Customs dual master power booster upgrade not working

Maybe put in a box by, not made. I think there's one factory in China making them for everybody to package up.

Apart from that, I agree with Cosmo.

 

The only thing done right is that it's below the level of the master. If you want to go the hydraulic switch route, there are proportioning valves made to plumb those in. You should always use as few connections as possible on a brake system.

 

I've been critical, now here is how *I* would do this job:
Get a master that matches the bore of the OEM master. That one looks too large, betting it's a 1 1/8", probably should be in the range of 7/8 to 15/16", but should match the OEM.
Get a booster from a car the same size as yours. Hydro-Boost has been mentioned (by me), and I see power steering lines, so no problem there, just plumb it in (if no room for a proper booster).
Mechanical brake switch!! If you are updating the car, UPDATE the bleeding CAR!!
Plumb the brake properly. The lines should loop once under the master for safety.
More rubber in that vacuum line, so the engine can move W/O damaging that.

As for the job that has been done so far: I do not think they really know what they are doing, unless they have you pegged for a sucker with money, and they are trying to bleed you dry. That "workmanship" frankly sucks as a job by supposed "Professionals". I further do not believe that they CAN actually "fix" this to the way it should be done. Any proof you need of this opinion might be in that you have needed come to the HAMB for advise, all the while entrusting your car, and your life to 'professionals', who have not been able to do a job properly IN THE FIRST PLACE!! It's not rocket science, its brakes, a science, true, but you are not re-inventing the Space Shuttle, you're just replacing a booster/master cylinder.

Cosmo

P.S. Yup, Harsh, capital aitch. But, paying for a job indicates a professional should be involved. You, your family, and all others on the road have their lives dependent on this job being done properly.

 

You have a hanging brake pedal so this switch will work, it's a common GM brake switch. http://www.carid.com/1975-chevy-nov...zqNrV2jqP0B7CGpr6GLX7K_fF8YfcHELtERoCPGbw_wcB
It mounts in back of the pedal so that when the brakes are applied it opens the switch which in turn supplies juice to light the brake lights. The only hook-up needed is to splice it into the brake light wire. Super simple and I can't remember ever having to replace one.

 

Isn't that adapter pipe threads vs brake? I was thinking of swapping out the MC for one with ports on both sides and screwing the switch directly into that then having them plug off the T that is there?

 

I appreciate your feedback and advice no matter how harsh. I came here for input because I'm not sure that the right job is being done. They are not a bad shop and have always done me well in the past, but I think my 'old car' is not their priority and they don't want to invest the time needed to really make this right. The owner told me yesterday to just get the original single rebuilt and put it back in and that should work because it did before...but it never really worked in real world testing. The thing eventually failed, seemingly due to a bad rebuild. The guy that rebuilt it in San Jose said we didn't break the new seal in quick enough after he finished the rebuild. He said if we put brake fluid in and let the car sit, then a leak could occur. Does that sound right???

As for the Hydroboost...if something happens to the power steering system, could that cause a brake failure? I never rebuilt the power steering pump so that's my only concern going that route. The bore on that MC is 1".

 

This T is 3/16" inverted flare at both ends and 1/8" female pipe in the middle. As Cosmo said , you should really put a mechanical switch on the pedal. The oem manufactures all do them this way now for a reason - reliability.



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hydroboost has a built in pressure accumulator that allows you to have a reserve of 2-3 full pedal pumps to get you stopped ( its like when you pres the brakes on your DD now you have 1-2 pumps before it goes hard enough to peel off the speed then allow the lower pressure to finish the stop ) . if the pump goes bad/ break a belt you just loose the assist but still have the reserve ( I have lost my belt and the pedal pressure isn't so bad once the reserve assist is gone )

the redudndent safety they build into the system is real good as they use it on all the heavy duty Pickups ( 3/4- 1 ton ) and some of the larger medium duty trucks ( u hauls and straightrucks and school buses )

as for the break in of the seals . then many cars would be going back from seal failure as I know from being in the parts business at one time some of them things can sit on the shelf for months or years before we got a call on them , and only time I saw one come back was because of they didn't bench bleed it properly or at all (#1 return ) , or the rebuild used crappy materials or improperly put together ( had one the cups were backwards) or the work was shotty ( not honed proper ( too rough ) or the bore wasn't inspected and pitted .) we had one place we tried because the owner said the prices were real low , basically they did as little as possible and reused lots of the parts and replaced only the bad ones , no honing , and a pretty paint job , we had failure rates out the Butt ( 1 out of 2 were bad) . sent the whole inventory back to the supplier , (they were on our shelf for only 3 weeks ) boss lost money .

 

Let me translate here: They are NOT a 'Rod Shop', they are a late-model repair shop that is in over their head.

Same as if your engine quit, you have a reserve. Hydro-Boost is decidely NOT new tech, been in use for many decades. And is ideally suited for larger cars without a lot of room.

The bore on the new master should match the old, what is the old master's bore??

Cosmo

 

Hydroboosts were common in GM station wagons and Cadillacs where diesel engines were an option. The master, PB are peculiar to the hydroboost, at least on my '84 wagon they were. I'm sure you could find the whole system used.

 

Everything GM Diesel, and most 1-ton dually stuff has hydroboost.

 

You need to get your hands dirty and do it yourself instead of some shop that doesn't know what they're doing giving you a half assed job and taking your money. Read and absorb posts 33 & 34

 

Power Brake Exchange in CA were the ones who told me that I had to keep using it within 6 months or the seal may fail. Every rebuilder I've spoken with says this can't be the case. The hydroboost is starting to sound really good....

