On places like the drive-shaft tunnel where it's difficult to clean the back for replacing spot welds for things like the front seat supports, could I just drill out the spot weld and replace it with a bolt and nut? I was thinking about replacing them with rivets, but from what I gathered, blind rivets were not going to be strong enough, so how about snugly fitting bolts with washers? Has anyone done this before?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Generally speaking aircraft grade rivets are going to be stronger than a nut and bolt because the rivet is designed to fill the hole - whereas a nut and bolt will always sit in a clearance hole. Over time I would expect the nut and bolt joint to work loose.

If it was my choice - I wouldn't go down this route.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Like these?:

http://www.bonanza.com/booths/rats502/items/Kayak_poprivets_aircraft_grade_black_20

I also remember someone recommending rivet nuts, would you not recommend those for the same reason?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

I think I probably recommended rivet nuts in a similar thread to this one - the aircraft spec type rivet nuts are very strong indeed - stronger than conventional (steel) solid rivets. Rivet nuts (well the good ones) should also expand into the hole like other rivets - you'd have to drill them out to remove them - they are not "unboltable".

I'm sorry to say that I can't state which type or product would be best for your use. I'm afraid you'll have to speak to some sort of technical sales geezer... it is a pain, I know, but they should be able to help you make a more informed choice.

Have you seen StaggerLee's welding repair thread on this forum? He's doing similar repairs:-

StaggerLee's Rust Repair Thread 1980 300TD

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Yeah, that's good stuff. I didn't think about cutting all that out. I should get new pieces instead of using generic metal, that'd make everything a lot easier.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

JE - Which one is being replaced - the seat mount or the metal underneath? or both? Driver side? passenger side?

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1981 300TD "The Green Lantern"
1980 300TD
1983 300D Euro "China Cat"

I was going to drill out the seat support spot welds, take it out, repair it, repair the base metal and then weld it back in. Both sides.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Gotcha. I strongly recommend using pieces from another car that overlap the hole from the bad metal you cut out. I welded on the inside, smeared seam sealer on the overlap underneath and then sprayed undercoating on it. The only thing I had to unhook underneath was the parking brake mechanism and I had pretty good access to the seams after that. Plus, it all wants to fit as opposed to having to make it fit.

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1981 300TD "The Green Lantern"
1980 300TD
1983 300D Euro "China Cat"