Until I get another brake master cylinder (or a rebuild kit) I think I'm gonna swap master cylinders on my '68 Amazons. One looks beautiful on outside, but has developed a slight leak; the other looks like garbage, but works perfectly.

Then I'll have to bleed the system, new territory for me.


Do I need any special sorta tool in order to loosen up the bleeder screws on the brake system? Or will a regular old wrench do the trick? Don't want to break those little devils off, already sprayed PB Blaster on them a few days ago.

If you are just changing master cylinders you do not have to bleed the system. Bleed it out at the line fittings on the master itself after the install. Those lines are the highest point and air will migrate up into the master without problems.
The biggest problem will be caused by stroking the master to a point it hasn't been in some time, as that will cause the seals to overrun the sediment and rust that probably exists further down the bore.
If it was me, and I was being cheap, I would strip the master and hone the bore and re-assemble, having removed the crap that will tear the seals. Then you can bleed it without damage.

Thanks for the tip Rhys!

I really don't want to bleed the system if I don't have to, and also possibly break one of those bleeder screws (my nickname is butterfingers, there is a good reason for that)

My brain isn't functioning at 100% yet (coffee needed fast), wasn't sure what you meant by bleeding it out of the line fittings on master. You mean fill up the MC with fluid after I've swapped them out, and let fluid run out of the holes on MC bottom where the lines attach? Any brake pedal pumping required?


Have the power bleeder standing by if needed...

Bleed at the fittings just like you would at the wheels. Gently push the pedal down, open the fitting, close, pump again. It will be done very quickly and easily, and no need to mess with stuck wheel bleeders.

Just wanna make sure I don't mess anything up! I have the dual circuit MC installed, so 2 lines/ fittings to deal with. When I try your technique, should I depress pedal, open primary circuit fitting, close, pump again, AND THEN repeat same technique on secondary circuit fitting?

OR do I depress pedal, open both fittings at that point, close them both, pump again?

Thanks much,

Damian

Do both fittings at each depress of the pedal. Just move the pedal slowly in both directions and you will be fine.
Rhys

I found if I bench bleed the cylinder and then hook it up, then push one
or more caliper pistons back it will expel any air back into the MC reservoir.
If you have old grungy brake fluid you might not want to do it but my DOT5
seems to stay good and clean.
--
George Downs Bartlesville, Heart of the USA!

A socket or box wrench is good. DON'T use a crescent or open-end.
6-point is better than 12-point also.
Also make sure it fits right. 10mm will probably round off the corners.
Most of the bleeders are 3/8".
--
George Downs Bartlesville, Heart of the USA!

Only use a 6 point socket or wrench. If they are rusted or tight, a 12 point wrench or worse yet, a regular open end wrench will round off the corners.
--
Beastdriver - '75 245 217K miles (Beast), '83 245 216K miles (Beauty),'87 244 DL 160K miles (Dodo)

Excellent, thanks for the advice gentlemen!

Damian