Advice on Swap to Dot 5 - New MC

[70DusterBob]

I decided to take the plunge and go with the Dot 5. I have heard it is better all the way around for the lines and cylinders. Any experience with it would be appreciated. I was planning on draining the Dot 3 out of it, bleeding forever the old MC and WC's until I have clean fluid, then swapping out the MC and WC's and bleeding again. Is that the best way to do it?

Is there a reasonably priced brake bleeding kit anyone knows of? Under $100? My good old Mighty Vac's diaphragm finally bit the dust.

I plan on using this MC:

Right Stuff Detailing Master Cylinder

It has a slightly bigger bore 0.030 or so than the one the called for on my 72 Dart Brake System, the MC that is in the car now came out of a 72 Dart. It is in a 70 Duster that had the good old /6 in it. So I swapped out the K, front end, and upsized all four drums. Got an 8-1/4" rear with 2-1/2" x 10 Shoes, front is 2-1/2" x 10 Shoes as well. Just replacing the motor don't have funds to go with disc at this time, but certainly will on the horizon. Just basically need to know if anyone has experience with this MC's front and rear line connections, if they fit or not, or is there too many different models, too many different set ups to know?

Thanks

 

[AJ/FormS]

Anything will work with almost anything, but you might have to re-engineer the front to rear proportioning.

For instance, your 10x2.5 rear set-up is way to powerful for the front. If you run no proportioning at all on a set-up like that, then when you brake hard, the rear of the vehicle will unload weight onto the front, and the rear brakes will lock up. This is a bad situation. If the car is not driving in an absolutely straight line, the rear end will skid around and try to pass the front. If this happens at speed, and you don't be ready for it, then you will be facing backwards likitty-split.
Most vehicles are engineered for about 85% front brake/15% rear. On A-bodies this would be 10x2.5 on the front and 10x2s on the back, but the 10x2 rear shoes are closer to 1.75; and there may be a proportioning valve in the line.
So as yours stands you will need an adjustable P-valve in the rear line to limit it's effectivness.........
Unless you are also running big and little tires. With big boots on the rear you can increase the rear effectiveness, on account of it's harder to skid those big tires compared to the smaller fronts.
As to the M/C and drum brakes;
The M/C has to have enough capacity to move all the shoes out to all the drums, and to be able to compensate for the occasional non-working self-adjuster. The tendency with drums is to forget about the adjusting business. So the pedal goes lower and lower and one day the rears don't rub anymore. Since they don't do much anyway, you probably never notice. But eventually you will run outta pedal and the stopping is pitiful. So you gotta keep that in mind with your engineering and also to keep aware of the pedal travel.

As to Dot 5, It needs to go into a pristine new system. If it is polluted with non-Dot5 then it's effectiveness will be reduced. And you cannot pump out every drop of the old stuff, by pumping in the new behind it. So if retro-fitting, you have to flush out the old. As for the stuff itself; it's a great product. Mines been in there since year 1999, and seems to work same as it ever did. One thing I did notice tho is that it likes to weep at the M/C lid. Mine has a bailing wire on it and I just can't seem to make it tight enough. No complaints.
I'm a streeter tho with a manual trans, so I hardly even use the brakes.Except I do run bigNlittles 235/60-14s up front,295/50-15s out back. And KH 4-pistons up front with 10x2s out back..... and no brake proportioning. ..IIRC the rear WCs are 15/16... but may be 7/8s, I forget; 1999 is a long time ago.
I wouldn't hesitate to use Dot5 again.
For a drum/drum dual system, both reservoirs could be the same size. Or the reservoir to the front brakes could be bigger....... like the one you linked. On a factory Mopar the rearmost reservoir goes to the front brakes.

 

[70DusterBob]

Thank you AJ,

I did use the proportioning valve from the 72 Dart as well. A mustang flying in a residential area took 'er out. Right in the DS front bumper. I had that Dart for about 14 years! So I swapped everything from it into the Duster pretty much, "EXCEPT THE BRAKE LINES"!!! Yikes!!! You know. As much as new MC, WC's, and Dot 5 fluid costs, Yeah, I should probably make it an overhaul and change out the lines. As for the stopping power, it hasn't been the greatest, but it does stop. The problem exists if I were to drive it in the City, or on the highway in the city, everyone else can stop 3x faster than I can. So I stay out of the cities all together. No need to drive there anyway, that's what the daily driver is for. Coming off the highway, 2nd slows me down and I put 'er in neutral when coming to a complete stop if I need to.

