4th Gen Front Brake Caliper Siezed

[RPS13]

I've looked into changing to a DOT 5 fluid, but its not advised according to Toyota and most people I talk to. The problem is that when switching to a DOT 5 you need to flush everything, run denatured alcohol through the system, and replace the "contaminated" seals; the synthetic stuff doesn't play well with the old stuff.

The other issue that comes into play is that DOT 5 is not designed for use in ABS systems as its fluid characteristics are different than DOT 3/4 (I can't remember it if was viscosity or what not.) Combined with the lack of a rebuild kit for the seals and gaskets in our ABS/VSC systems, DOT 5 is just not possible in a stock 4Runner.

I've thought about going with a DOT 5.1, which is supposed to be a non-synthetic version of DOT5 with similar boiling point and characteristics, but be safe in DOT 3/4 systems. So far I don't have enough information on DOT 5.1 to justify the cost of switching over and if that provides any benefit; I also believe 5.1 is hygroscopic as well.

http://www.toyota-4runner.org/4th-gen-t4rs/139051-dot4-vs-dot5-1-brake-fluid.html

Never use silicone DOT 5 fluid in a system not designed for it. It's actually a really old standard, and I can't think of any modern cars that use it.

DOT 5.1 is basically higher performing DOT 4. If you wanted to go to a fluid like that, some good ones are MOTUL RBF600/RBF660, Wilwood EXP600 etc. (average price is around $12-17/liter, depending on boiling point). Endless fluid is supposedly great because of its low compressibility (I've heard most Formula1 teams have switched over to it), but at the ~$80+/liter last time I checked, I don't think I'll ever experience it.

That said, it's completely unnecessary on a 4Runner. These fluids have a high boiling point, but the problem with old fluid is the water in it, and these don't prevent that.

These are more fluids that you use on a car you're taking to the racetrack and REALLY hammering on your brakes. Typical street pads (i.e. anything you'd find on a 4Runner), will give up the ghost and puke pad material all over the rotor (what people call warped rotors) well before even ho-hum DOT3 fluid starts boiling.

But I will say, never use Prestone fluid. I had to use it in a pinch and I boiled it on the 3rd lap in my 240SX. DOT4 my arse... Put in some Ate TYP200 which barely has higher rated boiling points and could do 20+ laps at a time with no issues.

 

[BlackWorksInc]

RPS13, my biggest concern isn't brake performance on-road. Rather I am worried about performance off-road, with how heavily our 4Runners depend on the braking system and ABS system during off-road situations I am concern about high fluid temperatures from constant cycling/pressurizing of the system. Granted, I doubt it'd ever get enough to boil the fluid (the solenoids would probably go before the fluid did) but its piece of mind I don't mind spending a little extra on.

 

[RPS13]

Your fluid won't get hot from the ABS pump going. In fact, it doesn't get hot from just compressing it, otherwise you'd boil fluid sitting at a traffic light with your foot on the pedal.

It takes a ton of heat coming from your pads, and that's something you won't ever see off road, or even on the street.

None of the fluids I mentioned are bad, and I've run Motul RBF600 on street cars just because I've got a stash of it for my track car. But they don't need it, and it absorbs water all the same.