Just Sharing This Brake Master Cylinder Trick

[Road Grabber]

I have been looking for an original master cylinder for a 1970 Dart Manual Disc Brake system.
I want to keep the original cast iron MC for the original look and still have to decide on the piston diameter. I have read from others that 15/16 is a good choice?

During my research I read product descriptions for aluminum MCs being used because of rust issues? Is this the main issue?

If this is an issue for those using cast iron MCs:

1. Years ago I ran into problems with DOT 3 fluid getting on the car and ruining my engine compartment and fender paint.
2. I used Dot 5 to solve this.
3. Since Dot 5 doesn't harm paint I have hand painted with a small brush Rustoleum brown primer inside the MC reservoirs carefully not to get it in the small return ports for the piston. The DOT 5 will not harm the Rustoleum primer and it is excellent rust protection for the inside MC reservoir.

It has worked great for my two boat trailers that sit outside, three restoration cars that have sat for over 30 years with never a problem. It takes patience and it is best to apply the primer when the cylinder is brand new but you can easily degrease the inside wiping it with some lacquer thinner.

Have at it or not - JUST SHARING

 

[66Valiant528]

I've had Dot 5 since I did the stop on a dime conversion way back. Steel braided flex hoses new rear cylinders and new calipers so it was time to flush and change the fluid. I have recently upgraded my master to a 2 bolt 15/16 aluminum job from Dr Diff. I like the pedal feel better.

 

[Road Grabber]

I've had Dot 5 since I did the stop on a dime conversion way back. Steel braided flex hoses new rear cylinders and new calipers so it was time to flush and change the fluid. I have recently upgraded my master to a 2 bolt 15/16 aluminum job from Dr Diff. I like the pedal feel better.

Interesting. Wonder what different feel using the same diameter between the cast and aluminum. You would think it would be the same mechanical advantage.

 

[jos51700]

Interesting. Wonder what different feel using the same diameter between the cast and aluminum. You would think it would be the same mechanical advantage.

Whatever difference you feel will be in your head

 

[Kern Dog]

I was shocked to see the price difference between standard DOT-3 and DOT-5. Holeeeee Crap! A quart of the DOT-3 is under $10 and the good stuff was almost $40.
I'm doing a huge brake upgrade in my Charger and DOT-5 is part of it.

 

[jos51700]

I was shocked to see the price difference between standard DOT-3 and DOT-5. Holeeeee Crap! A quart of the DOT-3 is under $10 and the good stuff was almost $40.
I'm doing a huge brake upgrade in my Charger and DOT-5 is part of it.

View attachment 1715975165 View attachment 1715975166 View attachment 1715975167

What rotors and calipers are those? Are those calipers aluminum?

 

[Ironracer]

Dot 5 is Silly- cone based ( see what in did there, lol) it Doesn't suck up and hold moisture....

 

[YY1]

As long as the reservoir is sealed (it IS sealed, right?) the inside shouldn't rust.

I did paint the outside of my MC when I converted to DOT 5, and it's still real purdy after 7 years.

I bought out 4 different Advance Auto stores of DOT 5 fluid when they were on sale "buy one, get one 50% off" and now have a whole shelf full of it, more than enough to do my next 2 project cars.

...and I haven't needed to add any to the original conversion.

 

[69hemibeep]

I don't think paint is needed with dot5. I have 3 cars with dot 5, one going back to 2004 on the restoration and the master and fluid looks new.

 

[66Valiant528]

Whatever difference you feel will be in your head

I changed the piston diameter to a smaller 15/16 the. So not in my head. Brakes were always OK and way better than my 11 inch drums which would fade after 3 quarter mile runs. The smaller bore makes the brakes feel like a new car!

 

[jos51700]

I changed the piston diameter to a smaller 15/16 the. So not in my head. Brakes were always OK and way better than my 11 inch drums which would fade after 3 quarter mile runs. The smaller bore makes the brakes feel like a new car!

Well, I was implying apples to apples lol. Yeah, for the same piston diameter, no difference

 

[Kern Dog]

What rotors and calipers are those? Are those calipers aluminum?

Those are from Dr Diff. 13" front rotors with 2 piston aluminum calipers and 11.7" rear rotors.
They are fancier than I expected.

 

[clementine]

I haven't filled the system on this latest build (going on 5-6 years) and Im wondering....can I use dot 5 in the hydraulic clutch?

 

[66Valiant528]

I haven't filled the system on this latest build (going on 5-6 years) and Im wondering....can I use dot 5 in the hydraulic clutch?

My McLeod hydraulic throw out bearing says to use Dot 3....so check with the manufacturer.

 

[jos51700]

I haven't filled the system on this latest build (going on 5-6 years) and Im wondering....can I use dot 5 in the hydraulic clutch?

Federal spec states that they be fully interchangeable, despite billions of internet bytes being wasted on the discussion. When HD changed from DOT5 to DOT3, the only thing that changed in the system? The label on the lid of the master cylinder!

I'm sure your clutch master and slave cylinder is no different.

 

[CRUZE 418]

Quick Silver is the least expensive I have found for DOT5, internet. I have it in both of my cars. No need to paint anything except the outside of your cast steel master, DOT5 doesn't absorb moisture like regular brake fluid. The moisture absorption of regular brake fluid is what kills your master, calipers and wheel cyls. I did have some brake fade on my drag bike under hard braking, but have never had an issue with my cars. Expensive? How much did it cost you to rebuild or replace your master cyl, calipers, wheel cyls and brake lines?Oh, and repaint your engine bay from the leaking master cyl?

 

[Joe Mc]

I recall reading (can't remember where, of course) that DOT 5 should "not" be used with disc / drum, only disc / disc systems. Also, can't remember why. Big help here right? Do some research before inadvertently swapping DOT, or other, fluids just to be safe

 

[Road Grabber]

I recall reading (can't remember where, of course) that DOT 5 should "not" be used with disc / drum, only disc / disc systems. Also, can't remember why. Big help here right? Do some research before inadvertently swapping DOT, or other, fluids just to be safe

Been using Dot 5 with disc/drum for 40 years. I don’t notice any problems. The only thing I heard was not to mix with Dot 3.

 

[jos51700]

I recall reading (can't remember where, of course) that DOT 5 should "not" be used with disc / drum, only disc / disc systems. Also, can't remember why. Big help here right? Do some research before inadvertently swapping DOT, or other, fluids just to be safe

It's been researched to death and argued for decades. DOT5 is safe in any non abs system that doesn't spec mineral oil

 

[Road Grabber]

It's been researched to death and argued for decades. DOT5 is safe in any non abs system that doesn't spec mineral oil

In your research can you mix the two?

 

[CRUZE 418]

Don't do that. Flush it. I flushed mine with the DOT5, sorta. Should have done it better, you can Google flushing possibilities for brake fluid.

 

[Road Grabber]

Don't do that. Flush it. I flushed mine with the DOT5, sorta. Should have done it better, you can Google flushing possibilities for brake fluid.

yes that's what I thought

 

[65TerrorCuda]

In your research can you mix the two?

I bought a used FZR600 that apparently had both in it. They don't mix at all, like water and oil. One fluid was sitting on top of the other after I drained it into a cup.

 

[CRUZE 418]

Yup. They don't mix. Wear rubber gloves when bleeding etc. Should do that for regular brake fluid too.
Think that I raced the Canada version of one of those with my Sportster. They were fast, but so was I.