How often do you REALLY flush your brakes?

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LarryM
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How often do you REALLY flush your brakes?

Post by LarryM »

Flushing brakes is easily my least-favorite maintenance task, and is made even worse when it also involves flushing the clutch hydraulics. I use a Motiv pressure bleeder but that doesn't make it any less of a chore. I just don't like working with brake fluid, period.

As we know, BMW recommends doing this annually which to me seems extreme. I've been doing it approximately every two years on both my E24 and E28, but even that seems like overkill on cars that live in a dry climate and are basically garage queens, driven only a few thousand miles/year in fair weather.

What kind of driving/environmental conditions is YOUR car exposed to, and do you actually adhere to an annual flush?
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Re: How often do you REALLY flush your brakes?

Post by plip1953 »

On race cars we generally bleed the brakes ahead of every outing, and maybe between sessions too, and probably flush the system completely every three or four outings. But on my road cars I have to confess to only doing it if I feel the brakes aren't working as well as they should rather than at set intervals (mileage or time based). I don't think I've touched the fluid in my 635 brakes for more than 10 years - oops!!
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Re: How often do you REALLY flush your brakes?

Post by Jlc »

I do it evey two years or when I do a brake job. I also use the Motive Power pressure bleeder.
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Re: How often do you REALLY flush your brakes?

Post by Da_Hose »

I do it every couple years. I also have a pressure bleeder, which makes it WAY less painful. Suck the reservoir dry, and refill takes about an hour.
I do have a mid-rise lift though.

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Re: How often do you REALLY flush your brakes?

Post by Super Coop »

I do it every couple years. I don't know that it needs it, I only drive the coupe about 2 to 3000 miles a year any more. When I get it ready for spring, I change the oil and filter, check the lubes and have a power bleeder so its really not that big a deal when I have it up on stands.
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Re: How often do you REALLY flush your brakes?

Post by GRNSHRK »

This a really good question, just did mine because I have the wheels off right now :-"

But honestly, while the 6er isn't getting many miles put on her, I don't do it nearly enough [-X

Since the recommended interval is time, not miles, I'm guilty :-({|=
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Re: How often do you REALLY flush your brakes?

Post by hornhospital »

I believe the flush is for corrosion protection. Brake fluid is hydroscopic, i.e. it attracts and absorbs water. Even though the amount of water is minuscule, it does attack the metal brake lines. Flushing removes the contaminated fluid and the water absorbed within it. It also can lower the boiling point of the fluid in a sufficient concentration, leading to loss of braking power when the brakes are worked hard.

That said, until about 3 years ago I was diligent about flushing the lines every year, then health problems got in the way. All my BMWs and other cars are way past due except for the Grand Cherokee and my wifes Equinox, which both had brake jobs and system flushes in the last two months.
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Re: How often do you REALLY flush your brakes?

Post by plip1953 »

hornhospital wrote: Mon Dec 14, 2020 5:42 am I believe the flush is for corrosion protection. Brake fluid is hydroscopic, i.e. it attracts and absorbs water. Even though the amount of water is minuscule, it does attack the metal brake lines. Flushing removes the contaminated fluid and the water absorbed within it. It also can lower the boiling point of the fluid in a sufficient concentration, leading to loss of braking power when the brakes are worked hard.

That said, until about 3 years ago I was diligent about flushing the lines every year, then health problems got in the way. All my BMWs and other cars are way past due except for the Grand Cherokee and my wifes Equinox, which both had brake jobs and system flushes in the last two months.
I'm not an authority on such matters, but I don't believe that modern brake fluids are corrosive to any significant extent, even if they've been in a system for many years. But fully endorse the point about brake fluid being hygroscopic and that this can lower the boiling point. But with modern, good quality brake fluids having extremely high boiling points anyway I think it relatively unlikely this would be a problem for 30+ year old cars making under 300bhp.
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Re: How often do you REALLY flush your brakes?

Post by nick88highline »

I flush my brakes once a year without fail as I don't want to have to replace the ABS, master cylinder or calipers themselves because of corrosion. I live in the driest place in the United Kingdom, but I use my car at all times of the year and the roads are salted around here. #-o
When I upgraded my brakes to E34 540 calipers I installed Stahlbus bleeder valves which makes the job of using my vacuum bleeder very easy and eliminates the risks of corrosion around the valves.

PS I also use stainless steel caliper pistons to further reduce the chance of caliper failure.
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Re: How often do you REALLY flush your brakes?

Post by LarryM »

Bentley implies that bleeding the clutch along with the brakes is a "good idea" but not absolutely necessary.

Do you guys include flushing the clutch hydraulics as a standard part of the job? And if so, how do you go about it? Pressure bleeder or "reverse" bleeding from the bottom at the slave cylinder? Bleeding the clutch means having to get the car up in the air, thus making the whole job a little more involved (unless you're also doing other under-car maintenance work at the same time).
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Re: How often do you REALLY flush your brakes?

Post by hornhospital »

Absolutely, do all five, four wheels and the clutch slave. I look at the clutch as part of the brake hydraulic system.I do the brakes with all four wheels off, car on jack stands, so it's no big deal to get underneath. I use a Motiv power bleeder, but have vacuum-bled the system many times before getting the Motiv unit.
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Re: How often do you REALLY flush your brakes?

Post by LarryM »

hornhospital wrote: Sun Dec 20, 2020 2:51 am Absolutely, do all five, four wheels and the clutch slave. I look at the clutch as part of the brake hydraulic system.I do the brakes with all four wheels off, car on jack stands, so it's no big deal to get underneath. I use a Motiv power bleeder, but have vacuum-bled the system many times before getting the Motiv unit.
For bleeding the clutch line with the Motiv bleeder, do you use it the same way as for the brakes? Simply open the clutch slave cylinder bleeder screw while under pressure and let it bleed for awhile?

Some recommend reverse-bleeding the clutch line but it seems that shouldn't be necessary if using a pressure bleeder.
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Re: How often do you REALLY flush your brakes?

Post by GRNSHRK »

Plus one, they all feed off the same reservoir, and having just done mine, I was surprised at the crap that came out of the clutch slave, as opposed to the brake calipers :-k

Obviously, it's way easier if the car is up on jack stands as Ken duly noted, but the task is a PITA anyway, might as well go all the way :-"

And pressure bleeder as well, just crack the bleeder screw and catch the effluent with a hose and container of choice \:D/
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Re: How often do you REALLY flush your brakes?

Post by hornhospital »

What he said^^^^^^. I use the Motiv bleeder on all of it. I used to use a vacuum bleeder, but the Motiv is way less messy and I believe faster.
Last edited by hornhospital on Tue Dec 22, 2020 4:05 pm, edited 1 time in total.
Ken Kanne
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Re: How often do you REALLY flush your brakes?

Post by GRNSHRK »

I'm using a Schwaben setup, available from ECS Tuning =D>

They have a huge array of automotive tools from this company, ask me how I know :roll:

Thanks for verifying Ken, never a doubt :-"

One last thought, the recommended use is to fill the 3 LITER container with brake fluid, obviously that's not gonna happen [-X

So I just fill the reservoir, connect the system, build up some pressure (10 psi is more than enough =; ) and bleed away \:D/

Bleeding the brakes (and clutch slave) has never been easier, I can assure you that it will take FAR longer to get the car up on jack stands and wheels off, than it will to perform the bleeding process [-(
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