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When I removed my original master cylinder on my 78, there was a rubber seal and some sort of metal retainer between the master cylinder and the booster. The seal, which I assumed was assembled at the factory, appears to have fallen out of the groove during assembly and was pinched and permanently deformed. I searched this forum and have not yet found any reasonable explanation of what this is for! In addition, I have yet to find a stock replacement on the corvette parts sites. I did read somewhere that others have replaced with an O-ring. If you know what the function is, please share, otherwise considering trying an O-ring or leaving it out since I can find an exact replacement.
There was no seal on mine when I replaced the master, and I haven’t come across any consequences of not having it.
In your case, if you don’t have an adjustable booster rod to compensate, not having that thickness may affect the booster rod interface to the master slightly. If your brakes are dragging (slightly engaged) when at rest after your install, this could be why.
There was no seal on mine when I replaced the master, and I haven’t come across any consequences of not having it.
In your case, if you don’t have an adjustable booster rod to compensate, not having that thickness may affect the booster rod interface to the master slightly. If your brakes are dragging (slightly engaged) when at rest after your install, this could be why.
I've read some old posts that many older C3's don't have. Mine wasn't even installed correctly at the factory so it likely wasn't sealing anything! My best guess it is only there to keep moister and or debris away from the booster rod...but only a guess. I see this flimsy looking thing that has the correct description.
I realize this is a rather old post, but I ran into this exact situation today as I was replacing the original master on my 79 today.
I have the same rubber seal and the same retainer with the 3 tabs.
TCollinz - what did you eventually do?
The new OE style MC did not come with either of these pieces, and I did not find much in a few parts catalog searches I did.
My retainer has some corrosion and build up, but I was able to clean that off with a small brass brush & solvent.
My rubber seal is fine on the backside where it meets the MC, but the front side is somewhat indented where the retainer meets it.
However, the seal, after being out for a while it now seems to be going back into shape.
I'm going to reuse them, as it looks like it should work.
C3 Seal between master & booster
