this isn't good...rust in the spare tire well...
 

I'd taken the spare tire out as part of my recent effort to replace the broken power antenna mast. I was nonplussed to see significant run in the spare tire well, especially in the front.
After grinding away the rust, there are (3) large holes, from quarter size to one that is about .75" wide by 1.5" long.
After grinding away the rust with a DOTCO I treated the whole thing with a chemical that 'converts' (kills) rust. Other than the three holes that are through or nearly through, the rest of the wheel well is sound metal.


I'm not quite sure how I want to go about fixing this. I suppose I'll take it to a body shop for an estimate to weld it all back up or something....


Suggestions?

What's it like on the underside?

There have been many threads a few years back about some drain tubes clogging or other things causing leaking into the tire well from various locations.

Search "spare tire leak."

YEP

Another bad spot is the passenger side rear fender/quarter panel area just behind the tire. Water will collect there if the antennae drain tube is missing or not placed properly. Or maybe the antennae is simply loose.

The underside looks fine...all the undercoating still in place, etc.


I think I know where mine came from, I'd had a bad rear glass seal that I had replaced about 8 years ago.
Never really thought to peek into the spare tire area...dammit.

I'm tempted to pop-rivet some aluminum or titanium sheeting (I've got various thicknesses from .015 thru .125 thick onto the bottom side, fair it all in and undercoat it liberally, then putty the inside, sand out, prime and paint.


Kind of a 'duct tape and baling wire' fix, but...should work.

I would honestly hold off on the pop-rivet until you get quote from a body shop. I can imagine it costing more than 300$ for those three holes.

+1 its a nice place to fix, as its not a complex panel, and matching the paint won't be a worry

Drop the tank and seam weld in a few plates in. Paint it with some decent epoxy and it will be as good as new.

Shouldn't be a bad job, maybe a mornings work :icon_tup:.

I bet you can get that whole panel from Mazda still...

Ouch ! I can feel your pain.

Mazda would probably sell you the whole trunk floor. although most period Mazda's probably have the same spare tire well stamping, so a donor should be easy

Yes, it is the hatch floor-

FDY1-53-710

We can get the part brand new from Mazda if you decide to go that route, its about $500+shipping though. Depending on how bad it is might be able to take a wire wheel to it or sand blast it out and repaint.

https://cimg0.ibsrv.net/gimg/www.rx7...0ab20c1539.jpg

Good info, thanks everyone.
Haven't even had time to go look at it again...work stuff taking all my time!

1cleancym has a parts car. He could probably beat that price by a good margin on the trunk floor. PM him.

Got the fix done for now; kind of a 'cheap bastard fix', but it should work. Ended up prepping the area down to bare metal, then did a "triaxial weave" of heavy fiberglass cloth and polyester resin patch on both the inside and outside of the wheel well. Then coated both sides with rubberized undercoating. Final element was to bond a .032 thick aluminum sheet into the inside so that the fiberglass wasn't taking any direct contact with the spare tire.


Now I'm looking for a replacement tire for the emergency wheel, as the original isn't holding air.

Have you found where the tire/wheel is leaking? It could be between the tire and wheel at the bead due to corrosion from the water, in which case you would need to clean up the corrosion and roughness on the wheel bead, but might not need a new tire.

IMO, corrosion is much more likely than the tire developing a leak. Also, it could be the tire valve leaking between it and the wheel.

^ good point, I'll check it out. The wheel DOES have quite a bit of corrosion...

In my experience that rust converter stuff isn't a finish coat, but a converter and primer.

If you plan to leave it for a while make sure you seal it with another product. Otherwise it can absorb water and will actually cause more rust to occur. Made that mistake doing repairs to the trunk of my E28.

Yep! I did indeed seal it with some 'professional' rubberized undercoating product.

Just an fyi but a polyester resin fix on metal will not last. The polyester resin is designed to breakdown the binders in chopped strand mat it is not a good adhesive.

To do that kind of work you and get a proper bond the metal surface should be a little rough and an epoxy resin with a fiberglass mat would be more durable.

Using any composite to fix to rusted metal is a bodge in my book. It needs to be cut back to good and a plate welded in really. It's a mornings work tops to drop the tank and fix it for good.

Did you ever find out for sure where your leak was? I discovered water in my hatch yesterday unfortunately after some heavy rains. She's back in the garage now but at least it discovered the problem for me. Time to play detective. Now that I think about it, my weatherstripping on the bottom is starting to curl up and I was considering getting it my glass reset with a new seal in the near future.

The leak had come from a bad rear glass seal, which has been fixed.


I definitely intend to fix it 'right' at a later date, but wanted to get it 'drivable' and not have a hole back there.