Brake fluid colour

[Tirpitz]

What colour should brake fluid be? Reason I ask is because I've read somewhere that it should be almost colourless and if it's brown it's old and needs replacing. The stuff I drained away when I stripped the system definitely was brown and gunky, so that follows. Yet I've just bought a new bottle of Silkolene universal brake and clutch fluid, DOT4, in a sealed bottle and I would describe it as a golden colour. It's clear but it isn't colourless. Surely it must be fine as it's new and from a sealed bottle?

[Daniel.p]

Yeh thats fine mate by colourless i think they mean not black, if you pour some fluid out it does appear clear but when in your resoviour it will be goldenish so dont worry

[Tirpitz]

Thanks Daniel, it threw me a bit when it came out golden coloured. Now I've just got to get a firm brake :smt013 The back bled easily, the front took ages to get the fluid through and although it is running through air free I can't get a good brake. I've pumped the lever up hard and left it tied up overnight and am hoping that will do the trick.

[cargo]

why did you drain it just pump fresh fluid thought it untill it's clean fluid coming through

Then again why did you allow your brake fluid to get into such a state in the first place................your life depends on your brakes !

Brake fluid should be changed once a year at the very least. My race bikes get new fluid every other race meeting

[Daniel.p]

I remember my first ever time bleeding my ar125 brakes what a bitch got the stuff everywhere, wheels, paint you name it i had fluid on it! But on the bleed nipple just slowly pull the brake while slowly tightening the nipple that way worked for me watch out though twist the wrong nipple youll get a slap and milk all over the shop

[U_h0rnet5]

Hey dude, are you using a proper brake bleeding kit or just pumping the lever while opening the nipple?

I use the vacuum pump makes its ten times easier. Pump it up and then crack open the nipple and then just keep topping up the res. never let it get too low as you will be back to square one! Once you start to get new fluid through close and then start on the other calliper (I always start with the right one as it is further away).

After that then I start to pump the fluid through using the lever until there is no bubbles coming through the pipes on both (this will probably be impossible as there most likely be still a little bit of air in the callipers). Once all the nipples are closed have a quick little pump to check the pressure of the brake lever.

Then I do one final thing which you might need another pair of hands with. With the nipple closed I start to squeeze the brake lever and then when it stops start gentle opening the nipple until the lever reaches the bar and then close the nipple. Repeat for a few times and then do the same on the other side.

Hope this might help otherwise there are plenty of other threads on this problem just have to have a look through. Most problems seem to be:
1. Master Cylinder - either upgrade or the mech and springs need changing.
2. Where the bleed nipple is placed
3. Could be the Calliper seals need changing.

I'm sure someone will have some other views on this but always done this and my brakes are sharp as anything only need to use a little pressure from two fingers lol.

Ciaran

[Tirpitz]

Right guys, don't panic. There's a very good reason why the brake fluid got in such a state and why I drained the lines. The bike has been stored for 13 years! The system was stripped down as it was full of crap and the calipers needed a full overhaul with new seals. Plus I rebuilt the master cylinder and fitted new braided lines. So no unsafe riding was involved, and I didn't have any option but to start with a dry system.

I was going to ask about bleeding the system as, yes, I have done it the old way by pumping the lever and I'm not happy with the result. There is no air coming out of the calipers, I've cracked open the banjo at the master to make sure there's nothing there, but I've still got too much lever travel - it comes back to about an inch from the bar. If I pump it up and leave it tied to the bar overnight I get a better brake in the morning but it doesn't last. I'm sure there is still some air in the system but I can't shift it. Would one of those vacuum bleeders sort it? I reckon it needs pushing out from the bottom up.

When I get a minute I'm going to take the calipers off and try bleeding with them on their sides and with the pistons pushed back in. Also I'll try taking the splitter off and jiggling that about. There's definitely a little bit of air in there but it's a bugger to get out. I knew it would be, past experience said it would be a right PITA bleeding the front, but no option.

[U_h0rnet5]

How come you still have the splitter if you have braided lines?

Yeah cool that is a good thing then, you might find that there may be a little bit of air still in the callipers and you might not be able to get it out due to where the bleed nipple is actually placed as it is not at the top of the calliper!

[Mori Man]

Bleeding front brakes is a nightmare for sure.

The ZXRs brakes are exactley the way they came with the bike just dust removed, lever travel is about a 1mm past hearing the brake light switch

When I get the fluid changed it will be off to the shop and have them do it with their pressure doofer, I have a compressor now and remote tanks so might invest in one But shop only charge 14 quid to do a fluid change and that includes the fluid ! I aint left with a jat of gloop either

Span adjusters also change the travel so set them to their max and see where your at.

