part #2 , yes discontinued.

 

It appears included in this AC Delco , see picture 8

https://www.rockauto.com/en/catalog/...+cylinder,1836

 

I realize that manufacturers don't have to make parts for more than 7 years after a model is discontinued, but how are you suppose to replace a part that is specified to be replaced such as this O-Ring? Maybe I will be lucky and the O-Ring will be on the new part.

 

I see it in the second pic for the Raybestos, but not what you post in picture 8 for the AC Delco. I'll wait and see what the new part comes with from Tasca Parts if I ever hear from them about shipping. I'm being more patient these days with delays. Understandable.

 

The 8th item, ACDelco, click the info button, there are 16 pictures. Some of them clearly show the O-ring. Hopefully the one you ordered has it also.

 

Thanks. I see the 16 pics for the AC Delco professional model with the O-Ring. I hope my oem replacement comes with it. Thanks again folks.

 

The Oring is as shown in the pic and in a wide selection of GM vehicles when failed or missing has caused a minor vacuum leak, which in turn has caused a low and/or soft pedal on braking.
The Oring may not be serviceable separately for all master cylinders, but should be included in new or rebuild masters with or without the reservoirs.

If you don't get one with the master, best choice is to take the master to a hydraulic supply house and have them match the diameter to fit. The cross section need not be too thick.
Tell the rep it's for compression and he should be able to supply you with a suitable oring.
Alternatively, they can be ordered from Grainger or MSC or any number of places, if you can measure accurately. The type of rubber isn't too important.
Metric Orings come in many more sizes than SAE Orings but not stocked as much.

 

Thanks, that's what I was thinking if it doesn't come with the replacement. I've had to be creative with O-Rings for my '98 Triumph Daytona motorcycle as well. I figured it was to seal vacuum from the booster.

 

That O-Ring only stops a vacuum leak.
Take the original to a quality hardware store, match it up and buy one.
Another thing you can do is install the original and start the car.
Spray the area with soap and water and see if gets sucked in. If not you're good to go.
Easy reading:
https://revolutionarywheels.blogspot...ter-works.html