dual chamber master cylinder

[Cav Trooper]

Is the master cylinder listed as availbale from Advance Auto compatable with Silicone brake fluid?

Thanks,

Cav Trooper

[Josh]

should be. Not sure why you would want to run DOT 5 though. A lot of people like DOT 5 because it doesnt absorb water. That's great, if you frequently clean and bleed your system, like on a race car. however, most people only look at brakes when there is a problem, so, what happens is the water that gets in the system goes to the lowest point in the system, which is usually the caliper, or cylinder, where it starts to rust the caliper or cylinder, or, if you're really lucky, when you brake hard, it will flash to steam from the heat of braking and cause brake failure.

I'd run DOT3 or DOT4. Yes, it will absorb water, yes, it will cause the boiling point to drop, but, it is still better than the boiling point of straight water,which is what you would end up with with DOT 5 sooner or later...

Other thing to be concerned with, is, if you leave the original drums in the back (I ssume you are doing a front disc conversion) is how those seals would react to DOT5.

[Cav Trooper]

The system already has Dot 5 in it on a single chamber master cylinder. All I'm going to do is switch to a dual chamber, I'm not going to all of the expense of discs in the front etc. I know I will have to plumb in a proportioning valve for the rears also. Any ideas on a part number?

Thanks,

Cav Trooper

[Tanner]

Info on the dual-circuit MC that Ugly Truckling uses on their swap... http://www.uglytruckling.com/M37%20Truc ... manual.htm

Charles Talbert may chip in some info here; I know that he has been using the dual-circuit MC's for his swaps, but not aware of his MC usage on full drum brake setups.

'Tanner'

[hbb]

I have read many of posts about what should or shouldn't be used as far as brake fluid and I am posting a break down of the pro's and con's of the different fluids. This should help you decide what is best for your application.
hb

Brake Fluid DOT Grades

DOT3
DOT3 brake fluid is the "conventional" brake fluid used in most vehicles.
Advantages:
DOT3 fluid is inexpensive, and available at most gas stations, department stores, and any auto parts store.
Disadvantages:
DOT3 fluid eats paint!
DOT3 fluid absorbs water very readily. (This is often referred to as being hydroscopic.) As such, once a
container of DOT3 has been opened, it should not be stored for periods much longer than a week before use.
Since DOT3 fluid absorbs water, any moisture absorbed by the fluid can encourage corrosion in the brake lines
and cylinders.
DOT4
DOT4 brake fluid is the brake fluid suggested for use in some late model cars.
Advantages:
DOT4 fluid is available at most auto parts stores, and at some (but not all) gas stations or department stores.
DOT4 fluid does not absorb water as readily as DOT3 fluid.
DOT4 fluid has a higher boiling point than DOT3 fluid, making it more suitable for high performance applications
where the brake systems are expected to get hot.
Disadvantages:
DOT4 fluid eats paint! Small leaks around the master cylinder will eventually dissolve away the paint on your
bodywork in the general vicinity of the leak, and then give rust a chance to attack the body of your car!
DOT4 fluid is generally about 50% more expensive than DOT3 fluid.
Since DOT4 fluid still absorbs some water, any moisture absorbed by the fluid can encourage corrosion in the
brake lines and cylinders.
DOT5
DOT5 brake fluid is also known as "silicone" brake fluid.
Advantages:
DOT5 doesn't eat paint.
DOT5 does not absorb water and may be useful where water absorption is a problem.
DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.)
Disadvantages:
DOT5 does NOT mix with DOT3, DOT4 or DOT5.1. Most reported problems with DOT5 are probably due to some
degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic
system.
Reports of DOT5 causing premature failure of rubber brake parts were more common with early DOT5
formulations. This is thought to be due to improper addition of swelling agents and has been fixed in recent
formulations.
Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can
cause localized corrosion in the hydraulics.
Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form
large bubbles over time. It may be necessary to do a series of bleeds.
DOT5 is slightly compressible (giving a very slightly soft pedal), and has a lower boiling point than DOT4.
DOT5 is about twice as expensive as DOT4 fluid. It is also difficult to find, generally only available at selected
auto parts stores.
DOT5.1
DOT5.1 is a relatively new brake fluid that is causing no end of confusion amongst mechanics. The DOT could avoid a
lot of confusion by giving this new fluid a different designation. The 5.1 designation could lead one to believe that it's a
modification of silicone-based DOT 5 brake fluid. Calling it 4.1 or 6 might have been more appropriate since it's a
glycol-based fluid like the DOT 3 and 4 types, not silicone-based like DOT 5 fluid.
As far as the basic behavior of 5.1 fluids, they are much like "high performance" DOT4 fluids, rather than traditional
DOT5 brake fluids.
Advantages:
DOT5.1 provides superior performance over the other brake fluids discussed here. It has a higher boiling point,
either dry or wet, than DOT 3 or 4. In fact, its dry boiling point (about 275 degrees C) is almost as high as racing
fluid (about 300 degrees C) and 5.1's wet boiling point (about 175 to 200 degrees C) is naturally much higher
than racing's (about 145 C).
DOT5.1 is said to be compatible with all rubber formulations.
Disadvantages:
DOT5.1 fluids (and Spectro's Supreme DOT4) are non-silicone fluids and will absorb water.
DOT5.1 fluids, like DOT3 & DOT4 will eat paint.
DOT 5.1 fluids are difficult to find for sale, typically at very few auto parts stores, mostly limited to "speed shops."
DOT 5.1 will be more expensive than DOT3 or DOT4, and more difficult to find.
________________________________________
________________________________________
________________________________________
© Copyright 2000 TCCoA.com
All rights reserved.

