How to: NBS master cylinder swap for firm brake pedal

[_Dylan_]

How to swap out the squishy brake pedal for a firm brake pedal. The OBS trucks are known for a horrible squishy brake pedal.

-NBS 1500 series master cylinder (mine was from a junkyard truck, IIRC it was a 2001)
-AGS BLF 26C brake line adapter (I got mine at autozone)
-DOT 3 brake fluid
-master cylinder bench bleeding kit

The OBS master cylinder has different sized ports. One is 9/16-18, the other is 1/2-20. The NBS master cylinder is 1/2-20 on both ports. This is why you need a 9/16-18 female to 1/2-20 male adapter. AGS makes an adapter #BLF 26C that I got at autozone. It was behind the counter, so ask for help. The bench bleeding kit was also behind the counter.



I first attached the adapter.

Then I bench bled the master cylinder. There are plenty of videos on youtube showing you how. In my case I used the kit and cycled the piston with a 3/8" socket extension against a tire stop.

Then I removed the 2 brake lines and removed the 2 nuts holding the old master cylinder on the brake booster.

picture of old master cylinder:

Bolt the new cylinder cylinder on with the 2 nuts. Then gently bend the brake lines to reach the holes. The NBS master cylinder is shorter than the OBS master cylinder.

Only thread the nuts back on just a little, enough to let brake fluid and air leak past.

Inside the truck use an object to press down on the brake pedal and hold it down. This may get brake fluid spray on the surrounding area, cover with a rag to catch any spray.

If the lines haven't leaked, loosen up the nuts just a tad on the brake lines to let out any air and let some fluid drip out. Then tighten all the way up.

Release the brake pedal after both lines are tight.

Very little air should be in the system. If you think there still may be air, go ahead and bleed the brake lines.

Finished product:

Enjoy the firm pedal your truck should have had.

 

[SunlitComet]

you did not just find out about this upgrade did you?

 

[_Dylan_]

uhhh yeah I did. About a week ago.

Get off your high horse.

 

[Gzes]

Lol. Yea alot of us knew about this mod for a good while just i didnt do it because my dad was giving me bs when i got the new one so i had to get the obs one. You should have done a brake test for both.

 

[_Dylan_]

Lol. Yea alot of us knew about this mod for a good while just i didnt do it because my dad was giving me bs when i got the new one so i had to get the obs one. You should have done a brake test for both.

The brake reaction time is much faster. The firm pedal begins braking after maybe a inch of pressing down. The original one didn't start braking until my foot was halfway to the floor.

I don't think that many people know about it either. I don't know why sunlitcomet is bashing a how to thread. Keep everyone in the dark buddy.

 

[SunlitComet]

just wondering it was in a few threads this year as well as the booster upgrade. thought you knew already. at any rate if you go hydro their will be some modding to the booster needed to make a nbs fit.

 

[slipping]

I don't think that many people know about it either. I don't know why sunlitcomet is bashing a how to thread. Keep everyone in the dark buddy.

I didn't know, will be looking into this. Don't usually see NBS at my yard though.

just wondering it was in a few threads this year as well as the booster upgrade. thought you knew already. at any rate if you go hydro their will be some modding to the booster needed to make a nbs fit.

Do you have thread handy? I'll look for it later tonight. Being lazy right now.
Found it.

 

[_Dylan_]

I read the 1/2 ton NBS MC won't fit a OBS hydro boost. You need to use a 3/4 ton NBS MC.

here is a writeup on the NBS and hydro swap. I would probably go with 3/4 ton calipers also.
http://www.fullsizechevy.com/forum/...brakes-obs-hydroboost-nbs-master-project.html

 

[Monstar_est87]

Sweet write up Dylan... Ive heard of this swap b4 but I thought it was only meant for the hydro boost... Either eay its gonna help alot of people out there...

 

[slipping]

I read the 1/2 ton NBS MC won't fit a OBS hydro boost. You need to use a 3/4 ton NBS MC.

here is a writeup on the NBS and hydro swap. I would probably go with 3/4 ton calipers also.
http://www.fullsizechevy.com/forum/...brakes-obs-hydroboost-nbs-master-project.html

Thanks dawg

 

[SunlitComet]

well you guys found the info i referred to before.

 

[mudslinger96]

First time I hear of this. I might do this mod since I don't want to change my ps pump to do hydroboost

 

[Gzes]

I've got everything besides fitting so might do soon. Couldn't find firing at autozone so gotta go to another autozone

 

[_Dylan_]

I had to ask for mine. It was behind the counter.

 

[97Tahoe2d4x]

Thanks Dylan for cool write up, especially the p/n for adapter needed.

Going to start collecting parts for this mod.

Peace.

 

[kc816]

i was late to this upgrade so thanks for the write up.

 

[Gzes]

I had to ask for mine. It was behind the counter.

I checked the back. Some auto ones don't have it. Haven't had time to do it yet

 

[nimrod.sixty9]

Wow, never knew of this. Wish I knew this before getting a new one a couple of months ago, and just replaced this one yesterday.

How I wish the tech section would get proper organization.

 

[PERICO13]

HEY WAT UP DYLAN!! IM NEW TO THIS FORUM AND RIGHT AWAY SPOTTED THAT M.C. SWAP MOD U DID!!I GOT A QUESTION FOR U BRO!IF I WAS TO BUY IT NEW SAY FROM OREILLY OR AUTOZONE WAT VEHICLE INFO SHOULD I GIVE THEM FOR THAT M.C.???I HAVE A 98 GMC YUKON SLE 2WD BY THE WAY!!THANKS BRO CANT SOLVE THAT F****N SQUISHY BRAKE PEDAL!!..LOL.

 

[imi4tth3w]

HEY WAT UP DYLAN!! IM NEW TO THIS FORUM AND RIGHT AWAY SPOTTED THAT M.C. SWAP MOD U DID!!I GOT A QUESTION FOR U BRO!IF I WAS TO BUY IT NEW SAY FROM OREILLY OR AUTOZONE WAT VEHICLE INFO SHOULD I GIVE THEM FOR THAT M.C.???I HAVE A 98 GMC YUKON SLE 2WD BY THE WAY!!THANKS BRO CANT SOLVE THAT F****N SQUISHY BRAKE PEDAL!!..LOL.

what in the ****? bro, lay off the caps lock. do some more reading before asking stupid questions.


also, if your going to replace that shit, your better off doing a hydroboost swap. MUCH more effective.