NBS master cylinder Swap

jjester6000 said:

$120?

You can do it much cheaper than that.

Try $12.

I went to my local junkyard and got a used master cylinder for $8 (every wednesday is 1/2 off) and picked up the adapter fitting for around $3. I already had brake fluid so it was all good.

I also cut the lines when I removed the cylinder, so I was able to use them to bench bleed it in the truck.

It's a night and day difference, and everyone should do it.

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Yea, I did the same thing when I did my swap. Paid next to nothing for the MC. Took mine off of a 2002 Tahoe. Tried it on a junk 400 before I left just to make sure it would fit my truck. Just had to by the adaptor. Had the fluid all ready. I figured if I didnt like the swap, I wouldnt be out much money, and I could always put the OE MC back on. Like I said, its been swapped over a long time, several years.

Did the same with the hydroboost, 1 ton master, p/s reservoir with the return nipple for the hydroboost and the pedal arm on the Express van. Just bought new p/s lines. All the rest for pennies on the dollar of new or reman off a junkyard donor. Its starting to leak after all this time. Might try a NBS Van hydroboost and master this time around if I can find one in the treasure yard.

If anyone ends up hydroboosting, need to pickup the pedal arm too. The apply pin for the boosters linkage is at a different location relative to the pedal arms pivot. Hydroboost on the left, vacuum on the right.



My 99 Tahoe is hydroboost too. Got the stuff off a 6.5 diesel truck. Same truck donated the accelerator pedal for the 8.1s DBW. Just got the new p/s hoses and a brass tee to tee the hydroboost return into the p/s return hose. Hydroboost pumps have a seperate fitting for the return line from the booster but I directed all the fluid into an early model GMT400 P/S cooler before returning it to the stock pump on my Tahoe which bolted directly in place of the 8.1 van pump that was on the 8.1. On the van I added the factory style 1-ton finned p/s cooler under the radiator core support that came factory on 4.56 geared vans. I cut an opening in the airdam under the bumper, leaving the lower portion of the cut attached and created a scoop to force air over the cooler while driving. Used some metal strapping material and pop rivets to hold it in place at the angle I wanted.

While I am on that kick....A power steering cooler will save your pump and steering box seals as well as keep the fluid from degrading in 6 months to a black, burnt smelling sludge when you drive hard and long with lots of RPM daily.

The GMT400 cooler I put on the 99 Tahoe came off an 88 K1500 350.

The one one the Express from a 3500 dually cut-away van.

Both were $10 wrecking yard finds. Just flushed them out with some mineral spirits, washed and straightend the fins, and used new bulk p/s hose with the good quality solid faced EFI pinch bolt style hose clamps.

First picture is the truck one, second the Express van one.

L31MaxExpress said:

Hardest part to find and swap is the brake pedal arm. Weirdest thing to get normal in your mind with the hydroboost is with the power steering fluid operating the booster, it feels and sounds like you are stepping on a garden hose that is at full blast when you put your foot on the brakes. Same feeling gets transmitted into the pedal. .

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The above got my attention.
I have Hydroboost (C2500 JD 7) and still a sinking pedal (despite replacing the MC with new) when stationary - only when stationary as the truck will come to halt long before the pedal has a chance to sink.
Noticeable though is that it doesn't happen when I first jump in and start the engine and am still stationary. Only after I've driven a bit does it start to happen. Hyd (steering) fluid hasn't been changed yet (and I have EVO and cooler). Does the condition of the hyd (steering) fluid (it looks red and clean) affect pedal feel, could it be the cause of my sinking pedal or is there something else - or is it normal on Hydroboost systems?
I've no reason to suspect anything else in the system as my steering is exactly as I'd expect it to be. It isn't a problem in driving but does kind of knock my confidence in the braking system.

Pinger said:

The above got my attention.
I have Hydroboost (C2500 JD 7) and still a sinking pedal (despite replacing the MC with new) when stationary - only when stationary as the truck will come to halt long before the pedal has a chance to sink.
Noticeable though is that it doesn't happen when I first jump in and start the engine and am still stationary. Only after I've driven a bit does it start to happen. Hyd (steering) fluid hasn't been changed yet (and I have EVO and cooler). Does the condition of the hyd (steering) fluid (it looks red and clean) affect pedal feel, could it be the cause of my sinking pedal or is there something else - or is it normal on Hydroboost systems?
I've no reason to suspect anything else in the system as my steering is exactly as I'd expect it to be. It isn't a problem in driving but does kind of knock my confidence in the braking system.

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Which master did you use. I had similar issues with hydroboost and the stock master. I switched to a master from a 2010ish 3500 and it was all good. I can't remember the exact year I was looking at piston sizes when I made the choice.

Knuckle Dragger said:

Which master did you use. I had similar issues with hydroboost and the stock master. I switched to a master from a 2010ish 3500 and it was all good. I can't remember the exact year I was looking at piston sizes when I made the choice.

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I used a Raybestos one from Rock Auto that was listed for model, year and brake system. Ran my choice past the forum at the time and got a thumbs up. Replaced the old one as it did go full travel during driving.

Pinger said:

I used a Raybestos one from Rock Auto that was listed for model, year and brake system. Ran my choice past the forum at the time and got a thumbs up. Replaced the old one as it did go full travel during driving.

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This site has a lot of talk about quick take up masters and low drag calipers and a lot of well intentioned guys tend to make it a little more black and white then it is. Hydraulics is all about fluid volume, nothing more. Low drag calipers have been around a lot longer then quick take up masters. The internet is full of guys with dire warnings, regurgitated information with no experience to back it up and experienced/educated guys that draw too hard of a line between right way and wrong way. What you have now isn't working for you; it might be time to go another direction.

It stuns me that removing the ABS is an accepted practice but increasing the fluid displacement of the master is taboo with some. It makes no sense to me.

Knuckle Dragger said:

Which master did you use. I had similar issues with hydroboost and the stock master. I switched to a master from a 2010ish 3500 and it was all good. I can't remember the exact year I was looking at piston sizes when I made the choice.

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Wait, so on my hydro boost on my C3500, I can replace the master with a 2010ish one? What kind of modifications did this require?

1. Why are you posting brake issues in "Engine Performance + Maintenance"?

2. "NBS" and "OBS" are vague and ambiguous terms.

3. JB3 and JB5 brakes have the ****** leading-trailing shoe rear brakes. It's uncommon to find them properly adjusted, and therefor they rarely work properly.

4. Replacing a Quick-Takeup master cylinder with a non-Quick-Takeup master is a FRIGGIN' DISASTER. You will LOSE hydraulic advantage, and you FAIL to supply the low-drag calipers with a "gush" of low-pressure fluid to push the pistons up to the rotor. GM put STEPPED-BORE master cylinders on these vehicles FOR A REASON.

Photo 1. Note HUGE rear piston, and stepped-casting. JB3 has a 1" nominal bore with 32 or 36 mm (I forget which) rear low-pressure piston. JB5 & (I think) 6 have a 1 1/8 nominal bore with 40 mm rear, low-pressure piston.



Some doofus removes a correct-but-failed master cylinder, installs an incorrect but working master, and thinks he's accomplished something. Then he tells other folks who also don't comprehend the concept of low-drag calipers and high-volume (stepped) master cylinder bores, and they make the SAME MISTAKE.

The JB3, JB5, and (I think) JB6 (well, xx3, xx5, and xx6) brake systems use low-drag front calipers, and NEED the quick-takeup (step-bore) master cylinder.