Good spotting on the proportioning valve. I rebuilt the Duster about 12 years ago and forgot about that little but crucial part to the braking system. I do have much larger/taller tires on the rear, 15's and 14's on the front that are normal size. So I think your right about that making it equal out a bit. I will have to pay attention to the difference in braking when I go to a lower profile back tire, 50's racing radials. But I do think I should change out the proportioning valve when I change out the lines. Now that I think about it, that may be a time when I switch to discs. I suppose if I get my discs system from a mfg they would have the right proportioning valve to go with it.

I'm just hoping like crazy that the front and rear connections to the MC fit. It is a beauty!

 

[ir3333]

Don't believe everything you read on the internet, the only real advantage of dot 5 is an increase in boiling temperature which is required for road coarse continuous braking and you will probably never need.
When swapping components stay with the factory pieces and you should be fine.i.e. take the front brakes off the car that you got the rear from.
As AJ says, too much braking in the rear will cause the rear to lock up first and then you will spin..it's physics.
I would go mopar discs up front before any other changes with the proper donor car pieces.The only knock on Mopar brakes is their power booster has no feel and is too efficient.In even a slight panic you will lock up everything.
I know a family of skunks that will verify this!

 

[70DusterBob]

Don't believe everything you read on the internet, the only real advantage of dot 5 is an increase in boiling temperature which is required for road coarse continuous braking and you will probably never need.
When swapping components stay with the factory pieces and you should be fine.i.e. take the front brakes off the car that you got the rear from.
As AJ says, too much braking in the rear will cause the rear to lock up first and then you will spin..it's physics.
I would go mopar discs up front before any other changes with the proper donor car pieces.The only knock on Mopar brakes is their power booster has no feel and is too efficient.In even a slight panic you will lock up everything.
I know a family of skunks that will verify this!

I have heard that the Dot 5 resists moisture and prevents the inside of the braking system from rusting out. That the longevity of the parts is increased significantly. Have you heard anything along these lines? I didn't hear it online, from a garage and a parts pro.

Other than that, do you know if the size of the brake lines make a difference in the stopping power? For instance a smaller diameter would be harder to push the fluid through than a larger one? I don't have the car the rear brakes came from, but I have never had an occasion to lock up my brakes either. They are manual, hard to push, but if I stomped on them, they probably would lock, will have to try it out somewhere safe when I get the new MC and WC's on. But the rear brake lines are the ones that came with the /6. Do you suppose I should really look into upsizing them? The front has the Dart 318 Factory brake lines, but the rear were made for the /6. Maybe this is why the braking seems even. It has been sitting for a year, way more on than off. I would not trust my life to the WC's and MC that are in there. The WC's are at least 7-8 years old, while the MC only about 5, but I want the chrome one on there. The rusty one just don't look right. See pic...

Someone posted a link to a company that sells Disc Conversion Kits. Do you or anyone know what that link is?

Thanks

 

[Tooljunkie]

Only one single reason why i would switch to dot 5. It wont destroy paint. Anything else is bonus. Denatured alcohol to flush old fluid, then a flush with dot5 and fill er up.

 

[flingdingo]

If you flush your brake fluid every couple of years, corrosion isn't an issue.

I use Castrol synthetic fluid (used to be called GTLMA) It's compatible with DOT 3 and 4, so if I have to, I can just pour in regular brake fluid.

It has a higher boiling point than DOT 4, and doesn't absorb moisture as readily. It costs a bit more than regular brake fluid, but not as much as DOT 5.

