OBS to NBS Master Cylinder Upgrade REPORT

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great white

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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...

If the brakes "pump up" then it's one of two things: air in the system or the master is bypassing.
 

michael hurd

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Yep, sounds like the master cylinder bypassing, they do wear out eventually. If in question, replace it, they aren't terribly expensive at all. ( think of what your life is worth, not to mention the truck )

Also, when bleeding the system ( don't forget to bench bleed the master cylinder ) cycle it slowly and wait 10 seconds or so between pumps.
 

K15 Blazer

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yeah... its only a year old though...
then again... the shop that installed it, I reported to the B.A.R. because they kept letting my truck leave in unsafe driving condition... so maybe its been wrong this whole time...
*starts writing down these part numbers*
 

someotherguy

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If it's a one year old "new" rebuilt unit, it was suspect the moment it came out of the box. So many rebuilt m/c's are bad-out-of-box these days it's ridiculous. I would never buy one at this point. Literal brand new only.

Richard
 

K15 Blazer

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yes, it was/is.

but, if it was bypassing the master, wouldn't the brake warning light flash to indicate the bleeding pressure?
im pretty sure the problem is air is seeping in... but where.........
>.>
<.<
 

K15 Blazer

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how can I possibly test this to find the real problem/source?

I don't want to start blindly replacing parts - like, it might be the master, the calipers, the etc etc etc im broke
 

MYT HI

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thanks for posting this. wanting to try this and glad to see someone has and posted about it.
 
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