Which brake master cyl? 12mm v. 3/8” switch?

[conesare2seconds]

Hi everyone. Appears I have a leak at the brake master cylinder so I’m preparing to replace it. Rock Auto lists 2 MCs for the 94 ZR-1: one with a 12mm long switch, the other with a 3/8” long switch. Is this referring to the pressure differential switch, and how do I know which one my car has?

[WVZR-1]

Hi everyone. Appears I have a leak at the brake master cylinder so I’m preparing to replace it. Rock Auto lists 2 MCs for the 94 ZR-1: one with a 12mm long switch, the other with a 3/8” long switch. Is this referring to the pressure differential switch, and how do I know which one my car has?

I don't shop RA and I didn't even look but I don't recall hearing that except it being mentioned by someone else who was shopping there. There should be some casting information on your old that could be used as a reference. I'm only aware that it was customary when using the service master assembly from GM the reservoir and level switch needed to be transferred from the old.

What casting information is on your master cylinder? You might need a mirror to read it.

[secondchance]

I replaced my master and the reservoir in October 2016 and did not run into part number/compatibility issue you are having.
Below is the vendor I got my parts from and had no issue. Perhaps part number listed can help you with cross-referencing.

https://corvetteparts.com/catalog?q=brake+master+cylinder

[Ccmano]

There are four listed for your car on RA. Only one is noted as 3/8’s. It’s aftermarket. The Ac/Delco unit is 12mm, go with that.
H
:cheers:

[conesare2seconds]

Good advice, so it’s done. I’ll update if any problems but don’t anticipate them. Ty all.