Bleeding hydraulic brakes after 1 year - worthwhile?

[pink poodle]

But she dont use butter...

 

[Binaural]

Yep, vac bleeding Guide RS or RSC , it makes a rear brake feel like a non vac bled front, eliminates a lot the sponginess. Makes a front lever feel rock hard and super responsive. The flip side to this, you're still left noticing the rear plastic lines swelling under pressure.

Since the thing I like least about my SRAM brakes is the sponginess , I'd like to give it a go. That said, the last time I bled a brake, SRAM were still Avid and you pushed in the fluid from the bottom and tried to shake/tap out the bubbles trapped in teh lines.. Is the following what you mean by vacuum bleeding?

http://enduro-mtb.com/en/how-to-correctly-bleed-a-sram-guide-brake/

 

[Mr Crudley]

I don't think avid run Dot 5, Dot 5 is silicone based. You can use Dot 4 and Dot 5.1, auto stuff is no different from the gen Avid stuff.

Point taken, 4 or 5.1 is the dot I'm looking for. I have some original Avid fluid here but would be a bit aged which is good for fine wine but not brake fluid I guess.

 

[Tubbsy]

So inspired by all this I've decided to open up the seven year old Hopes and give them a bleed.

Problem is, it doesn't seem to be working.

When I first opened the bleed nipple, about an inch and a half of fluid entered the hose, but pressing the brake lever isn't flushing the fluid through. From what I can tell I'm supposed to be needing to add fresh fluid to the reservoir every couple of pumps, but the level isn't dropping. The lever feels normal, as though it's all sealed up.

I took the pads and wheel off and have the little plastic block in between the pistons.

I've only bled Maguras in the past, and this process is new to me - what am I missing here?


PS - the fluid I can see actually looks pretty clean, nothing at all like the one year old fluid pictured on the last page?

 

[urallwrong]

That was a heavily taxed Shimano set.

 

[link1896]

Since the thing I like least about my SRAM brakes is the sponginess , I'd like to give it a go. That said, the last time I bled a brake, SRAM were still Avid and you pushed in the fluid from the bottom and tried to shake/tap out the bubbles trapped in teh lines.. Is the following what you mean by vacuum bleeding?

http://enduro-mtb.com/en/how-to-correctly-bleed-a-sram-guide-brake/

No, I built a proper vacuum bleeding rig. pics and some details here https://www.rotorburn.com/forums/in...-rs-brakes-lever-slow-to-return.304656/page-9

 

[teK--]

So inspired by all this I've decided to open up the seven year old Hopes and give them a bleed.

Problem is, it doesn't seem to be working.

When I first opened the bleed nipple, about an inch and a half of fluid entered the hose, but pressing the brake lever isn't flushing the fluid through. From what I can tell I'm supposed to be needing to add fresh fluid to the reservoir every couple of pumps, but the level isn't dropping. The lever feels normal, as though it's all sealed up.

I took the pads and wheel off and have the little plastic block in between the pistons.

I've only bled Maguras in the past, and this process is new to me - what am I missing here?


PS - the fluid I can see actually looks pretty clean, nothing at all like the one year old fluid pictured on the last page?

You need to close the nipple before releasing the lever so that it draws fresh fluid in from the reservoir. Otherwise your just pushing the same fluid back and forth.

 

[Flow-Rider]

Point taken, 4 or 5.1 is the dot I'm looking for. I have some original Avid fluid here but would be a bit aged which is good for fine wine but not brake fluid I guess.

If it's been in a tightly sealed container on the shelf for a while it's probably not going to be that bad.

 

[link1896]

If it's been in a tightly sealed container on the shelf for a while it's probably not going to be that bad.

yep, assuming lid has sealed, 120ml sram dot container half empty, 20c degree air at 100% RH occupied the empty void of the bottle, a cubic meter of air can hold 17.3 grams of h2o at 20c, so 60cc of air can hold 0.001038 grams of h2o, thats going to be 0.0000173% of the fluids volume is h2o in your bottle

unknown, is the bottle actually a perfect seal, through the HDPE bottle itself or the cap seal. I suspect not.

this is where we need our resident chemist, REDBRUCE!!!!!

 

[Mr Crudley]

unknown, is the bottle actually a perfect seal, through the HDPE bottle itself or the cap seal. I suspect not.

I would assume that it isn't in a vacuum. Might as well get fresh oil just in case.

