After much reading trying to decipher an aggravating and time consuming brake issue I offer you the following about trying to replace the grommets under the master reservoir . Don't do it!
It is in my opinion not worth the aggravation I just went through trying to figure out why I couldn't bleed the brakes after the Master seal kit rebuilt. I know you will find a lot of posts of how it was done successfully but I would strongly suggest just buying a new master and all that goes with it!
Costs are about $100 for the kit Vs. about $180 for the whole shebang!
What you get with option :
1) 2 rubber grommets, reservoir, res. filter, plastic flow cup, 3 flow cup seals.
2) all the above and a brand master and res. cap
Labor is about the same either way, probably less with option 2.
Risks? Well if you go with option 1 you may find you have damaged the inner seal or spring on one of the chambers in the master like I did. Why ? when you remove the plastic rear cap on the master the plunger is free to roam from side to side thus risking upsetting a seal or spring that may have been in there 15 years like mine. Fortunately for you I am here tell you what can happen
I spent days of research and hours of labor pulling it in and out and in and out looking for a solution to this mystery of why I could not bleed the brakes. I read everything from testsbooks to various bleeds to bad components to you name it! I tried all the procedures in the Rave and here and there and everywhere thinking I had done something wrong. When I finally gave up I concluded that the whole problem was that I upset the fine balance of the inner's of the master that had been working perfectly for those 15 years.
I concluded this was the best way for me ( although I know I will hear otherwise from the experts which I am not) .
1) Buy a new master assembly and install.
2)run two plastic tubes from the ABS intakes ( unscrew w/13mm and slightly raise above abs unit) back to the Res and slowly pump brakes until you get fluid back through the tubes. You have now "bench bleed" your master.
3) quickly slide off the tube and re-screw back into Abs unit. Do the right then the left as to not put pressure on the lines.
4) remove the abs relay from the engine compartment and hot wire the two side terminals . I used heavy gauge speaker wire and about 2 feet of wire. ***engine and key off!!!
5) bleed all four calipers by loosening nut and have ready to turn. attach plastic tube from bleeder screw to container. have an assistant touch the wire ends at the same time you are loosening the bleeder screw. The pump will run and the fluid and air will flow until clean. top off res after each wheel and do all 4.
Literally about an hour to do. You are done, all is well and you have a firm pedal and NO leaks.
Got the abs hot wire tip from an Aussie site. Work perfectly. Ran for about 10 seconds a wheel.
Conclusion
option 1 about 25 hours of dicking around
option 2 about an hour

 

Where did you buy your master cylinder unit

 

Here is the link. They are having free shipping and 10% fathers Day discount. I ordered the seal kit from them too, came next day for free. It was in an Atlantic British box so same exact part as the AB site for same price but free shipping. They were good enough to take the seal kit I bought for $100 back even though I installed it! I have bought many items from them for various cars. Most of the time it comes in a day to 2 days as did the master kit!
If you put it in and have any questions let me know !
Centric 130.22001 Premium Brake Master Cylinder | Auto Parts Warehouse

 

Hard earned sensible advice parkerlander.

 

Thanks for this. I am a newbie at this and this project is beyond my present skills.
You made that very clear for me.