 

[ir3333]

you will hear all kinds of pros and cons...because water doesn't mix with synthetic brake fluid it will pool in lo spots in your system and corrode those spots.Their should be no measurable amount of water in your brake system unless it's used in all manner of winter and rainy environments for years.Synthetic fluid will give you a soft pedal.Synthetic won't damage paint..for Pete sakes don't get it on your paint!These arguments will go on forever.Your line size shouldn't matter.If you have a hard pedal your master cylinder piston is too large.Different size tires can mess up your proportioning.Due your tests on a damp / wet pavement were there is no traffic.
There are numerous systems out there..i would still duplicate a disc drum factory set up because they got it right and parts are available and cheap. It's like suspension modifications..too many just add on heavy duty aftermarket parts and end disappointed or with poorly performing rides.
Brakes are so important.

 

[70DusterBob]

you will hear all kinds of pros and cons...because water doesn't mix with synthetic brake fluid it will pool in lo spots in your system and corrode those spots.Their should be no measurable amount of water in your brake system unless it's used in all manner of winter and rainy environments for years.Synthetic fluid will give you a soft pedal.Synthetic won't damage paint..for Pete sakes don't get it on your paint!These arguments will go on forever.Your line size shouldn't matter.If you have a hard pedal your master cylinder piston is too large.Different size tires can mess up your proportioning.Due your tests on a damp / wet pavement were there is no traffic.
There are numerous systems out there..i would still duplicate a disc drum factory set up because they got it right and parts are available and cheap. It's like suspension modifications..too many just add on heavy duty aftermarket parts and end disappointed or with poorly performing rides.
Brakes are so important.

With that said, I'm leaning on your side. I think I should just flush the system with new Dot 3 and be done. I have noticed the back tires lock up on gravel roads before the front do, but... Anyway, I think they are okay the way they are. I will try the wet road test. Perfect spot for it... Right where I floor it too. lol?

Thanks.

 

[AJ/FormS]

Drum brakes can be awesome especially at normal speeds. They are self-energizing so as you come to a stop, you usually have to begin decreasing the pedal pressure. I don't know why yours would not be adequate.
I prefer a smaller M/C like a 15/16; It's easier to modulate, while needing a bit more pedal-travel for the same stops.
I like the Mopar single diaphragm booster, and with an adjustable pushrod, you can dial in the amount of boost. It doesn't have to brake like a FifthAvenue.
The discs off an F-body or 73up A-body would work really well on your street combo, and are relatively cheap. To work on a 72, you would need the 73up UCAs

 

[famous bob]

Drum brakes can be awesome especially at normal speeds. They are self-energizing so as you come to a stop, you usually have to begin decreasing the pedal pressure. I don't know why yours would not be adequate.
I prefer a smaller M/C like a 15/16; It's easier to modulate, while needing a bit more pedal-travel for the same stops.
I like the Mopar single diaphragm booster, and with an adjustable pushrod, you can dial in the amount of boost. It doesn't have to brake like a FifthAvenue.
The discs off an F-body or 73up A-body would work really well on your street combo, and are relatively cheap. To work on a 72, you would need the 73up UCAs

`
Is there a fluid that will mix w/ any type / I need to bleed my right front wheel cyl. and forgot what type I put in /about 10 yrs ago !

 

[jos51700]

Don't believe everything you read on the internet, the only real advantage of dot 5 is an increase in boiling temperature which is required for road coarse continuous braking and you will probably never need.
When swapping components stay with the factory pieces and you should be fine.i.e. take the front brakes off the car that you got the rear from.

Both statements are untrue.

First, DOT 5 does not absorb moisture, so the boiling point is more consistent, and does not damage paint, as well.

Factory proportioning was very poor and somewhere in Missouri is a bunch of kids that were on school bus in '95 that saw a dumbass in a '72 Dart try to pass, slam the brakes mid-pass, and swap ends. Thanks but no thanks, 9" drums.

Only one single reason why i would switch to dot 5. It wont destroy paint. Anything else is bonus. Denatured alcohol to flush old fluid, then a flush with dot5 and fill er up.

Agreed but don't use alcohol to flush the system. It is NOT brake fluid, and absorbs moisture.

If you flush your brake fluid every couple of years, corrosion isn't an issue.

I use Castrol synthetic fluid (used to be called GTLMA) It's compatible with DOT 3 and 4, so if I have to, I can just pour in regular brake fluid.

It has a higher boiling point than DOT 4, and doesn't absorb moisture as readily. It costs a bit more than regular brake fluid, but not as much as DOT 5.

