Patching Up Floor Over the Rear Sub-Frame Mounts

I have the same issue on the passenger side of my car the only rust on my car is from leaks…, I was planning on cutting it out as a section then shaping the metal to the cutout section.

This is not a special area, just chop it out and weld in 20awg, drill two holes and done…

Just make sure you chop out the entire rusted area, you don't want it crawling back in

It won't effect the car's suspension?

That support plate that bolts on underneath is just a little reinforcement so the subframe pin isn't able to bend, which is theoretically possible hitting potholes with shot bushings, and prevents the subframe falling off the car in the off chance the bushing is totally destroyed… it's not a seriously structural part, just a safety thing

If you were to convert to solid bushings (paired with a solid diff mount) with tight tolerances, the bushings themselves would resist allowing the pins to bend under the same conditions, and likewise would never collapse like rubber

Is this problem caused by a fault in the T top roof drains?

T-top roof drains that are have the sealant cracking around them (in the case of my SS 820)

Rubber T-top trim that has shrunk over the years and allows water to drip between the seals
on the back corner (in the case of my black 84T).

If the rear window butyl seal fails close to the B pillar, then the water will make it's way behind the
panels and into the cargo hatch and into the carpet area behind the seats. (every Z31 eventually)

I had a beater Z that was in dire need of bushings a few years back. The bracket rusted through and fell off, taking the bushing with it. I was able to limp it home like that. The stud was fine and the car was repairable.

That happened to mine and I never had any T roof drain leaks. What I had was leaking quarter windows.

Its basically the lowest point of the car, internally speaking. Any water coming in from the centerline of the seats back will collect there. Very seldom is this a rust free area on any Z31. And I agree on the two bolts & plate: not structurally critical and more of a redundancy thing.

O_O I think I understand what you all mean…See attached picture for reference.

Yes, the picture does show an S13 sub-frame…but I see that the stock rear-subframe would have been mounted and pressed against that big beam (with the huge studs).

So…does this mean I can repair this rust without removing the rear sub-frame? Just jack the car up at the sub-frame, remove that bracket, and work from the car's inside? This is assuming there is no other rust in the area. Attached files

This should work, but you are going to want to coat your work to keep it from rusting and to get a good protective coating of primer/seamsealer/undercoating It wouldn't be a bad idea to drop
the rear subframe enough to access the area.

I'd like to see your repair work. I have to do the same kind of repair on my AE but don't have enough practice welding sheetmetal with my mig yet to feel comfortable doing it.

Where could one buy replacement subframe pins. Considering the extensive rust in that area I would like to get new ones just for piece of mind.

You can't buy new one's.

oem surplus used to have floor pans for sale