master cylinder for 90 ZR1

[carnold]

Is the AC Delco #174-820 (Chev. #10157996) master cylinder replacement for a 90 ZR1 a PBR? Has anyone rebuilt a PBR with the AC 175-619 rebuild kit and did it work out OK? If I choose to rebuild do I need anyother parts beside the rebuild kit.

[tomtom72]

Okay this may not be something you want to read but I just bought a master cylinder for my 90 in Mar 06. AC Delco p/n on box is 18M399. There is another # on the box, 18030641, I guess that's a good GM # as it comes back as a master cyl on two GM dealer sites' search engines.

The master cyl is a PBR/ made in Australia in an AC Delco box. I bought the rebuilding kit from RockAuto.com and it is an AC Delco kit in an AC Delco box listed as a wagner or raybestos kit(?) on the site, I forgot which.....I haven't yet done the work but it looks like everything the FSM lists is in the kit....I may send it off to a rebuilder locally to have mine sleeved first & have them put it together along with a DRM bias spring.

I can't explain why your #'s and the #'s on the master I just bought (bought it from the last detail in Atlanta) don't match. Did you get those #'s from the parts CD that whiteracing.com sells? If so those are original 90's #'s and alot have been changed over time by GM.


Tom

[carnold]

Actually GM and AC Delco have 2 different part numbers and know one knows why. They are both good numbers and the number I used cost about $80 more. I found a NOS PBR on ebay for $99 so I jumped on it.

[tomtom72]

They proly do that to confuse us!

Oh, I made a mis-type/brain fart on the rebuilding kit. The box has a Raybestos label on it and the contents are in a sealed plastic bag with a PBR instruction sheet in the sealed bag....I guess it's a good thing that this stuff is made by some one reputable....better than the clutch hydraulics!


Tom

[Tom]

Originally Posted by tomtom72

....I guess it's a good thing that this stuff is made by some one reputable....better than the clutch hydraulics!

The original clutch master cylinder in my '90 was made by Lucas Girling as well as the replacement clutch master cylinder I bought at a Chevy dealership. They are a very large and reputable supplier of hydraulic components, both clutch cylinders and brake components. They started making the clutch cylinders for the '84 model year Corvette and made them for many GM applications using hydraulic clutch actuation.

The dust boot on the end of the cylinder will have Girling molded into the surface if it is a Lucas Girling cylinder and also if you take the cap off the clutch master cylinder and look down at the bottom flat of the moisture barrier it will have Girling molded into it if the master cylinder was made by Lucas Girling.

Originally Posted by carnold

Actually GM and AC Delco have 2 different part numbers and know one knows why. They are both good numbers and the number I used cost about $80 more. I found a NOS PBR on ebay for $99 so I jumped on it.

You have two part numbers as there are two models to choose from. You have the original dual resevoir model, and the updated single resevoir model.

Either fits and no issues.

As far as rebuild kits, don't like them. Never have, never will.

[petefias]

Originally Posted by Jeffvette

As far as rebuild kits, don't like them. Never have, never will.

I took apart my leaking MC to see which seal was broken/cracked and could not see any whatsoever, no tear, hairline crack, wear of any sort. And I looked under a magnifying glass. There was no scoreing, or any wear in the cylinder. I decided not to even try the rebuild kit and got the new MC. Given, the leak was very small (about a half dollar size puddle overnight), pedal stayed semi-firm. I had to reuse the reservoir from the old unit (didn't have the nipple for the ABS pump feed). New MC works fine.

[Tom]

Did you take apart and inspect the parts for the valve that is built into the cylinder? I had one master cylinder where this valve was leaking. Brake fluid would go from one reservoir to the other as well as leak out around the switch that screws into the valve.