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How to de-rust the rear floor pan?

6K views 20 replies 6 participants last post by  the beard 
G
#1 ·
My car (156 SW) requires de-rusting of the rear floor pan. The drain homes are becoming hole holes.

Now I've had a read, and have found a number of informative posts.

However, if anyone could shed some light on a last few Qs I'd appreciate it.

The rust start inside, so treatment should start inside.

Q1) how much of the interior/ carpet needs to be removed to get access to the rear footwell area without cutting the carpet? I assume rear seat backs, bench side trims and boot trims?

Q2) my plan is to wire brush/sand away any surface rust, then treat with a rust neutralising agent, then prime, the lots of stonechip. Anything wrong in that?

Q3) the underside, I'm not going to attempt that as I don't like working under cars, what do I need a bodyshop to do specifically to make this a non-repeating fix?

Thank you.
 
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#2 ·
carpet is one piece so it all needs to come out really..

on saloon lower rear bench door trims front seats all center console etc...

wire brush is ok with a proper rust removing agent. prime then paint internally and maybe a anti-rust treatment like dinitrol clear coat but stonechip is really only external. when i did mine i took the opportunity to spray all the internal box section with dinitrol

same as the inside i guess but depending on condition better to weld the floor flaps shut or cut out and weld holes up to make it permanent
 
G
#3 ·
Bugger. I hate moving carpets they never go back without a fight.

This is a good 4 days work to do properly. August holidays are now looking all full up.

What would be the ideal product package for the floor?

Any brands of rust treatment/paint etc that are know to hold firm under carpet long term?

I really don't want to do this twice.

On the holes, several of the flaps have fallen out already, as they offer drainage for any water in the car, I'm thinking they can stay.

Do any aftermarket one at flap valves exist to do the job?
 
#4 ·
yeah took me a few days to remove it all and reinstall when doing the stereo..

so made the decision to do rustproofing and soundproofing all in one..

most of the flaps are covered in thick bitumen soundproofing so i really cant see them working as drain holes on top of which is think felt and carpet which holds any water so not sure on there design purpose really..

used built hamber products on mine. rc800 remover then primer and paint. new soundproofing and a coat off built hamber Dynax S-50 Extreme Duty Anti-Corrosion Wax. all from opie oils

mine were all ok and just needed treatment to prevent rust.. but i would cut them out all weld up as I really dont think they have a positive role as once undersealed from below they are sealed and the edges rust out .. maybe just leave one but the car interior should be dry unless you have other issues
 
#10 ·
I'm convinced that it's the heavy, butyl type sound insulation that causes the problem. As it ages, it cracks. Moisture gets into the cracks but can't evaporate fast enough. My floors were welded, primed and painted with old fashioned chassis paint. Literally poured the paint on and spread it around. I used some of the butyl sound deadening pads but only in the centre of the panels. The rest of the underlay was replaced with breathable, heavy, hair type stuff.
 
#11 ·
Not sure. The thread I linked to shows a full strip down of an S-reg 156, which is in progress. I should really weigh the thing in, but welding is fun....

I don't think the internal tar is to blame - you need to remove it to fix the problems, but it is not root cause. It is waterproof, and in ours there was very little corrosion underneath it - except where the floor had been shaped by the tabs or the attachment to the sills.

The tabs are an obvious edge point in the underseal beneath the car - and this is classic Italian underseal that holds moisture and allows rust to track underneath. They used the same rubbish on Alfasuds.

The sill attachment appears to have no corrosion protection and is just a spotwelded edge that flexes due to the stresses on the floor - inevitably it corrodes.

What I do love about these cars is the large number of bungs to inject sealant though - and the abject lack of wax etc behind them. The designer thought about it, but was let down by the guys on the line.
 
#12 ·
I'm really glad I found this thread.....or perhaps not. I'll try and explain although I'm sure some will decide that there is no choice to make.

We have a 2005 Panda MJ with 95K on the clock and a 2001 156 2.0 Veloce with the Momo interior. With over 100,000 miles on the clock and suffering the slings and arrows of outrageous fortune, oh, alright then, numerous scrapes and scratches courtesy of Mrs. Beard, we're struggling on the horns of a dilemma.

We could chop in the Panda and take what we can get (not very much) for the 156 and then replace them both with two cars of about £5,000 each; we could hang on to the Panda for another year and spend £10K on a 156 replacement then spend something similar on a Panda replacement next year.

Or, spend around £8,000 to replace the 156, stick the old lady in a garage and then spend some money on fixing the rear floor which needed welding at the last MOT.

From this thread, and the other one attached to it, it seems like there's a lot of work and it's years since I worked on any cars so I have no interest in doing any of the welding myself. I'm quite prepared to have the essential work done then lock it away for a few months then have a bit more done, followed by a bit more and so on.

I also don't want to have to get bits welded up every year so I'm wondering if it's realistic to have a large section of floor replaced and if there's any real risk of the structure being weakened by removing and replacing large bits of floorpan.
 
