power brake booster

[busguy]

ok, i am nebie at datsuns and my brand new , only has 30299 miles, 1974 620 w/ power brakes seems to need a new booster, i have to stand on the brake pedal to stop, any ideas where i can find a booster? or a place to overhaul the one i have.

thanx

[420n620]

Welcome to the form 1st off. 2nd you better get pic's/oic's up before you get banned.. JK :P

 

if it come down to needing a PB, I got several in storeage but lets wait and see if your problem is something else.

[datzenmike]

The 620s to '78 had four wheel drum brakes and as the shoes wear down the peddle gets lower to the floor and softer. Get all four wheels adjusted so the shoes don't have to travel so far to touch the drums. Don't forget to adjust the E brake cabel at this time as well.

[Cuts metal like mad]

Booster seldom fail. Its not out of the question though. That said, make sure you don't have a vacuum leak in the line going to the booster, and that it indeed has a vacuum source, also make sure your check valve isn't installed backwards (I've seen this before).

[busguy]

first, i will have pix asap, adjusted all the brakes, inspected and lining is ok, pedal is VERY hard and seems like the booster is not helping. lots like when you shut off engine and coast and use brakes. has vaccum, checked big line from maniford, but the vaccum does kinda stutter a bit, but seems strong. will put gauge on and make sure enough, it only has 30k miles and sat for a long long time. found paper work exhaust replaced at 28 k in 1988. i can drive it and maybe they will get better, but who knows. thankfully the emergency brake is good!

[datzenmike]

OK to test the booster do this:

 

Engine off, pump brakes to remove any residual vacuum in the booster.

 

Depress brake peddle and hold.

 

Start motor.

 

Almost right away the peddle should drop slightly as the vacuum builds from the motor. Booster is working.

 

 

I did an engine swap one fall and never finished the hookup until the next spring. Brakes were terrible. Eventually swapped out the one way valve in the vacuum line. The one I left unconnected for the winter was full of cocoons and spiders and basically plugged. No vacuum getting through.

[wayno]

Hi guys, Busguy has said it sat a long time, I would consider that maybe the wheel brake cylinders are not working properly, maybe half of them don't move anymore, they may bleed just fine, but that doesn't mean they work. wayno