Rear Hatch Rust Repair - A detailed guide.

[gav240z]

Hi Guys,

In a similar theme to the door skin tutorial thread, I am going to start a new thread on rear hatch repair. Given that most of the rear hatches will have rust by now and more than likely have had less than ideal rust repair done, simply finding a replacement is becoming less and less of an option. I've seen these early rear hatches on eBay / Yahoo! Auctions anywhere from $100 - $400 and even $800, but until you sandblast it you really don't know what you have and importing a panel and going through all that headache to find you have swiss cheese just wasn't an appealing option. So best make do with what's available locally I say.

 

This will give you some insight into repairing the rear hatch and how I go about it at each stage, very much like the door skin thread.

 

To emphasize my point about paint hiding previous horrors and botched repairs.

 

I was quite surprised at how 'rust free' it looks in the photos I was sent before I had it shipped to me from a fellow member. Although this isn't my first rodeo so I knew there was a chance I'd find some hidden nasties on the way and under the paint and I in no way hold the member accountable for what I found underneath, it's likely he didn't know either. Not to mention the other 2 early S30z hatches I have are in worse shape than this. So this is still the best candidate I have to work with.

 

First some photos of hatch #1.

 

It looks like previous accident damage and bog was used to give the panel it's original contour and shape. Just sand-blasting this would take forever!

 

Hatch #2 - Original hatch on the car.

 

I'd say it's still quite repairable, it's had a nudge from behind and there is quite a bit of bog showing on the underside of the hatch near where the latch / catch mechanism is.

 

So that leaves hatch #3

 

Before

 

 

 

 

 

 

 

 

Last night I sandblasted it and found quite a bit of bog in the lower portion of the hatch. Can't say I'm shocked but from the photos above it looked like it was nearly mint and an easy repair, wrong sunshine! Although I have to say it's much better than the other 2 as a starting point and still a relatively good rear hatch with no signs of previous accident damage. Just botched rust repairs.

 

After

 

There was quite a lot of bog in the lower corners of the hatch. You can still see it in a couple of the photos above, it is a dark grey color so looks like the metal but it isn't. It took a lot of effort to remove with the sandblaster, before I got told off for abusing the sandblaster at Tafe trying to remove that much bog. So it looks like I'll finish the rest using paint stripper and a flap disc on angle grinder and if that's too slow I'll take it to a local blasters to use a harder media.

 

[gav240z]

Because the sandblaster was really slow to remove all the body filler in the hatch, I decided to try the grinder with strip disc on it. The strip disc looks like a pancake of sandpaper (don't have photos) but any strip disc should be fine so long as you don't get too aggressive on it.

 

The only problem? I looked like I'd stepped off the planet mars afterwards with all the red dust that went everywhere. I wore a dust mask and face mask / goggles for eye protection as quite a bit of debris can go flying. I also wore my overalls because I'm happy to get crap and debris all over them. You wouldn't want to wear a white t-shirt you like. I'm not sure on the health hazards of body filler dust? But old paint can contain lead.

 

http://medicine.yale.edu/intmed/prep/worker/hazards/dust.aspx

http://www.hse.gov.uk/mvr/topics/dusts.htm

 

And what can I say? It worked brilliantly when it came to removing the bog and paint. Very fast and very effective compared to sandblasting.

Bottom left.

It is relatively straight except for the corners with rust. I think someone hit it with a hammer and then filled with bog.

Underneath.

 

I was pleasantly surprised to find no more rust or nasty surprises. So overall very happy with the hatch and much better than the other 2 I have.

 

I have a few ideas on how to go about the rust repair, but I'll consult my tafe teacher for his opinion on the best way to fix it and proceed from there.

[PB260Z]

Because the sandblaster was really slow to remove all the body filler in the hatch, I decided to try the grinder with strip disc on it. The strip disc looks like a pancake of sandpaper (don't have photos) but any strip disc should be fine so long as you don't get too aggressive on it.

 

Flap discs are an amazing piece of gear.

 

[thriller]

Bugger about the corners! I was trying to poke my phone up on the inside of the hatch to photograph the corners from the inside but they all turned out terrible. The insides looked OK from what I could see (though I guess they're double layered).

 

 

+1 on the flap discs being awesome. A handful of them and you can buzz a whole car back without too much hassle.

[gav240z]

Yeah in fairness it was pretty well hidden, hard to tell without stripping it all back. But honestly it's a 40 year old Datsun tailgate, if it didn't have any rust I'd be more surprised. It is still far better than the other 2 I had to work with and it looks very clear everywhere else so should come up good.

