Inner sill replacement S2 Coupe

[nthomas1]

Can anybody advise me on inner sill replacement on my Series 2 coupe?  I had no success with my request for advice on rear valance replacement - posted recently. Maybe my questions are not very well worded but I'm new to the business of re-building (and I think my wife thinks it's a daft thing to be learning in my late 60s!).

Anyway, here goes. The outer sills on my car seem sound, and the floor adjacent to and under the sills seems sound on both sides of the car. However, the inner sills have rust on the top surface, especially towards the front of the car. It may be that water has leaked into the car and settled under the carpet along the top of the sills. I see that full inner sills, and front sections can be bought re-manufactured. Question: can the old inner sills be cut out and new ones welded in from inside the car, without removing the outer sills?  I would not do the welding myself, but could probably cut the old sills ou

Any advice or pointers would be gratefully received.

[the.cern]

.......... "(and I think my wife thinks it's a daft thing to be learning in my late 60s!)."

It is never too late to start learning such vital skills ..... just enjoy it all!!!

                          Andy (dob 26/11/1946)

[frankxhv773t]

I don't have Fulvia expertise but if the rot is all above the level of the floor I see no reason why you can't let in sections where needed. I have seen similar repairs many times. Workshop manuals with a body section often have a cross section diagram through the sill so you can tell where the various layers intersect.

Also, if you are up for it then late sixties seems a perfectly reasonable age to give it a go.

[lancialulu]

A  few photos to help us understand???

The sill is a critical structural component so I would not cutting it about without understanding the integrity of the remaining sill structure. Indeed if you take off the outer sill you will have a very weak car. A common practice (as in my HF restoration) is to fit an inner steel membrane between the inner and outer to give added strength. It works!

[nthomas1]

That's an interesting option. Where was the membrane placed relative to the inner sill walls? Did it run parallel to the vertical inner wall of the inner sill, and how was it secured in place?

[nthomas1]

Tim, I just noticed your comment about providing photographs to help people understand what I'm describing. I'm away from home at the moment and then heading to Le Mans but will post pictures on my return. In the meantime, do you have any idea where I could find a cross-sectional diagram of the sill structure as suggested by Frank? That would help me understand how the inner and outer sills and the floor panels come together. I've closely studied all the rebuild blogs that I can find (by forum members, and swadeology, retrorides, rosso corsa etc) and while they show informative pictures of floor and sill replacement it is difficult to understand exactly how inner and outer sill and floor panels meet.

[stanley sweet]

Although not a direct answer to your question, it may give you something to ponder. Back in about 1996 I had to have sills replaced (inner, outer etc). Like Tim, I was given the option of a full length inner membrane. Apparently this is similar (or the same) as those fitted to works rally cars. It really stiffens everything up and adds a lot of strength. As I said, not the answer you were looking for but if you start cutting and discover you might have to go in further than you thought, it might be worth bearing in mind.

[Scott]

Hi Norm

My analogy for the inner and outer sills would be a match box. Nice and stiff with the inner box in-situ with the outer box. Remove the inner box and that outer box becomes very flimsy. Transfer this analogy to your Fulvia and you're in danger of warping something if you were just to hack great swathes of the inner sill out.

For me any decision would be based on the extent of the rust you're talking about. On reading your initial question it sounds like it might even be relatively superficial rust. Those inner sills are pretty chunky and if it was water ingress causing a damp carpet that rested in this area I would expect the floor to give out before the sill. And yet you say the floors are sound.

If after double checking you therefore find that it is surface rust then some work with a circular wire brush in an electric drill would be good. If you get back to shiny metal quickly and a vigorous whack with a screwdriver doesn't penetrate the metal I'd question why you'd want to embark on sill replacement. In this case remove all rust and treat with a good quality paint - I'm a big fan of POR-15.

If on the other hand there is a clear hole in the sill then, again, let's assess the size of it. Take a few inches of metal out of that inner sill to weld in a fix and you'll be fine; a few feet is a different story. Let's assess on the forum from my restoration experience and others what the scale of the situation is.

The membrane enhancement is a good one. With my matchbox analogy that's like gluing extra card between the inner and outer boxes; now it's super stiff. However this would normally only be done if you were having to replace the outer sill and did this at the same time and you thought this enhancement necessary.

