So I was about to install a new trailing arm kit when I ran into this lovely problem on the passenger side:



Now I know why she's crabbing to the right so bad. Not only is the trailing arm bent, but the rust has cause the bracket to completely separate at the front-most edge.

So time for some welding. My question is - which panel does this mount to? I can't tell if it's simply the rear passenger floor pan or not. Any ideas? Would I simply need to custom fit something or is this a panel I could buy somewhere?

Couple more angles:

That is a nasty looking bit of car cancer. I'm guessing it sits at the intersection of at least 2 or 3 different pieces of uni-body sheet metal. If it were me, I'd start by grinding, wire brushing, sanding around the area until I got to solid steel all the way around. From there I would decide if I wanted to replace all the steel pieces involved or fabricate something custom to tie back into the framework. It seems like some other folks on the forum have done this repair, perhaps they will weigh in.
Kirk

Time to remove the back seat and carpeting in the rear foot wells to fully vet things out. You really have to do the full forensics here and not just go on someones guess from one sided pics.

Inspect from both sides and please post pics of the results.

Have a look at this thread here, there is likely useful info regarding that area:

http://www.fiatspider.com/f15/viewtopic ... rossmember

One of the posters in that thread has a blog where he outlines extensive rust repair that he did. The trailing arm mounting area was one of the issues

I just patched this on my car. I had to cut
Out the rear crossmember on the passenger side to catch all the rust - good thing I did because the crossmember was terrible also. It's my belief that this crossmember is a vessel for water and once it finds its way in it rusts these areas from the inside out. Drill out the spot welds to remove the crossmember. The holes you create doing this will be crucial for re-aligning the crossmember. I think its pretty forgiving however - the holes in the sheet metal around the bolts that attach the trailing arm bracket are rather generous.

Here's pics of the inside. It's not as bad as I anticipated. The rear crossmember looks okay, and despite some surface rust on the right side of the pic, most of the floor pan is in good shape. The rust only goes right up to the wall so I don't think I'll have to patch that. The source of the rust was obvious though - it's right underneath the rear window where the convertible top is supposed to meet, but the velcro seam is broken. Water must have got in at some point and pooled.

The one thing I noticed which I'm curious about is that it seems that there are two layers of sheet metal. One inside and one outside. Is that accurate or did the metal just become separated?

You need to pull the back seat and continue checking the cross members condition under the seat.

That area is made up of several layers...

You have the floor panel which angles up under the rear seat crossmember.
This is where the trailing arm bracket fastens under the car

You have the rear seat crossmember spot welded in

You have a reinforcement plate welded to the front of the crossmember, you can see it in your photo rotted at the floor panel.

Here are some pictures of mine taken down to clean bare metal:

Crossmember:



Reinforcement plate:

Frankd1 wrote:That area is made up of several layers...

You have the floor panel which angles up under the rear seat crossmember.
This is where the trailing arm bracket fastens under the car

You have the rear seat crossmember spot welded in

You have a reinforcement plate welded to the front of the crossmember, you can see it in your photo rotted at the floor panel.

Here are some pictures of mine taken down to clean bare metal:

That's extremely helpful. Thanks!

I think I can see the extent of what I need to do now. You wouldn't happen to have a shot from underneath, where the trailing arm bracket is mounted, would you?

As diesel mentioned, pull the rear seat and carpets and check.

I'd want to know what's going on under that crossmember.....I would scrape the undercoating from underneath and look at the metal. If it's rotting from the inside out you will see brown rust from under the car as well.

If it were me, I'd consider drilling the spot welds and pulling the crossmember and repair as needed

Check out miscuglio blog, look at April of 2015. He tackles this area:

http://www.miscuglio777881.com/2014/04/rust.html

I will be home in a couple of days and I can take a picture and post then if nobody has already.

Basically the arm is bolted to its bracket, the bracket is then held by four studs which pass through from the inside of the car to the underside.

If you get underneath and scrape away the undercoating and dirt you'll have a better view

You definitely want to remove the rear cross member to ensure this is area is structurally sound. the bottom flange of your cross member has rusted away adjacent to the bent plate that the bolts for the trailing arm run through. Also remember to prevent this from spreading you need to remove all rust - or at least 'encapsulate' it.

The job has taken me two weekends to cut out, fabricate and reinstall the patched cross member and floor areas. I had zero welding experience so i took a class. If I can do it, you can do it too.

pwilliam wrote:You definitely want to remove the rear cross member to ensure this is area is structurally sound. the bottom flange of your cross member has rusted away adjacent to the bent plate that the bolts for the trailing arm run through. Also remember to prevent this from spreading you need to remove all rust - or at least 'encapsulate' it.

The job has taken me two weekends to cut out, fabricate and reinstall the patched cross member and floor areas. I had zero welding experience so i took a class. If I can do it, you can do it too.

Yeah, my welding experience is limited as well. Grandpa taught me a few tricks when I was 15 years old. I should probably practice a little first!

I had to remove the rear crossmember to repair the lower trailing arm mounts on my spider. The rust was not visible from under the car until the undercoating was scrapped away.





The repair panel was made from 16 gauge and I ended up making one for the left side also then replacing both floors with 16 gauge panels.