No brake pedal pressure after bleeding

That's what I gathered from the rest of the thread. All good stuff, and at least I learned a thing or two. Rock on!

 

Care to share the device name. Now that I'm up to '13 and '14 model years that could be useful. (Highlander was an '04)

 

Did you mean to say "without activating the ABS module/pistons"? I would think activating the ABS pistons would move any air trapped inside the module, no?

 

Autel AP200C MaxiAP 2022 OBD2 Scanner with ABS Auto Bleed, Airbag Reset, Oil, Throttle, DPF, EPB, SAS, BMS Services in-App Purchase, ABS/SRS Diagnosis, for iOS & Android, Specific Vehicles

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Yes, good catch.
You DO need it to Activate to get the air out.
You’ll hear it and feel it in the brake pedal when it’s activate.


(I’ll change it on the original to clear it up.)

 

So an update, after $329 trip to the dealership the pedal is still spongy and only minor improvement. Dealership bled the abs module with techstream and they also did a fluid flush and bleed with new fluid. When I picked it up the service writer said the tech said that there was a “possible code for a master cylinder malfunction” but it would be another $99 to diagnose and they couldn’t diagnose it for another 3 days so I just drove it home. Pedal is overall about 15% firmer and I can see no leaks anywhere.
In my experience, a problem with the master cylinder involved fluid leaking either at the reservoir or at the rear seal. There are no leaks I can see and the pedal holds pressure better now and doesn’t sink to the floor but it is very soft and spongy feeling. Any more thoughts? Thanks

 

Also what in the master cylinder would set a code? Is there a pressure sensor or something? I just feel like I got screwed at the dealership today but that’s the way I usually feel leaving there anyway.

 

If your truck has the hydraulic brake booster, as opposed to the more traditional vacuum booster, it will have the a master cylinder solenoid and ECU as a combined unit attached. Yes indeed it stores codes. I have been chasing one for the accumulator for quite some time and have finally ordered and received parts (not yet installed).

The codes can be read through the Techstream scanning/programming tool and may not necessarily set a CEL. Mine records the code every so often but has never triggered a dash light.

 

They have a low fluid sensor. Other than that l can’t think of what else would cause a master cylinder to throw a code. I’ve only ever seen it light up an idiot light on the dash.

Now that you have some braking ability you could try manually cycling the abs on a dirt or gravel patch. Thinking they didn’t get all of the air out. Then bleed it again like you normally would.

Something else I’ve seen is a master cylinder internally bypassing. Quite often there won’t be a leak externally. It would cause the pedal to sometimes feel normal. Sometimes you’ll feel it catch lower than normal. Sometimes a sinking pedal feel. Sometimes the pedal bottoms out. Usually if you slam down hard in the pedal it’ll stop as expected. But I don’t think you have these symptoms.

 

Did anyone ever check the rear brake adjustments?

 

I have a little more squish in my brakes than I desire as well so am following this thread closely. I took off my rear drums to see if the parking brake/auto shoe adjusters may not have adjusted the shoes out, and that was what was causing the excessive squish. No such luck; there is about 1/10th of a mm clearance between the drum and the shoes. I had to use the thread in ports on the outside of the drum to get it off ( I hate retracting brake shoes with the star fangled nut accessed through the backing plate.)
I'm going to try the abs activation method pretty soon.

 

You are doing it wrong:

Expand until the drum locks and cannot turn then back it off 15 notches.

One way to test this is to press in the parking brake a few clicks then drive and press the brakes. Is it better or the same? If it is better then the rear drums need to be adjusted as per below. Both sides.

 

I'm curious, when the time comes to release the adjuster 15 notches, can it be done with just the adjusting tool or screwdriver? Or do you need to push the lever off the adjuster star?

I've seen guys mistakenly tighten the adjuster so tight that the wheels won't move. Usually I'll get a long pick to push the lever, then back off on the adjuster. Occasionally there's no way to push on the lever so I've sorta forced the adjuster backwards flopping the lever over. Then adjust as if tightening to flop it back.

