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Rust under roof rack

Hey everyone, I have a 2002 toyota highlander that has major rust problems. Everything works really well, it’s fairly low mileage however the roof is leaking. So I took off the roof rack and found a ton of rust that ate through the metal in three different spots. I cut out those spots, (I looked into the holes with a flashlight and it looked like that metal compartment was rusted on the inside so I know this is going to be a struggle) sanded it down to the bare metal and bondoed it. Fast forward 2 to 3 weeks and the its leaking again. I took looked under the rack again and the rust is now growing round the bondoed area. I know this car is pretty much toast at this point however I do need to keep this car running for at least another year. Does anyone have any ideas? I was thinking of just packing the reservoir the racks sit it with fiberglass and bondoing it all shut…haha. is that even a realistic option? Anyone have any better ideas? Oh and I live in the pacific northwest so it’s super rainy here.

Do you need the racks? I’d toss them and seal everything up

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There is probably a lot of rust under there you can not see. Might be a good idea to get it up on a rack and check for fund on frame and floor pans.

Look into a product called POR-15.
You’ll need to take out the headliner so you can access the interior underside of the roof. Clean the painted edge around the rust on the outside with a solvent to remove any wax residue that will spoil the bond. Sand the edge until you see at least a strip of clean metal around the rust. Paint inside and out with POR-15. Beware of the instructions, if you get it on skin, you’ll be wearing it for a week or so. Then patch the roof holes and paint the patches with POR-15. Then topcoat the outside with color matching paint. Put it back together. It won’t rust through again there if you followed their directions…

Look at some youtubes on rust repair to get an idea. But bondo absorbs water unless it is sealed with paint. Fiberglass doesn’t so use that or the fiberglass bondo for one thing. Then if you don’t get rid of all of the rust, it will just come back again. You can try treating it which may work for a while and Por 15 is as good as any to paint the rust and can even be used with the fiberglass mat to fill holes. Without seeing a picture, hard to say exactly what to do.

I’d wrap the roof.

Tester