ok fitted a sunny b310 booster to my 1200

i have landcruiser 4 piston front calipers and r31 rear discs and calipers, and a 240k 7/8th master
without the booster the pedal was very hard

but now with the booster fitted i could pretty much throw my show at it and the brakes will lock up, as in there is NO resistance other then the return spring on the pedal

also the booster is only running off one port on my L20b as ive got twin 40s and the manifold only has the one provision

so any one offer some insight as to why the pedal is now so unbelievibly soft?
also feels like the booster or master is bottoming out, all soft then pedal just hits a wall....but its not any where near being on the floor and the pedal used to only travel an inch if that without the booster

That's crazy PIGDOG. mate, im sure you have tryied these things but im only trying to help.
Make sure you dont have a leak in a line and that the air has been all pushed out.
Also check the push rod inbetween the master/booster hasn't fallen out.
Try Clamping up the break hoses and pump the petal to see if that fixes the soft petal and pin point the problem for you.

let us know how it goes.

well i don't have an idea mine is the opperset my 120y never had a booster and i put one in it and now the front brakes seaze up all the time i am thinkin i will have to change callepers

push rod is still there, booster doesnt leak...havnt checked the line but you would think that the booster would be not doing anything if there was a vacuum leak, rather than being far to soft

will try locking the front off and seeing what happens, was going to do that the other day but cbf'd

datosun, how hard in the pedal on yours?
if i just jump on the brakes it will lock up....but thats coz the pedal if far to soft

Hey PIGDOG,
I have the same set up without drama - landruiser calipers and Sunny booster. Booster diaphragm may be stuffed but low pedal is usually an air problem. Bleed all (including master) and have a feel ??? I went from this booster and Stanza calipers to landcruiser no worries ...
How about the adjustment of the rod from the pedal?
You have to use the sunny boosed master cylinder as well I think, as the small rod that actuates the cylinder is longer on the boosted master - ie with the non boosted master cyl you may have to push the pedal half way before you start moving the piston in master cylinder. can anyone confirm ??? It was many years ago that I did the conversion.

Cheers

Check the reaction discs isnt broken in the brake booster. this is what the pushrod between the booster & the master cylinder attaches to. This was the cause of the low pedal in my sunny with the 7/8ths master cylinder, because somebody went ' what happens if i pull on this', which broke it. I now have a brake pedal that i can
heel & toe with.

blead the whole system before testing, but it has brakes...its just the lack of resistance through the brake pedal

240ks run a booster so there should be no problems with running that master on the sunny booster, pushrod was adjusted out to suit the 240k master

the brakes work ok (not quite the same as before) with the vacuum line dissconnected, same hard pedal as before....slightly further pedal travel due to the slack in the booster

reaction disc? is that on the end of the booster pushrod?
looked to be some kinda disc thing on it when i pulled it out, cant say it looked broken though

hey pigdog,
i had the same problem with the booster i brought off you!
the pedal was realy sort and the brakes would lockup without any force,
coming off the pedal and the bosster would get stuck and make a loud click.
gave me the ####s until i got another 1 from the wreckers, which doesn't work either now

and yes, the reaction disc is at the end of the booster pushrod.

might be a faulty return spring
good luck sorting it out

hmmm the booster out of my 120y worked when it was in it....dont remember if you got the 120y or 180b one though
both worked in the cars though
really dont want to have to rebuild the thing, and i really dont have the money to do it

my pedal doesnt get stuck or click or anything, just too soft