Brake Fluid Flush?

[NCGuy68]

Many of us know that DOT 3 and 4 brake fluid absorbs moisture over time leading to corroded caliper pistons, lines, etc. In the real world, how often should the fluid be flushed and refilled?

Thanks for knowledgeable replys Gents.

 

[dkryan]

I guess it depends on your owner's manual and the recommended service interval. I usually bleed the brakes and re-fill at 30K miles or three years, whichever comes first, followed by every two years regardless of mileage. That's in my '01 Infiniti I30.

 

[MarkC]

Well, let's see. I finally flushed the lines on my 96 Cherokee last month @ about 130K or so. What came out was nasty-looking, but I've never had any problems with caliper pistons, lines, or anything else.

 

[bdcardinal]

usually recommend a fluid flush with installation of new pad or shoes. i do mine more often as my calipers tend to need it. the pedal gets a little too soft for my taste every 6 months or so.

 

[bdai]

I've been told that DOT4 absorbs moisture faster than DOT3, but has better resistance to heat buildup. Any truth to this?

 

[Big Jim]

If you have ABS changing fluid more often is wise. Any junk at all in the ABS control module and you are in for an expensive repair.

Brake fluid is better than it used to be. It was not uncommon in the 50s and 60s for wheel cylinders to be frozen in just a couple of years from corosion from degraded fluid. Today you may get away with going longer, but the danger is still there. I've seen grown men cry when told that the clutch slave cylinder needs to be replaced and that the transmission must be pulled for access on a front wheel drive car. Slave killed from putrid fluid. Similar things with calipers and wheel cylinders. I helped my neighbor bleed the brakes on his ten your old Toyota a few weeks ago. The fluid was the color and consistancy of mud. He got the pedal to come back up but instead of spending money to buy new brake parts he has put the car up for sale (I'm not buying it).

So change it once in a while. Every two or three years if you really car about your car. At least every five years might keep you from severe trouble, especially if you do it sooner if the fluid gets black.

But leave it in there forever and at some point you will have some very expensive repairs.

Like the old commercial said "pay me now or pay me later".

 

[Big Jim]

Quote:

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I've been told that DOT4 absorbs moisture faster than DOT3, but has better resistance to heat buildup. Any truth to this?

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As a general rule, that is true. What you gain in higher boiling points you lose in fluid life. Some DOT 4 fluids are better than others. Some DOT 3 fluids are worse than others as well.

I prefer to use the higher boiling point fluid and know that as long as I change it at least every two or three years I'm still ahead.

 

[ITSMR2U]

Depends on application. Was on a BMW bike track session and saw a guy come in white as a sheet - his front brake lever pulled back to the handlebar with no braking due to old fluid that had boiled. BMW MC recommends annual change.
Every 2 or 3 yrs is probably OK with a car used for routine driving.

 

[mechtech2]

$5.00 a year will flush your brakes. And, it's easy.
At least, turkey baster the reservoir dry, and refill with new fluid. It mixes due to movement.

 

[Buffman]

^^ again, I feel that being able to actually bleed the brakes is a better way to flush old brake fluid. Then again if you can't undo bleeder screws, then the turkey baster will suffice.

 

[oil pan 4]

You have to change all the fluid.
Suck out the junk in the break fluid tank, wipe it out with a clean cloth. Then refill it with fresh fluid.
Then bleed out all the old fluid from the lines and pistons.
When your done you may have to refill the break fluid tank.
I refill my tank about 3/4 max, that way less break fluid leaks out rusting the master cylinder and every thing below it.

 

[oil pan 4]

If you cant undo rusted bleader screws file them to the next size down.
Last week I ran into a rusted bleader. 10mm, 3/8'' were to big and 9mm, 11/32 was to small but 11/32'' was close.
So I filed down the sides of the bleader untill the 11/32 would fit over it.
When I was done I replaced it new one with a rubber cap.
It took about 1/2 hour to do that one rusted bleader.

 

[mechtech2]

Right, a bleed IS better, but a few turkey baster fills are better than nothing.

 

[ThirdeYe]

It seems like using a baster would put more air into the system, would it not? Unless it just bubbles up after you put the new fluid in, i'm not really sure.

 

[bdai]

You can only suck out the reservoir fluid with a baster. It's not possible for air to enter the system through the reservoir unless you open the bleed screws with an empty reservoir.

 

[Benzadmiral]

My MB manuals have always recommended changing the brake fluid every 2 years, regardless of mileage, preferably in the spring. The reason being, I suppose, that you'll get out the moisture that's accumulated in there over the dampness of the last two winters.

 

[oil pan 4]

My guess is gases get in there form break fluid/water mix reacting with the cast iron. Making rust and some thing else.

 

[wgtoys]

Most European makers recommend a brake fluid change out once every two years. Honda recommends once every three years. I go with once per two years on our cars no matter what the make. It costs me less than $10 for a quart of high quality DOT 4 fluid and with a Motive Power Bleeder the job is under an hour of my time. Works out to $5 / year. An added benefit is that the bleeder valves don't get a chance to freeze up with this regular use.

http://www.motiveproducts.com/02bleeders.html

 

[unDummy]

Turkey basters do not put air into the fluid. Its just a method of siphoning and refilling the reservoir. This is a great way to remove moisture and refresh the fluid. It is NOT a substitute for bleeding and was never meant to be. And, if the master cylinder is always kept clean, bleeds are quicker.

In the real world, I'd rather see brake fluid bled every year. 2 years isn't all that bad. Maintenance isn't feasible anymore since we're lazy, cheap, and busy.
It also must be bled at all brake services.

Bleed method is for the owner to decide. Speedbleeders, 1 man bleeder hoses/bags, pressure bleeders, and vacuum bleeders, are available. But, learn your vehicle since not every vehicle tolerates all methods. Certain automakers also turn ABS into a hassle.

 

[Craig in Canada]

There's no circulation in the brake fluid system with the exception of the ABS loop of some brands of cars. It is extremely unlikely that simply refreshing your master cylinder fluid is ever going to replace any fluid down at the brake calipers. While you aren't hurting anything, you aren't really helping anything either.

A real bleed through is the only thing that's ever going to do the job right.

Suggestion for a "driven", performance car (ie. enthusiast) is to at least bleed anually, if not bleed through completely. I think a good general base would be a full bleed through no less often than every two years including the clutch.

Variables include whether you run DOT3, DOT4 or DOT5.1, the quality of your chosen fluid, whether your fluid sees high temps, whether you care about or notice brake feel or just "does it stop?".