Master Cylinder

Has anyone had any problems with a NAPA vacuum boosted master cylinder? I replaced mine on my '95 K1500 and it all seemed fine until I noticed my pedal get soft again as if the primary cup seal had busted. I checked and the master cylinder is leaking around the seal where the reservoir meets the case.

Sounds like more china junk. Stick with OEM.

Perhaps a moderator will move this thread to Axles + Brakes.

Robb_Perezz said:

Has anyone had any problems with a NAPA vacuum boosted master cylinder? I replaced mine on my '95 K1500 and it all seemed fine until I noticed my pedal get soft again as if the primary cup seal had busted. I checked and the master cylinder is leaking around the seal where the reservoir meets the case.

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What brake option code on the glove-box decal--JB5? What NAPA part number?

You're saying that the seal where the plastic reservoir meets the aluminum cylinder is weeping?

JOHNGAAA1 said:

Sounds like more china junk. Stick with OEM.

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The AC-Delco master I put on my '88 was made in China. Even the "good" brand names are outsourcing to the Commies.

Robb_Perezz said:

I checked and the master cylinder is leaking around the seal where the reservoir meets the case.

Click to expand...

My new Raybestos MC does the same. Just a weep, not enough to lose fluid and it doesn't affect brake operation.

Robb_Perezz said:

Has anyone had any problems with a NAPA vacuum boosted master cylinder? I replaced mine on my '95 K1500 and it all seemed fine until I noticed my pedal get soft again as if the primary cup seal had busted.

Click to expand...

I had the same (Raybestos - see above) - and a replacement MC for the new MC just fitted lined up - but bleeding sorted it out. Manually adjusting the rear shoes brought a further improvement in 'pedal'.