DOT 3 Brake Fluid

[goatfarmer]

1990 T4r 4X4: The master cylinder cap recommends using DOT 3 fluid, intend flushing system as much as possible using the 'mini-vac' system. I am not sure what type of fluid is currently in system, I have a container of both; if unknown whether it best to go with non??

Suggestions appreciated!

 

[shahsmerdis]

what it says on the cap.

if its been since 1990 since you have done a breakflush then you will in for a surprise. get every bit of that crap out of there.

 

[goatfarmer]

what it says on the cap.

if its been since 1990 since you have done a breakflush then you will in for a surprise. get every bit of that crap out of there.

Cap recommends DOT 3. Replaced the rear brake cylinders, the fronts not. Intend flushing as much of the old fluid as possible; since I do not know whether synthetic fluid was used in the past whether switching to synthetic from NON synthetic fluid would be an issue??

 

[goatfarmer]

Cap recommends DOT 3. Replaced the rear brake cylinders, the fronts not. Intend flushing as much of the old fluid as possible; since I do not know whether synthetic fluid was used in the past whether switching to synthetic from NON synthetic fluid would be an issue??

The old brake fluid was some nasty looking stuff. Went with the non synthetic. Flushed 1 1/2 small container's thru the system until the 4 brake cylinder's appeared clear. First timer using the vac. system, worked like a champ, can see a 'do it myselfer' every year or 2?

 

[Skuzz_84]

I'm pretty sure you can use DOT4 where DOT3 is recommended, but not the other way around

Sent from my SM-N915G using Tapatalk

 

[goatfarmer]

I'm pretty sure you can use DOT4 where DOT3 is recommended, but not the other way around

Sent from my SM-N915G using Tapatalk

Purchased the fluid couple days ago, next to it were containers of DOT 3-4? With new wheel bearings and fresh fluid, intend taking for a test drive this a.m.; hopefully all's well so I can move on to the next 4runner project?

Appreciate input!!

 

[yoshoto]

Yes you can use Dot 4 instead of Dot 3 but not the reverse. That is why some manufacturers will sell Dot 3 & 4 fluid because it is actually dot 4 but can be used in dot 3. The only one you need to stay away from is Dot 5, this is a totally different chemistry(silicone based) and so cannot be mixed. All the others Dot 3,4 & 5.1 are Glycol based.

The dot rating is a measure of the dry and wet boiling points of the fluid, "wet" being when the fluid has absorbed all the moisture it can from the air. "Dry" of course is the new clean fluid with no moisture. Dot 4 is higher rated.

Just like synthetic engine/ATF/Refridgeration oil, synthetic brake fluid is better.

I like the Valvoline Dot 3&4 synthetic, for around $8 its good value for money.

You can test the brake fluid with a test strip that indicates the moisture content, or just change it every 2 years or so, this is regardless of the mileage accrued in that time. For $8 every couple years the money saved in corroded and failed brake parts and rubbers is well worth it.

 

[goatfarmer]

Yes you can use Dot 4 instead of Dot 3 but not the reverse. That is why some manufacturers will sell Dot 3 & 4 fluid because it is actually dot 4 but can be used in dot 3. The only one you need to stay away from is Dot 5, this is a totally different chemistry(silicone based) and so cannot be mixed. All the others Dot 3,4 & 5.1 are Glycol based.

The dot rating is a measure of the dry and wet boiling points of the fluid, "wet" being when the fluid has absorbed all the moisture it can from the air. "Dry" of course is the new clean fluid with no moisture. Dot 4 is higher rated.

Just like synthetic engine/ATF/Refridgeration oil, synthetic brake fluid is better.

I like the Valvoline Dot 3&4 synthetic, for around $8 its good value for money.

You can test the brake fluid with a test strip that indicates the moisture content, or just change it every 2 years or so, this is regardless of the mileage accrued in that time. For $8 every couple years the money saved in corroded and failed brake parts and rubbers is well worth it.

Thank you for the valuable info!!

