e21 Brake Booster problems, help ASAP

[87e30]

Yes I've searched.

I know you're supposed to cut and thread the shaft

Or you can cut and weld the shaft.

Well I took the shaft to a machine shop 3 times and spent like 45 minutes with a welded.

The shaft on the e21 booster is significantly thicker than the threads, therefore in order to thread the shaft for the proper size of the cleave on the end it would need to be put on a lathe and shaved down. Well that's not going to happen.

The welder said he didn't want to do it b/c of the heat risk SO close to the booster.

So my only idea right now is to thread the shaft larger (not machine it down) and then tap the cleave to accept the larger size. The problem is the cleave has almost no extra material and the shop is worried about it not being strong enough or breaking.

How did all of you guys do this? If it wasn't my brakes I'd jimmy rig something up... or use JB weld.

[e30s52]

I cut one off my old booster and rewelded it on the e21 booster. Just take some wet rags shove them inside and on the inner side near the rod. just do light passes, after each pass cool the rod down.

[e30Rob]

oooor you can do what i'm gonna do, thread my 320i booster with a 12x1.5 die first, then file down the threads evenly, then thread it further with an M10x1.5 die. This will make it the proper thread pattern to just thread right up.

[87e30]

Ahh, the welder was scared of the heat alex. So he wouldn't do it. He also thought water might make the steel brittle if it was hardened...

So I just winged it myself and it worked.

I threaded it at 7/16's and then tapped teh cleave myself to 7/16ths. I haven't ut it all back together yet but so far so good, they thread together! woot!

Shouldn't have ran around all yesterday when I could have just done this myself...

thanks for the ideas guys. And e30 rob... what i did might work for you too.

I'll update when I get the booster reinstalled.

[e30Rob]

PLease take PICS!!!!! before reinstall of the pieces pwease...lol

Oh and jsut so you know i'm notloEnuf over on SW fyi

[87e30]

Yeah, I saw some rolling shots of your car.


I didn't take any pics... sorry dude.

It's SUPER straightforward once you see it though.

I've never touched the inside of my engine bay before this swap and with local help I'm managing to figure stuff out. The booster is super easy though, it's like 4 13mm nuts inside the car by the brake pedal and once you take it out and look at it next to the e21 you'll see right away.

[e30Rob]

oh ya i know how it comes out and all i was just kinda curious what the end product actually looks like during the modding and such.

[87e30]

Oh. Well it comes out looking pretty much like the e30 stock one. except mine has 7/16ths threads on the end... and a cleave to match!

Just got my booster back in. One of the nuts for it fell under the carpet though so I only have 3 of the 4 holding the booster to the firewall. It's tight though so I might just say fuck it and leave it. That one is SO hard to reach.

[FredK]

oooor you can do what i'm gonna do, thread my 320i booster with a 12x1.5 die first, then file down the threads evenly, then thread it further with an M10x1.5 die. This will make it the proper thread pattern to just thread right up.

This is exactly what I did.

Charlie just drilled out the clevis and threaded using a M12x1.5 tap. That works too.

[e30Rob]

IDK about threading the clevis..i'd rather just thread the post.

[87e30]

I threaded the clevis at 7/16ths and it's working fine!

I made it a tight push up against the brake switch with the brake pedal so I hope that is all good.

one of the nuts feel under the carput though so the booster is only held on by 3... I hope that's okay.

[e30Rob]

I threaded the clevis at 7/16ths and it's working fine!

I made it a tight push up against the brake switch with the brake pedal so I hope that is all good.

one of the nuts feel under the carput though so the booster is only held on by 3... I hope that's okay.

just take one of and stop by the hardware store next time your out, match em up and get another or just peel back the carpet n get that beeatch.

[87e30]

Yeah I really should. But it's such a pita to reach in the first place. It's kinda eh, it will be fine with out it. God I'm lazy.

[e30Rob]

Baaahahaha

[RedTRex]

I had the same issue with the 944 booster, but I just used a grinder tomake he shaft a touch smaller then threaded it further......