Paul22RE

I am thinking of switching to the silicone-base DOT-5, as it is the least prone to water absorption from what I read. What are the disadvantages of DOT-5 in a non-ABS brake system? I care more about longevity over the boiling-point rating since I am never hard on the brakes and our trucks are not racers!

As far as glycol-based DOT 3,4 or 5.1, which one is best for the least amount of water absorption? I read all different theories on what is best for longevity.

What are you guys using and why? Thanks

old87yota

I just use DOT 3 because that is what Toyota specified for these trucks.

I really haven't thought about switching to anything other than DOT 3, so I don't know what would be best.

I did recently buy a DOT 3 specific water content meter, but I haven't tried it out yet: https://www.otctools.com/products/br...d-tester-dot-3

I am sure I am overdue to replace the fluid.

2ToyGuy

I use the dot3 for the same reason. It's what Toyota specs.
Having said that, the DOT5 silicone wasn't available thn. It's entirely possible it's a better choice. I can't say. Sounds to me like it might be, though.

Pat☺

millball

Silicone based brake fluids should NEVER be used in ANY engine vacuum operated power brake system.

Most systems that call for silicone are electric, or engine driven hydraulic assist/

If the silicone fluid is aspirated into the engine, as in master cylinder cup failure; it combusts into super abrasive silicas. This equals ENGINE DEATH.

Use regular DOT 3 or DOT 4 glycol based fluids and change it out when it gets dark.

Silicone can be a good upgrade in antique and classic cars that do not have vacuum boost.

Paul22RE

Wow, good info! Never knew that.

millball

Either DOT 3 or DOT 4 is fine. Longevity is decent with either , so long as the system itself is clean and uncorroded. Change it out when it gets dark.

A brake system with no air in it should self bleed, just by opening a bleeder. I start by syphoning the master cylinder reservoir and mopping it clean with a lint-free cotton rag,
then fill with clean fluid and bleed every wheel 'til the fluid runs clean. Longest line to shortest. Only ONE bleeder open at a time.

Paul22RE

I use this to bleed, works great: https://capritools.com/shop/vacuum-brake-bleeder/

Blueman

I use this one, and have been quite happy with it:
Motive Products - 0101 Round Universal Brake System Power Bleeder

snippits

Pneumatic type from Harbor Freight has never let me down. Made in Taiwan, and it's good quality. Reasonable price especially with coupon discounts.


https://www.harborfreight.com/brake-...=brake+bleeder

2ToyGuy

I may sound like a broken record, but don't forget thee LPSV when you bleed the system for any reason. A lot of folks forget it, and don't bleed it when they do the brakes.

Just a thought.
Pat☺

Jimkola

I recently took my LSPV out and diassembled. It was a gunky mess. Cleaned up pretty easily though, there's not much to it once you get it apart.
I just got a compressed air bleeder. Works great, but I needed to put some grease around the bleeder threads to keep it from sucking air

wallytoo

iTrader: (1)

the entire brake system from the master back can be gravity-bled, without anything other than the correct size bleeder wrench/socket. no pumping the pedal, no helper needed, just patience and fresh brake fluid.

RAD4Runner

Theories are fine but I trust the kind that lasted 30+ years in real-life better

wallytoo

iTrader: (1)

i can attest to this. when i bought 4runner number 2, the rear brakes didn’t work, although the parking brake did work. thus, at least the mechanical parts of the system were operable.

no fluid at either of the rear wheel cylinders with the bleeders open. when i removed the LSPV bleeder, a little bit of fluid dribbled out. i used stripped solid wire to poke into the LSPV bleeder opening, and eventually fluid began to flow out a bit more readily. let it flow until clear, then put the bleeder back in and closed it. at this point, refilled the master, then checked at the rear cylinders; success, fluid now there.

bled the entire system, and have had working brakes ever since. entirely via gravity bleeding.

2ToyGuy

Ya know, I had to quit medical school. I had no <ahem>patience<ahem>.
Ba-dum bum BUMP! (rim-shot, I guess)

I know, stupid joke. Sorry about that.
Carry on, all!
Pat☺