147 floor rot - why did Alfa do this? - Alfa Romeo Forum
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(Post Link) post #1 of 30 Old 04-07-16 Thread Starter
Status: 159 2.4 20007 plate 19,500 DPF/EGR by Adie (AHM)
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147 floor rot - why did Alfa do this?

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/clar...d-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

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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(Post Link) post #3 of 30 Old 05-07-16 Thread Starter
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Damn, there are ones at the front as well!

I hadn't looked for the same thing there.
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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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(Post Link) post #5 of 30 Old 06-07-16 Thread Starter
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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.
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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...
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(Post Link) post #7 of 30 Old 07-07-16 Thread Starter
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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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(Post Link) post #10 of 30 Old 08-07-16 Thread Starter
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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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Sprint - 33 - Sprint - 33 - 155 - GTV - GTV - 156 - GT ...gone German for now though.
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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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Alfaseltzer and Pud237 what did you use to remove the bitumen. They are very clean floors.
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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.

You will never be cool driving a Vauxhall, especially if it catches fire.
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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?

Last edited by mj2k; 25-09-16 at 20:34.
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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.
Ah, that explains it then, that's the old Alfa Sud factory

Still doesn't explain why the Punto has the same odd drainholes though, that was built at a completely different factory.
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Alfaseltzer and Pud237 what did you use to remove the bitumen. They are very clean floors.
A small hammer just breaks it off a treat, a chisel helps for the more stubborn bits. Doesn't take long to get it all off. Easier to do on a cold day as the bitumen is more brittle then.
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As mentioned above, the drain holes are there to let all the phosphate or whatever pour out after the bare bodyshell has been dipped in the big tanks at the factory. Speaking of Pomigliano d'Arco my '82 sud sprint was built there and suds just had the one drain hole in the centre of each footwell. about 50mm dia. These were then filled with a pressed metal disc which was glued in place. On my sprint 3 of the 4 discs were missing (or so rotten they might as well have not been there) when I bought the car, and in the intervening 20 years I've managed to replace only one of them. Must get around to doing the other 2... Luckily, the floorpans themselves are still solid and have not needed welding at 34 years and counting.
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As mentioned above, the drain holes are there to let all the phosphate or whatever pour out after the bare bodyshell has been dipped in the big tanks at the factory. Speaking of Pomigliano d'Arco my '82 sud sprint was built there and suds just had the one drain hole in the centre of each footwell. about 50mm dia. These were then filled with a pressed metal disc which was glued in place. On my sprint 3 of the 4 discs were missing (or so rotten they might as well have not been there) when I bought the car, and in the intervening 20 years I've managed to replace only one of them. Must get around to doing the other 2... Luckily, the floorpans themselves are still solid and have not needed welding at 34 years and counting.
Yeah, those pressed metal bungs are (were?) the standard way of doing the job, and I remember the fix for the Leyland 'swimming pool in the passenger footwell' syndrome was to lever them out so the inevitable leaks had somewhere to drain to

Maybe times have moved on and having stupid little channels has replaced the more traditional bungs, but I still think it's very odd only two car ranges seem to have that problem, esp as they're (afaik) based on different floorpans and made in different factories.

Quality control has been drastically improved in Sud of late (I'm guessing yours must have been one of the rare properly-made ones), possibly too late given the current state of Italy's economy, but I wish they'd got the industrial problems sorted sooner - they were tasked with making some of the most interesting cars of modern times...
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A few years back, say the mid 1990's to the mid 2000's rust proofing on most cars was very good. Manufacturers were selling mainstream cars with 10 or even 12 year anti perforation warranties.

That was when people were used to cars falling apart after 5 years and 80,000 miles.

Now people assume that cars will last longer, so manufacturers have been cuttting costs in the corrosion resistance department. For example Vauxhall has cut it's anti-perforation warranty back to 6 years from 12.

The end result is that cars rust more and don't last as long. This makes them both cheaper to make, and as they don't last as long they sell more new ones.

I really hated my Mk4 Golf in many ways, but in terms of rust resistance it was leagues ahead of most other cars I have owned.
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