Why can’t I bleed my rear brake?

About the brake:
It’s a SRAM Code R from about 2019/20.

About me:
I can usually do most bike maintenance, albeit it’ll involve some cursing and the occasional re-do. I have successfully bled many a brake! For example, the front brake on this very bike! But also several Shimano XT successes on my hardtail and I think I had SRAM way back on the bike that preceded these without suffering unduly.

What’s going on:
It took me two goes to do the front one properly. The first time inexplicably made it worse.
The rear brake I’m now up to four or five attempts without success. I’m using Epic Bleed Solutions’ kit, it’s a Bleeding Edge port on the caliper, I’ve watched enough youtube videos and read enough instructions that I don’t think I’m missing a step. I do the bleed procedure, all air seems to be out of the system, I put it all back together and it’s spongey as hell with the lever pulling to the bar (yes after pumping it several times). When I start over, the first thing that happens is an absolute craptonne of air comes back out of the system as soon as I get going.

What to do?
Clearly air’s getting back in somewhere. Is there something a lot of people miss that I might be as well? Is there something defective on the hardware that isn’t my fault?

I might take it to a shop and ask them to do it, which feels like admitting defeat. Also no shop that is near me are ready for this sort of thing so it will be a ballache.
I might throw it all in the bin and get another set of XT brakes or something, which feels like it would be expensive AND I’ll probably get mad doing the hose routing anyway.

Thankyou for reading. Thanks even more if you solve my problem, ideally in a way that makes me feel better about it!

Have you taken the calipers off so you can tilt them to free up any trapped air whilst letting the fluid gravity feed back from the syringe at the lever before finishing up?

When you redo is the air coming out at the calliper or lever end? Either way I would suggest redoing the hose connection to the lever/calliper with a new barb and olive.

Thank you both. I have not tried removing the caliper. The air comes out mainly at the lever end. It’s way more than would be accounted for by being a few bubbles stuck somewhere, I would say. Barb and olive might be the go then.

Air can get in where the syringe connects to the lever so check thats tight and the o ring is ok.

How hard are you tugging on your plunger? You can easily pull air around the metal bit and into the tube and it looks like it’s coming from the lever.

I’ll bet its what sharkattack suggest …?excessive syringe pulling at the lever

Are you pulling up on the plunger to help soon all the air out? Close the system at the other end to do that.
After the bleed, and after the caliper bleed and lever bleed, I removed the lever syringe and make sure the fluid is topped up to the brim, then put bleed nipple screw back in. I then give the caliper syringe a wee push then nip the bleed nipple up. In my head that seems to mean there is no air in there.

I have had good results from doing the bleed procedure as per the video, closing the m/cyl end and just adding a bit of pressure before closing and disconnecting the bleeding edge tool.

What DickBarton says

If it was me pulling too hard on the lever syringe, the air wouldn’t actually be in the brake system, right? So I’m thinking that wouldn’t account for it being really spongey?

the last steps of the procedure are closing the bleeding edge port at the caliper, cycling the lever syringe a few times for any last bubbles, then compressing that plunger and putting the screw back in. You’re saying at this point you reopen the caliper port and pump some fluid in that end again?

I will say when I take off the lever syringe it feels like quite a lot of fluid wants to come out while I’m getting the screw closed.

I’m mid bleeding mine (front done), and though I’ve not experience the issues you report, I have had video popping on my feed suggesting adding pressure… might be worth a try in your case

ala  SRAM pressure hack

That looks like what DickBarton and others are suggesting. Must be worth a go!

closing the bleeding edge port at the caliper, cycling the lever syringe a few times for any last bubbles, then compressing that plunger and putting the screw back in. You’re saying at this point you reopen the caliper port and pump some fluid in that end again?

From this, the order isnt what I or I think DickBarton suggest.

Do the brake syringe thing (are you sure that you have the O ring on the syringe insert and the one out of the m/cyl on the port screw).
Remove the m/cyl syringe and I guess this will be full of fluid.
Replace teh m/cyl port screw.
At teh bleeding edge end, pressurise the system a little then close the port and remove the tool.

pressurising from the m/cyl end will work until you remove the m/cyl syringe then the caliper pistons retract and teh m/cyl port oozes fluid…

I connect both syringes and do a push from caliper to lever. I then lock the lever syringe and I bleed the caliper (which is basically drawing plunger back to suck any air out), once no air is coming out, I close the caliper syringe.
Both bleed ports remain open, the closing is the lock on the syringe hose.
I then do the same on the lever syringe, and also do a wee push on the syringe (forces fluid in and then when I release the plunger returns slowly), give the brake lever a wee squeeze a few times and help get the air out. I then draw the plunger back and help suck any remaining air out.
Once I’m happy, I remove the lever syringe and push fluid from caliper syringe so that the fluid is sitting at the very brim of the lever, then I install the bleed nipple (wiping the excess fluid.
Finally I give the caliper plunger a wee push and tighten the bleeding edge nipple, remove the syringe and tighten up the caliper bleed nipple.
I don’t pressurise from the lever as that just allows fluid to escape, so I do it from the caliper as the bleeding edge keeps things tidier.

I think SRAMs bleed process is the best.

1)Lever reach out, and contact point adjusted if you have it.

2)Both syringes connected, push/pull fluid from the lever.

2.5) (not official SRAM process) Close off lever syringe. Squeeze/hold lever in, easier to tie with rubber band. Pull vacuum at the caliper, remove rubber band holding lever in still. Compress syringe slowly releasing lever.

3)Close caliper bleeding edge

4) Open lever syringe, squeeze lever and release.

5)Pull vacuum on lever syringe, then compress to equalise.

6) Remove syringe and close lever.

People also re open the caliper and push a small amount of fluid in at this point. I don’t find I need to with Code Silver Stealth.

@rickmeister I thought you might be on to something with missing o-ring, I definitely have it on the syringe. I also have it on the bleed port screw, BUT I have to say it looks quite tiny, like maybe over tightened in the past? I’m really not sure how to check that (I suppose I could open the front brake again and compare now I think of it). It’s not mangled or split or anything, just looks quite deep in the thread if that makes sense. Been feeling ill for the past few days so not really had the energy to progress further.

thanks again for the help, everybody.