Do we really need to bleed the brakes? - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
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post #1 of 17 (permalink) Old 08-24-2018, 09:03 PM Thread Starter
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Do we really need to bleed the brakes?

Do we really need to bleed the brakes? I think not and here's my reasoning.

1) Periodically (every 3 years maybe) removing the old brake fluid from the master cylinder using a turkey baster and refiling with fresh new brake fluid should be good enough. The old and new fluid would mix due to Brownian motion (physics) and the overall quality of the brake fluid would be much better than the one removed. It is like gently pouring clean water in a glass of dirty water (without splashing) and in a few hours you will see them all mixed up and consistent. I would expect the same to happen in the brake system it may take a few hours longer compared to the water experiment due to the thinner tubing from master cylinder to the calipers.

2) Of course the issue of trapped air bubbles that make brakes spongy immediately comes to mind which is the main reason for brake bleeding. Air is lighter than the brake fluid, would'nt it escape from all the deep recesses of the braking system through the master cylinder when the cap is opened to fill in fresh fluid? There is a continuity of fluid path from master cylinder to the calipers so I cannot see a situation where air is permanently trapped permanently in the system even after opening the master cylinder cap.

Maybe I took a very simplistic view and missed something, would like to hear others' opinions.
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post #2 of 17 (permalink) Old 08-24-2018, 09:32 PM
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No. Just no.
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post #3 of 17 (permalink) Old 08-24-2018, 10:25 PM
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In a word, no.

The reason you flush the system is to get the old fluid and any debris in the lines and caliper out. Changing the fluid will of course help fluid quality, but doesn't remove any trash in the system.

Get a Motiv power bleeder (don't put fluid in it, just use it as an air pressure source!), remove old fluid with turkey baster, refill, put on Motiv, do first caliper (Right rear first.) Refill and repeat, left rear, right front, left front.

Takes about 2 beers start-to-finish. Do it every 2 years for a street vehicle. (If you track the car then you need to do this BEFORE EVERY TRACK SESSION since the depressed boiling point from absorbed water can cause you to meet Mr. Wall unexpectedly on the track -- if you get the brakes that hot in street driving you probably ought to be in prison.....)

I've never had a caliper fail on any of my vehicles while doing this every 2 years. But calipers aren't that expensive, nor are master cylinders to be frank. The real issue is the ABS pump. If the ABS pump gets eaten you will cry at the cost and avoiding that alone is well worth the hassle.
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post #4 of 17 (permalink) Old 08-25-2018, 01:18 AM
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I agree with flushing the brakes every 2 yrs. I also agree with either the pressure or the vacuum method. Never the two-person pump the pedal to the floor method (unless the master cylinder is brand-spanking new). I use the vacuum method at the caliper bleed screws.

BUT... someone please advise whether, when fluid courses thru the system while flushing, whether that flushing occurs through the ABS unit/pump? I have heard that for some cars the ABS logic module has to be commanded (with an interogating device) to operate the ABS pump and thereby flush fluid through it.

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post #5 of 17 (permalink) Old 08-25-2018, 08:37 AM
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It flushes through it (think about it; how else would it get there?); the "must command on" requirement is if you get AIR in the system, since there are high points inside the pump and they will trap air.

In that case, in virtually ALL vehicles with ABS to bleed the system IF air gets into the lines (and thus the ABS pump) you cannot get it all out without a service tool that can activate the ABS pump.
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post #6 of 17 (permalink) Old 08-25-2018, 08:41 AM
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Thx Ticker.

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post #7 of 17 (permalink) Old 08-25-2018, 10:11 AM
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Quote:
Originally Posted by Cdn17Sport6MT View Post
I agree with flushing the brakes every 2 yrs. I also agree with either the pressure or the vacuum method. Never the two-person pump the pedal to the floor method (unless the master cylinder is brand-spanking new). I use the vacuum method at the caliper bleed screws.
Why not?
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post #8 of 17 (permalink) Old 08-25-2018, 10:49 AM
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'Cuz once it's been in svce for a while the portions of the bore of the m/c that normally are not traversed by the seals becomes fouled and potentially corroded (brake fluid is hygroscopic - the source of the corrosion promoting element). The sealing elements of the m/c piston get scored. So, soon afterwards you suffer m/c failure. That's the rule i live by. YMMV.

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post #9 of 17 (permalink) Old 08-25-2018, 11:11 AM Thread Starter
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The reason I posted this thread is my car is five and half years old now and I was debating if I really needed to bleed the brakes and if not suffer some catastrophic fate due to crud/moisture/air etc in the system as everyone talks about on the net. The only way to get at a logical answer was ask the question what did I do with my previous cars and what was the result? In my previous 1997 model car I NEVER EVER bled brakes over its 16 yr 170K life simply because I DID NOT KNOW about such a thing as brake bleeding. It was just a normal fluid top off during oil changes which the quick lube guys did and never had a problem with braking system related to not bleeding. Only after buying my new Mazda and coming across this forum I learnt a lot of things about cars including brake bleeding. I feel like the more we know the more hypochondriac we get, worrying about every little thing, non-existent fears, analyzing and splitting hairs endlessly. Sometime ignorance is bliss but having knowledge is definitely better, most useful though is applying common sense and not not overdo/underdo things.
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post #10 of 17 (permalink) Old 08-25-2018, 12:07 PM
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I follow the Severe Driving Conditions Maintenance Schedule located in the Owners manual.

IF you were to go by that for the 2018 you would inspect the Brake fluid every time you change the oil. That's it. That covers up to 60 months or 60K miles (96km). From that point you would generally start over with the maintenance schedule.

While everyone has an opinion, what you decide to do is all about what you feel comfortable with. Unless you are driving your car hard or tracking the car there is no reason to change the brake fluid every two years other than for peace of mind.

Even though the manual does not call for replacement I'll be doing this car (if we still have it) at either 60 months or 60K miles, whichever comes first.

The vehicles in our transportation company run approx. 100K miles a year. At 4 years and 400K miles they are sold off and replaced. They follow a strict maintenance schedule. Changing/flushing the brake fluid is not one of them. 26 million miles and counting we have never had a brake issue in any way shape or form. Never. Ford E350's since 1993, and have been transitioning to Mercedes Sprinters for the last 2+ years.

I'll never chastise anyone for wanting to do extra maintenance on their car. It's your money and time but if you wonder what Mazda thinks, check out your owners manual.

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