Rusty roof repair

[PranK]

So, I finally started digging at the bit of my roof that was cracking and bulging a bit. Well, it was just thick filler that was covering some pretty bad rust. I didn't find the edges, I was too bummed to keep going. 

There are a few holes as you can see. There was just so much filler but looks like no attempt under the filler to prime or use rust converter, just slapped filler on exposed rust. 

Anyway, I'm going to take the windshield out and find the edges. I'd love to fix this myself as I'm pretty sure it'll be expensive to get done properly. I was thinking I could just get a cut piece from another E39 and just weld it in place as it would be the right size and shape. 

Thoughts?

[PranK]

Some of the filler.

 

Also if I look under the top flap of metal it starts looking good quite close to the edge. I get the feeling it doesn't go much further.

[MBS206]

Hot tip, stop picking at shit. Live in bliss instead

 

From my recent experience in rust repairs, white it may seem to not go much further back, you'll still need to cut back a bit further. 

From what I can see there, the outer skin, and the inner is rusted too. From what I can see you've got the inner one which is all structural, and window likely affixes too.

 

If tag Murray Calavera here, but my phone won't let me tag him, he'd probably be able to give the best advise.

 

I do know, welding roof panels is a right pain in the bollocks! Very heavy to heat distort the roof and warp it all.

[Murray_Calavera]

All good, I'll tag myself in lol. 

1 hour ago, PranK said:

Thoughts?

What car are we looking at here? What is its value/sentimental value?

What type of repair do you want to do, 100% perfect back to stock or are you happy just to have the rust gone?

My initial thoughts are not very positive but I'll wait to see what your goals and thoughts are first before I start raining on anyone's parade. 

[PranK]

I'm super realistic here. I love the car and want to keep it but I know it's days of perfect condition are well and truly over. I just want a fix that won't come back. 

[PranK]

Oh this is my 1998 E39 5 series. It's worth more to me than financial value. It's a project car for me to love and work on without fear of f**king up something that has lots of value or that I need to keep running.

[Murray_Calavera]

Just now, PranK said:

It's a project car for me to love and work on without fear of f**king up something that has lots of value or that I need to keep running.

Ok, thats a good starting point. 

So before we start.... do you mind if the car say isn't a strong as it was before? My first thought is go excavating for rust. You'll be left with a gaping hole, that will be filled with fiberglass. You could make it look factory pretty easily but yeah, if you never crash it will never be an issue right?

Before we look at other options, how confident are you welding? 

[PranK]

I've never welded but I own a welder and I've always wanted to learn. In fact I had already looked at a 1 day welding course in Sydney. 

I'd prefer some ugly metal fab than anything weak. 

I'm challenging myself a lot with this car. For so many years I've just paid other people to do things and I've always been keen to learn and get better.

[Murray_Calavera]

2 minutes ago, PranK said:

I've never welded but I own a welder and I've always wanted to learn. In fact I had already looked at a 1 day welding course in Sydney. 

I'd prefer some ugly metal fab than anything weak. 

If your current chain of thought is, I'll go somewhere like pick and payless (or equivalent) and causally remove the bit of roof with your BYO grinder then casually weld that into your car... oof. It might sound easy but you will 100% end up with a warped roof. You say you'd prefer some ugly fab work, but I don't know if your prepared for how ugly this will be lol. 

I've seen professional welders do similar but easier repairs and still end up with warped panels. 

It is reasonable to assume that from your current skill level, you won't be able to do this cut and paste job while keeping flat panels. 

Ok, but we are here to learn. This might be the go... jump on car sales, sort by price, buy the cheapest thing with rego and drive it home. This is your new practice vehicle. If you're thinking of doing the cut and paste job, try it on this car. Cut out the panel (hey it's a perfect fit) weld in the panel. See what you think of the results. 

Next thing you could try, practice removing the entire roof in one piece by drilling out all the spot welds etc. Have a crack and welding the roof back on. 

 

[PranK]

Ok so I will not defend my naivety. I regularly feel like things look easier than they are. 

As much as I'd love to, buying another vehicle is out of the question. It was hard to get this car through the family process and we just don't have the room.

[Murray_Calavera]

3 minutes ago, PranK said:

Ok so I will not defend my naivety. I regularly feel like things look easier than they are. 

As much as I'd love to, buying another vehicle is out of the question. It was hard to get this car through the family process and we just don't have the room.

Hmm makes things tricky then. 

I can't in good faith say, go forth my child and weld in whatever metal you remove in your quest for rust. I very strongly expect that adventure will end in sadness. 

But you can't leave the car as it is, you literally have a hole in the roof. Also, I know you think the rust doesn't go much further, but the more I look at those photos, I really think the rust does in fact go much much further. 

If you are 100% committed to being the only person working on the car.... stop where you are, hit it with rust converter, fiberglass, body filler, paint work, pretend you never discovered the rust in the first place? 