#15 ·
Anything wrong with the Panda? If not, keep it. The Multijet engine is a good one and 95k isn't much. Thats one car sorted. As for the 156, either save it or scrap it, but you will probably need to do a bit of investigation first to determine just how bad it is. We've welded up plenty that any right-minded person would have sent to the scrap yard. We've put whole complete floors in, new sills etc. But unless the car is something special, I would limit your spending to reasonable amounts, as you could go and buy a much better 156 for not a whole lot of money. Mine, for example:

Used 2005 Alfa Romeo 156 JTD 16V VELOCE (150BHP) for sale in Cumbria | Pistonheads

Floor is pretty much factory fresh, I made sure of it before I bought it, and mechanically it is as good as they get :thumbs: But a Q2'd, coilover'd, remapped 2.4 10v has captured my heart, I do have a proper soft spot for them :D

(Off topic, but I can't believe out of 137,000 cars for sale on Pistonheads there are only 2 diesel 156s! Where have they all gone?!)
 
#13 ·
impossible to say without seeing the car.. if its just the problematic drain holes at the rear its common easy and cheap enough.
if you have a read of the other thread linked above and its slightly more terminal then maybe not.. though if done correctly and treated its as good or better than new so no worry's about it being weakened.

best way is to get a quote from a specialist to the extent of the work required and at least get it treated to stop further spread while its being stored. also at a specialist you will get a better quote of what else might be required
 
#16 ·
I think I'll take her to Alfie at Heath Road Garage in Sandbach and ask him what he thinks. I'd like to hang onto her, partly because it has the Momo interior and partly because later Alfas had FIAT and GM engines and it still looks damn good

There are two stages of rot - the drain tabs and the sides of the floor pan. Drain tabs is easy, as you can see from my thread, a 12 year old can weld it up. If you strip out the seats yourself, then it will be pretty cheap - £150 or so to do a decent job. Once it gets into the edges of the floor pan, then it becomes much harder, and if the sills are gone, then you are "beyond economical repair". Cutting out sections of the floorpan is not hard, I'll be producing a full guide in that thread!
I'm afraid my car body repair skills don't match up to those of a 12 year old, probably more in the range of a 7 year old. I also have an issue with remaining focused on something that'll take longer than an afternoon.

Anything wrong with the Panda? If not, keep it. The Multijet engine is a good one and 95k isn't much. Thats one car sorted. As for the 156, either save it or scrap it, but you will probably need to do a bit of investigation first to determine just how bad it is. We've welded up plenty that any right-minded person would have sent to the scrap yard. We've put whole complete floors in, new sills etc. But unless the car is something special, I would limit your spending to reasonable amounts, as you could go and buy a much better 156 for not a whole lot of money. Mine, for example:

Used 2005 Alfa Romeo 156 JTD 16V VELOCE (150BHP) for sale in Cumbria | Pistonheads

Floor is pretty much factory fresh, I made sure of it before I bought it, and mechanically it is as good as they get :thumbs: But a Q2'd, coilover'd, remapped 2.4 10v has captured my heart, I do have a proper soft spot for them :D

(Off topic, but I can't believe out of 137,000 cars for sale on Pistonheads there are only 2 diesel 156s! Where have they all gone?!)
Although I prefer the frontal treatment of the later 156, I also really like the 2.0 TS motor. It doesn't sound like other 4 cylinder engines and if she ends up being preserved (sort of) and not used on a daily basis the fuel consumption and high car tax doesn't really come into the equation.

Thanks all for your replies, I'll try and keep you posted.
 
#14 ·
There are two stages of rot - the drain tabs and the sides of the floor pan. Drain tabs is easy, as you can see from my thread, a 12 year old can weld it up. If you strip out the seats yourself, then it will be pretty cheap - £150 or so to do a decent job. Once it gets into the edges of the floor pan, then it becomes much harder, and if the sills are gone, then you are "beyond economical repair". Cutting out sections of the floorpan is not hard, I'll be producing a full guide in that thread!
 
#17 ·
I really like my 2.0 TS as well, although its mostly on loan to people these days it always brightens up my day when it comes back and I get to drive it home (not before chucking a litre of oil in it!). It is probably the perfect engine for twisty Cumbrian backroads as you can just hold it in 3rd and use all the revs.

The diesel is far too quick, both the 1.9 16v and the 2.4 10v, in those cars I spend more time on the brakes than on the throttle compared to the 2 litre TS.
 
#18 ·
How to de-rust a 156 floorpan

I took the 156 to Alfie at Heath Road Garage in Sandbach today and went into the pit to look at the floorpan. His verdict? Surprisingly good actually. We've decided to get it in and get rid of the underseal, get rid of any scabbiness and re-seal it. The sills also seem in good condition, possibly because they've been hidden by the skirts, but then again there may be some unseen corrosion lurking there.

After that there's a nasty stone chip above the screen, which is chipped and needs to be replaced anyway, and a scrape on the lower left rear side.

Then it's time for a cambelt service then various trim odds and sods such as door seals need replacing and possibly some suspension bushes. Actually that sounds quite a lot of work but we've decided to semi-retire her while all this is going on and some friends have an unused garage behind where they live.

In the meantime we're a couple of small steps from buying a 2011 or 2012 Giulietta TB Veloce to replace the old gal and allow her to live out the rest of her life in leisurely dignity.http://www.alfaowner.com/Forum/images/AlfaOwner_2015/icons/post_thumbsup.png
 
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