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Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt


Roman

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Slap me if i'm telling you to suck eggs etc. But I recall having to get mine adjusted and just needed a tool the measured the depth of the master vs the poke of the booster, just had to match them up. Easy tool to make, or could just use calipers to measure.

Brakes can be such a nightmare, hopefully they have done what they are supposed to have and it's something simple. CBC did a good job of other stuff for me.

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I might make one of those tools to get it spot-on, but right now it's 16mm too short for the M/C so something is way out of whack. I understand that the reaction disk is loose and can fall out if the pushrod is pulled forward. Since I got it back from the first shop with the booster separate from the M/C I suspect that's what happened.


CBC re-did the M/C, not the booster (yet...)

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24 minutes ago, Nominal said:

I might make one of those tools to get it spot-on, but right now it's 16mm too short for the M/C so something is way out of whack. I understand that the reaction disk is loose and can fall out if the pushrod is pulled forward. Since I got it back from the first shop with the booster separate from the M/C I suspect that's what happened.


CBC re-did the M/C, not the booster (yet...)

Yeah sounds complicated. When I was pissing around with mine the whole rod came out and I lost it in the engine bay. Maybe I was lucky nothing went wrong. Think I pushed the brake pedal with no M/C installed, because smart. I thought they did booster too, was trying to remember. 

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1 hour ago, sr2 said:

What were the symptoms?

It's a journey.

I blew a rear slave cylinder out back in late Feb, and since I was having to work on the rear brakes I thought it was time to get the booster/MC rebuilt, it's just over 50 years old and never been off the car (I'm pretty sure). The front calipers were rebuilt last year.

I took the lot into the brake shop (ABC). They supplied new rear shoes and the slave cylinders easily enough but then took ages to get the booster done. They told me that the were having trouble getting the booster to hold vacuum when reassembled. Eventually they got it to work after replacing (one, both?) diaphragm. (I dunno I thought I was paying them to do that anyway). Instead of rebuilding the original big nut M/C they supplied a new pattern part with an alloy body. They also stripped down the brake warning switch/slider part and put new seals in it.

When I put it all back together initially I couldn't get the warning switch slider to reset properly. Later on I've worked out that the pin on the end of the switch is too short so the warning light never actually goes out no matter where the piston is.

I took it for a drive up the road but the brakes weren't right, quite grabby at the front (discs) and still felt like the rears weren't working (too much pedal travel). I wasn't even sure that the replaced M/C had the same pipe arrangement, in the stock setup the rear part of the M/C goes to the rear brakes.

So I sent the original M/C down to the place in Christchurch who rebuilt it. Thought I'd be sweet, but no. I couldn't get the rear brakes to bleed properly. Eventually I disconnected everything from the rear and just put a return pipe from the rear port back into the M/C, when pushing the brake pedal almost no fluid was coming out the rear port. So I sent the M/C back to Chch to be checked. They sent it back with no notes so I don't know if there was an issue or not.

I've made a rig to bench test the M/C and it seemed to be working OK, but when I put it back on the booster the pedal travel was massive so pulled it off again.

So after that I had a measure up and worked out that there is about a 15mm gap between the end of the pushrod out of the booster and the push point inside the M/C. Looking into the booster I couldn't really see if the reaction disc was in there (I've done a bit more googling of how boosters work) There didn't seem to be anything loose inside the booster.

So, I took the booster and the M/C back to ABC on Monday for them to have a look. I showed them the issue but I haven't heard anything from them. There must be something wrong inside the booster but I don't know what. I did have a go at splitting it, but gave up as the force I was applying seemed excessive. 

 

 

20220307_211448.jpg

20220624_094507.jpg

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On 30/07/2022 at 17:30, Nominal said:

It's a journey.

I blew a rear slave cylinder out back in late Feb, and since I was having to work on the rear brakes I thought it was time to get the booster/MC rebuilt, it's just over 50 years old and never been off the car (I'm pretty sure). The front calipers were rebuilt last year.

I took the lot into the brake shop (ABC). They supplied new rear shoes and the slave cylinders easily enough but then took ages to get the booster done. They told me that the were having trouble getting the booster to hold vacuum when reassembled. Eventually they got it to work after replacing (one, both?) diaphragm. (I dunno I thought I was paying them to do that anyway). Instead of rebuilding the original big nut M/C they supplied a new pattern part with an alloy body. They also stripped down the brake warning switch/slider part and put new seals in it.

When I put it all back together initially I couldn't get the warning switch slider to reset properly. Later on I've worked out that the pin on the end of the switch is too short so the warning light never actually goes out no matter where the piston is.

I took it for a drive up the road but the brakes weren't right, quite grabby at the front (discs) and still felt like the rears weren't working (too much pedal travel). I wasn't even sure that the replaced M/C had the same pipe arrangement, in the stock setup the rear part of the M/C goes to the rear brakes.

So I sent the original M/C down to the place in Christchurch who rebuilt it. Thought I'd be sweet, but no. I couldn't get the rear brakes to bleed properly. Eventually I disconnected everything from the rear and just put a return pipe from the rear port back into the M/C, when pushing the brake pedal almost no fluid was coming out the rear port. So I sent the M/C back to Chch to be checked. They sent it back with no notes so I don't know if there was an issue or not.

I've made a rig to bench test the M/C and it seemed to be working OK, but when I put it back on the booster the pedal travel was massive so pulled it off again.

So after that I had a measure up and worked out that there is about a 15mm gap between the end of the pushrod out of the booster and the push point inside the M/C. Looking into the booster I couldn't really see if the reaction disc was in there (I've done a bit more googling of how boosters work) There didn't seem to be anything loose inside the booster.

So, I took the booster and the M/C back to ABC on Monday for them to have a look. I showed them the issue but I haven't heard anything from them. There must be something wrong inside the booster but I don't know what. I did have a go at splitting it, but gave up as the force I was applying seemed excessive. 

 

 

20220307_211448.jpg

20220624_094507.jpg

 

LOL, I have to confess I haven’t had one of those in bits for a long, long time. Even when all the internal parts were available new they were pricks of things to work on. The two piece Bakelite valve body had a habit of breaking when you unscrewed them and it was often a mission to get them to hold a vacuum when reassembled. As a rule of thumb if an earlier style tandem PBR Mastervac is is working and most importantly dry inside all I would do is replace the output shaft seal & lubricate, replace the foam air filter and lubricate the input seal. In their defence they were reliable as long as the master cylinder didn’t dump brake fluid into them.

Yes the cans are hard to separate, even with a jig it’s quite easy to bend the studs or even rip them out. The trick is to work your way around the lip with a small pry bar to break the seal, even then the diaphragm rubber sticks to the steel can like s*** to a blanket!

Another option is to bite the bullet and spend around $500 AU on ebay and buy a new aftermarket booster/master cylinder assembly.

https://www.ebay.com/itm/222137052973

I think Flash bought something similar for his Mustang, could be worth contacting him re the supplier.

With rear brakes I never trust the self-adjusters, a little extra effort when assembling often avoids excessive pedal travel issues. It’s also important to radius the shoes to fit the drums.

Feel free to PM me if there’s anything I can do to help.

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