620 brakes

[hairy1205]

My 620 will not bleed the brakes to giv a good pedal. I have tried pressure bleeding from the master cylinder end and also have run hoses all of the way from the bleeder nipples to the master cylinder reservoirs, I am positive I have no air in the lines. If I hit the pedal with a quick stab I get pedal for one try, bul if I just press down normally I get no pedal(all of the way to the floor)

I am thinking a bad booster, probably a small hole in the diaphragm. I work for a cool shop that restores old mini coopers and puts Honda Vtec motors in them. We put minis together without boosters all of the time and they work fine. Has anyone removed the booster from a Datsun and had any luck? If so any advice would be welcome!:mellow:

[Fineline]

Get under there and adjust them. These are not self adjusting. My bet would be that the adjusting arm is not out far enough to allow the shoes contact with the drums.

[hairy1205]

They work when you get a pedal and the parking brakes work. the front is disk and they don't work without the quick stab either. the rears have like new pads also.

[Fineline]

My bad. Didnt see the year. In that case I would say the M/C is bad.

[hairy1205]

How other than watching it pump the brake fluid through the clear rubber lines would I check the master cylinder? It looks like it is pumping properly and when I pump with a stabbing motion it stops. Let me know what you think out there/

[mike]

Did you bleed the load proportioning valve too? It is on the inside of the passenger frame rail about under the passenger seat. There are 3 bleeders on the top.

 

Im going to agree with Fineline and say you need a new MC. Try bleeding them again though, you might get lucky.

[hairy1205]

Thanks, I'll try that first.

[datzenmike]

Booster has no effect on brakes other than making them easier to push. To test booster operation, pump brakes to release any stored vacuum. Depress brake and hold, start motor, pedal should drop slightly as vacuum builds.

 

Adjust rear brake shoes out as per the adjustment procedure. Be sure to adjust the E brake too. re-bleed including the proportioning valve and do in the proper order. If m/c is new or has gone dry at any time, 'bench bleed' it first.