Agreed, but all brake fluids (that are DOT approved) are compatible. That's part of the DOT specification.

`
Is there a fluid that will mix w/ any type / I need to bleed my right front wheel cyl. and forgot what type I put in /about 10 yrs ago !

See above post.

OP, please don't put alcohol in your system. Either pull the components apart and flush and dry them completely if you're worried about it, or do what is designed; pour in DOT 5, pump till it bleeds purple, move on with life. It'll exist in the system fine, but they don't 'mix' together inside, so if you get a pocket of DOT 3/4 somewhere that has moisture in it, that can cause corrosion. Existing DOT 3/4 absorbs moisture, DOT 5 does not so....

If you're suspicious of your existing fluid, I'd flush with fresh DOT 3/4 first to mix n' flush with existing fluid, THEN start pouring the DOT 5.

 

[Tooljunkie]

Both statements are untrue.

First, DOT 5 does not absorb moisture, so the boiling point is consistent, and does not damage paint, as well.

Factory proportioning was very poor and somewhere in Missouri is a bunch of kids that were on school bus in '95 that saw a dumbass in a '72 Dart try to pass, slam the brakes mid-pass, and swap ends. Thanks but no thanks, 9" drums.



Agreed but don't use alcohol to flush the system. It is NOT brake fluid, and absorbs moisture.



Agreed, but all brake fluids (that are DOT approved) are compatible. That's part of the DOT specification.



See above post.

OP, please don't put alcohol in your system. Either pull the components apart and flush and dry them completely if you're worried about it, or do what is designed; pour in DOT 5, pump till it bleeds purple, move on with life. It'll exist in the system fine, but they don't 'mix' together inside, so if you get a pocket of DOT 3/4 somewhere that has moisture in it, that can cause corrosion. Existing DOT 3/4 absorbs moisture, DOT 5 does not so....

If you're suspicious of your existing fluid, I'd flush with fresh DOT 3/4 first to mix n' flush with existing fluid, THEN start pouring the DOT 5.

I will add, flushing system with denatured alcohol was a procedure used when someone filled a reservoir with something other than brake fluid,power steering fluid is a perfect example. I did use dot 3 to flush it before i replaced every part that had rubber in it. It was a mess.

 

[ir3333]

Jos51700
My post says Dot 5 synthetic won't mix with water and won't damage paint.
Watch any of Bud Lindemanns' Mopar Road Tests....I didn't see any
mopar lock it's rear brakes first
Both fluids work,I wouldn't give an advantage to either other than the boiling point. Just pick your poison

 

[flingdingo]

Agreed, but all brake fluids (that are DOT approved) are compatible. That's part of the DOT specification.

Wrong. DOT 5 is NOT compatible with the others. From Wikipedia:

DOT 5 is a silicone-based fluid and is separate from the series of DOT 2, 3, 4, 5.1. It is immiscible with water, and with other brake fluids, and must not be mixed with them. Systems can change fluid only after a complete system changeover, such as a total restoration.

DOT 5 brake fluid is not compatible with anti-lock braking systems. DOT 5 fluid can aerate when the anti-lock brake system is activated. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.[6]

 

[Mattax]

Sorry to put the second disagree mark up but this is too important.

The brake fluid compatibility standard, S5.1.10, of 49CFR571.116 exempts DOT 5 from the requirement not to stratify when mixed with others.
"(2) Fluids, except DOT 5 SBBF, shall show no stratification."

Go with Silicon based or Glycol based depending on your uses.
Bob if you put silicon based fluid in I'm sure you'ld know it. But you take some out of the MC and place it on some automotive paint. If the paint get damaged you know it was the regular stuff! And if it is - 10 years is way too long in most places - so change it anyway. Silcone based less an issue but might want to bleed it anyway just to be sure no no little bubbles of water settled in a low spot.

 

[jos51700]

Jos51700
My post says Dot 5 synthetic won't mix with water.
Watch any of Bud Lindemanns' Mopar Road Tests....I didn't see any
mopar lock it's rear brakes first
Both fluids work,I wouldn't give an advantage to either other than the boiling point. Just pick your poison

Neat-o. Mine says it won't mix with water, too.

