924Board.org

dman58 · Joined: 18 Mar 2014 Posts: 4 Location: Rochester NY

hey first post here, excuse me if its in the wrong category.

anyways i need a new master cylinder+booster in my 80 924 N/A.

it does not have the performance package (it has 4 lug wheels).

it is curently plumbed dual diagonal from the factory.

i know the master is bad, the booster might be useable but id rather replace it.

everything is really expensive, and I'm not sure if i can even get the booster for it so…

i ordered in a master at autozone listed under a 1979. from what i read in the haynes manual the bore and stroke are different, so when it comes in I'm probably gonna end up returning it after comparing it to the old one.

so i was thinking of replacing everything, with this for $300:

http://www.jegs.com/i/JEGS-Performance-Products/555/631016/10002/-1?parentProductId=948836

and i was going to re-plumb it so the front and rear were on separate circuits and add a proportioning valve later if need be.

by doing that i would also be able to add this to one of the circuits to use as a inline staging/drift brake:

http://www.cncbrakes.com/hsb.asp?grp=hsb&subgrp=all&series=412&subseries=

so the problems i see arising from this would be:
attaching the brake pedal
the brake light switches were originally on the freaking master, not the pedal

could i just machine a little adaptor piece for the pedal?

could i just mount a little push switch behind the pedal?

Im wondering if anyones ever tried something like this before, and if theres any crucial problems I'm not seeing.

sorry for the post length i look forward to hearing your opinions/advice.

thanks!

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

You have to do the calculations to determine master cylinder bore size.

The later 924 and 944 used a brake pedal mounted switch, I converted my 79 to use one by cutting the master mounted switch wiring and pulling it into the cabin and connecting the appropriate wire to the switch. The mounting point was already there!

I also converted my car to use a later style brake line routing to use 944 brakes and master cylinder. It was a bit of work, but it allowed me to get away from the manually adjusted rear drums and solid front rotors.

I guess the question I have is this: are you sure the booster is bad? Does it hold vacuum?

Have you checked rockauto.com or other online places to verify you can't find the master slightly cheaper?
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

dman58 · Joined: 18 Mar 2014 Posts: 4 Location: Rochester NY

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Given any thought to a five lug conversion? Seems like staying Porsche would be the way to go if you are going to all that trouble.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

!tom · Posted: Mon Mar 31, 2014 4:22 pm Post subject:

A master cylinder rebuild kit isn't all that much.

And why replace the booster if there's nothing wrong with it?
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78 924 NA
5-lug

dman58 · Joined: 18 Mar 2014 Posts: 4 Location: Rochester NY

when i looked online i couldn't find any rebuild kits for under $100. its the ATE cylinder. unless the volkswagen rabbit or some other car used the same rings.

also i don't want to convert to a 5 lug because all my wheels are 4 lug.

and your right about not replacing the booster, I may just fix the master on there if i can get a kit or a decent priced master but i want to see what other options there are.

also i haven't done any measurements yet but i have a feeling the gm stuff is so big it won't fit behind the air/injection hose :/

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Rockauto has a reman'd master cylinder for $102.79

If you look around, you might find a 5 or 10% off coupon and/or enough other parts to pick up to make it worth your while.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

dman58 · Joined: 18 Mar 2014 Posts: 4 Location: Rochester NY

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Nope. Don't worry about it.

You might have to adjust the rod on the booster, but it will work and has been done that way several times without issue.

When you pull the master, pull the booster, remove the rust, clean it out internally with some brake cleaner (careful of your eyes/face), mask off the label and paint it with some black satin or gloss paint. Reinstall and get on with life.

If the booster fails, you'll just have brakes that are harder to use and a vacuum leak, but you won't lose all braking and can bypass it until you can get a replacement (don't forget to look at 944's for newer boosters as they physically bolt up the same way)
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

txjake · Joined: 17 Feb 2007 Posts: 395 Location: Oklahoma City OK

I don't have my booster hooked up and the brakes work ok, just a bit more pressure needed to stop. a twofah is light enough, I don't see the need for a booster. As soon as I can get/find/adapt, I will take the booster out completely. More room underhood and a few pounds gone.
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1978 924, aka The Red Rocker