Brake master cylinder

leftme · Post by **leftme** » 23 Jul 2006 19:48

My brakes are a little soft and it has been mentioned that I should replace my brake master cylinder. I want to get a 7/8" master for a 240z, what parts do I need for the change. Do I need to buy the piston assembly as well or should it all be included?

Thanks,
Clayton

Post by **datzenmike** » 23 Jul 2006 21:15

Before you go to the trouble of changing the M/C, make sure the 'soft' brakes arn't caused by air trapped in the system, or improperly adjusted rear shoes on your 240? Air and bad adjustment will use up peddle travel and give a spongy feel. Don't forget to adjuist the E brake as well.

A bad M/C may show signs of brake fluid leakage, also check your rear wheel cylinders too. Frequent refilling of M/C with brake fluid is a sign of leakage even if it isn't obvious. As for replacement, rebuilt units are available, just swap out the old, slip in the new, or if you are knowledgeable, rebuild it yourself with a kit.

good luck clayton.

Rehs · Post by **Rehs** » 23 Jul 2006 22:11

When changing from the stock 3/4" to 7/8" master cylinder, it depends on where you get it from. I've used a Brand New Ultra-8 P/N:P8980 product from Altrom through Lorco. Seems to work good. You'll need to swap the pushrod and find a way to retain it in the m/c with a bigger washer. What you need to do is find a washer thin enough so it doesn't push in the piston in the rest position or make one out of sheet metal. Make sure you bench bleed it and use good brake fluid. That's about it.

leftme · Post by **leftme** » 24 Jul 2006 06:37

Sorry, it's for a 510, I should have said I want to upgrade to a 7/8" MC from a 240z.
I don't think I have any air in the system, I've pumped about 2 litres of brake fluid through the system.

I'll have to check locally for a MC now that I have a part #, thanks Rehs!!

Clayton

banzai510(hainz) · Post by **banzai510(hainz)** » 24 Jul 2006 06:48

Howabout adjusting the back brakes.

I gave Icehouse a stock MC (used) and his car stops good. But it does have 86-87 200sx struts and brakes.

Post by **datzenmike** » 24 Jul 2006 07:43

Don't forget shoe adjustment! The flex lines, when in poor condition, will sometimes swell during braking also. Just a thought.

slodat · Post by **slodat** » 24 Jul 2006 08:46

Datsun master cylinders do not need to be "bench bled" this is something from GM and other cars. Datsun MC's have bleeder valves on the MC. You simply route a small piece of plastic tubing from the bleeder back into the MC reservoir and pump the pedal.

Rehs · Post by **Rehs** » 24 Jul 2006 08:56

bench bleeding is fun though. You get to get brake fluid everywhere! All over your vise, hands and other equipment close by! You'll probably have it in the vise anyway when you're attaching the pushrod.

Post by **datzenmike** » 24 Jul 2006 17:55

The "80 through '83 720 truck also used the 7/8 M/C, as did the 200sx from at least '82 and '83.
The '84 through '86 720 truck used the 15/16 M/C, as did the 200sx from '84 to '88 and 240sx '90 on.
The '89 through '92 Stanza used a whopping 1 inch M/C if you want more.

You would have to check the bolt pattern allighment for compatability, but you can make anything work if you want it bad enough. Also these M/C's work with a vacuum power booster, so there's that to consider also. These are just some of the M/C options available, and you don't have to pay a 20% Z car mark up.

leftme · Post by **leftme** » 10 Aug 2006 10:57

My 7/8" MC finally arrived and I am checking if anyone has close up pics of what needs to be adapted to get the 240Z MC to work in the 510. Keep in mind I haven't looked at the OEM 510 MC too closely, I just want to get an idea of how much work is involved. I have an autox on the 19th that I need to be done by.

Thanks,
Clayton

leftme · Post by **leftme** » 12 Aug 2006 09:32

Anyone???

Guess I'll have to take pictures while I'm doing the swap.

Clayton

leftme · Post by **leftme** » 16 Aug 2006 12:24

New 7/8" master solved the "brake to the floor" problem! I think the old one was internaly leaky, I'm going to pull it apart and see, just for fun.
And the swap was so easy that I was done before I remembered to take pictures!

Thanks for all the help.
Clayton

wagoneer · Post by **wagoneer** » 15 Jun 2023 06:49

slodat wrote: ↑24 Jul 2006 08:46 Datsun master cylinders do not need to be "bench bled" this is something from GM and other cars. Datsun MC's have bleeder valves on the MC. You simply route a small piece of plastic tubing from the bleeder back into the MC reservoir and pump the pedal.

Thanks for this.
I am pleased to read this; I was sort of anticipating having to bench bleed the MBC on my 71’ 510 wagon.
I installed 280Z struts and front brakes on the wagon and replaced the MBC with a new 240Z ( Tory Ermish suggestion) but never really have the brake petal action; I need to pump a bit.
So, I’m workin on the system.
I had my friend braze on 13 millimeter nuts on the rear brake adjusters and that helps a lot!
Anyways go’in to try bleeding the MBC soon and return to the 2 man procedure for the brakes.
wagoneer

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