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ziff73

Brake diagnosis question

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Hi all. I've read all the threads and just want to make sure I'm thinking straight about my brake issue. I'm not a first timer, so feel free to call me an idiot and say I missed 'the' obvious thing....;-) I just finished a ground up on the car, so everything is very clean and basically new or rebuilt.

So, my 69 1600 brakes are single piston fronts. Everything is new/rebuilt on the car, including the calipers that I rebuilt. I have braided lines, new pads, etc.

My problem is the brakes were weak to begin with when I first buttoned everything up and recently started to get worse, and now I have almost no stopping ability.

The early symptoms were that I couldn't get much brake force without the pedal going down pretty far (which I know the factory did not intend, even on these tiny 1600 brakes). I bled the system several times and adjusted the rears several times to make sure they were just off of dragging. In just the past couple days the pedal would stay part way down after I came to a stop and would come up after I tried pumping it a little...along with that, the braking force has been diminishing and my effort has needed to increase significantly. Last night, it almost totally disappeared...luckily I was in my neighborhood and I was fine with the hand brake for the last few hundred yards. (and NO, I'm not driving it. it's not a daily car)

I see no fluid level loss from the res at all...none. The calipers don't appear to have any fluid or seepage on or near them, either.

I just finished pulling the booster and master off and bench tested for vacuum hold...it held 5 or so psi until I got bored standing there, so I believe the booster is good.

The inside of the booster does appear to have a wetness to it...brake fluid. Problem is, I really have had no loss of fluid level (except maybe when I first was tuning and bleeding). the back of the mc is dry as a bone.

-Is there some way that I'm missing for fluid to get in the booster?

-Could the fluid have been from the initial start up and use of the system from a 20 month shelf sitting? maybe the mc pissed a little fluid on the first couple pumps until the seals moistened up?

-Does this all just sound like the mc is leaking internally and just replace it?

Thanks for reading through this whole post! I've tried to do my homework and just wanted a fresh look at it before I starting buying parts.

Thanks!!

Stephen

IMG_6251.jpg

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Stephen, check the booster for vacuum , not pressure, it's harder to pull a vacuum & maintain it. I'd say it is the booster. Run your car , switch it off & pull off the vac line to the booster it should suck (literally) also make sure the vac check valve is in the right way around , I made that mistake once, no boost . I have since deleted my booster (lengthened my pedal to restore ratio). Beautiful car !

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Thanks Steve!

Shit, I just realized I don't have the check valve!? Not sure how I missed that...can I get those at pep boys or do I need a specific one for 02s?

That might be the problem right there....geeeez.....I'm too close to the problem.

How do you like the boosterless set up? How tough is that to do?

Stephen

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is the master cyl new? how long ago was it new?

when the car is parked and off, is the brake pedal firm without a long throw?

if you hold pressure on the brake pedal with car off and parked, does it stay in the same place or gradually go to the floor?

i don't know the 1600 caliper arrangement, but is there any chance the right and left were reversed when car was reassembled and bleed screw is not at the top?

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DO NOT GO BOOSTERLESS - your not a race car / driver!!!

get the correct reinforced vacuum booster hose

that wont collapse on itself and the correct one-way

check valve - order from member BLUNT here abouts

only way brake fluid enters the booster is out of the back of

the master cylinder - and if this booster

had this 'condition' years/decades ago the seal inside

may have given up from the nasty presence of brake

fluid

- bad booster will result in a rock hard brake pedal

- - bad master cylinder will result in a pedal that

falls to the floor slowly at stops.

- - - if you have new pads with new front disks - you will

also have a spongy pedal until the pads have

seated with the rotors

- - - - - even softer pedal if you replaced just

the pads and are using the old disks.

Not the prudent thing to do!!

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Nice car - is that Sahara? I once had a similar 1600-2.

Odd that the pedal doesn't come back up.

One thing that can happen with rebuilt cylinders is that if bore has pitting, or rubber seal gets damaged on installation, fluid is simply pushed back over the seal instead of going out the pipes. So no fluid loss, just recirculation. Just a thought.

