G'Day,
The brakes on my 510 wagon are giving me some grief. We've reconditioned the rear drums with new wheel cylinders, rubbers, springs etc & had the drums machined & fitted brand new shoes. At the front I'm running 200B disks & calipers (girlock) - they've had new pads, seals etc etc. The front brake lines are all new. I've fitted a reconditioned 180B vacuum booster aswell. You'd think she would pull-up pretty good now but
when I stand on the anchors the pedal is seriously spongy & stops about an inch off the firewall !! We've bled the system about 5 times with only marginal improvement. Has anyone had similar problems ? What am I missing ?
Regards
SB

As an aside, why not just take it to a brake shop like ABS and have them drain and flush/refill the hydraulic fluid.
This should be done every 2 years anyway.
Then hopefully, the master cylinder to each wheel will be professionally bled. (It is my guess that there is air trapped in the M/C)
Also check that the booster tank is getting plenty of vacuum from the engine - if there is a one way valve in the vacuum line make sure it is connected the right way round.
Disconnect the line at the booster and you should hear vacuum from the hose when the engine is running.
A boosted system with an inoperative booster is a REALLY poor performer.
You can test the booster by resting yor foot on the brake pedal and when you start the engine the pedal should sink slightly towards the floor.
Often ABS have coupons in your local paper offering FREE fluid changes.
Even if you have to pay it is only ~$20 and they will do a top job.
Consider replacing the fluid with a higher boiling point fluid to give you a greater safety margin.

_________________
Regards, Graeme
Just trying to help...
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graemes@internode.on.net

I've had them professionally bled 3 times in the last 6 weeks. He even bled the individual little junction boxes in the lines. The last time they did it they really concentrated on flushing the whole system of any air at all.
.....still only a marginal improvement. I've checked the vacuum line from the block to the booster & it sucks (if u know what I mean) Maybe something has failed inside the booster unit itself ??
(We covered all the usual stuff) Am I using a bad combination of hardware ??
SB

Hi,
Have you tried adjusting the pushrod length between the pedal and master cylinder. I've done several of these brake conversions and have always found the need to adjust this. You should be able to adjust it with a 12mm spanner and some multigrips. Don't adjust it too far or your brakes will begin to activate. A bit of trial and error should get it just right. Hope this helps.
Joel

...yeah I adjusted the brake pedal pushrod on my mates' 510 once but I haven't checked it on my car. I've just assumed it's OK but now that u mention it I think I should check it. (Although if the pushrod was too short then the pedal would travel too far initially, but then bite hard, as usual further down. The problem I've got is that the brakes are working from the top of the pedal down, but you have to push almost to the firewall to pull the car up. The pedal just feels like you're pushing on a big marshmallow)
cheers SB

what master cyl were you running?

HEY, DO YOU KNOW IF YOU ARE USING THE RIGHT SIZE MASTER CYLINDER? I HAD PUT THE WHOLE VL TURBO CALIPERS AND MAGNA ROTORS ON MY 510 AND TO START WITH DIDNT USE THE RIGHT SIZE MASTER, THERE FOR I HAD A SPONGY PEDAL AND BASICALLY WENT RIGHT TO THE FIRE WALL... SHOULD SAY ON THE SIDE OF THE MASTER WHAT SIZE IT IS, I MYSELF HAVE A COLECTION OF TWIN MASTER SETUPS WITH THREE DIFFERENT SIZES BUT THEY ALL LOOK THE SAME. GIVE IT A SHOT ANYWAY.....

I've got no idea which size my master cylinder is. It's a twin resevior - that's all I know. What are the size differences ?? Which is better to use ??
cheers, SB.

7/8 would be a good starting point.
1" if your going for 4 spots and disc rear
they all have the size cast on them

_________________
1969 Datsun 1000 wagon (Daily)
1969 Datsun 1000 coupe (Next project)
1969 Datsun 1000 coupe (Long term project)
1974 L34 Torana replica (In the build)
1976 SS Torana hatchback (Restoration project)
1976 Cadillac sedan deville (Pimp cruiser)

JUST BEEN TO HAVE A LOOK IN MY SPARE PARTS, THE 200B MASTER THAT I HAVE HAS 13/16 STAMPED ON IT, OBVIOUSLY THIS WONT FIT YOUR 180B BOOSTER BUT THIS SIZE IS AVAILBLE TO SUIT 180B BOOSTER, NOT REAL CERTAIN FROM WHAT CAR IT CAME FROM THOUGH, I MY SELF HAVE A 3/4, 13/16, AND 15/16 MASTERS THE LAST BEING FOR THE VL TURBO SETUP, SO I RECKON THAT IF U CHANGE YOUR MASTER SIZE UP TO ATLEAST THE 13/16 THAT 200B BRAKES COME WITH YOU WILL GET A BETTA PEDAL, ALSO DID U REPLACE YOUR WHEEL CYCLINDERS WITH THE CORRECT SIZE??? TRY AND FIND OUT IF 200B ONES FIT, THEN WITH THE RIGHT SIZE MASTER AND WHEEL CYLINDERS YOU SHOULDNT HAVE ANY PROBS.... BILL

We had a similiar problem with brakes on our 1200 coupe. We bled them and still had a really spongy pedal.
We ended up taking the master cylinder off and taking it down to BGT in Hawthorn, Melbourne.
They tested it and found that one of the piston seals had gone and the bore was scored.
A new twin reservoir master cylinder only cost around $70 and this solved the problem. The brakes are now sensational.

You guys haven't been around conversions long enough I'm starting to sound and feel old...

I bet I know what the problem is!

I noted that you've installed a new booster. I bet the rubber/steel disc that sits on the end of the booster piston is missing, or floating about inside the booster unit. This thing is called the "reaction disc" and without it..VERY VERY strange things happen to your brakes.

Without the reaction disc, the brakes really "rip on", and exhibit a spongy pedal while the engine is running. It causes extreme front bias, I almost had my 200B brakes on fire once on my 1200, after some hooning about.

Let me know if I'm right.

Chris

cheers for the help fellas. I'll go thru my parts shed on the w'end & check the other master cylinders I've got. I think no matter what - I've gotta take the current m/c off the car & try a different/larger one.
The "booster piston disc" symptoms (front bias etc) seem very very familiar too. Last time I drove the car (on the way to a failed blue slip inspection !!) the smell was real strong when I gave the brakes a bit of a work-out.
regards
SB

Hey Chris i think you may have hit the nail on the head mate. Have had this fault a few times myself with clients cars

_________________
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Unfortunately I have to put my hand up as well and say i have the same problem and that i've had the same problem on both my 180b coupes.

The only thing that is the common dominator is my rotor / caliper combo.

I bled my brakes 3 or so times and just couldnt get the pedal hard when the car was running. Do I have the same problem?

In my defence I haven't messed with the booster on either of the cars, bought them both with this illness.