 

I usually use an O-ring Pick to move the lever out of the way so that I can adjust it. And when it is adjusted properly you can usually hear it scrub slightly on the shoes when you rotate the drum.

 

So here’s an update. Cleaned and adjusted rear shoes and drums- no change. Bled system 5 more times at all 4 wheels- no change. New master cylinder, bench bled master and again bled all 4 wheels again 4 more total times- no change. I don’t know what else to do. The dealership bled the abs system so it should be ok and there’s no air bubbles in the lines at the wheels when bled. Does anybody have any other ideas?

 

Damn! This sux azz... During this artillery barrage of parts, did the brakes revert back to how they felt before the dealership bled the brakes and ABS? Or did the minor improvement from their bleed remain?

With everything I've read here, it almost sounds as if there's a weak flex line expanding when you hit the brakes. Or leak in the ABS unit itself. Pushing an air bubble between a couple of cylinders, back and forth. I haven't had the displeasure of being in your situation, nor have I opened up an ABS unit. So this is all conjecture on my part.

Perhaps @Jimmyh has an exploded view of an ABS unit that could shed some light on my, what's is nothing more than a guess, thoughts.

At this point, not gonna lie, I hope that when you figure this out, that it'll be something minor that you've overlooked. You've thrown enough money, and time at it. And I think it's fair to say that we've all done it at least once, whether a pro or DIYer.

Good luck!

Edit rather than new post... @Torspd will that OBD scanner work with torque or is it proprietary software, communications? Can you access tpms as well? Thanks.

 

I’m wondering did the dealership do a complete system bleed or only the abs unit? When you’re bleeding it are you doing the 2 person procedure or using a vacuum pump? You’re absolutely certain you’re refilling the reservoir often enough? Have you tried bleeding with the booster on, engine running or key on if it has an electric booster.

You said you bench bled the mc. But it kinda sounds like it could have air trapped in it. I suppose it’s possible you got a defective one.

Recently I worked on a machine with a single disc motor brake. Regular bleeding wasn’t working. So I ran clear tubing from the bleeder back to the reservoir and pumped the pedal. Sure enough air came out. You could try something similar, use a bottle with some brake fluid in it. Run the tubing from the bleeder to the bottle. It needs to be tight enough on the bleeder to not let air in so it might need to be manually held in place or a little spring hose clamp. In the bottle the tubing end needs to be submerged in fluid. Then pump the pedal up and down. Down will push a little more fluid out than up will draw back in. Then tighten the bleeder, remove tubing, repeat on the next one. Clear tubing will be easier to see air coming out but regular black hose will also work. You could even bench bleed the mc in place by running the tubing from the bleeder back into the reservoir. Every time I do this I end up with the bottle tipping over so take precautions. Perhaps a second person holding the bottle and tubing on the bleeder while watching for air. When air comes out do a few more pumps to get any remaining tiny bubbles out.

 

I do not know if it will work with torque. Standalone unit. In my limited uses of it, it's functionality is limited to what the vehicle has avaliable to be programmed. My older model cannot pump the ABS module. It says "Not available on this year model." A newer model than the simple 2006 that I have, should.

 

Lets try one more thing.

Slightly engage the parking brake a few clicks ( either the Pedal (auto trans) or the pull handle (manual trans)). Then drive it with the parking brake engaged and see if the pedal improves.

If it does it is a rear wheel brake adjustment too loose.
If it doesn't there are issues in the hydraulics system.

Let us know.

My "Guess" would be that they didn't get all of the air out of the ABS System. When you say the pedal went to the floor after your brake job, there was a LOT of air in the system.

 

I am reviving this thread because I am having a similar issue. This past weekend I decided to do take on some DIY work and replaced my rear inner axle seals. I knew that I had to disconnect the ABS sensor and brake lines to remove the shaft and that this would require a bleeding afterwards. When I finished and started the truck, my brake light was on and I didn't have as much stopping power. I took it up to a shop near me, which completed a flush and bleeding. When they brought the truck out, I went from having spongy brakes with less stopping power to having no stopping power at all. Truck is still their and I will speak to their master tech Tuesday.

I'm thinking I should request that they do the bleeding again? Anything else specific I should ask?