Last summer, I purchased a new ate 19mm master cylinder. For some reason, my cylinder did not have the rubber grommets for the reservoir lines. I purchased new grommets and installed them. I was constantly having a slow leak from the top of the MC- not from the lines.

Earlier tonight, I removed the MC. I assumed that I probably didn't install the reservoir lines into the grommets. I removed them and found that I had not installed the washer under the grommets.

Tonight I installed the washers and new grommets. I unhooked the fluid reservoir so I could get some slack on the lines. Because of the slack, I was able to push the lines into the grommets easily. I pushed them as far as I could.

My questions-
1. Could leaving out the washer under the grommets cause a leak?

2. Does it matter which reservoir line goes in the master cylinder holes?

3. How do I know if the reservoir line is properly seated?

4. Anywhere else on top of the MC that could cause a leak?

1. Yup ! leaving the washers out can cause a leak.

2. Usually I prefer front to front and rear to rear so if there is a loss of fluid I know which end of the horse to check first.

3. You can feel when the "barb" clicks into the grommet. A tiny bit of brake fluid for lubrication on the grommet when installing the reservoir lines really helps.

4. I've seen lines leak themselves and fluid make it from the bottle down the line to the master, but both are rare and obvious. If it was dry an inch above the master and wet at the grommet, your leak was most likely caused by the missing washers.

I hope this helps a little !

Is there a method to seating the reservoir lines. I have no fluid in the system, so I have no hard lines on either. Giving me as much room as possible. I have tried with the grommet in the MC then lube the pipe. I have tried putting the grommet on the tube and lubing the grommet, then trying to insert the two at once. I get about there, but you can see the mark on the tube where it was seated last time. Just short of the bottom. I have used anything and everything to pull down and no luck.

Should I take the whole thing off and try to insert the metal tube in the MC on the bench?

Later the same night....
By 10:30 I am done. Finally did just take the MC off, set it on the floor and insert. Lots of force and a bit of wiggling. Then getting it all back with the tubes mounted is a trick, along with the sealant and the pushrod inserting. May not be original, but I figured out how to get the pushrod inserted without a helper. I put a wrench under the pushrod to raise it up to the center of the hole.

Good night JohnBoy
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Yes

You should also bench bleed the master cylinder. Mount it in a vice, fill the tubes with brake fluid, plug the outlets, and pump away for 20-30 min. This will save you quarts of brake fluid when you bleed it on the car.