Flushing Brakes

[Paddler]

Why do we need to flush our brakes every two years in our motorcycles, but not our cars?  It doesn't make much sense to me, same fluids, right?

[Etienne Lau]

What do you mean? I do my cars and motorcycles every 2 years, it's standard practice for both every 2 years. Even written in maintenance as schedule.

[Hosstage]

Cars should be done too, it just isn't done because people don't read their owner manuals, the dealer service department doesn't do a good job of education. And it's expensive, most people don't think it needs to be done.

Motorcycle owners are generally a little more in touch with their vehicles, especially brakes and tires.

[Rougarou]

People don't change their differential fluid in their cars/trucks, nor do they change their transmission fluid, they barely put wiper fluid in and when I get in a vehicle after my wife drives it, it barely has any fuel injection fluid.  Knew a guy that never changed the oil in his car, just checked it, added more when needed, car went 80k +/- miles before he traded it in, ran just fine.

 

People don't even flush their home water heaters every couple of years either, then wonder why they start running outta hot water.

 

Lotsa things don't get done.

 

The brake fluid on my RT has been flushed once in 155k,......seems to stop just find.

 

There's something about recommended vs required. 

 

 

[dirtrider]

9 hours ago, Paddler said:

Why do we need to flush our brakes every two years in our motorcycles, but not our cars?  It doesn't make much sense to me, same fluids, right?

Morning Paddler

 

Because that is what BMW suggests you do. 

 

So during warranty you should at least follow the service recommendation. 

 

If you go back to the earlier (1100)  BMW oilhead days BMW motorcycles had rubber type brake hoses, those could allow moisture to wick into the brake fluid through the rubber hose & cause fluid moisture issues. So BMW had a number of service bulletin's on fluid service  (bleeding) intervals.

 

Next came the BMW 1150 bikes with I-ABS systems, those also had rubber brake hoses (except for some very late bikes) BUT they had the I-ABS system & that system had open ABS module venting so that allowed moisture to enter the system  (later 1150's had a sort of moisture trap but it didn't work worth a hoot). So these needed more service (I used to service every year on the 1150 I-ABS systems)

 

Next came hexheads bikes, those had updated Stalflex brake hoses to prevent moisture wicking issues & those are pretty well sealed but BMW stuck with the more frequent service intervals.  You could go longer but it is so easy & quick to service the later (I-ABS gen 2) 1200 hexhead systems that it's kind of  a no-brainer to service per BMW schedule.  The later hexhead has a servo rear brake using the front lever so the pump is kind of shearing the fluid as it pumps. 

 

The newer (later)  BMW 1200/1250 bike could probably go longer than maintenance schedule suggests but keep in mind the service intervals are written for worse case riders in worse case weather conditions.  The killer on a lot of motorcycle brake systems is a large number of motorcycles are seasonal use only so they can sit for months in damp, cold, changing weather conditions without even one pull of the brake lever or one push of the brake pedal. 

 

Could you stretch out the brake service intervals on the wethead & shift-cam, sure, but with it being so easy to service why even try. 

 

 

[Paddler]

I was just curious, I'm doing the flushes as recommended.  I fell seriously behind on my '98 R1100R and paid the price.  I rebuilt all three calipers and flushed everything out thoroughly.  It's time to do both bikes again.  I don't ever remember flushing the brakes on our 2000 528i.

[Hosstage]

Might not notice a problem with poor quality brake fluid until running down some long grades and that fluid starts to heat up. That's when you will start thinking about brake service and what hasn't been done on a timely basis. Hopefully not too late.

[Hosstage]

When I flush the fluid on my older HD, (non abs, non linked) the front doesn't look too bad, but the fluid in the rear looks like hell, dark and dirty, kind of yellow, kind of not, almost burnt looking. I think the heat that it is subject to being blocked from wind flow and near the exhaust, running past the motor and tranny, cooks it pretty good. Feels good when I see that nice purple tint new fluid start to come out during the flush. I can just hear the brakes saying "Aagh!"

I think the front fluid looks better because it gets so much air flow and stays cooler.

[lkraus]

10 hours ago, Etienne Lau said:

What do you mean? I do my cars and motorcycles every 2 years, it's standard practice for both every 2 years. Even written in maintenance as schedule.

I've never seen a brake fluid flush in a car or truck maintenance schedule. 

