7" brake booster repair and restoration

[Patcon]

@kats

This may be one situation where those of you in Japan could order rebuild kits for these booster from a vendor in the US. I haven't completed the rebuild yet but the early Mustang kit seems to have all the right pieces

[kats]

Patcon , I agree , after seeing this thread  I googled “Mustang power brake Japan  “ , lots of shops in Japan are listed , they will provide the kit . I really want to introduce this to Japanese S30 owners if the price is better than buying a GTR master vac . Some S30 repair shops already might know about this , just people like me do not know about it . Even so , it is very nice to know that we have a choice more than one .

BTW , 47210-E4625 and 4626 were discontinued 

and will not be available anymore, I have just received that  reply from Nissan .

Still waiting for the reply of 47210-R55@@ , a kit for Ken & Merry GTR master vac .

Kats 

[kats]

A kit for GTR master vac is not available and will never be available ,  Nissan said .

Kats 

[Namerow]

7 hours ago, kats said:

BTW , 47210-E4625 and 4626 were discontinued 

and will not be available anymore, I have just received that  reply from Nissan .

@katsToo bad, but at least we now know with certainty.  Thanks for investigating.  We will now need to hope for a successful outcome from Patcon's experiment with the Mustang kit.

[Captain Obvious]

22 hours ago, Patcon said:

when will you be shipping that fixture to me?

As soon as I'm done with it? Haha! Let me see what I can come up with.

You can see a whole complete poppet valve plunger in the bag in pic that Kats posted. Complete with seal already on the assembly and crimped together. So it's clear, not surprisingly, that Nissan was never expecting that plunger to be disassembled:

I had mentioned it before, but the only reason I even ever started messing with taking it apart was the one that came in my rebuilt booster had been disassembled and had a new seal installed by the rebuilder company. So I knew it was at least "possible".

Here's a question for ya.... What is the recommended replacement procedure for that poppet valve seal on the Mustang booster? It's included in the kit, so clearly they are expecting you to use it. Did you find any pics or instructions for the expected use of that rebuild kit from Harmon? In other words... Does the Mustang poppet valve assy come apart and go back together easier than the one from Hitachi? Is the Bendix version easily repairable or is it crimped together like the Hitachi version?

[Patcon]

56 minutes ago, Captain Obvious said:

Here's a question for ya.... What is the recommended replacement procedure for that poppet valve seal on the Mustang booster? It's included in the kit, so clearly they are expecting you to use it. Did you find any pics or instructions for the expected use of that rebuild kit from Harmon? In other words... Does the Mustang poppet valve assy come apart and go back together easier than the one from Hitachi? Is the Bendix version easily repairable or is it crimped together like the Hitachi version? 

That's a good question and I don't know the answer. No real instructions in the kit, just the exploded diagram. I searched online and only really found one Bendix booster rebuild video. It's ok but not really helpful. Really only has the tear down. No rebuild video and it's 2 years old. So I assume a second video is not forth coming.

I made a set of "anvils" yesterday. They are sort of down and dirty. Not nearly as elegant as you would have made Bruce, but I think they will suffice.

I made a quick tool to pull the plunger rod. 2 anvils and a short section of 1 1/4" pvc and a plate with a hole across the end. Set the anvils in the vice and tighten a nut from the other end and it pulls right apart. Really didn't take much pressure. I will have to come up with a punch now on reassembly

[Patcon]

Exploded view of the plunger

and after plating

Now I need to come up with a punch. Maybe a reworked flat head screw driver

[Captain Obvious]

Nice plating! You're clearly getting better results.

And I like the way you pulled the plunger apart. I wasn't sure how much force it was going to take and I didn't want to use the threads to jack the assy apart. But now that we have seen that it's not a huge amount of force, your fixture is clearly capable and is a lot less wobbly than what I did. I'll do that next time (if there is a next time).

If you use one of your anvils to support the bottom 180 degrees (and spread the load), you should be able to re-peen the other side. Mine had three punch marks 120 degrees apart. How about yours? The same?

[Patcon]

10 hours ago, Captain Obvious said:

If you use one of your anvils to support the bottom 180 degrees (and spread the load), you should be able to re-peen the other side. Mine had three punch marks 120 degrees apart. How about yours? The same?

Yes 3 punch marks and they are like little rectangles. Sort of like the head of a screwdriver. That's why I thought it might be a good candidate as a punch. I wonder how hard that part is? It's steel because I checked it. Maybe the body is thin right there?

[Captain Obvious]

That part is steel and is not hardened. It had to be malleable enough to deform for the original retention, and although it's not what I would call "thin" there, it will take a significant amount of force to upset the metal. I'm not sure you'll get enough force with a plastic handled screwdriver. I think it's going to require metal to metal to metal.

A thousand ways to approach the task, but here's my thinking... I was picturing three pieces for a fixture to do the peening. One semicircular support anvil for underneath, and an identical piece for the top except that it is drilled on the top dead center for a punch. Then the punch would be a short stub of round hardened steel (1/8 diameter maybe?) that would fit snug into the hole and would be ground at the business end to a shape similar to the original punch mark.

You can make the two anvils easy by drilling an appropriate sized hole in some 1/4 thick plate and then carefully cutting through the middle of the hole on the bandsaw. Poof. Two smooth semi-circles with the saw kerf supplying the necessary clearance between the two.

Put the support anvil under the plunger, cover with the sliding punch top anvil and use the hydraulic press to push the punch downward through the hole into the valve assy.

More work than just whacking it with a screwdriver, but much more controllable. You should be able to feel the rod sticking out of the retainer tip seal as you apply the force and make sure you don't go to far. That piece needs to be wobbly on the tip in order to work right.

[Patcon]

9 hours ago, Captain Obvious said:

That part is steel and is not hardened. It had to be malleable enough to deform for the original retention, and although it's not what I would call "thin" there, it will take a significant amount of force to upset the metal. I'm not sure you'll get enough force with a plastic handled screwdriver. I think it's going to require metal to metal to metal.

A thousand ways to approach the task, but here's my thinking... I was picturing three pieces for a fixture to do the peening. One semicircular support anvil for underneath, and an identical piece for the top except that it is drilled on the top dead center for a punch. Then the punch would be a short stub of round hardened steel (1/8 diameter maybe?) that would fit snug into the hole and would be ground at the business end to a shape similar to the original punch mark.

You can make the two anvils easy by drilling an appropriate sized hole in some 1/4 thick plate and then carefully cutting through the middle of the hole on the bandsaw. Poof. Two smooth semi-circles with the saw kerf supplying the necessary clearance between the two.

Put the support anvil under the plunger, cover with the sliding punch top anvil and use the hydraulic press to push the punch downward through the hole into the valve assy.

More work than just whacking it with a screwdriver, but much more controllable. You should be able to feel the rod sticking out of the retainer tip seal as you apply the force and make sure you don't go to far. That piece needs to be wobbly on the tip in order to work right.

That sounds above my paygrade. ?

You know I am going to end up at the Whack-a-Mole method?

I figured I would hold it assembled with a clamp, because you have to resist the spring pressure. Then mount the semicircular anvil in the vice and punch it. It's true it's not very precise. I am more worried about too little crimp than too much. I can always use the puller tube slightly to provide some free play if it's over punched. I figured I would use a handleless flat head as a punch.

[Namerow]

Thinking out loud here (always dangerous, I know).  Instead of the factory strategy of staking the part, is there enough wall thickness to take three short pins?  Dress the ends to make them round-ish.  Drill the holes for a close fit (Loc-tite) or a light interference fit.  The pins wouldn't be subjected to much in the way of long-axis loading.  Just 'wobble' loading.