[Tirpitz]

I kept the splitter as there were two kinds of lines advertised - OEM set-up and racing. With the benefit of hindsight I now realise that I could have saved myself money by going for the race set-up and eliminating the splitter. At the time I decided to go with what I knew and replace like for like. But hindsight's a great thing

I've had everything off in turn this morning. MC reservoir cap off. Started with the calipers unbolted, twisted them every which way whilst slapping them to dislodge any trapped air. Unbolted the splitter and did the same with that. Then took the MC / brake lever assembly off and turned so that the connection to the reservoir was at the highest point, gave it all a good slap, banged the hoses about and pinched along the hose to the reservoir.

Back to the calipers - pushed every piston right back in to reverse bleed and push out any air trapped at the top of the system. Calipers back on and ten, with the brake lever / MC assembly still removed, and with the banjo at the highest point, I cracked open the banjo and depressed the brake lever to release any trapped air. Fluid came out but I can't say I noticed any bubbles. Closed it off before releasing lever.

Everything back together, pump brakes to get pads back in place. Bled calipers - not so much as the tiniest bubble came out, pure liquid all the way. Situation now is that the brakes start to bite as soon as the brake switch clicks and the lever stops about an inch and a half from the bar. It's hard with no sponginess. You can operate the brakes with one finger and the lever travel stops well before touching your other fingers. Now, I can't see me getting it any better than this, so my question is - is this about right or do I give to the dealer to fettle? I'm reluctant to give it to a dealer - it will be hassle getting it there and I don't like giving up on something I could do myself. I don't mind buying a vacuum bleeder if that will do the trick - it will be cheaper than the dealer anyway.

Edit - been searching some more about this issue and found this http://www.gbbikers.co.uk/gbb/index.php?topic=29039.0 which is that close to my experience it sounds like an echo. I reckon it's a vacuum bleeder for me - fingers crossed it does the trick.

[Tirpitz]

Another thing occurs to me. A couple of times now, after leaving the bike overnight, when pulling the brake lever for the first time it feels like the MC piston is stiff and sticking. After the first pull it's fine and moves smoothly. I suspect what is happening is that overnight the trapped air in the system is percolating up the lines to the MC so that on first pull of the brake lever the piston seal is moving in a dry cylinder. This didn't happen with the lever tied back overnight as the piston seal is a specific shape and moves more smoothly in a dry piston when returning to the normal position. I reckon I'm going to try leaving the bike overnight, in the morning get the bars on full right lock to get the MC banjo at the highest point, then crack it open and slowly pull the brake lever. That might expel the percolated air bubble which has accumulated.

[cdstirland81]

if you are having major snags getting the air out of the banjo bolt/master cylinder area, why not get a banjo bolt with a bleed nipple on? i'm sure goodridge do them, or have i imagined it?

[Tirpitz]

No, I don't think the issue is a problem getting air out of the MC area, the air is in the braided lines, which I understand can be a common problem when you fit them dry. The air sems to be accumulating in the MC when left overnight. Whilst a bleed nipple on the MC banjo would ceretainly make bleeding less messy it won't do anything that cracking it open will do just as well. If I was starting over then I'd certainly think about a MC banjo with a bleed nipple, but as it's done now I'll do it the messy way.

I'm pretty sure this proves that the problem is trapped air. If I'd had a vacuum bleeder to start with I suspect this would have been a 10 minute job. My understanding is that the pumping method just moves the air down the line a bit, then when the lever reaches the end of its travel, it moves back up and you get nowhere. The constant flow induced by the vacuum bleeder keeps it moving right out of the lines.

Apparently

[Tirpitz]

Yep, it is trapped air. Cracked the MC banjo open this morning and slowly pulled the brake lever and air bubbles fizzled out before it ran to fluid. Makes me a bit happier now I've identified the cause of the problem for definite, just a matter of solving it now. Brakes are now better but still not perfect. Vacuum bleeder should do the trick.

Way I see it the tying brake lever back 'trick' is a red herring. The claim is that it allows air to percolate up and clear through the reservoir overnight, but the way I see things when you have the brake lever pulled the reservoir is isolated from the line - it has to be or else the pressure you create by pulling the lever would just push fluid up into the reservoir. My understanding is that the MC reservoir is connected to the line only with the brake lever unpulled. I reckon that's why tying the lever back doesn't work, it produces a temporary feeling of hard brakes in the morning which disappears after a few operations of the lever. As soon as you release the lever in the morning you start pushing the accumulated air back down the lines. Theoretically, another method which should work is to allow things to settle overnight, then connect a syringe full of fluid to the caliper bleed nipple and pump more fluid in from that end. That should push the air in the lines / MC out via the reservoir. You will need to make sure the reservoir doesn't overflow mind.

[RedexRobB]

The other thing about leaving the lever tied, is that ive regularly read it involves leaving the reservoir cap off. This exposes the brake fluid to moisture in the air, and since brake fluid is hygroscopic it'll absorb the moisture its exposed to and degrade the fluid.

Personally i think a vacuum pump is the best choice, so long as you keep the reservoir topped while your doing it you shouldnt have any problems sucking air in.