this is a new one i have brake issues and i did a search.

[91hrdbdy]

ive done a search. but im still having problems with my datsun brakes

 

i have a 74 that the previous owner did a disc brake swap. when i got it i had to do a double pump to stop so i bleed the brakes no air in the lines. i then replaced the master cylinder bench bleed it no psi at all now so i got a different master thinking the master my be bypassing internally. bench bled it and re bleed all the line had a little bit of air in all 4 lines but the air was towards the end of the line nearest the brake caliper/cylinder. so i was thinking i must of not bleed them well enough when i replaced the master the first time.

 

well i have no brakes at all still pedal goes to the floor with little to no resistance. i for the life of me don't know what to do next.  im no stranger to brakes. I build brake kits for GM g bodies. but i really didn't want to dump hundreds of dollars in a B.B.K. for a truck im just using to pick up parts and materials for my shop. 

 

any help would be great. 

 

I have a 78 620 master from autozone on the truck right now. as my understanding is they came with a disc/drum setup.

 

[datzenmike]

Are the bleeders on the calipers at the top? It's easy to swap side maybe and you won't get all the air out. Try opening a front bleeder and then doing the rears. If the fronts are bled it's hard to get enough travel to push the air out the rears. With the rears now done, do the fronts.

[91hrdbdy]

bleeders are at the top. ill try opening the front bleeders and rebleeding it. 

[DanielC]

The rear wheel cylinders on my 521 only have one port in the wheel cylinder itself for fluid to go in and out of.  If there is air in the wheel cylinder, and you close the bleeder fitting too quickly, the shoes and springs cannot contract quickly enough to push the air in the cylinder back out the bleeder fitting.  If you use a pressure bleeder on the master cylinder to push fluid through system, it may also keep enough pressure at the wheel cylinder to not allow the air in the wheel cylinder to flow back to the bleeder fitting.

[hawaii_620]

If you are running a booster, did the little rubber disc in the brake booster fall out of place when you replaced the MC? That disc makes up a good amount of pedal rod travel.

[Dawa]

when i swapped my front drums for disc/z32 calipers, i bled all the lines (starting at the rear first)

then did a quick test drive. almost had to put the pedal to the floor. i already knew that i had to bleed

the BMC, but wanted to see what happened if i didnt.

 

so i bled the BMC then rear lines then front and it worked out fine.

 

i would recommend buying all your parts from rockauto.com

they still have some japanese or australian made parts, which are preferable to chinese made.

and theyre usually a whole lot cheaper as well.

 

stock bmc is 3/4 i think? they will suggest running a late 620 or 720 bmc since you swapped out

the front drums for discs but i didnt and the car brakes fine. initially i didnt like it and wanted

a firmer pedal feel but i guess i got used to it?

[erichwaslike]

did the previous owner replace any lines. i had a bad flaring tool onece that made flares off center adn you could pump up the brakes but it eventually leaked down.... check that too

[Dawa]

^oh yeah

when i TRIED to loosen the flare nuts attached to the wheel cylinders, the nuts stripped.

(yes i was using a flare nut wrench. however they were from HF, so time for better quality flare wrenches.)

and even a vise grip and penetrant couldnt loosen the damn things. i ended up having to replace the

lines. luckily oreilly (and similar) sell pre assembled, flared lines and i was able to use those.

 

i say all that to say that it is possible the lines were replaced.

[91hrdbdy]

Im ove the brakes on this damn thing. for the life of me i cant get the air out of the brake system. spongy shitty brakes.  i had this damn truck a month and ive never been abe to drive it.  blah .. so i doing full wilwood brakes all the way around just like i have on my malibu. here is what i drew up for my brake rotor hat and caliper adapter. ill be running a 12.19 x .81 rotor and a wilwood 4 pot caliper in the front and ill run a 11.5 rear disc off a yukon in the rear with a 78 caddy rear caliper in the rear.  ive got the all the master and brackets all ready ill just pick up some calipers off ebay. 

 

 

so any way im going to ditch the 78 disc front setup and run a hardbody spindle not booster just a dual master pedal with 1" front 3/4 rear master cylinders. 

 

 

[flatcat19]

Wait!

 

I thought there was a free Datsun in this thread.

 

 

Do you have a build thread for this?

Is all of that stuff fitting properly?

What is this going on? 

 

If you were just venting-a status update would've been a better place.

Why post a thread and populate with little to no usable information?

[Z-train]

Have you bled the NLSV per the book?

[datzenmike]

Yes do you want it moved to your other post on it... http://community.ratsun.net/topic/56274-this-is-a-new-one-i-have-brake-issues-and-i-did-a-search/ or the other other build post ... http://community.ratsun.net/topic/56106-new-to-the-forum-heres-is-my-new-620/page-2. 

 

This should be in the build thread

 

 

Have you bled the NLSV per the book?

.

Bill I believe the NLSV as used from '76 on.

[Z-train]

Bill I believe the NLSV as used from '76 on.

Hmmmmmm.Then faulty MC would be my next choice.All other things being equal.

[91hrdbdy]

okay ive bleed the NSLV per FSM replaced the master twice, im getting not pedal pressure and getting no air out of any bleeder valve. just clear solid fluid. opened the front bleeder and bleed the rear. still nothing. totally over it. 

[flatcat19]

Did you start by bench bleeding the master?

Is your pedal push rod properly adjusted?

[Z-train]

. opened the front bleeder and bleed the rear.

Clarify this please.

[91hrdbdy]

some on here sugested that i crack opnen the front bleeders and then bleed the rear. ive never heard of this but i gave it a go so i places a hose that ran up to a collection bottle about 2ft above the caliper and so pressure could escape and air would not be drawn in. i then bleed the rear brakes but was a fruitless effort. 

[Z-train]

No need to touch the front when doing the rear or vise versa.

[91hrdbdy]

I thought so but at this point it was worth a shot. I took the truck to a local brake shop today so well see what he says. Ive never been fed up with a simply brake system. lol.