One road test on the internet does not years of empirical observation make. They'll swap ends. Or maybe Lindemann should road test my Dart.

Wrong. DOT 5 is NOT compatible with the others. From Wikipedia:

DOT 5 is a silicone-based fluid and is separate from the series of DOT 2, 3, 4, 5.1. It is immiscible with water, and with other brake fluids, and must not be mixed with them. Systems can change fluid only after a complete system changeover, such as a total restoration.

DOT 5 brake fluid is not compatible with anti-lock braking systems. DOT 5 fluid can aerate when the anti-lock brake system is activated. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.[6]

It's all right here, in the federal standard for brake fluid:
49 CFR 571.116 - Standard No. 116; Motor vehicle brake fluids.

Specifically:
S5.1.10 Compatibility.

(a) At low temperature. When brake fluid is tested according to S6.10.3(a), the test specimen shall show no sludging, sedimentation, or crystallization. In addition, fluids, except DOT 5 SBBF, shall show no stratification.

(b) At 60 °C. (140 °F.). When brake fluid is tested according to S6.10.3(b) -

(1) Sedimentation shall not exceed 0.05 percent by volume after centrifuging; and

(2) Fluids, except DOT 5 SBBF, shall show no stratification.

They can't talk about stratification if they're not mixing them, and they specifically state that DOT 5 is exempted from non-stratification requirements. They wouldn't be talking about stratification if it wasn't mixed!

Additionally, it is stated:
S5.2.2 Certification, marking, and labeling.

S5.2.2.1 Each manufacturer of a DOT grade brake fluid shall furnish to each packager, distributor, or dealer to whom he delivers brake fluid, the following information:

(a) A serial number identifying the production lot and the date of manufacture of the brake fluid.

(b) The grade (DOT 3, DOT 4, DOT 5) of the brake fluid. If DOT 5 grade brake fluid , it shall be further distinguished as “DOT 5 SILICONE BASE” or “DOT 5.1 NON-SILICONE BASE.”

(c) The minimum wet boiling point in Fahrenheit of the brake fluid.

(d) Certification that the brake fluid conforms to § 571.116.

S5.2.2.2 Each packager of brake fluid shall furnish the information specified in paragraphs (a) through (g) of this S5.2.2.2 by clearly marking it on each brake fluid container or on a label (labels) permanently affixed to the container, in any location except a removable part such as a lid. After being subjected to the operations and conditions specified in S6.14, the information required by this section shall be legible to an observer having corrected visual acuity of 20/40 (Snellen ratio) at a distance of 305 mm, and any label affixed to the container in compliance with this section shall not be removable without its being destroyed or defaced.

(a) Certification that the brake fluid conforms to § 571.116.

(b) The name of the packager of the brake fluid, which may be in code form.

(c) The name and complete mailing address of the distributor.

(d) A serial number identifying the packaged lot and date of packaging.

(e) Designation of the contents as “DOT - MOTOR VEHICLE BRAKE FLUID” (Fill in DOT 3, DOT 4, DOT 5 SILICONE BASE, or DOT 5.1 NON-SILICONE BASE as applicable).

(f) The minimum wet boiling point in Fahrenheit of the DOT brake fluid in the container.

(g) The following safety warnings in capital and lower case letters as indicated:

(1) FOLLOW VEHICLE MANUFACTURER'S RECOMMENDATIONS WHEN ADDING BRAKE FLUID.

(2) KEEP BRAKE FLUID CLEAN AND DRY. Contamination with dirt, water, petroleum products or other materials may result in brake failure or costly repairs.

(3) STORE BRAKE FLUID ONLY IN ITS ORIGINAL CONTAINER. KEEP CONTAINER CLEAN AND TIGHTLY CLOSED TO PREVENT ABSORPTION OF MOISTURE.

(4) CAUTION: DO NOT REFILL CONTAINER, AND DO NOT USE FOR OTHER LIQUIDS. (Not required for containers with a capacity in excess of 19 L.)

Please note that nowhere is it stated that the fluids should not be mixed.

The rest of the regulation is all about testing and guaranteeing that DOT5 won't ruin your soft parts, won't clog your lines, etc.

