Rust in brake booster?


Nov 6, 2017
I ordered a used OEM booster on ebay from a JY with good FB. I always forget to avoid rust belt places being that it's hardly an issue for me at home! This yard was in IL.

Anyway, the part was rustier than I'm used to and I noticed this rust in the "bore" of the booster. Hopefully you can make it out. This is the low point when mounted so it's where water would pool and the rest is not as bad.

Not sure if it's a concern?

I sprayed a little WD in there (reasoning WD tends to get along with most rubbers) and rolled the booster around a bit, but I don't actually know if anything "scrapes" those interior walls as the pedal is depressed? I need to watch some vids on exactly how boosters operate as I don't know precisely.
That has been left off the car probably outside or in a leaky shed for a while, personally I wouldn't accept that.
I thought that, too. Looks like it was left open to the elements
Well, it's installed and working way better than our old booster.

I didn't have much to lose as our old one was basically like driving a car from the '60s when "power brakes" were an option.

I ordered the booster back on 9/4/22 so I don't have any recourse with the ebay seller. I paid $39 so not out a ton of $

If it fails it's on me for not inspecting the part upon arrival back in September.
I am not sure what the seller represented in the description of the part, but I would only buy something as critical as this as a rebuildable or restorable part. I am pretty anal and I would only put that on my car if it was fully restored or rebuilt to factory new condition.
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Often times rust in the booster can be caused by a leaky master cylinder leaking into the booster. And since brake fluid can hold moisture it can cause rust.
I wouldn't use one that is rusted inside. Since it is the braking system, I would never use a used part in my braking system. Order a new booster and have confidence that it will perform when you need it most.
I agree, junk.

Even if the diaphragm is in good shape, it's in the process of being rust jacked and WILL leak. It's only a matter of time.

No reason to wait for it.