 

I also managed to get that snapped bolt out of it without too much hassle (where the rear strut attaches).

 

Thanks for attaching the pic of the strip disc / flap disc that's exactly the 1 I was using.

[CroS13]

what you are talking about is a brumby disc or strip it disc, It looks more like seaweed on a grinding disc. It cuts through bog and paint but doesn't grind away any metal.

 

Like shown...from Bunnings:

 

 

 

 

That first rear hatch photo looks like my passenger side dog leg which i attacked on Sunday with said Brumby disc, nearly lost the grinder in it, kept getting deeper and deeper:

 

 

Rudolf.

 

 

[gav240z]

So after bringing the rear hatch into tafe and speaking with the teacher, the decision was that the easiest way to repair this will be to fabricate the lower section of the hatch. Now you might be wondering why? If it's only the lower edge that's rusted? Well the bog that was in it, was also covering up several low / high spots and previous damage. It would be possible to repair what is there, but the idea here is to undo the spot welds where the glass goes on the lower edge, make a small cut on the right and left hand sides and then replace with the new section, do a few spot welds and small weld lines on right and left hand side of glass.

 

The other advantage of cutting the bottom section off is that I'll be able to get access to the bottom of the hatch to remove any surface rust forming and treat the area to help prevent any further corrosion.

 

So here is how it will be done.

 

Paper template is used to mark out exactly where each line, fold etc.. will be in relation to other parts of the hatch.

 

Can you spot what's missing?

 

 

Yep the lock / key-hole. I forgot to trace that out first time.

 

Notice how we're also tracing out the vents? Well... hindsight is a wonderful thing, but that basically means I could have got a regular 240z rear hatch and turned it into an early hatch. However I wasn't to know, but for anyone else out there just grab the best condition hatch you can get and you can relatively easily add the vents in.

 

Once I had the pattern ready I got a fresh sheet of steel and then used a scribe to start marking the fold lines etc.. Next week I'll start shaping the metal hopefully.

 

[gav240z]

Ok so now that I had traced out the pattern on a flat piece of sheet metal using a scribe. I had to then join all the lines I made with the scribe using a straight edge for the lines that were straight and for the lines that had a curve I had to use best guess free-hand to join each reference point.

 

Using a roller we gave the piece some shape to mirror that of the rear hatch.

 

As you can see it's a bit large, so the next step was to trim the excess length off the sheet metal - closer to where the scribe lines were.

 

Next was to start the fold for the lower half of the hatch (which isn't quite 90 degree's it's like 70 odd degrees).

 

To start with I used pliers to fold this piece up.

 

 

You can see the 70 degree bend more clearly here.

 

The next challenge is that the hatch has both a curve east / west, but it also curves north south in both directions. So we used a shrinker on the newly folded lip to pull the edges inward and create the curve east / west.

 

A hammer and dolly was used to help dress up the hatch edge and give it a nicer more defined and sharp edge. The hatch has a bevelled edge and isn't completely straight though.

 

Next I trimmed the upper edge where the spot welds are - after checking how the piece was lining up now that we've done some work to it. Apparently my markings were looking good.

 

 

The next step will be to fold down that top edge and give it a slight curve where the spot welds go. Once we are satisfied the shape of the replacement piece is looking good we will clamp it down and double-check how the hatch vent markings overlay and make adjustments if necessary. When you re-work a piece of steel like this it can cause things like this to be out of alignment - even if your markings are good.

 

And that was about it... last class for 2014. Will have to pick up again in Feb 2015.

[gav240z]

Long time between drinks, but some progress (although it doesn't look like much) on the rear hatch in the last couple of weeks.

 

You can see the lower edge has improved since the last photos where it was bent with pliers. This involved quite a bit of work with dolly and hammer.

 

But to be honest it also involved a lot of mistakes on my behalf that were corrected or put 'more correct' by the teacher.

 

The top edge where the outer skin joins the frame and the rear glass goes was also bent down using the same technique since it's a concave shape and you can't just use a folder to do this section. It was also 'dressed' up with a hammer and dolly and again I made a few mistakes.

 

 

The edges where it curves were achieved using a metal stretcher/shrinker tool at the workshop.

 

 

Notice how I haven't cut the holes for the vents or key hole yet? I'll do that once I've clamped it all down and scribed the underlying hatch where it will be cut. Don't want to cut it now then fit it and weld in place and find it's slightly crooked. Since it would definitely catch the eyes if that were the case. So we still haven't cut the hatch skin itself, and this new skin is sitting on top to get a feel for how it will all go together, but that obviously means it's not quite sitting how it will once it's been cut etc..