Sorry, Wikipedia, and you, are flat-out wrong.

 

[jos51700]

Sorry to put the second disagree mark up but this is too important.

The brake fluid compatibility standard, S5.1.10, of 49CFR571.116 exempts DOT 5 from the requirement not to stratify when mixed with others.
"(2) Fluids, except DOT 5 SBBF, shall show no stratification."

Go with Silicon based or Glycol based depending on your uses.
Bob if you put silicon based fluid in I'm sure you'ld know it. But you take some out of the MC and place it on some automotive paint. If the paint get damaged you know it was the regular stuff! And if it is - 10 years is way too long in most places - so change it anyway. Silcone based less an issue but might want to bleed it anyway just to be sure no no little bubbles of water settled in a low spot.

Re-read it. It's saying, if you mix 3 or 4 or 5.1, they can't stratify. DOT 5 is exempted from this requirement.

Put another way, 5 can be in the same system, and it can 'layer out', whereas the others have to be miscible.

 

[jos51700]

And if you really want to get nuts:
When you research "When brake fluid is tested according to S6.10.3(a)When brake fluid is tested according to S6.10.3(a)"...

S6.10.3 reads:
Brake fluid is mixed with an equal volume of SAE RM-66-04 Compatibility Fluid, then tested in the same way as for water tolerance (S6.9) except that the bubble flow time is not measured. This test is an indication of the compatibility of the test fluid with other motor vehicle brake fluids at both high and low temperatures.

Compatibility Fluid?? Whassat?

SAE RM-66-04 COMPATIBILITY FLUID8
This fluid is a blend of six proprietary polyglycol brake fluids of fixed composition, in equal parts by volume. The six fluids selected comprise five factory-fill and one aftermarket fluid, as follows:

1. DOW HD50-4
2. Delco Supreme II
3. DOW BF2000
4. Wagner-Cooper H-112
5. Toyota BF2500H
6. Hoechst BF-6-M

You can read the SAE test procedures with appendices HERE:
(R) MOTOR VEHICLE BRAKE FLUID

Guys, it's all right there. Always has been. Stop being gullible and look it up for yourselves.

 

[flingdingo]

Still wrong. Oil and water stratify too. I guess that means its okay to dump some coolant into my engine if I don't have a quart of 10w-30 laying around.

 

[Mattax]

They can't talk about stratification if they're not mixing them, and they specifically state that DOT 5 is exempted from non-stratification requirements

Re-read it. It's saying, if you mix 3 or 4 or 5.1, they can't stratify. DOT 5 is exempted from this requirement.

Put another way, 5 can be in the same system, and it can 'layer out', whereas the others have to be miscible.

"Test fluids, except DOT 5 SBBF, shall be examined for stratification."

Agree. Silicone Based Brake Fluid is not tested for stratification.

 

[ir3333]

Jos51
Bud Lindemann has tested every mopar muscle car and they are all on you tube, watch a few.
You said my statements were untrue and then said the same thing?
What do you think will happen if you add Dot 5 silicone to a Dot 3 system?

 

[Mattax]

Still wrong. Oil and water stratify too. I guess that means its okay to dump some coolant into my engine if I don't have a quart of 10w-30 laying around.

Correct. They do not mix.
and you might logically conclude it's not a good idea the put them in the same system if it can be helped.
Since the characteristics of both are different - in some ways opposite - having both in the same system would generally be counterproductive.

Rick E-berg has posted that military vehicles running SBBF have a sticker like this.

Certainly a fair number of manufactures advise not to mix.
eg. https://www.penriteoil.com.au/assets/pdf/tech/Nov2015/Brake_Fluids.pdf

 

[AJ/FormS]

I sorta remember years and years ago,topping up a motorcycle reservoir with the correct fluid, according to the cap . I immediately saw I had done the wrong thing. I contacted the owner who said he had switched over to silicon. I had to remove what had become gunk.

 

[ir3333]

gunk..that would indicate some mixing unless the gunk was already in there AJ?
It seems that if they won't mix then the brakes should work fine as long as neither fluid will compress?
I don't think i'd add coolant to my engine oil but a different kind of lubricating oil or viscosity should be OK?