7" brake booster repair and restoration

[Captain Obvious]

Yes, there is a little U shaped retainer at the bottom of the plunger that holds it in. But the only thing that holds it in is friction from the plunger spring. If you push the plunger in a little, it will unload that pressure and that clip will most likely fall out unless it is a little rusty and stuck. If that's the case, a small magnet can help pull it out.

But to answer your question... Yes, you have to take the pressure off. And that is done simply by pushing the plunger in a little bit. If you push it in a lot, it will spring load in the other direction... There's a small "sweet spot" in the middle where that clip isn't under any load. In fact, the only thing that holds that clip in when you pass through the sweet spot is the rubber diaphragm sitting in the groove.

I've got some pics that would help describe, but my picture hosting server is not cooperating today.

[Captain Obvious]

Oh, and BTW... It's not just you.

On my first booster disassembly, it took me an hour to figure out how to get that clip out. Mine was a little gummy and a little rusty and if not for that, it probably would have fallen out by accident. But between the rust slurry making a little sticky and the not knowing what I was doing, I spent at least an hour on it.  

If it's clean, put it on the bottom side, press the plunger slowly, and it will fall out simply from gravity.

[Patcon]

19 hours ago, Captain Obvious said:

 

In fact, in preparation for you to send it to me, my spare poppet valve fell apart earlier today:

How does this disassemble? I finally got the plunger out but I can't figure out how to break this down. Does the metal end just snap onto the round rod head?

I sort of got medieval getting the plunger out. I don't think it's irreversible I will post pictures later...

[Patcon]

Ok so I may a little progress disassembling the booster but I also damaged it some

So I was tring to get the piston keeper out. Banging it on the counter, pressing on the piston and not. Wasn't coming out, so I soaked it in undiluted Muriatic over night. The keeper was much cleaner but still not coming out. The keeper side and the reverse side

So I didn't want to break the disc banging on it so I drilled some holes in it so I could punch it out

Now this will create four holes that I will have to seal up. I will probably use JB weld

Keeper is out. Even after soaking in acid over night there was still a lot of rust. If I had left it longer it might have come out then

But I damaged the disc

My punch had a flair on it and when I drove the keeper out the flaired section cracked off the flange. More JB weld. shouldn't be a big deal because it just needs to seal. No real pressure there on the flange

Now I need to figure out how to break this plunger down. Can't figure it out even from CO's picture

Worked on my booster tool some too

Made the metal plate and welded on a lever arm

and a piece of 2 1/2" PVC conduit about 6" long to help squeeze the can

 

Edited August 25, 2018 by Patcon

[kats]

Hi , nice work!! And it is a great source for you in the US .

In Japan, Skyline Ken - Merry GTR master vac is usable for 6 inch vac , internal parts are only usable, not usable the outer case  . And it was still available at 2013 . I now am asking local Nissan if  it is still available new .

https://blogs.yahoo.co.jp/power_planning/56600650.html

Kats

Edited August 25, 2018 by kats

[kats]

Oh , Nissan said 47210-R5511 still available!! 42200 JPY without tax .

It is weird that Ken-Merry GTR was sold only 197 ? cars , but Nissan is still selling  it for the car . We have to push Nissan making more parts for our S30s which are still enjoyed so many people around the world !!

Or, powerful GTR owner’s club boss threatened Nissan to make it , ha ha .

Kats

 

Also , Prince Craft in Nagano Japan 

[Namerow]

6 hours ago, kats said:

Nissan said 47210-R5511 still available!! 42200 JPY without tax .

@kats

Thank you for investigating.  This is the equivalent of about US$400.  When compared with the current price for a rebuilt unit -(US$200), that seems a reasonable price for a comparable-design, new-old-stock Nissan part.  As you note, however, only the internal parts are useful for the owner of an S30. 

If you have the time, would you please ask your Nissan parts source whether either of the original re-build kits for the S30 MasterVac are perhaps still available?  They are:

KIT-A REPAIR FOR MAS - 47210-E4625

KIT-B REPAIR FOR MAS - 47210-E4626 (includes Kit 'A', plus the plunger, check valve, and filter-silencers)

According to the manual, these kits were designed for use only with S30's produced up to Aug. 1971.