 

Just checked the warranty/maintenance booklets for our Toyotas, and the closest they come is to say "Inspect power steering fluid (if equipped) and brake fluid level/condition"  every 6 months/5000 miles.  The schedules cover the first 12 years/120,000 miles.

 

I also have access to the factory service manuals. No mention of a flush or fluid replacement there, either.  The only mention of bleeding the lines is in conjunction with a component replacement.

 

If I squint, I can convince myself that the original fluid in the 2011 Camry has yellowed a bit.  I've never needed to add fluid. At only 12 years and 193,000 miles, I still don't feel a need to flush the fluid.

 

On the other hand, the whizzy brakes on the RT get a complete flush every two years. It's painful, and I'm not convinced it is necessary, but I don't want to risk an expensive failure.

 

 

[Etienne Lau]

Check brake fluid condition is the same as brake fluid flush. If you did check the condition you would have flushed it. 

[Skywagon]

Fluid is cheap and maintenance (except whizzies) is really easy.  I'm looking for the data on heat cycles, but haven't found anything I would post...some stuff, but didn't seem very scientific.

 

Keep in mind the heat from the brakes, rotor, etc, does cause brake fluid to heat up.  It can cause it to boil and create fade if you are really pounding the brakes.  I'm not sure how many heat cycles brake fluid can take before it breaks down.  

 

I change mine every year.  It cost me about $4-5 and a whopping 20 minutes of my time.....and my wife saying how many more times to push this lever...it's hot out here.

 

Car's and trucks....I change it when I change the pads.  Hook up the little vaccuum pump and I can bleed the master and all four wheels in 30 minutes.  Pads usually last at least 50k miles so cars/trucks usually get changed one in the lifetime I own them.

[greiffster]

10 hours ago, lkraus said:

I've never seen a brake fluid flush in a car or truck maintenance schedule. 

 

 

 

 BMW X1 has a brake fluid change at 30K miles and every 60K after in the maintenance schedule. 

[Mellow]

I actually don't do a flush, once a year I'll take a syringe and suck out the fluid in the reservoir and replace with new.  So, it' will never be 100% but some new is being circulated w/old.  Maybe at some point I'll get bored and do a flush to get the small contaminants out but this lazy option works for me.

[Steveyacht]

It's so damned cheap, easy and simple to do, it's damned near foolish not to.

[Hosstage]

3 hours ago, Mellow said:

I actually don't do a flush, once a year I'll take a syringe and suck out the fluid in the reservoir and replace with new.  So, it' will never be 100% but some new is being circulated w/old.  Maybe at some point I'll get bored and do a flush to get the small contaminants out but this lazy option works for me.

Brake fluid doesn't circulate unless maybe thru the abs if it is activated substantially. Even then, that new fluid probably isn't making its way thru the system in any meaningful way.

[Twisties]

20 hours ago, lkraus said:

I've never seen a brake fluid flush in a car or truck maintenance schedule. 

 

Just checked the warranty/maintenance booklets for our Toyotas, and the closest they come is to say "Inspect power steering fluid (if equipped) and brake fluid level/condition"  every 6 months/5000 miles.  The schedules cover the first 12 years/120,000 miles.

 

I also have access to the factory service manuals. No mention of a flush or fluid replacement there, either.  The only mention of bleeding the lines is in conjunction with a component replacement.

 

If I squint, I can convince myself that the original fluid in the 2011 Camry has yellowed a bit.  I've never needed to add fluid. At only 12 years and 193,000 miles, I still don't feel a need to flush the fluid.

 

On the other hand, the whizzy brakes on the RT get a complete flush every two years. It's painful, and I'm not convinced it is necessary, but I don't want to risk an expensive failure.

 

 

Just a bought a used Xterra and brake fluid flush is in the maintenance schedule, every two years.  But, I think this is the first cage I've owned that had it.  Most cages use rigid steel brake lines, have larger reservoirs, and so far as I understand the brakes would be bled when you have brake service (pads and rotors) done, although that could be a long time, I suppose.  

 

I think in general bikes have higher maintenance, perhaps because the consequences of even little things can be large.  MSF trains to inspect your bike before each ride.  Few do that with a cage.

[Mellow]

Geesh fine I'll go do it now.

[Mellow]

Fine, that was pretty fast.  Much easier than the ST1300 procedure.

