Brake bleed trouble

Hey, all -

I replaced my calipers yesterday. I used NAPA brand. I'm sure they are remans.

Using a Motive power bleeder I bled right rear, left rear, right front, left front, and LSPV. The rears and the LSPV all bled fine. The fronts, however, never stopped bubbling. I push probably 2 quarts through each one, twice. Constant stream of bubbles.

The first five seconds or so are perfectly clear fluid, then bubbles. If I pinch the bleeder hose off for a few seconds then let if flow again I get that same 5 seconds of clear fluid.

I gave up and test drove the truck. Pedal feels fine. Truck stops good.

Any idea what's going on?

Thanks

 

YEP /\ that's it.

And if you don't have air in the system (indicated by the firm pedal) you're good to go.

For future reference, before you bench bleed the calipers (assuming they were shipped empty) remove the bleeder screws completely and wrap about 1 turn of Teflon tape around the treads and reinstall them. That will solve your air problem with a vacuum type bleeder. Make sure the tape is ONLY on the threads and not the tip that seats inside the caliper.

You can get bleeder screws for motorcycles that have check valves built into them and some of those will interchange with automotive type calipers.
Those "self-bleeder" devices are awesome and I wish more manufacturers would use them. They take about 90% of the headache out of bleeding brakes. Those screws have a sealant on the threads that allows the screw to be opened and closed several times without letting air in the system.


Here's a source:
https://www.ecstuning.com/b-speed-b...erm=4579809528057783&utm_content=All Products

 

Not a suction bleeder. This one is pressure. It sits on top of the master cylinder and pushes fluid through the system. If there was a leak I'd think it would manifest itself in a fluid leak, not an introduction of air.

I didn't bench bleed the calipers. I don't even know how to do that. I've bench bled master cylinders before, but I don't know how I'd push the pistons around in the caliper.

 

Don't over think this.

If all of the air is out of the system, you're done.

 

*sigh* After driving it to work I'm second guessing myself. Maybe there's air in there. Dammit. I'm going to have to get someone else to drive it and see what they think.

 

If in the process air got into the ABS, you have a more complex issue.

Try some hard stops in an open paved area and see if ABS works, or attempts to. Then re-bleed brakes in the traditional way.

If there is air in the ABS, and you can't get it to self clear via field activation (not easy) you may have to resort to a TechStream process, which works the servos in intervals to keep them from burning up.

 

The brake lines were open for a couple of hours (NAPA didn't have the parts and I had to wait for them to arrive). How likely is it that there's air in the ABS system?

What is a TechStream process?

 

Did the master drain? Then there is likely air. The actual process of installing a new master is normally what creates an ABS problem, having an empty one is about the same thing.

TechStream is Toyota's proprietary software. They use it as part of the process when bleeding brakes to cycle the ABS.

So. If you can't resolve the issue, you'll either have to get a cracked copy of TechStream and try it yourself, or pay the dealer to bleed your brakes.

It's quite unlikely independent shops will actually have TechStream in house.

 

The master never drained. It stayed above half full. If it's unlikely to get air in the abs from bubbles coming from the wheel wells then I'm probably ok. I think I've got my head too far in this. Sure would like to know where those bubbles are coming from, though.

 

I use a Motive to bleed all our vehicles. Never have any issue and it makes the job an easy one man operation. Sometimes I do continue to get little bubbles...I mean very small. Its air from the bleeder valves not the system and since you are pushing from the master cylinder they affect nothing. I just run until I have clean clear fluid and tighten it off. If your brakes function fine and you have no ABS issues you are overthinking it. If you have ABS issues you will have to have the dealership complete the bleed by cycling the ABS modules. That is unlikely though.

 

I've never used a pressure bleeder, only vacuum. But i know that one of the things that can give you false reading is air coming in and bubbling from around the bleed screw threads. If you put a bunch of grease around the bleed screw it should prevent air from coming through and give you a better reading.

 

I bled them again this evening. It turns out that it was my bleeder hose. If I use the same hose I used on Sunday I get bubbles. If I use a different one it's clear. It baffles me how a pressure bleeder leak can produce bubbles instead of a fluid leak.

 

Awesome! Nothing like peace of mind that everything is good

 

@EatSleepTacos