Even if the body was repaired, painting the roof is a pain. Were you planning to use rattle cans to paint the roof?

[PranK]

Well the roof has a bunch of clear coat damage as well and I have done a little bit of spraying before so I was planning on doing the whole thing anyway. 

I mean I could definitely clean it all up, rust converter it and cover it with filler. Same as the last guy. If that's the only sane option. 

[MBS206]

5 minutes ago, PranK said:

Ok so I will not defend my naivety. I regularly feel like things look easier than they are. 

As much as I'd love to, buying another vehicle is out of the question. It was hard to get this car through the family process and we just don't have the room.

Welding thin sheet metal, is hard.

Welding thin sheet metal and keeping it in the shape you want, is REALLY hard.

Welding RUSTY thin sheet metal, and keeping it in the shape you want is nearly impossible.

 

A dodgy fix... Is cut the rusty crap out... Expanding foam, and putty/bog to rebuild that corner...

At least then you can reshape it to look half decent... Sprinkle some metal shavings into it too, then at least a magnet will stick to it. 

 

Probably more bodge than Murray's bodge idea...

[Murray_Calavera]

1 minute ago, PranK said:

I was planning on doing the whole thing anyway. 

With rattle cans?

2 minutes ago, PranK said:

I mean I could definitely clean it all up, rust converter it and cover it with filler. Same as the last guy. If that's the only sane option. 

There's a reason why the last person did that repair.

It's my advice for you as well, do as the last person did. Resist the temptation to go digging for rust, the hole you will be left with may wind up being so large that it's a nightmare to reform that corner of the roof. 

[Murray_Calavera]

4 minutes ago, MBS206 said:

Welding thin sheet metal, is hard.

Welding thin sheet metal and keeping it in the shape you want, is REALLY hard.

Welding RUSTY thin sheet metal, and keeping it in the shape you want is nearly impossible.

Yeah this can't be overstated, this job is crazy hard even for a professional. 

[PranK]

I have a decent compressor and spray gun. I haven't done anything this big but between it and the bonnet the paint currently is absolutely terrible and there's no chance I'd make it worse. 

Ok so should I cut back the top flap to get to the end of the rust? The bottom bit looks bad but feels strong still, even with the holes. 

Will filler seal the holes? Or should I put some silicon in them first? 

Love your work guys, thanks. Can't tell you how bummed I am to have found this. Wish I'd never looked and I'd still be happy! 

 

[MBS206]

3 minutes ago, PranK said:

I have a decent compressor and spray gun. I haven't done anything this big but between it and the bonnet the paint currently is absolutely terrible and there's no chance I'd make it worse. 

Ok so should I cut back the top flap to get to the end of the rust? The bottom bit looks bad but feels strong still, even with the holes. 

Will filler seal the holes? Or should I put some silicon in them first? 

Love your work guys, thanks. Can't tell you how bummed I am to have found this. Wish I'd never looked and I'd still be happy! 

 

Filler will set solid and water tight.

If you need to, get in around the inside with silicon between the window and edge of the car, but only if that spot is leaking.

[Murray_Calavera]

Just now, PranK said:

I have a decent compressor and spray gun.

Nice, saves me ranting about how painful it is painting a roof with rattle cans lol. 

2 minutes ago, PranK said:

Ok so should I cut back the top flap to get to the end of the rust? The bottom bit looks bad but feels strong still, even with the holes.

Personally, I wouldn't chase the rust back any further. What happens if your 30cm deep into your roof and still going?

3 minutes ago, PranK said:

Will filler seal the holes? Or should I put some silicon in them first? 

This is why I was suggesting fiberglass, the holes are quite large but easy to patch with fibreglass. There will be a million youtube videos of people doing this shonky job you can check out for a visual. 
Once the holes are patched with fibreglass, you can rebuild the corner with body filler (like the last guy did). 

6 minutes ago, PranK said:

Can't tell you how bummed I am to have found this. Wish I'd never looked and I'd still be happy! 

Indeed, its a shit go  

[MBS206]

@PranK to help you feel better, this is what happens when you run two of the big ones and have a heavy foot...

 

[PranK]

15 minutes ago, Murray_Calavera said:

Nice, saves me ranting about how painful it is painting a roof with rattle cans lol. 

Haha 👍🏻 

15 minutes ago, Murray_Calavera said:

Personally, I wouldn't chase the rust back any further. What happens if your 30cm deep into your roof and still going?

Yep ok, I'll just blast down between the panels with the converter.

15 minutes ago, Murray_Calavera said:

This is why I was suggesting fiberglass, the holes are quite large but easy to patch with fibreglass. There will be a million youtube videos of people doing this shonky job you can check out for a visual. 
Once the holes are patched with fibreglass, you can rebuild the corner with body filler (like the last guy did).

Ok cool.

If I spray enough converter and seal it all up with glass and bog will it likely keep getting worse or will that do enough to stop it spreading?