There is only a small possibility, I know, but I think worth investigating. 

[Captain Obvious]

Bummer about cracking the bakelite disk. I would have been with you on using JBweld to seal up the small holes, but I'm not sure I would try to repair the rest of that damage. I'm thinking a replacement would be prudent.

And I'm sorry that it's too late, but here's how I got my stuck retainer clip out. Couple small rare earth magnets. Very strong for their size:

And this is what my poppet valve plunger looked like when it first came out. Looks just like yours:

As for disassembly of the poppet valve assy... The end piece is crimped into place and is not meant to be disassembled. You can see the dents of deformed material that hold the end on. The only reason I even knew it was possible to take it apart was that I had bought a rebuilt booster and it was clear by the marks on the valve that it had been disassembled and subsequently reassembled. I don't have any pics of the "rebuilt" one, but you could see that they had "repeened" the dents that held it together. Of course, the workmanship there was suspect... It looked like they whacked it with a center punch a couple times around the circle. But the point is... They were doing it, and I figured I might try it on my spare valve. Had nothing to lose.

So I cobbled together a "fixture" from cut-offs and shorts and whatever chunks of metal I had laying around:

And put it on the hydraulic press to push the end off the valve shaft:

Here's what it looks like when it comes apart:

If I was going to be doing more of these, I'd build a better fixture for taking them apart, but since I wasn't even sure it would work, I spent very little time on it. It came apart easier than expected. Might even be a small enough force that you could cobble up a "puller" using a large C-clamp instead of using the hydraulic press.

And for the reassembly, I would try to recreate the original dimples, but I won't move to that part until I get the seal from you. 

[Patcon]

24 minutes ago, Captain Obvious said:

 

And for the reassembly, I would try to recreate the original dimples, but I won't move to that part until I get the seal from you. 

That's funny. I think my poppet seal is ripped, so I will probably need it. I think you could call Ed at Harmon Classic Brakes and he would send you one. Is that seal just supposed to stretch over the plunger or do you suspect they disassemble the plunger and then repeen it? I would like to clean all the parts and plate some of them to make them last a little better. I thought about trying to use magnets to pull it out but I figured if banging it repeatedly on the counter didn't move it at all then the magnets weren't going to help. Oh well, "tuition"...

I wonder how difficult it would be to repeen the fixture?

I will still probably JB weld the flange. The only thing it really does is gives the disc a slot to seal in so it's worth a try. If the booster holds vacuum then I'll go from there

[Captain Obvious]

Haha! I figured when you were thinking of taking that poppet valve apart, you would need that seal. I believe replacement does require disassembly. I don't think there's any way that seal will stretch over the end for replacement without tearing it. It's just too large of a change. And the rebuilt valve I have was clearly reassembled by Cardone.

I don't think it would be too difficult to build a little fixture to re-peen the end. I was picturing a half round support for underneath made out of quarter inch thick plate and then a small punch on top to press the dent in. Do it on the hydraulic press.

[Patcon]

17 minutes ago, Captain Obvious said:

 

I don't think it would be too difficult to build a little fixture to re-peen the end. I was picturing a half round support for underneath made out of quarter inch thick plate and then a small punch on top to press the dent in. Do it on the hydraulic press. 

Of course I was ?

By the way when will you be shipping that fixture to me? ?

[kats]

Hi , I am asking the repair kit , I hope Nissan still making it .

Here is a link of my friend Mr . Watanabe was doing about repair job using Ken & Merry master vac .

http://z432.sakura.ne.jp/bmv01.html

And Prince Craft is doing repair job for numerous Prince and Nissan master vac .

http://www.princecraft.net/pc04.html

I miss the 47210-E4626 , it was on Yahoo auction some years ago about 10000 JPY ( 90 USD ) , sometimes we see it , so I hope more coming in someday.

Kats