Long story short I think we need to assess what the rust damage is to your sills before you potentially embark on unnecessary or OTT work. I'll be interested in seeing your photos when you get a chance to post them.

Regards,
Scott.

[nthomas1]

Thanks Scott - that analogy is very helpful.  I decided to return home prior to the Le Mans trip so can now provide some pictures.
The first shot shows the main problem area at the front end of the left hand inner sill.  The second shot shows a further rusted-through area a bit further back.   The third shot shows the sill towards the rear.  It looks quite sound - although there's evidence of prior rust treatment just inside the flange - but no rust showing through.  I was planning to cut square sections out where the two rusted-through areas are in readiness for having plates welded in, if the forum experts think that makes sense.  I thought that cutting out holes would also facilitate inspecting inside the sills to see what the condition is like there.   

The fourth shot shows the floorpan adjacent to the sill after some preliminary wire-brushing.  It is worse than I had thought before fully removing the glued-down carpet, but is sound over most of its area. Several areas where rust has broken through are visible.  Would it make sense to have a rectangular section welded in, or would I be better to replace the entire front left floor section?

[frankxhv773t]

That looks an interesting place to have a hole. I would have expected water to seep down into the foot well and cause rot there.

Depending on how big a job you want to do, you could buy the appropriate sill section off e-bay and cut sections to let in where the holes are. I would think that so long as the outer sill is well supported (say using a wooden beam with an axle stand at each end) then repair patches could be welded in one by one.

[lancialulu]

To me looking at this there is a lot more rust than meets the eye (sorry to say). The test is to get a zip wire on an angle grinder with suitable protective eye hand and body protection. what looks like brown metal will turn into metal filegris. the only way to stop rust returning is to cut it out in the first place. Depending on funds gear up to replace the floors inner and outer sills then you will have a sound car to drive for decades.

I thought I had a crosssection showing the middle membrane but cant lay my hands on it. Any one else help?

[chriswgawne]

Ever since his post started, I have been worrying about the rear subframe mounts as the rusty position described seemed a slightly odd one being inside the car on top of the sill section.
Back in the day, even with Dinitrol rust proofing when bought new, we owned Fulvias which needed major repairs in these areas due to corrosion at 10 years old........and now they are > 40 years old!
I think you have no choice but to fully investigate this area and the sills on both sides of the car even if it appears that repairs have already been done in the past.
The good news is that good quality repair sections are readily available.
Chris

[Caracad]

Norm,
I would be a bit more up beat than Tim. Looks like you basically have a structurally sound car. Serious rust starts inside the box sections and doesn't make an appearance until the car is well and truly rusted out.
The corrosion on you car comes from being damp under the carpets for many years.
I would just do local repairs, where there are holes. There is no reason why the surface rust cannot be treated and painted over.
Replacing floors and sills would be a major carve up.
If you can get a look inside the sill box sections to see if there is any corrosion inside. A torch in through one of the access holes or better still hire or buy one of those inspection cameras. Useful for all sorts of things.
If it's rust free in there I would be even less happy with cutting it all out.

[frankxhv773t]

I am with Caracad. It all depends on how major a job you are prepared to do. It looks to me like you have already had a good go at it with a wire brush in a drill or angle grinder. You can probably get a look up inside the sill through that hole using a small mirror on a stick. I would cut out the section in the top of the sill with a view to patching it and in doing so you will find out if the rust goes on and on. Also I generally grind down surface rust, treat with a rust converter that you can paint over, give it a couple of coats of rust proof primer then finish with a colour coat. Again, it all depends if you want to do a practical fix to keep you motoring or are aiming more at a full restoration.

[nthomas1]

Thanks to all who've commented so far.  As next step I'm going to cut out the badly rusted sections and then inspect inside the sill before deciding next course of action.  I'm learning that the rebuilding/renovation process is all about compromise.   If I were aiming at a concours/show car the decisions would all be simple (replace/renew), but I'm looking to get my car in excellent (not mint) condition with the intention of driving it a lot so will accept some compromise on appearance - both visible and hidden (in this case under the carpets) provided the solutions selected are safe.