hey guys,

having a bit of trouble with my 180b and my 1600 (fitted with a brake booster)
when im braking its firm as it should be but then all of a sudden it sinks into the ground i assume its losing vac
it used to do this and i tightened the hoses and it worked fine, untill recently i installed a elec dizzy from a bluebird now im having a problem.
when i rev the car and put my foot on the brake its hard as it should be, after between 10-60 seconds it sinks in (differant each time)

any help would be much appreciated its kind of unsafe to drive in this condition

Thanks Jack

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Its not that i have no money, i just have a huge investment in my datsuns!

Is the vacuum line from hooked up to your new dizzy? If not make sure it is.

If that doesn't work then I would be tempted to try replacing the hose that runs from your manifold to your brake booster. It's over 30 years old now so it is possible that it will have failed. Also, get a friend to pump the brake pedal while the car is running and see if you can hear any vacuum leaks. Parts do wear out over time so you may have a pinhole leak elsewhere.

Is this happening in both of your cars or just your 180B?

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green200b - aka Alistair

The fleet:

Australia:
'80 200B GX - the green200b - hibernating
'81 RX-7 - 12A extend port - daily
'74 RX-2 - 13B bridgeport - cruiser

Europe:
'93 200SX - CA18DET - tourer

its happening in both cars, i checked and double checked all the lines, the 1600 is a bit differant it doesnt completely fail it just changed from hard to softer, my 180b pedal goes straight to the floor, scared the sh*t out of my through the hills it is possible it could be a line, just coincidence with the new dizzy do you reckon? maybe i should try putting a clamp on the line to the dizzy and carby.

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Its not that i have no money, i just have a huge investment in my datsuns!

Power brakes are a creature comfort to reduce pedal pressure applied by the driver.
In other words, you can disconnect the vacuum booster and plug the vacuum line to the inlet manifold and the brakes should still work but with increased pedal pressure.
If your pedal sinks to the floor, that indicates that the hydraulic system is at fault.
If the brake booster doesn't have a one way valve in the vacuum line, it may be worth while fitting one.
The valve allows the tank to store vacuum and prevents the vacuum from bleeding away.
The vacuum advance line to the distributor can be temporarily disconnected and plugged to aid in the fault finding process.
You may have a faulty vacuum actuator on the distributor which could be allowing the vacuum to escape to the atmosphere.
Not quite scientifically correct but you get my drift
Vacuum advance on a distributor is a fuel economy device and does ZIP for acceleration and full throttle performance.

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Thanks Alot, will try all that tomorow,

Jack

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Its not that i have no money, i just have a huge investment in my datsuns!

ok i tried plugging up the line too the dizzy, so i think we can assume its not that, i did everything the book says, and think either the valve is leaking or the seals, can you get overhaul kits for these? or maybe just another valve to try?

Is there any other ways to test or is it just trial and error now ?

_________________
Its not that i have no money, i just have a huge investment in my datsuns!

could it be the master cylinder? i havnt heard of problems with it being intermittent?

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Its not that i have no money, i just have a huge investment in my datsuns!

i took the one way valve out and blew air into both ends, and only went one way (which my manual told me to do to test it) so seems to be working properly so that only leaves the brake booster, or master cylinder, i can't imagine how it could be the master cylinder since when i rev the car the brakes are rock hard, but on the other hand it goes all the way to the floor and doesnt get hard, so its got symptons of both problems.

anyone got any idea's of things to try? should i overhaul the master brake cylinder and see what happens or are there other tests to try?

_________________
Its not that i have no money, i just have a huge investment in my datsuns!

Depending on how well you are doing financially that my be a good idea, at the end of the day a new brake master cylinder can only be a good thing. Do you have the Australian-spec Girlock or PBR type? Or the more traditional style such as the 240K type? If the later, you may as well buy a brand new 7/8 cylinder as this will be excellent for future brake upgrades.

With your booster, I guess it is possible that it is leaking. I had to get mine modified for my recent conversion and while I was at it I decided to get it overhauled, some local brake shops quoted me around $250 but Datsport did it for considerably less. Something else to consider? If you do it now then you won't need to worry about it for another thirty years.

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green200b - aka Alistair

The fleet:

Australia:
'80 200B GX - the green200b - hibernating
'81 RX-7 - 12A extend port - daily
'74 RX-2 - 13B bridgeport - cruiser

Europe:
'93 200SX - CA18DET - tourer

yeah well i mean i guess its just part of running a old car, was hoping to buy some bucket seats with the money for my 1600 but maybe ill just get this done, well i have to really its the girlock type, ive seen overhaul kits for the master cylinder and was going to try one of these but might see how much datsport can do it for,

hopefully give them a ring tomorow, i dont really plan on upgrading the brakes for the 180b plan was to keep it stock and try get it neat just for a daily while i get my 1600 all done, but like you say new master cylinder can only be good

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Its not that i have no money, i just have a huge investment in my datsuns!

just incase anyone was interested, it was the master cylinder i replaced with a 7/8th datspot one and works wonderfully with a few mods and new brake lines
Jack.

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Its not that i have no money, i just have a huge investment in my datsuns!