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Help with Shimano hydraulic brake install

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Help with Shimano hydraulic brake install

Old 06-17-18, 10:04 AM
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Help with Shimano hydraulic brake install

I'm having trouble setting up the Shimano ST-RS685/BR-RS785 lever and caliper groupset that I recently got. The installation seemed pretty straightforward, and the levers, hoses and calipers all seem to be properly mounted. The last step, filling and bleeding the brake lines is where I'm having issues.

I used the Shimano disc brake bleed kit, and things appeared to have gone well. By that I mean I was able to fill each brake line from the caliper slave cylinder to the master cylinder successfully, with fluid accumulating in the funnel at each MC. The issue is that after closing the bleed valve, removing the funnel and replacing the MC screw ( and its O-ring), there is no pressure being generated in the lines when the lever is pumped (i. e., no resistance at all). This is the case for both the front and rear brakes. All the connections are snug, there are no leaks that I can find anywhere in the system and both calipers have the bleed blocks in place, .

Any idea of what I'm doing wrong here?

Last edited by Yossarian22; 06-17-18 at 10:07 AM.
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Old 06-17-18, 07:02 PM
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You aren't describing the full service procedure. With a bleed block inserted, you should push fluid from the caliper into the bleed funnel until no more bubbles come out. Then you should close the bleed port at caliper and operate the lever tapping and rotating it to dislodge any additional bubbles before replacing the lever. It sounds like you just pushed fluid to the top and closed the bleed port.

It's also possible there's still air somewhere. Try unbolting the calipers when pushing fluid so that there's a good direct line to the levers and gravity is helping air rise. Bleed a bit more.
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Old 06-18-18, 10:24 AM
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Originally Posted by cpach
You aren't describing the full service procedure. With a bleed block inserted, you should push fluid from the caliper into the bleed funnel until no more bubbles come out. Then you should close the bleed port at caliper and operate the lever tapping and rotating it to dislodge any additional bubbles before replacing the lever. It sounds like you just pushed fluid to the top and closed the bleed port.

It's also possible there's still air somewhere. Try unbolting the calipers when pushing fluid so that there's a good direct line to the levers and gravity is helping air rise. Bleed a bit more.
Thanks. Guess I didn't do a very good job of describing what I did, but in fact I did just that: Pushed fluid from the caliper to the bleed funnel, closed the bleed port at the caliper, then operated the lever with the bleed funnel in place while tapping it gently. Didn't rotate it but I did repeat the procedure, still with no success. For whatever reason, it would appear that there is no fluid in a key part of the master cylinder.

Think I'm going to try using the My-T-Vac that I use to bleed the brakes on my motorcycles. This method is the reverse, so I'd connect the My-T-Vac to the caliper after attaching and filling the bleed funnel, then draw the fluid out, topping up the funnel as needed.
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Old 06-18-18, 11:52 AM
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There is a step that I'm not seeing mentioned in this thread. After filling the system from the caliper up to the lever, you are supposed close the bleed port on the caliper, remove the syringe and attach a tube tied to a baggie. Open the caliper bleed port, and let the oil and bubbles flow into the baggie. After the bubbles stop, close the bleed port again on the caliper, and squeeze the brake lever. With the lever still squeezed, quickly open and shut the bleed port on the caliper to get more air out. Close the caliper port and the operate the brake lever a few times. The lever should definitely firm up. Once that is done, then remove the funnel and put the lever bleed screw back in. I have the same brake setup and have gotten good bleeds from following the dealer manual steps.
Manuals & Technical Documents
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Old 06-18-18, 01:09 PM
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Originally Posted by RocThrower
There is a step that I'm not seeing mentioned in this thread. After filling the system from the caliper up to the lever, you are supposed close the bleed port on the caliper, remove the syringe and attach a tube tied to a baggie. Open the caliper bleed port, and let the oil and bubbles flow into the baggie. After the bubbles stop, close the bleed port again on the caliper, and squeeze the brake lever. With the lever still squeezed, quickly open and shut the bleed port on the caliper to get more air out. Close the caliper port and the operate the brake lever a few times. The lever should definitely firm up. Once that is done, then remove the funnel and put the lever bleed screw back in. I have the same brake setup and have gotten good bleeds from following the dealer manual steps.
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Thanks and you're right - haven't done that. In my defense, I didn't see it listed in the Shimano literature I have.

Will try that step and see what happens!
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Old 06-20-18, 09:31 AM
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RocThrower is correct...that is an important step. You can also try pulling on the syringe at the bleed port to suck a few more bubbles out, optionally while pumping the lever a bit to reverse the fluid flow (make sure there’s clean fluid in the funnel). It’s also very important to rotate the lever body to different positions as mentioned in the Shimano instructions. That usually finds a few more bubbles. When doing a first fill of a completely dry system, there is a *lot* of air trapped in weird places. You may have to try a bunch of different things to the last of the air out. The Shimano dealer manual can be kind of confusing IMHO as it’s not always clear which steps to do in which order, so just try ‘em all. On some TRP Hylex brakes I have, I didn’t get the last of the air out of the rear caliper until I unbolted it and just let it hang down with the hose coming out vertically from the top.

Last edited by Metaluna; 06-20-18 at 09:34 AM.
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