First hand experience with changing to the NBS master cylinder WOW!

[400sbctruck]

Thank-You!!! Awesome thread, I have driven many of these trucks, and this always bothered me.

This WILL happen ASA I need another M/C.

Curious about the NBS 13" vs slotted replacement(I can drill
And/or slot at work).

[Tom]

Originally Posted by burkey05

do you have a link to this thread?

http://www.fullsizechevy.com/forum/g...i-install.html

[speedygonzales]

Originally Posted by Tom

So friggin simple its blowing my mind.

Originally Posted by Tom

http://www.fullsizechevy.com/forum/g...i-install.html

Are you kidding me? Have you read the instructions for the rear discs?

Let me grab a few little tid bits.

but there is a little alignment pin on the plates that needed to be cut off

The other 3 issues were that the backing plates needed to be spaced out about a 1/2"

elongate the bolt holes on the axle a little

the outside of the axle flange needed to be ground down some so that the backing would slide over it

And the guy that wrote this article no longer has ABS.

Originally Posted by 400sbctruck

Curious about the NBS 13" vs slotted replacement(I can drill
And/or slot at work).

I do not care for drilled since they tend to crack. I like slotted or dimpled where the cuts don't go all the way through.

http://www.summitracing.com/parts/ebc-usr7013/overview/

[Tom]

Originally Posted by speedygonzales

Are you kidding me? Have you read the instructions for the rear discs?

Let me grab a few little tid bits.

but there is a little alignment pin on the plates that needed to be cut off

The other 3 issues were that the backing plates needed to be spaced out about a 1/2"

elongate the bolt holes on the axle a little

the outside of the axle flange needed to be ground down some so that the backing would slide over it

So lets translate: grind a little here, and there. Yes thats simple to me.

[tismy55]

will this MC set up work on my 89 C2500 Silverado

[speedygonzales]

Originally Posted by tismy55

will this MC set up work on my 89 C2500 Silverado

Use this information to determine what you need

Originally Posted by speedygonzales

Just wanted to clarify for those not sure what we are referring to.

If you have one of these:
crappy master cylinder
replace it with one listed above that looks like this
good replacement

[tismy55]

I have the crappy type. Does the rear ABS have any affect as far as bleeding the system goes? Thanks for help

[speedygonzales]

No bleed like normal. Use the bottle method I mentioned.

[Keith Seymore]

Originally Posted by tismy55

will this MC set up work on my 89 C2500 Silverado

Going from memory - no, I don't think so. C2500 already uses a different master cylinder than the C1500.

K

[tismy55]

my C2500 is the 72 gwv,, the 86gwv may use a different one but mine is just like the one in the picture that speedy put up the crappy one. I found a cardone 13-2881 for $64 .

[tismy55]

Got the MC mounted and the lines all hooked up. Ready to bleed the brakes do I pump about 3 times and hold ,,Or just press down on pedal one time and hold.

[CDR]

Just press down one time and hold. Otherwise you can introduce even more air bubbles...

[speedygonzales]

If you put the hose you attached to the bleeder in a clear plastic bottle and immersed in brake fluid, you can pump away all you want. Just don't allow the fluid level in the reservoir to get too low before you refill it. This way you can get done fast and you don't need another person.

By keeping the end of the hose in fluid, you won't allow air to get back into the system before you tighten the bleeder.

Also, if your bleeding out old discolored fluid, when the clear fluid makes it to the bottle, you know you did the entire circuit from the reservoir to the bleeder.

[tismy55]

so I can immerse the hose into a jar with fluid in it and pump until new fluid comes through without bubbles, and I don't have to close the bleeder screw in between pumps? Is that correct

[speedygonzales]

Yep just don't let the reservoir get too low.

Oh and always buy new fluid and if there is any fluid left over in the bottle, toss it. Don't keep it laying around. It draws moisture right through the plastic container sides. Metal cans won't but try finding brake fluid in metal cans.

And I'm sure you know this but start with RR wheel then LR wheel then RF and last LF wheel in that order.

I forgot to mention, after you start the engine. Press the brake pedal a few times before even putting it in gear. After you do put it in gear, allow the vehicle to stop as soon as you can. Don't wait until you need to stop. Stop moving a few times long before you come to the need to stop. In other words, try them when you don't need them in case of a problem.

[tismy55]

Do i need to bleed the dump valve as well

[speedygonzales]

If you have a way to do it, sure but I never have.

[tismy55]

Mine has a bleeder valve on it

[speedygonzales]

You got me there. I just checked the shop manual and it does not mention anything other than the normal bleeding at each wheel. Nothing else. It only mentions the pressure modulator valve if it's been replaced or if you suspect is has air in it.

The antilock bleeding procedure never mentions to open anything other than the bleeders at each wheel. It mentions to use the GM scan tool to run the automated bleed procedure. Then go back and do each wheel by hand.

So it doesn't look like you're gona be able to do any ABS bleeding. Just do the normal method and you're done.

[Red88]

I've got an 88 w/RWAL and the dump valve with a bleeder port on it. You use the same bleed procedure with the dump valve as with the wheel cylinders/calipers. The order would be Right Rear, Left Rear, Right Front, Left Front, Dump Valve assuming you don't need to bleed the master cylinder.

