Misc: Everything Else Problem Reverse Bleeding Disc Brakes

[squiggles]

Sometimes the inner core of the rubber brake line becomes detached from the outer and thus can block.
Also you could try reverse bleeding after disconnecting the brake pipe union from the master cylinder. If fluid flows then the master cylinder is faulty.

 

[andrew peters]

I've had a similar problem on my BMW R100CS with dual front disc brakes and a master cylinder at the handle bar. My hydraulic hoses were shot. I replaced them with new aftermarket ones and they never worked better. Use a good quality brake fluid as per manufactures instructions. Usually the D.O.T. rating is on the master cyl. cap. I bleed mine right wheel first, then left. I usually replace fluid every two years. My bike is parked inside. I talked with a Harley mech. and I was told they never bleed the front brakes unless there is a problem. Yikes. I cleaned out a master cylinder on my friends Harley. It looked like black mud inside. About an hour later she was on the road again. If you can squeeze the brake lever and nothing comes out the bleeder, then something is blocked. Hope this helps, Alyson

As a factory trained Harley Tech I’m quite insulted by your viscous accusations that Harley owners never change their brake fluid!!! Although I’m sure more Harley owners would do it if it involved more chrome.. I change a lot of brake fluid in my shop although I’shave to say I have to offer the service as I’m rarely asked, like I say, if it doesn’t enhance the look… old brake fluid, contaminated with moisture in an aluminium master cylinder will cause problems of course, in the last few years Harley have gone from Dot 5 to Dot 4.. I’ve always been told the seals are not compatible although someone who knows better could correct me.. I tend to believe the manufacturer who stamped the number on the cap knows what’s best for the system he designed..
back on point though, if you can’t get a brake to bleed and fluid isn’t flowing through then the issue is usually a ‘mechanical’ blockage and you have to find it, usually this involves dismantling and cleaning then trying to bleed fresh..
Btw, Alyson, pulling your leg, I’m rarely insulted as a Harley Mechanic, I work on them but I don’t ride one myself, although I admit to owning a few, my ride of choice for many years is my R90S (44 years now) until I got my Rapide of course

 

[Speedtwin]

Do NOT interchange or replace fluids DOT4 for DOT5 or visa versa do not let them mix or even live in the same neighbourhood or garage shelf together ever.

If changing one for the other, 4 to 5 or vice versa God knows why anyone bothers to do this, replace all hoses and seals and make sure all the new components are compatible with the new fluid chemistry.
The argument that DOT5 will last for years in vehicles is partly true the fluid will last for years and does not absorb as much moisture as DOT3/4.
The components/seals o-rings, boots however don't care much about fluid type, they just don't like not being used,they sit about stainionary, drying out and deteriorating, awaiting the first time the owner slams down the brake peddle or pulls hard on the lever, to say, "cheerio" see you in the morg.
So why leave a fluid in a vehicle for years?
Change fluids regularly and exercise your brake components regularly as you would your favorite sheep.

The fluids are very different and have interesting detrimental possibly lethal effects on braking components when mixed... or crossed over.

Change ALL your fluids regularly it is the law, it is cheap and it means you and or your machine will not die.
Stick to the fluid designed for the system and check you use the correct fluid every time.
You would not leave the same engine oil in your bike for years why do the same with the system that stops you from dying.
It is easy it is cheap, did I mention how cheap brake fluid is, change it every year if you can be arsed.
Saves time on stuck and deuteriation of system parts and it may keep you above the sod for another summer of riding.

On the bleeding you have a problem.
It it could be the following stuff, the master cylinder, if you cannot drive fluid down and out of the caliper furthest away bleed valve I suspect you have poor lever hydraulic pressure,restriction,blockage,seizure..
Suspect One -Master Cylinder Seal
Suspect Two- Brake line/hose hose condition, was the fluid removed black? if so dump hoses immediately and replace with lovely goodridge ones.
Suspect Three- Check the pistons are moving freely in the calipers back and forth, if stuck then there is another reason why bleeding is poor.
Suspect Four_ Check condition of caliper piston seals cost pence have them replaced by someone competent.

Use a professional, brakes are nasty dirty things they mess up are lovely vehicles wheels but there functionality will without doubt stop you from a premature death.

Rant Over.

Love your brakes look after them they will look after you.

 

[oexing]

As said, the silicon fluid in the Jag is 30 years old now, the car not used much in last 10 years - and you would not want DOT 3 or 4 in the Jag rear disc brakes next to the differential , the Dunlop type calipers, all cast iron ! This is a total mess to change the fluid, so the silicon is brilliant. No unwanted effects with this fluid on any other vehicles we run, for many years. Do you lot change oils in gearbox or differential on your cars in intervals ?? Or grease wheel bearings on your cars in 30 000 miles periods ? On most of these places there is NO way anymore to do this and cars typically run decades and 100 000s of kms just allright. Why the worries about silicon oil which does not produce rust or wear in brake systems with only minimal strokes of moving components in there ? You can certainly change it as well, say 10 years, does no harm to paint , unlike DOT X which can be used for paint stripper too. No , thanks, old brake fluid never again anywhere. As to seals drying out - hmmm , there is fluid around them all the time, maybe silicon may help here too. Anyway, old DOT X brake fluid swells hoses in decades so that the i.d. blocks flow and no brakes then - not so positve about that stuff, I say.
While having remains of DOT 4 and all in a brake system that you fill up with silicon it does not produce ill effects from mixing. But you can get corrosion from these remains in places which don´t flush easily in a fluid change. Better do a full overhaul and you are done for lifetime.
Silicon brake fluids were developed for the US military use as their vehicles don´t get operated regularly so in long storage you cannot accept DOT 4 or whatever for obvious reasons. So ??

