Synthetic brake fluid?

fishguy1123

Original poster
Member
Dec 5, 2011
310
I am planning on useing a turkey baster to drain and then replace with new fluid. Bought some prestone synthetic brake fluid (dot 3) yesterday and it dawned on me that I not all the fluid I've seen said synthetic on the lable. Is it ok to use this even if the old fluid isn't? Or are all brake fluids synthetic and they just put it on the lable to make it seem better? Thanks
 

Badbart

Member
Nov 20, 2011
633
The best way to replace the brake fluid is to bleed the brakes at all four wheels. The turkey baster will only remove what you can see in the master cylinder. You'll still have all the old fluid and trash in the lines. And, no, not all brake fluid is synthetic.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
I know the bleed is the best. Was just gonna do the res for now since I'll be do in pads and rotors in the spring and bleed then. Figured it couldn't hurt. So is it ok to mix the fluid or will it cause problems since it's not a full swap?
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
I use DOT 4 and thought we were supposed to use it and not DOT 3, but I may have imagined that.
 

Hatchet

Member
Nov 21, 2011
2,405
i have a dot 3/dot 4 synthetic in mine...

the mixing i dont know. but if ur gunna do a bleed you mite as well wait till then. why waste the good new stuff by mixing it with the old crap over winter.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
I was going to do the same thing to the ps fluid and just dicided to do the bf at the same time I guess. Mostly was gonna tinker around a lil bit and it sounded like a good idea to me.:smile:
 

Mark20

Member
Dec 6, 2011
1,630
As long as its DOT3 or DOT4 you can mix them. From what I've read DO NOT MIX DOT5 with either though.
 

RayVoy

Member
Nov 20, 2011
939
It is my understanding, that DOT 3 and 4 fluid is glycol based and will absorb water.
The only diff between them, is the boiling points.
The DOT 4 has additives to raise the boiling point; therefore, it is considered high performance.

You can mix them, but doing so will lower the boiling point of the DOT 4.

I also believe, that synthetic is considered DOT 5 and is not prone to absorb water.

I do not believe these can be mixed (but the bottle/can should tell you that).
 

Mark20

Member
Dec 6, 2011
1,630
The absorbing water part is to keep water from pooling in one spot and corroding the brake system.
 

gmcman

Member
Dec 12, 2011
4,622
DOT 5 is a silicone-based fluid, and absolutely cannot be mixed with DOT 3&4 fluid.

DOT 5 is also not compatible with ABS systems so it's not even a possibility.
 

n0kfb

Member
Dec 8, 2011
104
fishguy1123 said:
I am planning on useing a turkey baster to drain and then replace with new fluid. Bought some prestone synthetic brake fluid (dot 3) yesterday and it dawned on me that I not all the fluid I've seen said synthetic on the lable. Is it ok to use this even if the old fluid isn't? Or are all brake fluids synthetic and they just put it on the lable to make it seem better? Thanks

What's the point to only changing the fluid in the master cylinder reserviour? if you do this, do it right. Step one is to check the owners manual so you buy the correct fluid. Step two should be to review the process to bleed the brakes on your specific truck in a service manual. Step three might be to make certain your bleeder screws are loose and actually are not crudded up so bad they don't pass fluid.

If you are not careful, this could be a lot larger job than you had hoped.

-- Dan Meyer :coffee:
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
The fluid is dot 3, just happened to say synthetic on the lable. As far as the turkey baster method goes I figured it couldn't hurt even though it isn't a full swap/bleed. Not ready to do that till spring and for 7 bucks I did it. Thanks for all the replies.
 

Fire06

Member
Dec 18, 2011
7,223
If you are planning to do the brake fluid flush in the spring like you mentioned presoak the bleeder nuts a few times over the winter to help in the freeing of them in the spring. Sometimes they are a real pain in the ass to brake free usually friends and familly because they never bleed their brakes or squirt them with penitrating oil to keep them from siezing
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
Good idea, I'll do that for sure. I have had to "argue" with them on previos vehicles in the past! :hissyfit::yes:
 

Fire06

Member
Dec 18, 2011
7,223
You do realize though that doing something like that takes all the fun out of it. You never know it maybe a job that must get done on the coldest wettest day of the year.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
Fire06 said:
You do realize though that doing something like that takes all the fun out of it. You never know it maybe a job that must get done on the coldest wettest day of the year.