[bimmers]

Brake fluid is hygroscopic, whatever the system is like it will get bad over time. On All my cars I have been asked by dealers, service independents (in particular high performance car and race car service providers) whether to flush or not. I always say check the condition of the fluid and flush if needed. On the cars they generally flush every 50k miles or so. On the biles I take it even more seriously after had some issues in the past. The 2006 with the servo system is the one I care for most in this department. So ar all good after 40k miles and now over 15 years and a few flushes. the 2021 brakes feel a lot more effective though when comparing the two. 

 

H

 

[kon]

in the last 30+ years, I've never flushed the brake fluid of any vehicle I've ever owned and I've never had any issues. If I have a bad hose, I would change the hose, add brake fluid and bleed the system. I doubt that flushing the brake fluid makes any difference except for draining your wallet.

[Hati]

4 hours ago, kon said:

I doubt that flushing the brake fluid makes any difference except for draining your wallet.

 

Well, you can believe what you want of course, but here is the technical description as to why brake fluid replacement is needed.

 

Brake fluid within your braking system contaminates in one of two ways. It can get water in via seals that do not function correctly, the reservoir rubber in particular is a common location. 

 

The other way is metal particles from general ware. That usually shows up as dark/dirty fluid. Failing to clean this out should not need any justification.

 

The water in the brake fluid is trickier because you can rarely see it. Under normal circumstances you will not notice any difference because water, like brake fluid, is uncompressible in liquid form. However, if you heat that water up it will turn into steam given enough time and heat source. Now steam is compressible so you end up getting spongy brakes as a minimum or loose brakes all together as a worst case scenario. 

 

While it is hard to heat up the brake fluid (and potential water in it) outside race conditions on a track, it can be done and it has been done. Enthusiastic, what you Americans call "canyon" riding is one possible way of achieving this, but some downhill riding and one or two emergency braking instance can get you there too.

 

So do your own risk assessment. If you think it won't happen to you, be my guest, keep you brake fluid forever. It's your bike, your life buddy. But realistically it is cheap insurance that would be silly not to use.

 

 

[dirtrider]

18 hours ago, kon said:

in the last 30+ years, I've never flushed the brake fluid of any vehicle I've ever owned and I've never had any issues. If I have a bad hose, I would change the hose, add brake fluid and bleed the system. I doubt that flushing the brake fluid makes any difference except for draining your wallet.

Morning Kon

 

That is a choice a rider has to make on BMW motorcycles, sometimes you get lucky & have no issues & other times you can end up with a failed $2000.00 + labor  Pressure Modulator with no warranty support. 

 

It just seems to most that $12.00 worth of brake fluid & a half hour of time every couple of years is a good trade off against an expensive  brake module failure or pitted internal brake system parts.

With linked brakes the servo pump runs every time you use the front brake lever & the brake fluid is not only the braking hydraulic fluid but also the "only" lubrication for the servo pump & servo valving. The brake fluid itself might last longer but the additives in the brake fluid are perishable. 

 

One of the basic problems on a motorcycle is a number of motorcycles are not year-round ridden, if ridden every day, or at least ridden very often then a little moisture in the brake fluid it usually not a big deal. But on motorcycles that are parked for off-season storage then a little moisture in the brake fluid can become a big deal.

 

DOT3, DOT4, DOT4 low viscosity are a moisture magnet so it is about impossible to prevent eventual moisture contamination. 

 

In any case, if you choose not to flush your BMW braking system then here's hoping that your 30+ year no-flush luck still works on the  modern complex BMW braking system. 

 

 

[Cap]

On 8/19/2023 at 10:58 AM, lkraus said:

I've never seen a brake fluid flush in a car or truck maintenance schedule. ...

 

My 1992 Acura Legend had anti-lock brakes, which was an advanced feature at that time.  And the whole system needed a flush every 2 years.  And WOE to anyone who neglected it, because a replacement ABS controller cost about a quarter of what the car was worth, and was not rebuildable.  DAMHIK .  Sort of like the EVO brakes on my 2004 R1150RT.

I think there have been many advances in technology and manufacturing processes since the early ABS systems, and they need less maintenance now.  Nevertheless, I think it is worth doing a complete flush from time to time on an older car that you intend to keep.  I follow the "Car Care Nut" on YouTube, and he has shown several examples of older Toyotas that eventually require new brake reservoirs and controllers because they were never flushed.  On my Suzuki Vstrom DL650 with ABS, there is no scheduled maintenance on the ABS system.  But on that bike, there is a tendency of the ABS controller to fail after about 10 years due to internal corrosion, which could be mitigated by replacing the fluid.   I think Suzuki figured that 10 years of service life was adequate for a bike in that cost category, and that most of their bikes would be on their third owners by then, or out of service.

