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Discussion Starter #1
Well last weekend I put all new brakes on my son's 2002 2.0 147. Whilst doing so I spotted that some of the underseal didn't look too great around the rear of the floor pan. You can guess the rest as this weekend I investigated and spent most of Saturday and Sunday welding new plates into the rear floor on both sides each plate about 16" x 9" plus a couple of smaller patches.

So can anyone tell me why Alfa put those silly half moon slots in the rear of the floor pan that seem to be the starting point for all the rust. Every one of these slots was its own rust pocket and one of them ended up being a 4" diameter hole.

The frightening thing is that every year I walk under the car with the MOT tester and it had always looked reasonably good. It was only the slightly flaky under seal that I wanted to fix that eventually led me to discover this very bad rust. A garage repair would have been uneconomical and made the car worth nothing more than scrap or parts.

On a plus point I did buy one of these and having always used a conventional mask this is a revelation making welding so much easier:-
https://www.machinemart.co.uk/p/clarke-gwh1-grindingarc-activated-solar-power/

Anyway back to the original question; why did Alfa put these slots in the floor? Drain holes, no I don't think so as they are almost completely covered in underseal. It just seems crazy.
 

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I think they were meant to be drain holes but considering they got covered in a sticky thick tar mat any fluids spilt would never get out. didnt it say in the bible " The Italians work in mysterious ways " oh wait no that was the Lord but should have been them :biglaugh:

BTW i have just done mine as well but once done its done . but as advice re-seal the front semi circle ones as well
 

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Damn, there are ones at the front as well!

I hadn't looked for the same thing there.
Front ones are rarely anywhere near as bad as the rear ones.

Even 145/146/155/GTV etc have these drain flaps but most of those cars have them pushed shut and seam-sealed from the factory so even after all this time, they aren't the places where the rust starts.

I've welded up 06 plate GTs now with rusty flaps, it is shocking in this day and age.
 

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Discussion Starter #5
The bit I found most concerning was that the rust was quite extensive but completely hidden. It is now my opinion that the ONLY way to check when buying a second hand one of these is by having a darned good poke with a screw driver but i don't suppose many sellers will permit that.

I do honestly suggest that without doing that you are effectively buying blind. The rust really was invisible and didn't even have the normal look of bulging beneath the under seal.
 

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The bit I found most concerning was that the rust was quite extensive but completely hidden.
....
The rust really was invisible and didn't even have the normal look of bulging beneath the under seal.
Sadly I think that is quite common on these (ie 156/147/GT).

MOT Testers are only permitted a very limited amount of poking/knocking too. So by the time it is noticed as an MOT failure, it will have spread quite a long way... :grumpy:
 

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Discussion Starter #7
Not blaming the MOT tester in any way.

I am a trained mechanic (though now only working on family cars) and have walked under the car with the tester on each of the last two MOTs and apart from what appeared to be minor peeling on the under seal it looked sound. Didn't even think it needed a poke to see what was happening.
 

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The bit I found most concerning was that the rust was quite extensive but completely hidden. It is now my opinion that the ONLY way to check when buying a second hand one of these is by having a darned good poke with a screw driver but i don't suppose many sellers will permit that.

I do honestly suggest that without doing that you are effectively buying blind. The rust really was invisible and didn't even have the normal look of bulging beneath the under seal.
Ignorance is bliss!
 

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I re-sealed mine about 18 months ago when I was under there sorting the exhaust .. and I did poke it in exactly the same place and it was OK .. so it doesn't take long ..

It must have been getting in somewhere else and still getting behind the original layer of sealant as I wasn't exactly stingy with the gloop ...
 

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Discussion Starter #10
The welded in plates and floor is now treated with "galvafroid", then anti-stonechip, then under seal.

Hopefully that will do the trick for a few years.
 

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Just had the same problems with rusty floor pan flaps. Pretty ridiculous to see this on a 10 year old car in this day and age. Doesn't seem to be helped by the fact the metal in the floor pan is like tin foil, seems incredibly thin stuff.

I came to the conclusion these flaps were simply put in to allow liquid to drain when the freshly welded bodyshell was dipped in vats of treatment prior to being painted. I suspect they should have been bent shut after treatment and sealed up with paint and underseal subsequently but poor Alfa QA meant it wasn't done properly.