I was not clear whether I could use 'synthetic' fluid if the current fluid is 'non-synthetic'? Rather than going with the Dot 3 synthetic ended up using, what I believe is 'non' since there was nothing on the can description that indicated otherwise. Within the next few day intend replacing the front disc. pads and possibly switch to the Dot 3-4, or if understand correctly, the better option would be switch to Dot 4, and assume I should stay with the non synthetic?

I thank you!

 

[Chuckles89]

I have my brake system so clean that whenever I have to bleed my brakes, clear fluid comes out right away

Just do a complete flush several times and your brakes will be happy.

 

[goatfarmer]

I have my brake system so clean that whenever I have to bleed my brakes, clear fluid comes out right away

Just do a complete flush several times and your brakes will be happy.

Regret I did not take pic's of the nasty mud colored fluid. Decided to flush again, just returned from auto parts after purchasing non-synthetic Dot 4. probly hold off until I have installed the front pads. May resort to the ole school method of bleeding, peddle a bit spongy after using the vac method?

Thank you for the input!

 

[yoshoto]

Dot 3&4 is actually Dot 4. it is marketed as Dot 3&4 to avoid the confusion for ppl such as yourself that may not know or understand.

its quite alright to mix 3 with 4(for a Dot 3 application) or synthetic with non synthetic.

If the pedal is spongy, there may be air in the system or master cylinder. Did you ever let the master go dry when vacuuming?

To bleed(air) at each wheel it is not necessary to get someone to pump the pedal, just start at the furthest wheel from the master cylinder with the vehicle on a level surface, pop off the rubber caps, loosen the bleed screw and let the fluid drip out a bit on its own, re tighten the bleed screw (very little torque is required). Do this at each wheel moving closer to the master cylinder. Afterwards wash off any fluid from inside/behind the wheel area with water and after everything is dry replace the rubber caps on the bleed screws.

If it still fells spongy after that then most likely the master cylinder needs to be bled.

 

[goatfarmer]

Dot 3&4 is actually Dot 4. it is marketed as Dot 3&4 to avoid the confusion for ppl such as yourself that may not know or understand.

its quite alright to mix 3 with 4(for a Dot 3 application) or synthetic with non synthetic.

If the pedal is spongy, there may be air in the system or master cylinder. Did you ever let the master go dry when vacuuming?

To bleed(air) at each wheel it is not necessary to get someone to pump the pedal, just start at the furthest wheel from the master cylinder with the vehicle on a level surface, pop off the rubber caps, loosen the bleed screw and let the fluid drip out a bit on its own, re tighten the bleed screw (very little torque is required). Do this at each wheel moving closer to the master cylinder. Afterwards wash off any fluid from inside/behind the wheel area with water and after everything is dry replace the rubber caps on the bleed screws.

If it still fells spongy after that then most likely the master cylinder needs to be bled.

Although I paid particular attn to ensure the M/S did not go dry while bleeding the system I did use the vac pump to remove as much mud fluid from M/S as possible, as a result, probly need to bleed it.

Front pads should arrive by Wednesday, once installed will bleed the system starting with the M/S.

An ole dog can learn new stuff; over these many years I was not sure whether or not one can mix non with synthetic, I now know I can use Dot 3 synthetic for future use.

Thank you for the info!

 

[Chuckles89]

Regret I did not take pic's of the nasty mud colored fluid. Decided to flush again, just returned from auto parts after purchasing non-synthetic Dot 4. probly hold off until I have installed the front pads. May resort to the ole school method of bleeding, peddle a bit spongy after using the vac method?

Thank you for the input!

I have found that the old school way of having someone pump the pedal makes a less spongy pedal feel. I was amazed the first time I bled them that way.

 

[nevada]

as was said, synthetic, or not doesn't matter. they can be mixed together without issue.

also, all brake fluid is not equal, even if they are the same DOT number.

the boiling temperature should be listed on the bottle somewhere, go for the highest number.
I have seen DOT3 with a higher boiling point than some DOT4. just depends on who is making, and rating it.


also, to add a bit more confusion to this, DOT 5.1 can also be used where DOT 3 and 4 are called for.

