DOT 5 brake fluid

Not to hijack but I am redoing the braking system on a 72 RR...Power Disc/Drum. I am replacing the brake lines front to rear. Going to rebuild the calipers and the wheel cylinders. The car is currently DOT3. Would you say to go to DOT4 or DOT5? What do I have to do to the Master besides Bench bleeding it? Do I need to clean it out with something?>

I used it in this car. I won't burn your paint off if you have a leak or bad cap. That said you have to empty the entire system, clean it and then you can add it. You can't mix the 2 as far as I know.

what kunkel said is correct.
federal LAW says DOT 5 brake fluid MUST be to coexist with other brake fluids without causing harm. if it wasn't it wouldn't be able to be sold in the US.

i don't have time to look this up and post it. it has been posted several times in the past.
do a goggle search on moparts to find lots of info on this subject.

The link above is to a personel anecdote, has nothing to back it up. I wish it'd go away. Oh that's right, it's the Internet so it must be right. And, Wikipedia is full of errors. It ain't the Encyclopedia Britannica.

R.

Yep, while it makes sense to drain and flush your system when going from glycol based fluid to silicon based fluid, having both will not cause catastrophic failure.

I use Dot 5 on my restored 'Bee because I don't want paint damage. On all my other vehicles and motorcycles, I use Dot 4.


Dave

it isn't that it won't function if you mix the two.
it is you won't get the benefit of full silicone if you mix.
in other words some of the left over dot 4 could still melt your paint.

We've done over 100 cars with dot5 and have not experienced any noticeable difference. I will clarify that these are street driven cars not on the track.

as i understand it, and i may be wrong (again) dot 3 brake fluid is hydroscopic and can/does absorb H2o effectively diluting it throughout the entire brake hydraulic system. If H2o finds its way in (and it will) dot 3 can handle a considerable amount of moisture (relatively speaking) without it severely affecting its performance, and by diluting it, the corrosiveness is greatly reduced. Dot 5 on the other hand, isn't as friendly to H2o. Water can and does find its way in and accumulates in condensed ratios causing very focused corrosion of the brake system components.

I know I've been bumped on the head many times and may be way off so check for yourselves, as for me, I will be using Dot 5 in my classics when possible, just don't rely on it lasting forever on cars that don't see much drive time regularly.
"You get what you pay for"

Sorry if O/T, but can it be used for hydraulic clutch TO bearings?

Every aftermarket hydraulic TO bearing that I've researched says no DOT 5 fluid. Dunno why.

Probably difficulty in bleeding the air out of the clutch system. Many of them are hard enough to bleed with DOT3.

If the silicone brake fluid has a problem it is with air entrainment. That is well-known, it'd probably respond to backwards pressure filling from the bottom of a can. Air gets entrained from shaking or from a free jet entering the liquid's surface in a container.

Now on the DOT3...if you think that DOT3 is better because it absorbs water, you haven't ever had your brakes vaporlock. I have. It's not a happy feeling to be facing a seven mile 8% grade and have the brake pedal go to the floor.
The brake fluid maximum boiling temperature is with the fluid being completely dry. As the hyGroscopic brake fluid picks up water, the boiling point decreases. That's one reason to change your brake fluid every couple of years.

So take your pick, use what you like, but don't think that just because the brake fluid absorbs the water that it's better!

Oh, one more thing...the DOT3 will hold different amounts of water depending on the temperature. So if the brake fluid is saturated with water and the temperature drops, what happens to the water? It comes out of solution and forms water pockets in the low spots. That's why brake cylinders have rust pits in the bottom of the bore.

R.

VaporLocked Brakes? Never heard of that before.
Ill consider it another lesson on how little i know.