 

Replacing the brake fluid on our wetheads is so easy... I do it every two years.  The challenge is to get the old brake fluid out of the ABS controller.  The GS911 has a function to activate the ABS while you are flushing.  On my Vstrom, there is no service function like that -- I found a report by an enterprising owner who cobbled together an Arduino to spoof the ABS wheel sensors to simulate a skid, thereby triggering the ABS motor.  I use a more direct method: I do a flush, and then take the bike out on my local street and mash the brakes at low speed to activate the ABS.  That serves to verify that the ABS is still working, and I think it also rotates some of the old fluid trapped in the ABS when it sits unused for most of the time.

 

Cap

 

[Skywagon]

There is a whole cottage industry e.g. Module Masters who charge hundreds of dollars with months in que for those who have failed to properly care for the ABS modules. Just saying…

[Hosstage]

Harley did not specify a flush schedule on their ABS systems. After a few years, people started having trouble with a no brake condition, a hard handle or pedal (no linked system). It was found that those who never or rarely activated the abs system would have crystals from in the module due to stagnant fluid. It is now part of regular maintenance every 2 years to flush the system and that the module be cycled during the flush to completely circulate new fluid thru the module.

[Twisties]

If it hasn't been mentioned yet, speed bleeders are your friend!

[plepper]

I just bought a 2003 R1150rt with working ABS brake system, but no service records, If the brakes are working and I flush them can I assume they will perform in the future? I will be adding SS lines or is it better to just do the delete? I've read so much about the brakes failing it has me concerned. The bike is in very good shape with no butchery by previous owners and I plan to do a complete service ( everything up to and including the 24 month service ) to bring it up to date on recommemded service schedule. I also plan on SS clutch lines and a new slave cylinder, and adress the fuel system ( replacing the conponents and lines ). I want to begin next spring with a reliable bike. I realize nothing is guarnteed in life but I'm hoping to end up with a classic bike that I can rely on. I will also be checking the HES and clutch splines and driveline for wear and fixing as needed. Any other suggestions appreciated!

 

[dirtrider]

29 minutes ago, plepper said:

I just bought a 2003 R1150rt with working ABS brake system, but no service records, If the brakes are working and I flush them can I assume they will perform in the future? I will be adding SS lines or is it better to just do the delete? I've read so much about the brakes failing it has me concerned. The bike is in very good shape with no butchery by previous owners and I plan to do a complete service ( everything up to and including the 24 month service ) to bring it up to date on recommemded service schedule. I also plan on SS clutch lines and a new slave cylinder, and adress the fuel system ( replacing the conponents and lines ). I want to begin next spring with a reliable bike. I realize nothing is guarnteed in life but I'm hoping to end up with a classic bike that I can rely on. I will also be checking the HES and clutch splines and driveline for wear and fixing as needed. Any other suggestions appreciated!

 

Evening plepper

 

If the brakes are working and I flush them can I assume they will perform in the future?-- In a word NO, it is the correct thing to do & should increase your ABS module reliability but those I-ABS modules can & do fail, not all do, but some do. 

 

Removal is a trade-off, you are balancing a possible future  ABS/servo failure against ABS removal but then no ABS available at all. 

 

The slave cylinder replacement & high pressure fuel line replacement is also a very good thing to do to prevent future issues with those.

 

On the slave, you might also think of slotting the bottom of the gasket, or drilling a drain hole into the trans case  pushrod area, so IF you have a future slave leak, it won't ruin your clutch disk. 

[Cap]

1 hour ago, plepper said:

...Any other suggestions appreciated!

 

 

Well you may not appreciate this as much as you hoped... but the frog on the table is the transmission input shaft.  There is no way to inspect it without separating the engine and transmission.  They seem to be working fine right up until the input shaft completely strips, at which point you lose all drive.  My 2001 R1150GS stripped the shaft while under warranty.  My 2004 R1150RT was treated with kid gloves before I sold it -- to a savvy owner who bought it with the assumption that it would need a new clutch and maybe a new input shaft at 30k miles.  And sure enough, he tore it down and discovered that it was nearing failure.  I think they all do that... they are ticking time bombs.

