In memory of that recent pesky pink poster’s post !

Asking fur a friend ! .... and me - on the entire new BREAK system on the Carrotvan

I was told by the place that I use to rebuild master cylinders and boosters that mixing DOT 5 with regular brake fluid will cause the fluid to gel. They said that you must remove all traces of the standard fluid to keep this from happening.

I have used nothing but the silicone fluid in my muscle cars for 20 years or more. Mostly so I didn't damage the paint anywhere. But I don't use it in any of my driver vehicles. No advantage there for me.

If you do convert, be sure to flush the entire system with alcohol and them blow the system dry with air. As mentioned, don't mix the different kinds.

Agree, I converted when restoring my car, every component had not been used and clean.

Same here.

But ONLY when everything is brand new

when i converted from dot 3 to dot 5 on one of my cars i disassembled the master cylinder and wheel cylinders for a thorough cleaning and flushed all the lines. the two fluids aren't compatible. they won't gel but they won't mix either.

Converted a long time ago to silicone BREAK (?) fluid. First time I was flushing brakes completely. In fact aren't the shelves in stores almost solely silicone fluid now? I use DOT 3 (whole new can of worms)

use it in all my cars.. works great so far... been using it since the 80's iirc..no paint issues or braking issues

I used it buy everything was new.
If I did a conversion and switched would drain best I could and mighty vac till I had all clean DOT 5

No, its synthetic now.

"some" ABS systems say to NOT use dot 5 fluid because it does something to the accumulator in those systems.
at least up until the 2002 MY, dot 3 was the only fluid to use in minivan ABS systems according to the FSM.

besides, DoT 5 is tOo ExPeNsIvE for the ol' DoC.......................
TiTeWaD that he is............

mopX...truth be told HERE ... and yOu said it elsewhere!

Youz beez the tightest tItEwAd anywhere !

DoC iF YoU hAnG oUT At SoMe SHoPs MaYbE tHeY wIlL gIvE yOu sOmE uSeD DoT3

LarryLOVEit... you must have been VERY TIRED typing that ALL OUT !

The humidity in Florida is a DOT3 fluid killer ... and THAT is a phenolic piston SWELLER

E-booger says:

Tech Question
Gary Boak, Chilliwack, BC, Canada, 1969 Dart Swinger 340

I notice in the April 04 issue you say that DOT 5 brake fluid can be used without flushing the system. Everything I have heard and read states that Dot 5 does not mix with anything except DOT 5. When switching to DOT 5 are you not supposed to use new rubber?

Gary-

Another old wive's (or Mopar Muscle) tale. First, realize that DOT specs don't specify the composition of the fluid, the rating relates only to the boiling point. So, therefore, it would be possible to have DOT 3 fluid that's silicone, and DOT 5 that's not (and this latter combination does exist.) These specs are covered in detail in Federal Motor Vehicle Safety Standard section number 571.116, which is part of the Code of Federal Regulations, #49, Chapter V Subchapter S6.5.4 addresses miscibilty, specifying that the fluid being tested must mix with a standard type fluid, and this miscibilty test DOES apply to DOT 5 fluids, and can't gel, swell cups, etc. when mixed. So there!"

From what I understand DOT5 will foam and when the ABS pump runs, it will foam up and fail as if there was air in the system.

JK you are CORRECT.
the 2 different fluids won't cause each other to gel.
the 2 different fluids won't mix with each other also.
they also have a slightly different compression rate so mixing A LOT of the 2 fluids together can give you troubles.

i have replaced regular brake fluid with silicone on a LOT of old vintage cars without flushing anything. i just remove as much fluid from the master as i can. them pour the DOT 5 in. now bleed the brakes until you see the DOT 5 come out of the bleeders.the DOT 5 will push most of the old fluid out of the system without giving you any troubles. after doing this to all 4 wheels i start over and bleed another cup or more of fluid from each wheel just to make sure the old stuff is out. i also like to tap on the brake lines to get any small air bubbles out that like to hide in sharp bends of the brake lines.

keep in mind DOT 5 brake fluid RETAINS AIR just like the old fluid does water. this is why you can't use it on ABS cars.
i also like to heat up the new DOT 5 in a pan of hot water to force any air mixed into the fluid when it sits on the shelf or shaken up during shipping.some installers don't do this and can never gets the brakes bled properly. this is why DOT 5 brake fluid gets such a bad rap.


DO A SEARCH on DOT 5 brake fluid. this subject popped up a lot in the past so there are multiple threads with the exact same info already here.

I wouldn't use it unless it was specified - some motorcycles, etc. - or the system was all new and/or rebuilt.

No advantages and a number of disadvantages for me. DOT 4 or 5.1 if you need the higher boiling point.

Your requirements may differ.


Doc gonna do some breakdancing?

No PhEnOlIc PiStOnS FoR Me. SteEl.

I converted my Barracuda about 30 years ago when I put all new components . I have converted several other Mopars through the years , some with all new parts , and others by flushing fluid through , with great results both ways !