OBS to NBS Master Cylinder Upgrade REPORT

[great white]

For the sake of sounding ignorant, can someone explain the difference in the two MC's? Does the newer type exert more pressure?

1998 Master cylinder piston:

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2001:

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works like so:

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Clear as mud?



As to more pressure, I would need the piston diameters to tell. Larger master piston will exert more pressure on the calipers and rear brake slave cylinders for the same amount of stroke on a smaller piston.

Basic hydraulics.

 

[HighRollerRich]

Been driving for 3 days now and no leaks anywhere on the brake system. I was worried the extra force would blow something out. I've never seen it happen but people were always wondering. The mounting on the booster is not leaking either.

Oh and don't worry about the plugs on the fluid reservoir, they're okay, OBS doesn't have a plug for them. I think they're for a low fluid indication light on NBS

 

[Frankp]

Thanks Great White, the newer piston looks a little beefier than the old. I may look into this upgrade.Thanks for posting Highroller.

 

[98_k1500]

Nobody tried this on a 3/4 ton?

 

[great white]

Thanks Great White, the newer piston looks a little beefier than the old. I may look into this upgrade.Thanks for posting Highroller.

Thats not it.

Look a the length of the stroke and the size of the return spring....

 

[HighRollerRich]

Update: it's been below freezing in Dallas for the past two days and still no issues with the new brakes/ braking system. Although I park it 3 stories underground in a garage so it's not cold very much.

 

[HighRollerRich]

Nobody tried this on a 3/4 ton?

I would GUESS that you would swap an NBS 3/4 ton MC to a OBS 3/4 ton for similar results.

 

[98_k1500]

When i get my 3/4 ton done i may buy one just to see. The brakes on it are decent but there is always room for improvement on the gmt400 brakes.

 

[K15 Blazer]

it fits in a parking structure!? LOL

my picture uploading is not working....

mine virtually looks exactly like that though. all I have is the junction block, and the abs/proportioning unit... no other hardware, just lines.
but the 1993 master cylinder looks pretty huge....
I just hate how it always feels like there is air in these brakes!!! driving or engine off you can pump the pedal and feel pressure build. it always feels low at the start.
im saving to do all this when convenient: the new master, pads, rotors, and check all line flares for cracks (last year the truck got all new rubber lines so those seem just fine)

I wonder I the calipers could be drawing in air...

 

[michael hurd]

If it feels like air in the brakes, there probably is, I went through about 3 liters of fluid before I had good brake performance, even though there was flow to the back drums and there was no air bubbles in the fluid, the back wasn't working properly.

This was with a new master cylinder, new wheel cylinders, new lines, new backing plates, new drums, shoes properly adjusted, new hardware, new hoses, calipers, pads... basically everything in the brake system replaced, even one of the park brake cables.

The truck stops on a dime and will give you change.

Without knowing the history of a vehicle, you don't know what previous people have done to it. Half tons with the 14 bolt semi floating axle get a larger master cylinder bore than one with a 10 bolt. ( 1 1/4" 14 bolt vs 1 1/8" 10 bolt) The wheel cylinder diameter is also different from a 14 bolt SF to 10 bolt. ( 1" - 14 bolt vs 1 3/16" 10 bolt )

When the system was opened prior, there may have been trapped air in the ABS hydraulic unit.