[gav240z]

Minor update...

 

So now that I've cut the original lower section of the hatch skin off (see photo below) it's time to do some treatment of the surface rust and rust holes in the frame. They are only small...

 

But first 1 thing I need to replicate is a brace that sits on the underside of the skin. This is behind the keyhole about mid way down the hatch. There is 2 spot welds on the top where the rear window goes but the rest is glued in place.

 

Getting the old glue off was a pain in the butt and you can see the tools I used to help with this. I expected to find lots of surface rust under here, but to my surprise there was bare metal underneath in relatively good shape, around the key hole moisture had got in and there was light surface rust. I guess the good news is that the glue keeps most of the moisture out and so most S30z's shoudn't rust here, the bad news is the factory never primed the metal underneath.. so you take your chances if you don't attend to this section.

 

Once I removed the old piece, I then hammered it back into shape.

 

Checked to see if it aligned with my keyhole scribe marks on the fabricated panel (it did) and then created a new 1, pretty simple to fabricate but no picture of it yet.

 

I sandblasted inside the hatch frame and found a few holes, I managed to patch them up with the oxy welder (no pics yet) but need to tidy up the welds with a finger sander / linisher and then check for any pin holes etc.. It looks like the hatch had at least a couple of repair attempts in the past as there was evidence of a couple of welds on each side. A somewhat proper repair, where as the bog must have come later .

 

Before re-attaching the new fabricated skin it's likely i'll get the rear hatch frame dipped and treated for surface rust and then apply rust proof paint and epoxy primer etc..

 

[gav240z]

Oh and 1 thing that wasn't obvious is that the inner frame had some weird damage to it. In that it was slightly bent on the underside. I don't have photos of this but on 1 side it was  a concave sort of shape where as it should have been a smooth flat piece. The best photo where you can see this is here.

 

 

Top left of the photo near the hole you can see the light refracts a bit funny, removing the top skin gave me access to the other side to hammer and dolly it back straight, which as you can imagine may have had some impact on the alignment of the rear hatch also, since it may 'pull' the skin inward (which in fairness someone might have whacked it here to try and align it on another car in the past?) either way it's back to how it should be... But as I say not something easy to photograph...

[benny]

Nice work Gav, though I cant help but think you should remove the rest of the skin properly too as to ensure its 100% rust free. Seems like and awful lot of work for the rest of the frame to "pop out" one day.

[gav240z]

Hey Benny,

I agree and I'm currently looking at solutions that involve dipping the hatch in a rust converting, neutralizing bath etc.. I don't know a whole lot about this process yet! But I just read this.

http://www.autospeed.com/cms/article.html?&title=Dip-and-Strip&A=111165

 

and found this - which I'll read later.

http://www.hotrod.com/how-to/paint-body/hrdp-0901-rust-removal-guide/

 

The good thing about dipping is getting into areas you wouldn't usually be able to access without cutting / removing more bits of metal etc.. For example inside the frame is another bracket (where the lock mechanism / latch part bolts to) and I can't easily treat under this in a conventional way. Dipping and then dipping in a rust proofing type material will hopefully take care of those areas.

 

I'll be sure to update this thread on what I find and how it goes. I generally don't see S30z hatches rusting at the top (Unless you own HS30 00019 sorry George can't help myself) and it's been sat in a field for many years. It's usually the lower areas where moisture and water gets trapped that rot out. I agree though last thing I want is for rust to re-appear anytime soon.

 

I'll also be restoring the bonnet next which I've already separated frame from skin but there are bits of the frame spot welded together that I can't get in between easily without separating them and so this process will be handy for many other areas on the S30z I'd imagine.

[gav240z]

What's been going on?

 

Well you can see I replicated the brace for the rear of the hatch lock.

 

To get the cut outs correct I used a 'square' file. I also used a circular drill piece (sorry forgot the name *edit - it's called a hole saw*) that was about the right diammeter to cut out the circular nicely, which is easier than using tin snips.

 

After sandblasting the bottom of the hatch and finding rust holes etc.. it was time to crack out the oxy welder and patch it up.

 

 

here's the tricky part though, once you start to sand down these welds you discover a few pin-holes.

 

The thing I did that wasn't so good was use the linisher to try and tidy it up. This was a bit too aggressive and it can thin the metal out a bit too much which means when you go to weld up these patches you blow holes and have to patch it up again etc.. In some ways it seems like it would be easier to just replace the hole section but it's at a good place now.