That when I call the GMT back up crew. :rotfl: No sense in me haveing all the fun to myself!
 

Fire06

Member
Dec 18, 2011
7,223
Sorry I think I am busy that day I think or I am busy the other day you are thinking of . Sorry I really wanted to help on that cold wet day.:rotfl::rotfl::rotfl:
 

91RS

Member
Dec 4, 2011
105
You are fine to mix the synthetic, it will not hurt anything. Also' changing the fluid in the resivor befo flushing will help with getting he fluid cleaner. If you really want it clean do that a few times in the mean time and right before you flush the system.
 

SBUBandit

Member
Dec 5, 2011
597
I got a Motive Power Bleeder for Christmas from my wife, so I plan to flush my brakes in the spring. Will most likely replace it all with Valvoline or Amsoil synthetic DOT4. Any one have a rough idea how much fluid it takes on the TB to do a full flush?
 

91RS

Member
Dec 4, 2011
105
SBUBandit said:
I got a Motive Power Bleeder for Christmas from my wife, so I plan to flush my brakes in the spring. Will most likely replace it all with Valvoline or Amsoil synthetic DOT4. Any one have a rough idea how much fluid it takes on the TB to do a full flush?

It doesn't take much to do a flush, but I usually use at least 2 of the big bottles and empty and fill the resivor first to try and get the fluid really clean. I actually ran 3 bottles through my truck.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
91RS said:
It doesn't take much to do a flush, but I usually use at least 2 of the big bottles and empty and fill the resivor first to try and get the fluid really clean. I actually ran 3 bottles through my truck.

I used about a 1/3 of a 32 oz bottle the first time when I removed it from just the res. Figure I'll do it a couple more times before spring then do a full flush.
 

MichEnvoyGuy

Member
Dec 3, 2011
519
I seem to remember there was a recommended sequence of which bleeder to open first, to flush the brake system...didnt see it posted yet. Anybody remember the sequence or have it handy to add to the thread?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
I found How to Bleed Brakes

Must brakes be bled in a specific order?

Bleeding is done one wheel at a time. The "old timers" will tell you to start with the wheel furthest from the master cylinder and work your way closer. Typically, this would mean RR, LR, RF, then LF. However, it doesn't really matter if you start with the front or rear wheels, since they are on separate circuits on modern cars with ABS and/or dynamic stability control systems.
 

MichEnvoyGuy

Member
Dec 3, 2011
519
the roadie said:
I found How to Bleed Brakes

Must brakes be bled in a specific order?

Bleeding is done one wheel at a time. The "old timers" will tell you to start with the wheel furthest from the master cylinder and work your way closer. Typically, this would mean RR, LR, RF, then LF. However, it doesn't really matter if you start with the front or rear wheels, since they are on separate circuits on modern cars with ABS and/or dynamic stability control systems.

Cool. The last time I flushed I think I used that sequence. I guess it doesnt really matter anyways though!
 

Skier

Member
Feb 8, 2012
3
Folks,

All Brake Fluid purchased now days is synthetic.

The "glycol" based starts out with Methanol and a trace of Potassium Hydroxide. Next Ethylene Oxide and Propylene Oxide are pumped in to some specific molecular weight. Then the uncapped Hydroxyl group is capped with Methyl Chloride. Called William ether synthesis. There may also be some other newer ways to cap off the Hydroyl group.

DOT 4 is vacuum stripped to a higher boiling point than DOT 3. There are probably various additives for various reasons, rust prevention, etc.

DOT 5 is either Dimethyl Silicone or Methyl Phenyl Silicone or some blend and can only be used in older non-ABS vehicles. All rubber parts also need to be replaced.

A synthesis chemist
 

rodehawg

Member
Jul 19, 2012
13
Mark20 said:
The absorbing water part is to keep water from pooling in one spot and corroding the brake system.

That doesn't sound right to me at all. Being hydroscopic, it will apsorb moisture from outside and bring it into the fluid. The more moisture in the fluid, the more chance of corrosion.
 

tblazerdude

Member
Dec 4, 2011
321
Also, a sign of water in brake fluid is a greenish tint. Example, "My brake fluid was spotless but had a green tint." This means there is too high of a moisture content, and needs to be flushed and replaced. Even if you never, ever, took your master cylinder cap off, moisture will find its way in.
 

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