How to: NBS master cylinder swap for firm brake pedal

[MarkD51]

Hard to push pedals in the first couple of inches is the vacuum booster holding you back. your booster might have malfunctioning seal or valves inside the unit from your description of what is going on. your first push on the pedal should be easy.

So then SLC, it then sounds to you unlikely that there's possibly air somewhere in the system? That it is more likely a Booster going bad?

I'll probably still do the Bleed should I find the Power Bleeder Adapter Plate properly fits the MC Resovoir. I'm only out $44 with the Bleeder Kit from Amazon, and figure another $7 for a qt of Brake Fluid. (And of course an hour or so time hooking all up, and crawling under the truck.

So then sir, should it then come to a replacement for another Booster, where should I purchase such? Oreillys/A-Zone-NAPA which we have here) for a rebuilt Cardone Unit, or go direct to Chevrolet?

I know you folks frown on rebuilt MC's, but what about Boosters? If you suggest-recommend a Chevy Dealer, will these then be new Units, or do they simply run over to Oreillys themselves, and grab a rebuilt to sell me?

Also, should the Booster then be changed, what about the MC? Just re-install the original, or go new with that too? (I know you folks say go direct to chevy for that) I'm gathering you'll probably say the latter, that if I do change the Booster, and since the MC is already off, do it once, and do it right and go with a new MC too.

Thanks again for your help.
Mark

 

[SunlitComet]

It is hard to say 100% because i am not there with pressure and vacuum gauges and what not but it kinda sounds like wear inside. Let me ask when this hardness or softness is happening do es effect the braking power or does it just seem like it it just needs more foot power to achieve the same effect? How long are we talking between these brake applications? And when braking do you seem to loose braking power after a lot of hard stops or does it stay about the same? If the booster needs to go, remanned ones are fine. However only try to source gm, delco, a1cardone, rebesto or bendix units. do not buy house brand stuff like brake best, masterpro, valuecraft, duralast, dorman or proformer and such. It can be a crap shoot on quality and reliability with them. Same applies to mc but always get a new one. If a booster gets changed you can reuse the mc you just unbolt it and move it out of the way carefully with lines still attached if you like. I would forget about changing it now until you have more experienced with the questioned posed above and be absolutely sure there is no air in the system, wheel components are in proper working order and the mc is doing it's job(tho the absence of a brake warning light form the proportioning valve would see to indicate the pressure for front and back are working properly). Based on recent events with my own vehicle I would strongly suggest converting to a hb unit if your booster was screwed. There is a big difference in power assist and reduces user fatigue a bunch as well. You will have to relearn your braking actions too. You can go from being one who veers off to an open lane during a panic stop because your vehicle would not stop quick enough to avoid an accident to the person who is hit in the rear because the car behind you could not do the same all because they might be caught off-guard with the ability of you to slow down so quickly. I have seriously been looking into stickers for the rear that state stuff like sudden stops or stay back so much feet hoping the person behind me will stay back farther because I am almost always drafted by those attempting to get better gas mileage or propagate their ego's. Maybe it just might make a difference. I can be kind on the road as much as the next person but I am more often aggressive and braking is no exception. I have overheated rotors, pads, rear linings and have pushed my brakes to the point of serious brake fade before. At the moment I have slotted rotors that have micro-cracks on the full faces of pad contact areas as well as one hotspot. Imagine that all that was done with a vacuum booster old brake fluid and existing 18 year hydraulics.

 

[MarkD51]

I sent a PM SLC, Thanks!

 

[qukon 95]

I feel my rear brakes sticking I think this happened after I did the MC swap I will check for leaks in the drums. I might need to put The old MC back on.

 

[MarkD51]

Short update: SLC did correctly diagnose my particular problem, a bum Brake Booster.

With his knowledge and help. I accomplished this Booster Swap this Morning, and all seems well. Tomorrow I'll do a Power Bleed at all Wheels.

I deeply appreciate the help, and I thank you folks for your kind tolerance, as I knew I perhaps posted my particular issues in a wrong area, and thread, sidetracking the NBS Booster Thread. Thank you, I'm a little tired, but a happy man! Mark

 

[bowtiefreak]

sunlit is the man.

 

[SunlitComet]

 

[bowtiefreak]

I have been debating the Firm feel SSBC master cylinder for many, many years now. Which we all seem to agree is a NBS master with the larger bore. I need a little more brake pressure on the burb. I am very tempted to try this swap ASAP....

 

[Nak]

I have been debating the Firm feel SSBC master cylinder for many, many years now. Which we all seem to agree is a NBS master with the larger bore.

I respect all of the expertise and experience represented here, but I'll have to disagree with that statement. An NBS master cylinder is designed for a wildly different brake system than found on the OBS. The NBS is a 4 wheel disc master, the OBS has disc/drum brakes. Very different requirements for a master cylinder. Firm feel does not equate to better brakes. To get better brakes, go with hydroboost, or JB6 brakes--the two easiest answers--or go with NBS 4 wheel disc brakes. Just make sure you swap out all the brake components that go with the new system.

You wouldn't build an engine with 5 cylinders at 10:1 compression and 3 at 9:1 compression, would you? Swapping out the MC for one designed for a different type brake system is the same thing, but worse. The former will just ruin your engine. The latter could kill you.