 

Talking about my mistakes, you'll recall I used a flap disc to strip the hatch when I found loads of bog, well you can actually do some panel damage when using an aggressive method like that to strip a panel.

 

Here is an example, we filed the top edge of the hatch (since the bottom is being replaced anyway).

 

You can see the low spots are all those dots where the file hasn't touched it.

 

Enter this machine.. The Easy Beat..

 

What you do is point the end of the tip onto the low spot on the metal and it creates a very mild tach like weld. Then you use the slide hammer portion to pull the low spot up, it's a very weak weld so twisting the gun causes the weld to come unstuck and leaves a little pimple in the metal. Using a body file you then go over the area which will knock it down and level with the surrounding metal.

 

After a couple of hours of playing with it, you can see improvements.

 

Still a few low spots but running your hand over them you'll see they are not that bad. In the end it looked like this.

 

So now I'll still require a small amount of filler but it should be very light and give a good finish, bottom line is don't use aggressive methods to strip paint or if you do keep it as flat as possible don't approach at an angle like I did. Lesson learnt...in fairness a ham-fisted blaster could do the same thing.

 

This tool is very useful for pulling out dents when you don't have access to the other side of the panel easily, so think of the bonnet I pulled apart here:

http://www.viczcar.com/forum/index.php?topic=14677.0

[gav240z]

So a bit more progress on this. After great hesitation to cut the vents into the hatch after taking ages to shape this piece I finally took the plunge and started it.

 

I measured the inner lip which was 5mm and traced a square inside of the outer marketing for where the vents go. Then I drilled 2 holes and used a saw (see photo below) to cut a line between the 2 holes.

 

This is what I had after.

 

NB: The pitted metal was due to surface rust build up from having left it sitting so long unprotected. I'll sand it down to clean it up before paint.

 

 

 

 

Double-checking it all still aligns.

 

5mm lip on inside of original piece.

 

Once the holes were drilled and the line cut, it's time to use the tin snips to trim the inner square area. This is tricky and tedious work, plus time consuming. I've certainly got a lot better at using tin snips since I started working at the TAFE - I was all thumbs in the beginning...

 

Before tidying up with a file.

 

Compared to original piece. My biggest concern was making sure they were aligned correctly. Otherwise I'd always notice it...

 

 

The lower section vent holes look smaller. That's because they are, I still need to bend the inner lip on them which will increase the size of the holes and give them a rounded/beveled edge. Since you can't just bent a perfect square shape, first though I need to file the edges to give them a rounded shape.

 

I do this with a rounded file. You want to aim for a shape that reminds you of dogs bollocks lol...

 

 

Then I quickly overlaid the new panel on the hatch to see roughly how it will look..

 

The vent hole on the far right has the inner lip partially folded, still got to do the others. Takes quite a while to do fiddly stuff like this. Honestly if I could find a rust free early hatch, it would have been far less work. However they are very hard to find now and most of them have lots of rust around the bottom. So I'm persisting with this 1.

 

[gav240z]

Small update.

 

Have cut out both sides for the vents and started to bend into shape.

 

This will still need a little more dressing up to get the really defined edges, which I'll do in class on Tuesday night.

 

[Cozza]

Nice Gav. You are getting some great experience at the TAFE course. I hope the course is still running when I have the spare time to commit to it.

Keep up the great work

[gav240z]

Nice Gav. You are getting some great experience at the TAFE course. I hope the course is still running when I have the spare time to commit to it.

Keep up the great work

 

Thanks mate, I do love learning this stuff but it does take a lot of time. Especially because I'm still learning, things can move at a crawl of a pace at the best of times. But I certainly have much more appreciation for good bodywork professionals.

 

This week was a slow week, in that the teacher was busy with other students and whilst he was busy I started to work on a new section for the rear slam panel area, really just experimenting to see if I could shape the area correctly. Anyway I'll detail that in another thread.

 

But it just means progress on the rear hatch was minimal. You will recall previously I mentioned needing to dress up the vent holes more. The right side in the pic below is just the beginning and you can see compared to the left side it's starting to look a bit more refined.

 

 

The hardest part was getting the curvature of the corners right. To do this I used a solid rounded edge (like a screw driver but thicker) and pushed it into the corners and then whacked it with a hammer to push the lip in the corners into shape.

 

In the photo below you can compare the side i've done (right) vs the 1 that still needs doing (left).

 

 

Both sides.

 

Compared to the original piece.

 

Left hand side.

