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Sure the bleed is better, but is it that much better?
Kind of a hassle to get to a shop w/my wife's car (long hours, when she's home we are apt to have family time), so I'm thinking of just sucking out the PSF and BF and replacing them, but don't really want to take the tires off if that's overkill.
Most of the fluid is in the reservoir, so if you use a syphon to suck that fluid out and then refill with fresh fluid, that will replace a majority but not all of the fluid, and the new and old will quickly mix, leaving you with a better overall condition to the fluid. Fluid in the lines will naturally cycle back up to the reservoir with use, so the new fluid will spread out.
It is not a full flush down the line, but it is easier and better than nothing. If you try this, I'd recommend you do this a few weekends in a row to really get most of the fluid refreshed.
I have never replaced the brake or PS fluid in any of my cars been driving since I was 15 now I'm 60 and have had over 40 or so cars and trucks in my life never a problem with brakes or PS.
Well congrats at winning the automotive neglect trophy
Changed the fluid on a 2000 audi that has never been changed. We immediately noticed a firmer brake pedal.
I shudder to think what the boiling point of your brake fluid has been reduced to due to your neglect.
If you want to PROPERLY maintain your car, you will change all the fluid every two years. Dot 3 and 4 sucks up moisture like a sponge and that water is hard on the brake components. You will extend the life of very expensive brake parts by replacing all the inexpensive brake fluid at that interval.
Do most people do that ? No, but that is why shops do so many brake repair jobs.
I have never replaced the brake or PS fluid in any of my cars been driving since I was 15 now I'm 60 and have had over 40 or so cars and trucks in my life never a problem with brakes or PS.
I'm with you. I have made a living working on cars since I was 12, I'm 70 now. I have owned cars since I was 17. I not only have never changed my break fluid but I have never changed it for anyone else. It is my opinion that any moisture in the fluid is evaporated by the temp of brake hardware
I'm with you. I have made a living working on cars since I was 12, I'm 70 now. I have owned cars since I was 17. I not only have never changed my break fluid but I have never changed it for anyone else. It is my opinion that any moisture in the fluid is evaporated by the temp of brake hardware
And that is why there are good mechanics and hacks ! Just because someone owns some tools and claims to be a mechanic, that does not make them a GOOD mechanic.
You could not be more wrong. Fluid does not burn off moisture, it continues to absorb it. Even an opened bottle of fluid should be discarded after a while because it has absorbed moisture.
You did not do your customers any favors with your lack of maintenance.
I don't see how replacing the fluid ONLY in the MC does anything. That fluid does not actively flow through the system, so any moisture and contamination occuring in the calipers will not be replaced. And if oyu do have moisture in the calipers, and stop hard and boil it over to air, bleeding the fluid in the MC only won't help expel this.
Basically, do a full bleed every 1-2 years and anything else is a waste of time.
I'm with you. I have made a living working on cars since I was 12, I'm 70 now. I have owned cars since I was 17. I not only have never changed my break fluid but I have never changed it for anyone else. It is my opinion that any moisture in the fluid is evaporated by the temp of brake hardware
And this is why brake fluid is one of the most undermaintained aspects of vehicle maintainence. Lots of misconceptions about how the system works and needed maintainence.
By design, what you state is NOT allowed to happen.
Brake fluid is hydroscopic. That means it's designed to ABSORB moisture. Even though brake systems are sealed, the moisture finds its way in through the rubber brake hoses, and the gaps in the seal of the MC fluid cap, and any time you open the cap up. The fluid is always absorbing moisture from the surroundings.
Brake fluid is designed to absorb water to prevent it from accumulating in quantity in your system and causing issues such as internally rusting your lines and calipers, as well as boiling over at a lower temp and turning to gas , which is compressible, so you end up with a nice long brake pedal travel and no result in terms of the car actually stopping.
If you were to use a non-hydroscopic fluid as brake fluid, the water would constantly be boiling (at a much lower temp as well), but remain in the system as it has no escape really as it would just accumulate in the calipers over time. So you would need to bleed the brakes constantly to remove the air bubbles in your system. So if what you stated were in fact true, you would actually need to bleed your brakes MORE just to rid yourself of the moisture that is boiling off into a gas.
But since the fluid is hydroscopic, it's constantly absorbing moisture, and filling with water. This, in turn, lowers the boiling point of the brake fluid which is not very desirable. Bleeding the brakes essentially purges the lines of the moisture ladened fluid replacing it with clean fluid with a higher boiling point, as well as a pure fluid which will not react with the components of the system and possibly damage them long term.
Brake fluid usually has two specs. A DRY and WET boiling point. DRY point is the boiling point of the fluid when it's fresh out of the bottle. The WET point is the boiling point after it's abosrbed a certain amount of moisture. For example, Valvoline Dot3&4 brake fluid has a DRY point of 480* and a wet point of 311*. That's a 169 degree difference there between fresh fluid, and moisture laden old fluid. Water boils at 212* so that should show you why you want your brake fluid to absorb the moisture by design.
With that lower boiling point, all you need are a couple heavy stops to generate enough heat in the calipers to boil a tiny amount of fluid off. A little bit here and there and your pedal gets spongier and spongier over time. You don't notice it because it's so gradual, but i've routinely bleed my brakes every 1-2 years and always noticed a firmer pedal immediately after bleeding along with increased braking response.
To make a really long story short. Bleed your brakes. I challenge someone to present a logical technical arguement against bleeding brakes. The only arguement against it, is stubborness.
Last edited by BostonMike7; 03-12-2015 at 12:26 PM..
If you want to PROPERLY maintain your car, you will change all the fluid every two years. Dot 3 and 4 sucks up moisture like a sponge and that water is hard on the brake components. You will extend the life of very expensive brake parts by replacing all the inexpensive brake fluid at that interval.
Do most people do that ? No, but that is why shops do so many brake repair jobs.
Don
No, they do it because it's an upsell. Why do you think many places offer free or discounted oil changes. To get you in and upsell you with mostly unnecessary repairs.
I'm sure there are honest mechanics or shops out there but I haven't seen one.
I take it the Op is talking about flushing the entire system over just changing master cylinder fluid. Yes its much better to flush the system and then replace with new brake fluid. and bleed out air .
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