OkeeGuy

ok...we made a pressure bleeder and we are going to flush out the old stuff and do the swap to synthetic...
my question is...what do i use to flush the system out?
it is already very clean as it has all been rebuilt recently...
i should have made the change then but...oh well...i didnt...
do i just buy extra synthetic and flush it out with that?
are the two compatable if any traces are left behind?

mrvette

A good friend of mine for decades now has replaced dot3-4 with dot5 fluids by just pumping it through...bleeding it out...and had over with it....

seems to be happy, haven't heard otherwise....

personally, I have allways done the switch with the first set of rusty brakes and never gone back....

GENE

70ZZ3 96LT4

You could use denatured alcohol.

Twin_Turbo

anyone here running DOT5.2? It's a kind of misleading denotation but it IS glycol based, not silcone like DOT5. Apparently it has the highest boiling point of all the fluids. I haven't come to the part where I decide on the fluid but I'm definitely not gonna run DOT5, I don't think the advantages outweight the disadvantages. I'm interested in the 5.2 but have yet to see the price tag on this stuff. It's probably liquid gold :)

OkeeGuy

ttt

theandies

I think that you need to flush the system before switching over to DOT5. Denatured alcohol would be a good choise as stated above. You want to flush the line with something that will evaporate, which in turn will remove moisture. Then you need to have a good clean dry supply of compressed air (make sure you have a drier on the compresser) to blow through the lines just to make sure you get any and all liquid out. Thats the way I would go about it. If there is a better way I am sure someone here has done it.
John

vettfixr

I've had DOT 5 in my car for probably 10 years now. I converted over when I put all new calipers and flexible lines on the car. I drained the master cylinder and then pumped DOT 5 fluid through the system until it ran clear at all the calipers. Since I was using new calipers all i had to be concerned with was flushing the fluid out of the brake lines. So far no problems but I wouldn't recommend the changeover to synthetic unless you are aware of the problems inherent in this fluid. First of all it's unbelievably hard to bleed the air out of the system. It probably took me 2 months to bleed the system to my satisfaction. It also gives a somewhat softer pedal feel and I believe the conversion back to regular brake fluid would be harder since the silicone is thicker and would probably be more difficult to clear out of the system. On the plus side you will get much less rust in the system since the silicone fluid doesn't attract water like regular brake fluid does and you won't have to worry about damaging your paint if you spill it. If you're looking at using your car for high performance driving I would suggest going with a high performance regular brake fluid and flushing it at regular intervals to keep the water in the system to a minimum. I understand Ford's fluid is one of the best. If you are going to use your car for a boulevard cruiser that spends a lot of time in the garage (like mine...less than 2K miles a year) then I would suggest going with the synthetic.

gliot1

I used the Valvoline DOT 5, and it notes right on the bottle that it can be mixed with orignal DOT 3-4. I cleaned out as much fluid as I could then used the Valvoline, and bled the system 4-5 times. At this point I believe I've totally cleared the system of the old stuff anyway. :smash: :smash:

theandies

Good info.......Thanks
john

OkeeGuy

i am very hesitant at putting any solvents in the system as it could harm rubber seals etc...
i like the idea of draining well then flushing the silicone stuff thru and bleeding...
i have never heard that it is harder to bleed a system when using it...
hhhmmm???
has anybody else experienced this?

Twin_Turbo

harder to bleed DOT5? Yes, it's not hygroscopic so instead of being absorbed moisturesinks to the lowest point.

70ZZ3 96LT4

I have been using silicone in my 68 and 70 for 14-16 years. The 68 is manual brakes and the 70 has power bfakes. Did not have any trouble bleeding the calipers and getting good pedal. My 70 has such a full brake pedal and stops so well. With its four four pistons per caliper it seems to have better braking than my 96 LT4.

Touringpro

Just out of curiousity, why are you thinking of changing over to silicone? Unless one has a detailed engine bay and is concerned with paint damage, I don't see much advantage to it.

BTW, all brake fluid is "synthetic". As I'm sure you know DOT 3, 4, and 5.1 are standard glycol ether, whereas DOT 5 is silicone based.

MYPET70

You probably won't like this answer...but my opinion is that you should stick with good ole (and fresh) DOT 3 until you're ready to overall your whole system. At that point you can run alcohol thru the lines to clean and dry them out and your calipers and master cylinder will be completely fresh for the new silicon fluid. If you've ever taken a caliper apart you'll see there's just no way to flush it thoroughly while it's on the car...the water (and most contaminated fluid) stays on the bottom and the bleeders are at the top (as they should be of course for bleeding...). Nice fresh DOT 3 will help though because it'll mix best with what you won't be able to flush out. I changed mine out completely and have been using the purple stuff for 22 years. Good luck! :steering:

OkeeGuy

higher boiling point...for one...
and...yes...i AM concerned about my engine bay...

cardo0

I had wanted to run the silicone in my brake system at rebuild time but a corvette restoration book talked me out of it - sorry but I can't remember the title. The books author had done the research and convinced me fresh Ford brake fluid products are the best. Still expensive stuff. Most NASCAR pit crew tape over cans to hide the Ford label used on thier non-Ford car. Aparently silicone gets spongy when heated. Recommend use fresh cans only and change/power flush every 2-3 years.

427V8

Silicone foames when you pound the brakes, like in racing environments, thats why racers don't like it.

For show cars it's great