 

[bowtiefreak]

You disagree with my statement about the SSBC Firm Feel Master Cylinder , Part number A0463 is the same at the NBS Master Cylinder? Or that I want to try to increase the brake pressure and see what it yields? This is a not a daily driver anymore so to try altering the brakes just takes some time, if it doesn't work the old MC goes back on.

If I do opt to run discs in the rear I will still need to upgrade the master.

 

[Nak]

Sorry man, I totally misunderstood. Never post tired... I was commenting on swapping to a NBS MC for brake feel. My bad. Anyways, absolutely different for an off road machine as opposed to a DD.

I looked at the SSBC website. They list the same MC for disc/disc and disc/drum? So these can't have a residual pressure valve built in. They do sell those as well, so you probably want to consider adding one of those if you go with this type of MC with disc/drum.

 

[bowtiefreak]

No problem, confusion happens

Yeah or even just adding a proportioning valve on the rear line.

I see many guys getting into trouble when swapping for larger calipers and things like that too. So many mixed reviews out there. I started yet another thread that people will hopefully just post result good or bad about the swap

 

[SunlitComet]

Bowtie, I don't have one far sure but I think they claim firm feel because they don't have the internal valve like the obs mc quick take up feature which lets the pedal sink a bit and the fact that it may apply the drums sooner instead of letting them apply differently. That coupled with the fact that the physical volume in the hydraulic system has change with no change in the proportional valve is how they get there claim i believe. In short unless you get a rear disc setup with all the parts on mods included from someone like summit or ssbc do not bother with just the mc. Convert booster and mc to an obs jb6 configuration. just make sure loose items in the cab are tied down.

 

[bowtiefreak]

My suburban has the JB6 brakes already. Is it possible that the wrong master is on it?
My Tahoe has the JB5 brakes. Shame on me but I thought the difference was only the drum diameter. Please correct me if I am wrong as this would be a big problem is the MC is incorrect. So is there a difference in the JB5 and JB6 master cylinder??

Would a JB7 Master Cylinder fit?
Is there an upgrade on the rear wheel cylinders? I read you can upgrade the 14SF axles with larger bore cylinders but noting about the smaller set ups.

I can try multiple things. Temped to upgrade the burban to disc and put the 11" drums on the Tahoe to replace the 10" set up.

 

[Nak]

The JB6 and the JB5 brakes use the same MC. The only difference between the two is the size and type of rear drum, and the combination valve. It's possible the factory used the wrong C-valve. That's why I was trying to find out about your brake balance. The JB7 brakes used a different C-valve than the JB6, and in fact there is a Service Bulletin requiring the JB7 brakes to get rid of the C-valve and use the C-valve from the JB6 brakes. The original JB7 C-valve limited brake pressure to the rears far more than it should have. I think I read it had an 85/15 ratio front to rear? This led to poor brakes and fast front brake wear. Anyways, if your rig has always had bad brakes, it might be the JB7 C-valve was installed by mistake. The only visible difference between the two is a sticker. The good news is that the proper C-valve is still available new. I saw it on Amazon for around $120 I think?

 

[bowtiefreak]

Here's another one to ponder. The SSBC firm feel master calls to have the brakes lines switched from the factory positions (front to rear, rear to front). Why would that be?

http://ssbrakes.com/attachment/63706-Instruction Manual

 

[Nak]

??? That makes no sense. If the MC is designed for disc/disc, it should have two identical size bores. The only reason you'd have to reverse the lines is if the residual pressure valve was in the front, but if it has a residual pressure valve then it would be no good for disc/disc brakes. If it does have a residual pressure valve, it's clearly designed for drum brakes, but with two equal sized bores. I'm pretty sure the page you linked to specified the MC was good for disc/disc or disc/drum? Of course, that makes this pretty undesirable anyways. An MC really needs to be specified for one or the other. I'm very curious to hear the explanation for such an odd setup.

 

[benblaquetahoe]

is that master cyl the same as police version? will installing the police version masterly/ booster/ calibers give my LT better braking?? and will they just swap?

 

[Johnny Racer]

Wow am I late to the party.

 

[hawgnutts]

The JB6 and the JB5 brakes use the same MC. The only difference between the two is the size and type of rear drum, and the combination valve. It's possible the factory used the wrong C-valve. That's why I was trying to find out about your brake balance. The JB7 brakes used a different C-valve than the JB6, and in fact there is a Service Bulletin requiring the JB7 brakes to get rid of the C-valve and use the C-valve from the JB6 brakes. The original JB7 C-valve limited brake pressure to the rears far more than it should have. I think I read it had an 85/15 ratio front to rear? This led to poor brakes and fast front brake wear. Anyways, if your rig has always had bad brakes, it might be the JB7 C-valve was installed by mistake. The only visible difference between the two is a sticker. The good news is that the proper C-valve is still available new. I saw it on Amazon for around $120 I think?

Hi Nak I've been following this thread today & I'm installing a '98 14-bolt SF w/TSM disc kit on my 95 Tahoe w/stainless braided lines front & rear. You guys spent a lot of time on disc/drum large & small but not much specific to disc/disc. Only that the NBS M/C was for that setup. In my case would that NBS master cylinder be a better fix since I'm going to 4-wheel disc? Would I need to change the hydravac booster? Would the ABS need to have the prop/comb valve changed out?