 

The bore on my original was odd...It measures 21/32". The systems that didn't have power brakes were a 1" bore. The dual master upgrade I got was a 1" bore as well. Couldn't find anything close to a 21/32 and figured if 1" is good for a standard system on the same car it would be good for mine.

If I had all the gear to do this myself (lift, flaring equipment, etc...) I would. I'm probably going to trailer it out of there if they don't get this straight within the next day. The manufacturer is sending replacement parts and said to test the booster off the car first by attaching an electric vacuum pump and manually pushing on the rod to make sure it goes through easily. If it has a problem when it's mounted, and there is enough vacuum at the booster, they said the shop probably isn't hooking the pedal up right. Either way, I'm already looking onto the hydroboost systems. Would you recommend an OEM rebuild or aftermarket?

 

You effectively went from just over 5/8" all the way to 1" based on the thought that if it was good enough for a different car, it's good enough for you??

Leverage-wise, that's HUGE!!

Any thought that the manual brake car may have had different sized wheel cylinders as well??

You NEED someone who knows what they are doing, really.

Cosmo

 

Is there a chance that there was a plastic plug in the front of the power booster where the master cylinder bolts up? When I ordered one of those 8 universal boosters it was sent with a " remove before installing/only for shipping" plug in it. If it wasn't removed it could keep everything from moving....


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At the recommendation of several hot rod shops, I went with the 1" based on their advice. I didn't know enough about these things to make a decision on my own. I was trying to make an informed decision based on everyone's advice at the time and five shops said go 1". I will check into the wheel cylinders. Valid point.

 

I question the original master cylinder bore only being 21/32". The only master cylinders I have seen with bores that small are clutch master cylinders. How about double checking that original master cylinder size?

 

Was the OG system a treadle-vac? If so, the 21/32" master bore may have been suited for that and that only. I'd think that either a 15/16" or 1" would work fine for use with a modern 'booster.

 

The info from one of my old Motor's manual shows the mid-'50s Buick used the Moraine piston type power booster. The '56 std. (non-power) master cylinder bore was 17/32" while the power was 21/32". The '57-'58 std. bore was 1", and power was 21/32". The '59-'62 masters went back to a 1" bore, and mated to master vac-style booster.
Wheel cylinder sizes were the same 1 1/8" frt./1" rear from '55 (maybe earlier) to '64.
As stated previously, these small bore masters were OK for the that design power booster, period. But these old Moraine, Bendix Treadlevac/Hydrovac and similar boosters were very complicated, expensive, cannot be compared to and should be replaced by later design vacuum boosters, unless the car will sit in a museum, imo. Pedal ratio needs to be checked, however, as modern boosters usually require a 3-4:1 ratio, and may be different with the early boosters. Pedal travel has to be checked also, and verified that the master can be fully stroked (both systems open) before the pedal runs out of travel.
There's no reason you can't use a 1" dual master with your '58 drum brake system, and that 8" tandem booster should work just fine as long as it's not defective, and your engine can provide adequate vacuum. The Bendix-designed Hydroboost is a very good choice for vehicles that require power assist, but have low or no (diesel) engine vacuum.

 

Yes. It is definitely 21/32" bore. I told the shop to make sure I have a 4:1 ratio at the pedal, which is what the specs say it needs to be. They said there's no easy way to do that because it's pivot point is not the same as a lot of pedal assemblies, so they are basically going by the feel of it and making sure they have 5-6" of clearance from starting point to the floor, which they say is how it should be. Is there a way to adjust the pedal on this? It's driving me nuts. Tomorrow the new master and booster will be in and I asked them to test it off the car first by hooking it to an electric vacuum pump and pushing the rod through. If it does, I said we know it's good and go through with the install. The new master has an extra port for the brake light switch and I told them to use that and get rid of the 'T' in the line they made for it.

 

I'm not familiar with your pedal assembly, so it may be difficult to make it a 4:1 ratio. One option would be change out the pedal assembly. The important thing is to make sure the master can be fully stroked with whatever you end up with.
One (of several) problems using a hydraulic brake light switch in a dual system is if the system it's plumbed into fails, so do the brake lights. You are much better off to install a common internal mechanical switch on the pedal or bracket, as previously suggested.

 

I'm definitely going to switch out to mechanical switch once I get the car from the shop. Not something I want to pay them to do. I just want them to get rid of the 'T' they put in the line, so for the time being the one on the master will do to get me down the road to my garage. Here is a diagram of my brake pedal assembly. Not sure how to calculate the pedal ratio since it's not your standard pivot point assembly. Any ideas?

 

In this case, I would carefully measure and divide actual pedal travel by the corresponding push rod travel.

 

Do you still have the original master cylinder? If so, could you measure the total travel?

 

PM twochops. He redid his 57 Buick and I remember him telling me it was a job getting everything figured out, replaced and working right

 

Don't lose sight of the original issue.. the booster does not seem to be working. I'm personally leery of aftermarket items like that. I would have gone with a remanufactured or new GM master/booster combo. Like something off a '66 Riviera for example.

 

If you used the original pedal; that is probably the biggest part of the problem, ratio is way out of line for a normal booster and master.

 

Ok, how do you calculate the ratio on the original pedal and what would be an ideal pedal to use? Everything I'm finding is pretty much the same universal design.