Master cylinder abberation

[dpledger]

Have been reconditioning the master cylinder from my '53K -wasn't used for many years. Discovered the smaller hole from the resevoir to the cylinder (bypass) was totally plugged with crud to the point where it wasn't initially even visible. Managed to clear it with great difficulty, but it appears plugged at the very end-metal in the way and not rust. Now I used this cylinder for many years and never had problems, but without that aperture being clear the brakes should have constantly stuck. It appears that the bottom part of that hole should be 1/32, so I suppose I can drill it out to that size, but I am perplexed as to how it could be jammed like that and still have worked. Anyone have any insight, or a reason I shouldn't bore it out? the cylinder is in fine shape otherwise. Thanx

[Kenn Evans II]

Look at another cylinder and make sure that hole is supposed to be there.  It could ba a port fom the original sand cast and it may be solid and not a through hole.  If the cap was not air tight it would allow for the fluid to return to the resivoir and the brakes would not stick with a vacuum but would be harder to apply. The fluid would have been drawn back.  Do you have the remote filler that is an after-market that mounts on the firewall.

[joefrazer]

The hole should be there. If the cylinder is assembled, it's the piston that you're hitting. If the cylinder is not assembled, it could be rust or a small piece of the casting that came loose and is now wedged in the hole. That happened to a friend with a 47K.

[HJ-ETEX]

Why are you worrying about rebuilding that master cylinder? It is the same as used on 49-53 Fords and Wagner apparently ran off a batch of replacements about 15 years ago.

[dpledger]

By grinding down the end of a thin tool I was able to get something 1/32". Put it in a drill and was able to clear the bypass hole. Have never seen anything so thoroughly jammed. The first response to my question seems to have nailed the reason I never had any problems-for some reason there was a very small hole through the filler cap, which apparently provided the air leak mentioned. Never seen another cap like that. So anyway thanx to all for the advice-always like to have some consensus before doing something unusual. Cylinder should work better than ever now. Since I already have a rebuild kit and everything else looks OK, I hated to spend the $100 or so for a new one.

[joefrazer]

The cap SHOULD have an air hole in it. The cylinders were designed to allow ambient air to get pulled in when the brakes were applied. Putting on an airtight cap will cause other problems. It is true, however, that by having a breather hole in the cap, moisture is introduced and since DOT3 fluid absorbs moisture, a whole new set of issues arises. That's why auto manufacturers used to recommend a brake system flush at regular intervals.