 

But all is not lost.  There are special retrofit clutch assemblies that have an extended center, and will ride on the unstripped portion of the transmission input spline.  So, if you are proactive about it, you can catch the problem before you need to replace the input shaft or replace the whole transmission.

[plepper]

Thank's for the input! I'm planning on deleting the ABS and fitting SS lines, Changing out the clutch slave cylinder and doing the gasket as per DR's suggestion. As for the clutch spline input shaft issue I have no problem with doing a new shaft and extended clutch disk. I know it's a lot of work and can still be problematic but I like the bike and won't be putting serious miles on the bike so it will worth the investment to me. I enjoy wrenching on bikes and I'm retired so time spent working on the bike is not an issue. Form what I've been able to determine checking alignment of the cases, input shaft and the extended clutch assembly will give the best  results.

[JCtx]

Neglecting your expensive braking system is a very stupid mistake to make, simply because your life (and others... if you hit them, because no freaking brakes) depends on them. They're the most important component of any vehicle. Sorry for being so blunt, but it's the truth. Now, I think 'flushing' sounds a lot more complicated than what we actually have to do, which is a simple BLEED job, meaning just replacing old fluid with new one (just don't suck any air. Ha ha). It literally takes minutes to do on a BMW bike, since we only have to do the brakes (clutch has mineral fluid), and there are just 3 valves now (I remember bleeding my ex-2002 K1200RS with servo brakes that had 14 valves to bleed... and in a very specific sequence). And it costs less than 10 bucks, since you only need an 8-oz bottle. And if you don't have a fluid extractor (which is my preferred method), you don't need any equipment, other than a wrench, and a line to hook up the caliper nipple to a glass jar; that's it. Cars take longer, but it's still easy, but you need a 16-oz bottle. But to each his own, of course.

[dirtrider]

Morning___

 

Future readers take note:

 

There are 2 separate BMW braking systems being referred to in the above posts, 

 

The posts that are just above JCtx's response are about a 2003 1150RT.   The original thread  is about a basic brake system flush posted in the ShiftCam forum.

 

JCtx response mentions  (clutch has mineral fluid), that is not correct for the 2003 1150 RT as it used DOT4 for clutch fluid. Do not put mineral type fluid in the older DOT4 systems or you will have a big mess to repair.

 

JCtx also mentions,  "Now, I think 'flushing' sounds a lot more complicated than what we actually have to do, which is a simple BLEED job, meaning just replacing old fluid with new one (just don't suck any air. Ha ha). It literally takes minutes to do on a BMW bike, since we only have to do the brakes (clutch has mineral fluid), and there are just 3 valves now"   This is true for most of the later  BMW (R) bikes but is not correct for the 2003 1150RT  mentioned in the threads just above as those do require the Tupperware & fuel tank to be removed/or at least the tank unfastened & moved back, then a number of ABS module bleed screws bled in the proper order  to properly bleed the I-ABS  braking system. 

 

 

 

 

[JCtx]

Thank you for the clarification. I assumed it wasn't needed, since we're talking about shiftcams... but the more information, the better. And yes, bleeding my 2002 K1200RS with 'wheezy brakes' was a major job. Not only it required removing a lot of parts, but the complicated procedure to bleed the 14 valves had to be followed to a 'T'. I still enjoyed doing it. Ha ha. And yes, only newer bikes have mineral fluid on the clutch, which is clearly stated on the clutch reservoir cover... BUT ALWAYS READ FIRST (NEVER assume).  Plus mineral fluid is super dark, so unless you haven't changed brake fluid in 10 years, you'd know it's not brake fluid.

[9Mary7]

34 year old Honda, 5820 miles, gonna assume that the brakes were never serviced.....

The stuff was like glue..... The brakes did work but I think it is clear that the fluid needs care on a regular basis. Enjoy!

 

[dirtrider]

2 hours ago, 9Mary7 said:

34 year old Honda, 5820 miles, gonna assume that the brakes were never serviced.....

The stuff was like glue..... The brakes did work but I think it is clear that the fluid needs care on a regular basis. Enjoy!

 

Afternoon 9Mary7

 

Yes, either not-serviced or someone dumped some DOT5 in to bring reservoirs up to level by mistake.