BTW Speedy, great writeup! I've installed the fenco version from autozone this weekend, along with new drums/cylinders/shoes/hardware/brake hoses. Am finishing up the hose installations today along with the bleeding process. Already a much firmer pedal. I'll post up results once I'm done but wanted to take the opportunity to thank you!

[BigRed76]

So what is it about the NBS master cylinder that is so much greater than the OBS master cylinder? I see that the piston diameter is slightly bigger on the NBS MS, 34mm NBS vs. 28.5mm (1.125") OBS...so is it the difference is piston diameter? Or something I missed earlier in this thread?

[Tom]

Originally Posted by BigRed76

So what is it about the NBS master cylinder that is so much greater than the OBS master cylinder? I see that the piston diameter is slightly bigger on the NBS MS, 34mm NBS vs. 28.5mm (1.125") OBS...so is it the difference is piston diameter? Or something I missed earlier in this thread?

OBS has stepped piston and is overall larger. Larger piston=less pedal effort. Thats all.

[Red88]

First of all, thanks to all the contributors here most especially speedygonzales. As others have noted the brakes on my '88 k1500 have always been a source of worry in any hard stopping situation and knew it could be better. Had already replaced front pads/rotors/calipers, rear shoes/cylinders/drums, flushed and bled system to little improvement in the braking ability of this truck. Did this mod about a month ago and wanted to report my experience.

I found the Fenco master cylinder locally at Autozone along with the AGS #BLF-26C adapter. Removed OBS master, bench bled and installed NBS master with line adaptor. Had to carefully bend lines and was afraid they might snap but there is enough "slack" to allow the realignment to the NBS master. Bled system and found firm pedal but less braking power. No good!

I suspected my booster might be bad, did the various tests which it passed. In the process I looked up a new one and found 3 different ones listed for my truck; a single diaphram 10.75" (standard brakes) stamped "AB", dual diaphram 9", and a dual diaphram 10.5" both stamped "HR". My truck had the single diaphram 10.75" "AB" booster from factory which I assume was standard equipment for the cheapest brake setup from factory. I looked up the 2002 Silverado that my NBS master cylinder was originally designed for and found that the booster from this truck was an 11" dual diaphram. I figured the new master was designed to require the additional boost from a dual diaphram booster so I went and bought the 10.75" dual diaphram booster that came on some versions of my truck. For my truck, that was the key to good brakes. Firm pedal and much much better stopping power.

Bottom line, for those of you with original equipment single diaphram brake boosters: install the dual diaphram 10.5" along with the rest of this mod. You won't regret it!

Parts list:

Fenco NM3089 Master Cylinder (Autozone) $85.99
AGS BLF-26c line adaptor (Autozone) $2.49
Brake Best 54-71046 brake booster (Oreillys) $104.99

[speedygonzales]

Hey Red, what's involved in changing it and how do we identify which a vehicle has?

[Red88]

Sure.

Unbolt the master cylinder assemply from the booster, pull it away from the booster and leave it hanging by the steel lines.

Disconnect the vacuum line that runs from the intake to the booster. It's a pre-bent steel line coupled to a 1/2 rubber vacuum hose near the booster. In my case I couldn't get the hose off the steel line so I slit the hose along its length and pryed it off the steel line.

The booster has 4 studs in a square pattern that extend thru the firewall and are held on by 13mm (if memory serves) nuts inside the cab up and behind the brake pedal. 3 out of 4 nuts were pretty easy to get to, just pull back your carpet/vinyl a bit to expose them. The 4th required a u-joint socket adaptor and took awhile to get out. The booster "push rod" slips over a stud on the brake pedal assemply and a retaining clip holds it in place. A pair of pliers or screwdriver will remove the retaining clip, slip the booster push rod off the stud, remove the nuts from the mounting and the booster is free.

Note: there is a short steel machined cylinder stuck in the master cylinder side of the booster. Your new booster will come with it's own. Make sure it stays inside the booster or your brakes won't work!

I can't vouch for the 9" dual diaphram booster, but both the 10.75" single diaphram and the 10.5" dual diaphram booster have the same bolt pattern and push rod so the new booster will bolt right into place, connect up to the brake pedal assembly. Was a little nervous moving the master cylinder around to allow enough room the put the larger booster into place but I got away with it

Oreilly's didn't have 1/2 vacuum hose so I used 1/2 fuel injection hose which has worked fine so far for the replacment booster vacuum line. That with a hose clamp and I was back in business.

As far as how to identify here are some pics that make the visual difference pretty obvious, at least when it's off the truck. The booster have stamp id's on them, as I recall about 1/2" letters. The 10.75" single is stamped "AB" and both the dual diaphram boosters are stamped "HR". You could see the "AB" stamp on mine while in the truck. Just take a flashlight and take a close look at the master cylinder side of the booster body.

For the purposes of this mod I wouldn't bother with the 9" booster, cost is about the same as the 10.5". This is all about increasing the area of diaphram and thereby increasing the force applied thru the booster to the master cylinder and reducing the amount of pedal force needed to stop the truck.

From my research the standard brake system came with either no power booster or the 10.75" single diaphram booster. The heavy duty brake system variations came with the dual diaphram boosters at higher cost.

10.75" single diaphram:



10.5" dual diaphram:



9" dual diaphram:



Hope this helps!