 

[Flow-Rider]

I change brake fluid on my 3 cars every year and just buy a 4 litre container, sometimes the left over just sits for 2 years and never had any issues. I've even tested it with a brake fluid refractometer but probably dependant on where you live. How many people do you know that don't change brake fluid on a car for six years or more and they're not dead yet from brake failure.

 

[Tubbsy]

You need to close the nipple before releasing the lever so that it draws fresh fluid in from the reservoir. Otherwise your just pushing the same fluid back and forth.

So I'm doing a sequence of:

open nipple - squeeze lever- close nipple -release lever

In the video I watched this seems to move quite a lot of fluid through the system; I just did the above sequence about 10 times and the reservoir dropped by may be 2mm, and a little bit has entered the hose.

Should it be flushing through more quickly, or have I left this so long that something has gunked up inside?

The brakes have been perfect for years, hence I never cracked them open - the fluid looks pretty clean, but maybe I've created a problem for myself?

 

[link1896]

I change brake fluid on my 3 cars every year and just buy a 4 litre container, sometimes the left over just sits for 2 years and never had any issues. I've even tested it with a brake fluid refractometer but probably dependant on where you live. How many people do you know that don't change brake fluid on a car for six years or more and they're not dead yet from brake failure.

Oh I'm so there right now with my Subaru, 4 year old dot 5.1, has become quite average even with bendix ultimates but still work.

Do need to bleed them for fear of corrosion.

 

[stirk]

So I'm doing a sequence of:

open nipple - squeeze lever- close nipple -release lever

In the video I watched this seems to move quite a lot of fluid through the system; I just did the above sequence about 10 times and the reservoir dropped by may be 2mm, and a little bit has entered the hose.

Should it be flushing through more quickly, or have I left this so long that something has gunked up inside?

The brakes have been perfect for years, hence I never cracked them open - the fluid looks pretty clean, but maybe I've created a problem for myself?

That should do the trick, if you think how small the master cylinder is it's pushing much fluid but the whole system won't hold much so it doesn't take long, you should have it finished by now.

 

[Flow-Rider]

Oh I'm so there right now with my Subaru, 4 year old dot 5.1, has become quite average even with bendix ultimates but still work.

Do need to bleed them for fear of corrosion.

Yeah good idea if you're going to keep the car long term. You used to be able to get litmus paper test strips for brake fluid, they weren't the best but better than nothing.

 

[teK--]

So I'm doing a sequence of:

open nipple - squeeze lever- close nipple -release lever

In the video I watched this seems to move quite a lot of fluid through the system; I just did the above sequence about 10 times and the reservoir dropped by may be 2mm, and a little bit has entered the hose.

Should it be flushing through more quickly, or have I left this so long that something has gunked up inside?

The brakes have been perfect for years, hence I never cracked them open - the fluid looks pretty clean, but maybe I've created a problem for myself?

What I do is pump up and then hold pressure on lever. Then open nipple and close it quickly before the lever bottoms out. Then release lever.

This way the pressure buildup pushes the fluid out with more force to shift any bubbles that have latched onto various areas in the caliper.

For stubborn bleeds you may even need to extend the pistons out and them back in a few times, tap the caliper with a wrench to shake off any bubbles, or remove the caliper and tilt it at various angles whilst doing all of the above before bleeding again.

 

[teK--]

I would assume that it isn't in a vacuum. Might as well get fresh oil just in case.

I reseal half used bottles of brake fluid and tyre sealant by sandwiching a couple of layers of aluminium foil between the bottle neck and bottle cap before screwing it down.

 

[Tubbsy]

What I do is pump up and then hold pressure on lever. Then open nipple and close it quickly before the lever bottoms out. Then release lever.

This way the pressure buildup pushes the fluid out with more force to shift any bubbles that have latched onto various areas in the caliper.

For stubborn bleeds you may even need to extend the pistons out and them back in a few times, tap the caliper with a wrench to shake off any bubbles, or remove the caliper and tilt it at various angles whilst doing all of the above before bleeding again.

Should the lever move when I open the nipple? It doesn't appear to.

 

[Oddjob]

Should the lever move when I open the nipple? It doesn't appear to.

Yes. Sounds like you have a blocked nipple. Unscrew the nipple all the way out and visually inspect. If nipple is clear then the problem is in the caliper and its time to go to a trusted lbs.

I would put money on water in dot fluid causing corrosion.

Sent from my SM-G900I using Tapatalk

 

[Tubbsy]

Eek, ok.

They felt perfect, shouldn't have opened the fucker up.