85 new master cylinder design fail
Burning Brakes
Joined: Jan 2015
Posts: 876
Likes: 76
Both switch and brakes lines were the same size for my 86. Other than the lines being reversed front to back at the master it installed just like the original.
There is a small, very small, difference in piston size. I don't have enough seat time in this car with the stock master to tell if there is any
difference in pedal feel or not but the brakes seem fine to me. I'm pretty confident that for a regular driver it's fine. Being
able to get rid of the goofy reservoirs on the early model MC's was very welcome.
There is a small, very small, difference in piston size. I don't have enough seat time in this car with the stock master to tell if there is any
difference in pedal feel or not but the brakes seem fine to me. I'm pretty confident that for a regular driver it's fine. Being
able to get rid of the goofy reservoirs on the early model MC's was very welcome.
Melting Slicks
Joined: May 2019
Posts: 3,245
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From: Mid-Atlantic
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Pro
Joined: May 2025
Posts: 616
Likes: 148
From: OK
about what brands were the same re-boxed MC's while trying to find a decent one. The crappy reservoir caps previously mentioned are a clue.
And if you have a brand/vendor to suggest you should do so and be productive in your post. Unless it's some sort of secret.
I've been selling car parts for living for 25 years, you guys with domestic cars are getting screwed more often than not
on the quality vs price of most of this stuff from my experience the last few months bringing this 86 back to life.
Thread Starter
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Sorry for the delay in posting an update... incorrect master was Oreilly house brand, Brake Best, part # NMC22424. After the second one was also wrong I returned for credit. I ended up going with Autozone house brand Duralast NM4004, also new, not rebuilt & lifetime warranty. It was correct, installed fine after a long bench bleed process works just perfect. No leaks & can lock up brakes as this '85 has no ABS.
Burning Brakes
Joined: Jun 2005
Posts: 1,191
Likes: 15
From: Wallingford Vermont
Burning Brakes
Joined: Jan 2015
Posts: 876
Likes: 76
Note that era had two different sized brake line fittings, that PN has the right one for an older C4, I don't remember what the sizes are off hand. I found the suggestion to use the later one on this forum or another one. The lines are reversed in position but there is plenty of slack to install them.
I'll have to do more research to see if there are some articles explaining the putting a later master cylinder on an earlier C4. As I've hated the grommets leaking. Any time I mess with the master cylinder like remove the caps, the grommets will leak for a while. Was thinking of putting in the bias spring mode, and figured it would be better to put that in a new master cylinder than an old one that would probably start leaking right after putting it back together.
Here is a thread of someone talking about their master cylinder having a nipple and hose. What years had this version so I can avoid it?
1994 Brake Master Cylinder Reservoir Replacement - CorvetteForum - Chevrolet Corvette Forum Discussion
EDIT:
I was reading back through that thread and read somone say:
"The 92-94 uses the additional port down to the ABS pump. The 95-96 did not use the extra port and it seems that what they are selling to cover all years."
So, according to that person, the 92-94 had that nipple and hose to supply the ABS pump. And then they did away with that for 95-96. So I assume one would want to look for a 95-96, though will have to do more research.
Pro
Joined: May 2025
Posts: 616
Likes: 148
From: OK
That delco 19336904 I posted does not have the aux port. Least it's not open if it has it. Lot of times you'll see manufacturers put a port on that can be opened if needed, and left alone if not.
There was some note about the size of the fittings changing for the lines as I recall.
There was some note about the size of the fittings changing for the lines as I recall.
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Burning Brakes
Joined: Jan 2015
Posts: 876
Likes: 76
That delco 19336904 I posted does not have the aux port. Least it's not open if it has it. Lot of times you'll see manufacturers put a port on that can be opened if needed, and left alone if not.
There was some note about the size of the fittings changing for the lines as I recall.
There was some note about the size of the fittings changing for the lines as I recall.
Last edited by colter; Sep 3, 2025 at 12:56 AM.