[rixm37]

Nice work HB. Lots of good info laid out all together.

[cuz]

Nice work HB.

One point I wish to clarify is the absorption of water by DOT 3 & 4. It is not really a disadvantage. Absorbing water into the fluid prevents it from laying loose on metal parts and starting corrosion. When the water is absorbed by the DOT 3 & 4 it stays suspended in the fluid. This is a good thing until the DOT 3 or 4 reaches it's saturation point which will cause several problems. It performs poorly in the heat category and corrosion prevention category after it is saturated. This is why the fluid is to be flushed and changed every 2 years. You will have a great trouble free system with DOT 3 or 4 by simply following the rules and flushing and changing fluid every 2 years.

As for the DOT 5 you made it very clear above that not absorbing water is a detriment since it lays in the system's low points and causes corrosion issues. This can be avoided to some degree by simply flushing and replacing the fluid every 2 years.

It is this point and the cost difference between DOT 3 & 4 vs DOT 5 that for most folks proves the DOT 3 & 4 route is just fine and least expensive.

[SOTVEN]

DUMB QUESTION. HOW DOES WATER FIND ITS WAY INTO THE SEALED BRAKE SYSTEM?

[MSeriesRebuild]

DUMB QUESTION. HOW DOES WATER FIND ITS WAY INTO THE SEALED BRAKE SYSTEM?

Dumb question huh; you better check yours. I'd bet you will find evidence of moisture in it.

Sealed system, it has a vent doesn't it?

[SOTVEN]

I MEANT MY QUESTION WOULD BE DUMB. APPARENTLY BECAUSE I GIG NOT THINK OF THE ANSWER. "VENTILATION" HENCE WATER THROUGH HUMIDITY IN THE ATMOSPHERE. MAKES SENCE.

[hbb]

I MEANT MY QUESTION WOULD BE DUMB. APPARENTLY BECAUSE I GIG NOT THINK OF THE ANSWER. "VENTILATION" HENCE WATER THROUGH HUMIDITY IN THE ATMOSPHERE. MAKES SENCE.

I'd be blaming the water there! That would be my story and I would stick with it.
hb

[k8icu]

I MEANT MY QUESTION WOULD BE DUMB. APPARENTLY BECAUSE I GIG NOT THINK OF THE ANSWER. "VENTILATION" HENCE WATER THROUGH HUMIDITY IN THE ATMOSPHERE. MAKES SENCE.

Stoven... Your questions wasn't dumb it was a good question.

[Cav Trooper]

Another question. I've looked at the link about installing the master cylinder, looks pretty straight forward fabricating and wrenching, they mentioned a proportioning valve but hadn't done that yet. Has anyone had experience with the proportioning valves on all drum brakes. I don't want to convert over to discs in the front. I've seen valves for sale that are adjustable and I am inclined to think that is what I'll have to install to get the proper pressure ratio between the two systems. Any thoughts, advice, help???

Thanks,

Cav Trooper

[Rick C]

I did the dual chamber master cylinder conversion with the stock brakes and didn't ut in a proportioning valve. My truck stops fine as long as everything is adjusted properly.
Rick

[SOTVEN]

I MEANT MY QUESTION WOULD BE DUMB. APPARENTLY BECAUSE I GIG NOT THINK OF THE ANSWER. "VENTILATION" HENCE WATER THROUGH HUMIDITY IN THE ATMOSPHERE. MAKES SENCE.

Stoven... Your questions wasn't dumb it was a good question.

THANX FOR THE CREDIT FRIEND, BUT SEE, THE ONLY ENCOUNTER I HAD WITH DOT 5, IS IN MY 2000 HARLEY DAVIDSON. AS FAR AS I CAN TELL, THE TWO BRAKE FLUID RESERVOIRS, SEEM TO BE SEALING TIGHT ONCE SCREWD CLOSED, AS THEY PREETY MUCH DO ON ANY OTHER BIKE I HAD OR SEEN. THAT IS WHY I WAS LED TO BELIEVE THAT "HOW WOULD THE WATER GO THROUGH?" APPARENTLY THERE IS MORE THAN MEETS THE EYE THERE