They're certainly not there to allow drainage in normal use because Alfa stuck a lump of bitumen sound deadening on top of them which effectively blocks them anyway. Or at least it blocks some of them and not others depending on how well the bitumen was pressed into place, leaving you with a nice moisture trap. Pretty ropey bit of design all in all and not something I've seen on other cars ... I wonder why ?
 

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I came to the conclusion these flaps were simply put in to allow liquid to drain when the freshly welded bodyshell was dipped in vats of treatment prior to being painted. I suspect they should have been bent shut after treatment and sealed up with paint and underseal subsequently but poor Alfa QA meant it wasn't done properly.
You're absolutely right, the GTVs which use the same rear floor pans were fully sealed over at both the Arese (Alfa Romeo) factory and the Giorgio Canavese (Pininfarina) factory when they were built. Only the Alfa Romeo models built at Pomigliano d'Arco factory had them left unsealed.
 

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A quick snap of my ex-GT last week having failed the MOT due to these pesky flap things, my sills were looking ropey in places too and I briefly considered breaking the car before paying to have the welding done and selling up with a fresh ticket. (Not all holes are visible before people start shouting it shouldn't have failed btw)
Very disappointing as though not perfect there was no sign of this problem last year, I had some welding done on the sills but the floorpan looked solid enough...it seems the build quality of these cars was variable at best?
 

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Unfortunately underneath these stiffening plates is another source of rot (highlighted the plates on your photo)

They're only present on 04-plate onwards 156/147/GT. I think I might start removing them as a matter of course when doing floor repairs.
 

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Pics of the last one I did - with the stiffening plate removed you can see rust beginning to form around every spot-weld, with the floor below and the stiffening plate above you will not even notice this rust until it comes through the floor from above.
 

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My GTA had rusted in exactly the same place in exactly the same way, only a good poke with a screwdriver revealed the 2 inch diameter holes around each drain hole (with presumably more crustiness still hidden) but I bet it'd have passed it's MOT just fine if I hadn't started exploring for rust...

Wonder how many 147 / 156 / GT / GTA owners are still under the impression their rear floorpans are perfect when they've really turned into swiss cheese underneath the bitumen and underseal?
 

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Sadly I think most of the Alfa 156's which have died went because of tin worm.

My last one was a W reg, and was 9 years old when I bought it. Not only did it have really bad rust in the floorpan at the back it had holes on the inner sills, and bad rust inside the front inner wings.

My and my brother welded it up, but it was a long and arduous process.


I just hope the Giulietta isn't going to suffer the same fate. The underseal seems pretty thick, but that might mean that it is better at hiding nasties until they get really bad. :(
 

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Alfaseltzer and Pud237 what did you use to remove the bitumen. They are very clean floors.
I just levered it off with a flat screwdriver, much to my relief it broke apart into biscuit sized pieces and came off cleanly...both sides took about 15 mins all in.
 

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Just had the same problems with rusty floor pan flaps. Pretty ridiculous to see this on a 10 year old car in this day and age. Doesn't seem to be helped by the fact the metal in the floor pan is like tin foil, seems incredibly thin stuff.

I came to the conclusion these flaps were simply put in to allow liquid to drain when the freshly welded bodyshell was dipped in vats of treatment prior to being painted. I suspect they should have been bent shut after treatment and sealed up with paint and underseal subsequently but poor Alfa QA meant it wasn't done properly.

They're certainly not there to allow drainage in normal use because Alfa stuck a lump of bitumen sound deadening on top of them which effectively blocks them anyway. Or at least it blocks some of them and not others depending on how well the bitumen was pressed into place, leaving you with a nice moisture trap. Pretty ropey bit of design all in all and not something I've seen on other cars ... I wonder why ?
AFAIR the 147, 156, etc shared their platform (and therefore presumably floorpans) with the original Tipo, so I wonder if they had more use in that car, and remained as an appendix-like weakness in later cars?

Edit: I've been scanning the Tipo forum for rust, etc and though I found many interesting things (including hideous wheelarch rust and an Alfa V6 engined project!) there was no mention of floorpan rust at all...
Edit2: Looks like the Punto had exactly the same idiotic drain holes in the floorpan. What the...? That's a completely different platform isn't it?
 
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