DOT 5 is an animal all its own.

 

[goatfarmer]

Greatly appreciate the feedback. Found still a slight color to the fluid, went with the min-vac system this a.m. in attempt to purge the lines. The pedal is still a bit spongy but not going to get overly concerned until the front pads have been installed. Since the fluid is slightly discolored, intend using vac sys. to try and evacuate as much of the old fluid then go with the old school bleeding method to finish.

Again, thanks to all!!

 

[Kean]

....probably more than you want to know about brake fluid but it s a very good read nevertheless IMO:

Brake Fluid

There is an interesting note at the end of this article which I have heard from other sources before. I don't have a dog in this fight so take their advice as you like. If anything, you may think of it more as a disclaimer:

One last note on the DOT ratings: Systems designed for a particular type of fluid (especially prior to the wide distribution and use of DOT 4 fluids) should continue to be filled with that fluid. For example, in a car that was delivered with DOT 3 fluid, the internal components of the system (seals, brake hoses, and fittings for example) were specifically designed and tested for compatibility with the chemical composition of DOT 3 fluid. Because the DOT 4 grade fluid typically contains a different chemical composition, compatibility of system components may be an issue.

 

[goatfarmer]

....probably more than you want to know about brake fluid but it s a very good read nevertheless IMO:

Brake Fluid

There is an interesting note at the end of this article which I have heard from other sources before. I don't have a dog in this fight so take their advice as you like. If anything, you may think of it more as a disclaimer:

Greatly appreciate the information. Just completed the brake system on the 4 runner; or at least at this time as much as need be? The issue with the brakes came about due to leaking axle bearing seal resulting in oil soaked passenger side brake assembly. Front pads arrived today, after closer inspection decided to hold off since current pads appears to have some mileage left on them.

Used the mini vac to purge as much of the old fluid as possible, in bleeding the system there still appears to be some residual old fluid but much cleaner and now there's a solid pedal.

I did go from Dot 3 to Dot 4 in my final purge but stayed with the non synthetic? Overall very please with the results.

Again I thank you!!

 

[ntsqd]

Once it became commonly available I've bought DOT 4 for everything. i only buy 3 in emergencies.

Always, always, always start with an un-opened bottle of brake fluid. As soon as you break the seal the fluid starts gathering moisture out of the air. An opened, partly used bottle that has been sitting on the shelf for 6 months is seriously compromised and you're fooling yourself if you think that the cap actually sealed it. I buy multiple small bottles unless starting with a dry system and I throw away partly used bottles once the project is done.

"DOT 5.1" was a dumb idea, it should have been called "DOT 6" to avoid confusion.

When you get tired of hand pumping that mighty-vac buy a long piece of vacuum hose to connect the reservoir to the intake of an idling engine.

When you get tired of the tiny capacity of the mighty-vac reservoir save your next empty peanut-butter jar and buy some J-B Weld putty and some 1/8" copper tube.

Brake systems should be flushed bi-annually in dry climates and more frequently in moist climates. Brake fluid is hydroscopic so that it acts a bit like a "filter", but a critical part of that process is that the moisture saturated brake fluid needs to be removed before the moisture can start to do damage. Were it that I could remember to flush these systems often enough..... :frusty:

Don't forget the bleeder in the front brake system on the LSPV of trucks so equipped.

 

[goatfarmer]

Great idea, would never have thought of using engine vacuum to bleed the brake system!

While brain storming with very little to work, had my last attempt at using the mini vac not been successful, came across my air gun that has a vacuum nipple; connect it to my compressor, connect one end of a clear hose to the vacuum nipple and the other end to the bleeder then direct the fluid into a container, if not careful imagine I could evacuate the entire system with 1 blast? O'Yea

 

[ntsqd]

Just might happen.

If you do use the engine you should probably also first remove the bleed nipples and coat *just* the threads with silicone dielectric grease. It absolutely can not be a petroleum based grease (the rubber in the brake system will NOT like any petroleum products!) and dielectric grease is the easiest that I know of. This will keep air from coming up past the bleeder's threads and looking like there is still air in the system.