 

With all this messing about the vents had some high and low spots, so I spent a good while with a hammer and dolly trying to minimise this. But that is harder to photograph and show here. The vent holes could use a little more tidying up and I'll probably do that next week, but I am also aware that the plastic vents will actually cover these, so they are unlikely to ever be seen. However I want to do it to a high level still. 

[gav240z]

Today's progress was slow, but I guess important bits.

 

I drilled the holes for the plastic vent covers to attach to the hatch. I also drilled the hole for the lock.

I spent ages making sure the holes would be in the correct spot. I also had to use a body file to try and remove low spots and high spots and get the panel consistent around the holes etc..Next step will be folding the lip around the edges and welding it to the rest of the hatch trim.

 

 

I'm also having second thoughts about the patched up corners, I may fabricate them out of new steel and weld them in. I figure if it's taking me this long to do the hatch, I may as well spend a little longer and make sure it's perfect...

[PB260Z]

I'm also having second thoughts about the patched up corners, I may fabricate them out of new steel and weld them in. I figure if it's taking me this long to do the hatch, I may as well spend a little longer and make sure it's perfect...

Sounds like the correct approach, but that is how things get way bigger than originally planned.

[gav240z]

Sounds like the correct approach, but that is how things get way bigger than originally planned.

 

Tell me about it, it was supposed to be a rat rod remember? But my OCD kicked in...

[Hokin]

Looks the goods Gav, im liking the progress and its always great to learn a new skill set.

 

PS: Nice Socks

[gav240z]

Looks the goods Gav, im liking the progress and its always great to learn a new skill set.

 

PS: Nice Socks

 

Thanks, but those socks are not mine. They belong to member Thriller in South Australia (maybe his dad's knee socks?).

 

I feel better about the time invested in this hatch, knowing that a NOS rear hatch is a fortune here:

http://jdm-car-parts.com/products/datsun-240z-series-1-rear-hatch-nos

 

In terms of new skills yesterday I was using a slapper (no not that sort), the other sort. With a dolly to help bring low areas up and get it nice and even around the vents (since they were somewhat distorted after cutting them out and shaping them).

 

Of course it's difficult to take photos of that stuff and document it well, but that's where a lot of time goes.

[gav240z]

Small update.

 

So last night I folded down the edges of the replacement skin, as you can see the skin sits a bit high on the left hand side.

 

 

This is because of the shape of the hatch, it sort of bows upward toward the middle of the hatch and down toward the edges to give it a rounded feel. As a result the edges were bit high and we needed to knock the inner edge a bit lower (where the spot welds go under the weather seal).

 

 

This was a bit tricky, so I can't claim I did much here other than watch the tafe teacher reshape the edges a bit to make the skin fit properly. I now understand what he was doing, but couldn't make the mental leap there without seeing it.

 

You can see below the new skin now just sits slightly above the original.

 

 

 

 

We will need to scribe the edge where the old and new skin meet then carefully trim the original skin to meet the edge of the new skin for welding in place.

 

 

However before I can weld the 2 pieces together there is a few other things to do.

 

1. I am going to get some KBS rust seal and pour it into the hatch. I contemplated unpicking the entire skin and frame but that would upset the edges of the frame and require work to get the skin nice and level again later for paint. Also the upper hatches don't tend to rust, it's usually the lower areas, so I think putting some rust seal into the hatch and swishing it around will hopefully coat and protect most inner areas of the hatch.

 

I also need to coat the inside of the new skin and spot weld the support piece that goes behind the lock. The good thing about the new skin is it's slightly thicker than the old so a bit more sturdy. I noted on the Lithuanian restoration discussed here. They ended up making a brace for the rear hatch because the metal was so thin in the hatch after repairs. I don't think I'll need to do that here thankfully. That's 1 advantage of spending ages fabricating the lower section like this.

 

2. I still plan to remake the lower sections of the frame, as I'm not happy with the way we have repaired it. If I'm going to spend this long on it, a couple more weeks to get it right are worth it...I think, sometimes..not sure..

 

I also bought some OEM vents to fit to make sure I'm happy with their alignment before paintwork in future etc.. That way if I need to re-drill a hole I can do it before paint, not after.

[gav240z]

Since Facebook links often don't work properly later. I attached a photo of the aforementioned brace piece made to prevent 'oil caning' of the hatch (at least that's what I'm guessing it was for.

 

Photo description from Facebook.

 

 

 

Trunk - he fabricated support bar for the sheet metal that was too soft, this way it will be easier to get all the surface nice and flat, and it will be tighter