Vic

 

[Speedtwin]

DOT4 and DOT 5.1 are glycol based.

DOT 5 is silicon based and was used by some manufacturers then dropped some years back, including Harley Davidson.
Was designed for wet applications such as motorcycles.

DOT5 can not be put into any system that has had any DOT 3,4,5.1 based fluid in it.
It most diffinity produces very serious ill effects which result in brake failure.

I do love to change all my fluids regularly why would you not?
They are the largest moving part in any machine.
Sealed auto transmissions yes chage fluid and filter every 20k miles.
Even Volkswagen/Audi recommend this now for there auto and semi systems.

We see synthetic oil or long life oils that have allowed premature engine failure every day in cars and bikes.
Change every 20k or every year they say on the label, when ever comes first, folks dont understand oh my oil is good for 20k ah yes but it has been in the engine for four years that's why it blew up it has lost its performance protection.
All things have a shelf life.

 

[ClassicBiker]

While on the subject of fluids in motorcycles, recently an acquaintance at my veteran's club asked if I would look at his father's 2004 Kawasaki Vulcan 1500 Drifter. It wouldn't go into gear and he was convinced the shifter forks were bent and he wasn't confident enough to pull down the motor. After doing a bit of research on the internet on these bikes I learned they have a "Positive Neutral Selector" that doesn't allow them into second gear or above unless the rear wheel is spinning. Dirty engine oil will add to the difficulty. So I supported the rear wheel, spun it and managed to get it into all the upper gears. So I changed the engine oil. After warming the engine I pulled the drain plug and what came out plopped out with the viscosity of cold molasses. Removing the oil filter, which in itself was a total PITA, revealed what appeared to be grass clippings or straw in the filter. Figuring I had cured the problem I popped into gear to go for a check out spin. Wrong. So I knew I could see the clutch through the oil fill, I had a look. I could see the driven plates spinning against the drive plates. Figuring the clutch was shot I went back to the internet to see what I could learn. Which was a good move as it saved my friend's father money and me time and work.
The clutch slave cylinder is located in the hottest area of the engine, next to the bevel drive of the shaft drive. Failure to change the brake fluid that operates the clutch on a regular basis causes all sorts of problems. In the clutch master cylinder is a little bleed off hole that regulates how much fluid the system pushes. So I used a pin to clear this hole, which resulted in a 6 inch squirt of brake fluid shooting across my garage. Now new brake fluid reminds me of vegetable to look at in color and viscosity. What greeted me when I had taken the top off of the clutch master cylinder resembled lumpy steak/HP sauce. I imagine this change was the result of dirt and moisture in the fluid. Well as the brake fluid was saturated with moisture and water expands as it warms up, the slave cylinder is in the warmest area of the engine, and the pressure relief hole was blocked, you can guess the issue. When the engine warmed up the clutch disengaged. So I flushed the system and went for a brief ride. If I hadn't been a firm believer in checking and changing brake fluid semi regularly I would be now. I asked my friend when this had last been done, the distant look on his face told me all I needed to know.

 

[oexing]

Again, silicon fluid was a product designed for military vehicles just for the purpose of long storage conditions and no practical change schedules. It was not an idea from Harley or other commercial companies, these would have other ideas like producing a steady demand for services and sale of spares ! So exactly this long storage property is what I expect from silicon fluid and it does its job perfectly. No good reason to compare that with oil changes of engines with very different operating conditions - and certainly no comparisons with glycol brake fluids and their nasty chemicals. And for oil changes , I don´t buy tales about regular changes of gearbox and differential oils on private cars, instead typically run till the thing gets wrecked by other reasons. Sorry, lots of opinions on the subject, same in other forums but no hard facts from own experience. Anybody is free to change silicon fluid as well , if he feels better, just it is a waste of time for decades. At least you don´t have to buy new spares due to rust in the components.

vic

 

[Speedtwin]

I looked at a friends BMW K1 which has ABS it had terrible brakes and was not bleeding well.
I noticed the fluid was purple which made it DOT5, he had renewed the complete system and decided to run it on DOT5.
Reason being the bike resides in a very cold area of northern europe.
He had failed to notice on the can that DOT5 is not suitable for ABS brakes as the pump introduces air by cavitation hence the terrible brakes.
Was an expensive lesson all the hoses and seals replaced again and the pump cleaned, back to DOT4 which is the fluid for ABS systems as it copes with the tiny air introduction and boiling.

 

[oexing]

Well, his decision to replace seals or hoses with no reason as it does not matter for changing back to DOT 4. You are saying the ABS shit introduces air into the fluid - seriously ? I cannot believe this as no brake system will be effective with air bubbles. Yes, silicon may need some more time for air bubbles to climb to the bottle after a change but then no more hassles. So maybe the US are keeping losing their wars with silicon in their tanks and all ?

Vic

 

[Speedtwin]

Harley had to drop it due to the modernisation changes in their brake systems, ABS.
It is widely used in very cold climates such as Russia and is great stuff when used in a system designed for it.
All I was saying is use the correct fluid for your system and change it regularly.
I have bikes with hydraulic brakes some fifty years old fluid is changed every year to stop any corrosion of the parts by the nasty DOT4.
Takes ten minutes and the brakes always feel grateful for it.