What did you mean by "check valve"? On the manifold?

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is the master cyl new? how long ago was it new?

when the car is parked and off, is the brake pedal firm without a long throw?

if you hold pressure on the brake pedal with car off and parked, does it stay in the same place or gradually go to the floor?

i don't know the 1600 caliper arrangement, but is there any chance the right and left were reversed when car was reassembled and bleed screw is not at the top?

Thanks for the reply!

-Master cylinder is old...don't know how old. That's pretty much why I was going towards that as bad.

-with the car off, the pedal feel is much firmer with less of a throw.

-I'm honestly not sure if it goes slowly to the floor with car off...(it's in pieces now)

-Calipers on on correctly (I made that mistake once 12 years ago!)

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DO NOT GO BOOSTERLESS - your not a race car / driver!!!

get the correct reinforced vacuum booster hose

that wont collapse on itself and the correct one-way

check valve - order from member BLUNT here abouts

only way brake fluid enters the booster is out of the back of

the master cylinder - and if this booster

had this 'condition' years/decades ago the seal inside

may have given up from the nasty presence of brake

fluid

- bad booster will result in a rock hard brake pedal

- - bad master cylinder will result in a pedal that

falls to the floor slowly at stops.

- - - if you have new pads with new front disks - you will

also have a spongy pedal until the pads have

seated with the rotors

- - - - - even softer pedal if you replaced just

the pads and are using the old disks.

Not the prudent thing to do!!

Thanks for the reply CD!

-Not going boosterless...just curious..:-)

-Yes, I found my ATE valve in my stash of parts....stupid me

-I totally understand the mc leak being the only way for fluid in the booster, but the back is really dry...could it have just been a leak due to the mc sitting for 20 months and now it's not leaking? I know, strange...

-Definitely not rock hard pedal feel..plus booster holds vacuum from a mighty vac, very well...booster seems good.

-Feeling more and more like an internally bad master

-New pads, new discs...I did think about that, too, but the pedal feel got worse, not better as mileage increased...still could have a small effect on it, though..only 280 miles on it since resto. I'd never do the pads and not the discs...:-)

Okay....all questions answered...thanks for the help! It's really looking like the master, huh?

would the lack of the valve cause all that? cheap insurance to replace an unknown master, anyway...which I'll be doing.

Oh...the color is Manila! Original color for her..;-) I believe only a 1600 color?

Thanks everybody!

Stephen

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I like the no booster, I made a tube adapter to replace the removed booster , then extended the pedal by tig welding an overlap onto the pedal, hammer welded (I am a certified welder so no problem there) I got used to it really quick . I now have the room for my Dellortos & velocity stacks.

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and one more thought about the non-returning pedal ?

did you molest the pedal linkage to the booster/master in

anyway? Lots of folks here have and later found the

binding there from improper tightening/adjusting/no lube ?

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That's a good call, too. I didn't muck with it, but cleaned, painted, etc...it may be a bit stiff and need some lube...wow, that last part did not sound like I was talking about a brake pedal...

Thanks CD!

Unfortunately, I'm stuck till next week sometime to find a new master...grrr... nice weekend and no toy to play with...;-(

Anybody in SoCal have a new MC they want to unload tomorrow?..:-)

Stephen

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..." unfortunately, I'm stuck till next week

sometime to find a new master...grrr...

nice weekend and no toy to play with...;-( "

then good time to vacuum the house!

NOT!

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Ha! no...I can find other projects to do before vacuuming...:-)

Actually, I've been playing with the brakes again and found that there's a really bad 'catch' in the pedal travel..the pedal pushes down part way, then it gets really stiff and thunk! it goes to the floor..(THIS IS WITHOUT THE MASTER HOOKED UP, btw)

I checked linkage without the booster on and it travels fine...with the booster, bam, the hard catch... Is this a known failure of the booster? Not the traditional vacuum failure...

Thanks guys

Stephen

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If you need another booster I have my old one , it worked fine , it's in Whittier at my shop

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