"NEW" Power Disc Brake Master Cylinder?

[y3chargerrt]

DOT 5 DOT 5 !!!!!!!!!!!!!!!!!!!!

[Mfr426]

Who is this DOT lady?

[resq302]

DOT 5 DOT 5 !!!!!!!!!!!!!!!!!!!!

Thing is about DOT 5 is that there are some rubbers that are not compatible with it and will swell causing the part to distort or not function like it should.  Also, if a system is operating properly, it should not leak causing that problem.  DOT 3 and 4 will absorb moisture so it does not cause rusting of the internal parts.  DOT 5 will NOT absorb moisture and allow the internal parts to start rusting.  Personally, I would rather flush out the DOT 3 or 4 every so many years than to have to worry about what moisture is collecting or rusting out the insides of my brake system.

[Just 6T9 CHGR]

Im sure with this sealing surface leaks wont be a problem.  Spray bomb away I say! 

[Chatt69chgr]

My take on the DOT 3&4 brake fluid is that its basically hygroscopic, ie, it absorbs water and as the water is dispersed throughout the total volume of the brake fluid in the system it is exposed to all the iron surfaces in the system and slowly begins to rust them.  This appears as a mud in the system.  It does take time and if you flush out the system every couple of years I don't think you would have to worry about the rust issue.  And you always want to pull the fluid out of the system preferrably with something like a Vaccula which is a device that creates a small amount of vacuum by way of compressed air.

DOT 5 fluid being silicone based is not misable in water.  If any water does get in the system it would tend to just sit in one place.  It could rust out that place.  I've seen this happen in antenna connectors like the ones that were used for CB radios on car roof tops when the connector was packed with silicone grease.  Any space not filled with grease could capture a water droplet and corrode the diecast antenna base connector.

Which is best?  I don't know.  Both are used extensively.   

[Charger_Fan]

Nice find Chris, thanks for sharing the info & comparison pics!
The only bummer is that it's yet another thing that's made in China, but beggars definitely can't be choosers in this case.

My take on the DOT 3&4 brake fluid is that its basically hygroscopic, ie, it absorbs water and as the water is dispersed throughout the total volume of the brake fluid in the system it is exposed to all the iron surfaces in the system and slowly begins to rust them.  This appears as a mud in the system.  It does take time and if you flush out the system every couple of years I don't think you would have to worry about the rust issue.  And you always want to pull the fluid out of the system preferrably with something like a Vaccula which is a device that creates a small amount of vacuum by way of compressed air.

DOT 5 fluid being silicone based is not misable in water.  If any water does get in the system it would tend to just sit in one place.  It could rust out that place.  I've seen this happen in antenna connectors like the ones that were used for CB radios on car roof tops when the connector was packed with silicone grease.  Any space not filled with grease could capture a water droplet and corrode the diecast antenna base connector.

Which is best?  I don't know.  Both are used extensively.   

That's what I've known to be the case, too.
I'll also add one more thing...DOT 3 & 4 are supposed to attract moisture at such a rapid rate that you want to make sure you don't leave your M/C cap off any longer than possible. Especially on a humid day. It will wick up moisture pretty rapidly.

   I have a '70 and was just in the market for a master cylinder and my local Napa ordered one for me and a rebuilt one arrived like yours. My lines are on the left side of the master so I couldn't use it. I had them cross reference the part # on my old one and it showed for 71-up. Are 68 & 69 different from '70?

That sounds about right. My brakes were swapped from a '71 Satellite, way back when. The '71 & later disc M/C's look like this.
Pardon my dirt, I haven't cleaned in oh...15 years or so. 

[resq302]

 :rofl:Nice heat stove you got there.

[Just 6T9 CHGR]

.  The '71 & later disc M/C's look like this.

Yep, thats what I have on the car now....I had to resort back to this one because my first "correct" one crapped out on me

[Charger_Fan]

:rofl:Nice heat stove you got there.

Thanks!   It worked fairly well, but the damned carb still used to ice up on some rainy days.
I finally had the intake boiled out, to uncork the exhaust crossover...that fixed it.


Geez Chris, yours looks so much better than mine for some reason.

[Mfr426]

I just put on the new MC. I replaced the rebuilt one that I got from National about 4 months ago.

All is good and my car now stops like a disc brake car should. Incidentally, disregard the "new and improved" brake bleeding sheet that comes with the new MC. I tried that (again) today the first time and my brakes went to the floor. I pulled out the MC, did the bench bleed procedure (with lines running from fittings into the reservoir) and they worked perfect. So much for "new and improved" technique...