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Patcon

7" brake booster repair and restoration

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Booster looks great.

I'm not positive how those studs are held in place, but I would assume they are resistance welded. It could just be a press fit, but I'd be surprised if they didn't do some welding there as well.

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So I really wanted to protect the studs on the booster before I reassembled it. I have both halves of the case finish painted. So I plated them in place. I wired them up and suspended them in the tank

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This is how the other half turned out

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Now I'm working on plating the MC push rod. I'm working on removing the pitting from the rod.

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I may attempt reassembly next weekend. I think I am have most everything ready for that. The MC push rod can go in after the shell is assembled.

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My booster recently failed and had thought about rebuilding it.  Found a much easier process that comes with a warranty and only costs One Ben Franklin plus shipping to Texas (A little over $100):

- Believe it or not, Rockauto is signed up with a good rebuilder in Texas.

- Took one week turn around

- I removed my original sticker from the booster as I figured they would be media blasting it off anyway

- Arrived nice condition, wiped it down with prep and painted it.  

- Rebuilt for sometimes less than what I saw a rebuilding kit cost (about $120 was what was showing up if you could find it)

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5 hours ago, racerock said:

My booster recently failed and had thought about rebuilding it.  Found a much easier process that comes with a warranty and only costs One Ben Franklin plus shipping to Texas (A little over $100):

- Believe it or not, Rockauto is signed up with a good rebuilder in Texas.

- Took one week turn around

- I removed my original sticker from the booster as I figured they would be media blasting it off anyway

- Arrived nice condition, wiped it down with prep and painted it.  

- Rebuilt for sometimes less than what I saw a rebuilding kit cost (about $120 was what was showing up if you could find it)

The rebuild kit I am using was $75 from Harmon Brakes in GA off Ebay. I thought about having him rebuild it and I may do that on the next one, but this way I can replate all the hardware inside and out first and treat the rust inside the shell and paint it. If I have him do one, I will break it down for him and plate all the pieces first. Then send it to him for reassembly. Whether that happens will greatly depend on if I have a working booster at the end of this process

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So I messed with the booster some more today. It's only been a bout 6 months. So I reassembled it. It went really well with the new lever. Almost no effort needed.

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I used a mixture of old seals and new seals. The old seal that goes around the disc shaft on the passenger end of the booster was reused. I was unsure the new seal would go in or work properly. I also reuse the old bellows for that end.

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I just put enough pressure on it to get the space out between the cases

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This is locked

So pleased with myself until I saw this on the bench :facepalm::facepalm:

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So opened it back up and did it again

The real "chapper" is it still won't build vacuum, at least not by hand. I blanked out the MC end with some sheet rubber and it wouldn't. so I wrapped a zip lock around the plunger side and it still wouldn't build vacuum. Now the mighty vac will build and hold vacuum it I pinch the vacuum line. So I am kicking around ideas

Maybe the seals need to bed in and higher vacuum might help?

Leaks around the perimeter of the case? I sort of doubt this because the edges were good and it's pretty compressed to get it to lock close

Leaks in my testing setup?

Not able to build enough vacuum, quick enough by hand?

Leaks at the MC plunger side?

Leaks at the passenger plunger side?

I wondered if I could tap it into my S-10's vacuum booster with a gauge to see if I could get it to build and hold vacuum?

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So i went back to the shop and did a little more work. There was a small leak in the mighty vac tube and one in the black line. I also found a check valve and clean it up and put it in line with the booster. If I clamp the mighty vac in the vise and work it fast I could get it to 15" of Hg. It would slowly bleed off at a rate about 3 times the FSM spec (.9" in 15 seconds). It would be curious to know if rebuilt boosters from other sources will hold the FSM spec. I suspect the old seal I used and the slight corrosion on the MC plunger are contributing to the bleed off. For now I will consider that a success. This was not the cleanest 7" booster I have. I may take another stab at it later but for now I'm moving on.

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@Captain Obvious

You're up next...

Edited by Patcon
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The large pits are actually outside the seal. I was working on building up the plate on the plunger and polishing it but then had to redo some of it. So I went with what I had. It is actually much smoother than it was originally. I would still be curious to know if the reman boosters can pass the spec

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