a good dose of Waxoyl, but only after any welding jobs have been carried out, as the Waxoyl stays very flammable for its life.
Thom
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Wow! Knowledge bomb there Thom! Haha thanks! So, they shouldn't/don't need/no benefit to bunging them too?
No, don't block them off, air circulation is better than no air circulation! You can however give the box sections a good dose of Waxoyl, but only after any welding jobs have been carried out, as the Waxoyl stays very flammable for its life.
Thom
Brilliant, thanks Thom!
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I always thought them holes were something to do with a body re-alignment jig. I think vw would have wax injected all the box and sill sections. I know when I was welding a patch on the section just ahead of the rear axle mounting plate on my mk2 the darn thing kept catching fire and there was wax dripping out to. but I suppose a bit more wax wouldn't hurt :smiley:
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I always thought them holes were something to do with a body re-alignment jig. I think vw would have wax injected all the box and sill sections. I know when I was welding a patch on the section just ahead of the rear axle mounting plate on my mk2 the darn thing kept catching fire and there was wax dripping out to. but I suppose a bit more wax wouldn't hurt :smiley:
Some of the holes on the underside are datum points for body alignment , they tend to be located on the chassis legs, and be approx. 12mm in diameter,
VW heavily waxed lower box sections of the body shell, which did do a pretty good job up to a point lol.
Thom
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Yeah where wax has survived, there is a lot of it! Where it has failed, there is quite a bit of rust... Haha