Is brake fluid still good or not?

LouisTB

Original poster
Member
Apr 12, 2016
120
Tampa, FL
So weather permitting, I plan on doing a full brake job (Pads, rotors, and brake fluid flush). Question is I bought a gallon of brake fluid when I first got the car because the brake fluid was disgusting. So the first thing I did was flush the brake fluid and put new fluid in. Now I'm not exactly sure how long ago that was but it was easily at least a year if not very close. I know that brake fluid hates moisture and has a shelf date after opening, but would it still be good if I've kept it in my room this whole time? I recently tested it with one of those test strips to test the copper parts per million and it showed zero. I'd hate to waste it since there's a good amount left but I definitely don't want to risk putting contaminated fluid in my TB. So I was wondering what you guys thought?
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Not sure about copper but it's moisture that kills brake fluid. I have an electronic one that checks the moisture content and says when it should be changed. Do those strips also give moisture? Since brake fluid is hygroscopic, that's what you would worry about.

Either way, I think as long as the container was kept closed, it should be good.
 

LouisTB

Original poster
Member
Apr 12, 2016
120
Tampa, FL
Not sure about copper but it's moisture that kills brake fluid. I have an electronic one that checks the moisture content and says when it should be changed. Do those strips also give moisture? Since brake fluid is hygroscopic, that's what you would worry about.

Either way, I think as long as the container was kept closed, it should be good.
I'm not quite sure ill grab another test strip from work tomorrow and test it again, ill make sure to see if it says anything about moisture.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
I had a previously opened bottle that sat for so long that the manufacturer changed their logo before I used it again. I did an emergency repair one sunday night and that was the only fluid available and in it went. No issues whatsoever.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Or usually a foam disc in the cap.
 

hockeyman

Member
Aug 26, 2012
726
Isn't the condensation (that it absorbs) supposed to cause rust within the brake lines, rather than have any effect of how the fluid performs?
 

Sparky

Member
Dec 4, 2011
12,927
Compress? Liquids don't compress :confused:
 

Harpo

Member
Dec 4, 2011
411
Sweden
The water content can become steam when it gets hot and cause very unpleasant surprise, and steam gets compressed and you end up with the brakepedal on the floor.
Been there done that,barley got it stopped with 50cm marginal.:yikes::wowfaint:
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
That's right. The water lowers the boiling point of the fluid.
 

paul2005tb

Member
Nov 26, 2014
299
Massachusetts
I did a complete brake flush, replace pads and the brake performance greatly improved... BUT, it is not as good as new. My brakes still require significant pedal compression. I have no signs of brake line failure.

My only guess is that my master cylinder is just getting old .
 

hockeyman

Member
Aug 26, 2012
726
I did a complete brake flush, replace pads and the brake performance greatly improved... BUT, it is not as good as new. My brakes still require significant pedal compression. I have no signs of brake line failure.

My only guess is that my master cylinder is just getting old .

Your master cylinder can actually have an internal seal failure, leading to pedal loss with no signs of an exterior leak. No amount of bleeding or new fluid will help. I'm not saying it's definitely your problem, but I would keep that in mind. Old rubber lines (going to your calipers) can begin to over-expand too. You can also have a faulty piston (or pistons) within the calipers that aren't working properly due to rust, inner seal failure, etc.

All I'm saying is that there are many things that can cause your pedal to lose compression. It's a good time to do some inspecting when installing new pads and/or rotors.
 

paul2005tb

Member
Nov 26, 2014
299
Massachusetts
Your master cylinder can actually have an internal seal failure, leading to pedal loss with no signs of an exterior leak. No amount of bleeding or new fluid will help. I'm not saying it's definitely your problem, but I would keep that in mind. Old rubber lines (going to your calipers) can begin to over-expand too. You can also have a faulty piston (or pistons) within the calipers that aren't working properly due to rust, inner seal failure, etc.

All I'm saying is that there are many things that can cause your pedal to lose compression. It's a good time to do some inspecting when installing new pads and/or rotors.

When I replaced my pads I noticed serious corrosion on the calipers and this corrosion extended behind the piston boot. Is my problem the calipers or the master cylinder, it may be time to replace all of them, I have 11 years and 120k on this vehicle.
 
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hockeyman

Member
Aug 26, 2012
726
When I replaced my pads I noticed serious corrosion on the calipers and this corrosion extended behind the piston boot. Is my problem the calipers or the master cylinder, it may be time to replace all of them, I have 11 years and 120k on this vehicle.

Corrosion and rust happen to almost all daily driven calipers. Depending on the severity & movement of the pistons, along with the condition of the seals, you just have to find out if it actually needs a rebuild or not. Me?...I'd just go ahead and replace all of them. But that's just my opinion. Others may have a different outlook on it.

You can remove each caliper and rebuild it, but I know that each caliper for my wife's vehicle were $60 for each front and $72 for each rear at autozone. There was a $45 core charge, so I just removed and walked in with the old ones so I didn't get charged for the core(s). That option was a much better choice for me since I knew I was getting a rebuilt caliper with all new seals already installed.

I don't like to take any chances when it comes to brakes, suspension and tires. I try to buy decent (or better) products to give me peace of mind. Anything in question, gets replaced. Then again, I make $100 million a year... (yeah, I'm full of *#%!)
 
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mrrsm

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Oct 22, 2015
7,642
Tampa Bay Area
OP ...You don't mention whether or not you kept the Brake Fluid Reservoir Readily Filled as you Bled the Brakes... but if you allowed the Brake Fluid Level to drop to the point where Air could be ingested back through the Master Cylinder Body and down inside... then the Air remains and will become trapped inside in an Endless Cycle of Spongy Compression. So the only way to properly Bleed the MC... is by first completely removing it off of the vehicle and performing what is called "The Bench Bleed Procedure" which literally means... "On The Bench".

If you are lucky, and this problem did not occur... then you will need to obtain a New Quart of DOT 3 Brake Fluid and after topping off the Master Cylinder Reservoir ...you must work your way...systematically...from the FARTHEST to the NEAREST Wheel...and instead of using a simple Bleeder Wrench, Nipple Hose and Collection Bottle... Obtain a MITAC Vacuum Pump Pressure Brake Bleeder ...or one similar to it from HF. After filling a Plastic Mason jar with some Fresh Brake Fluid... feed your Bleeder Hose into the very bottom of the Mason jar... and as you Bleed each wheel... NO AIR CAN BACK UP INSIDE OF THE LINE before you have the chance to lightly snug up each Bleeder Fitting. You must remember to RE-FILL THE BRAKE RESERVOIR QUITE OFTEN... Here are some videos for additional visual guidance:


..and to perform a Basic Bench Bleed of the Master Cylinder:

 
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