Bleeding brakes - nothing but bubbles in the rear

[Tom Powell]

Unedited dialogue for the "I want to buy a van" bay window cartoon character.

Hey, I'm underneath my car, can you help me bleed the brakes please. Sure, what do you want me to do? I have a flare nut wrench on the bleeder nipple, a clear vinyl tube on the nipple going into a glass jar. I want you to push down slowly on the brake pedal when I tell you, tell me when you're half way down and stop pushing when I tell you. OK I can do that, what else? There's an open can of brake fluid on the floor. Pour some in the reservoir when it gets halfway down, don't let the reservoir get empty and don't spill the fluid, don't get it on painted surfaces or your skin. OK I'm ready. Yeah, start pushing down on the pedal. OK I did that and it went down a bit but feels mushy. Yeah that's OK. I'm going to crack the bleeder a bit now. Hey the pedal started going down. It's almost halfway. OK just keep pushing gently while I close the bleeder. Hey, it stopped again. Yeah, that's OK check the reservoir. It's down a bit but still more than half full. Excellent we're going to do the same thing again and Ill keep closing the bleeder while you're still pushing. That was easy but the reservoir needs filling, Good we'll do the same thing when you get it filled. It's full and I'm pushing. I opened the bleeder and started to see some fluid in the vinyl tubing and a few bubbles. Keep pushing and I'll close the bleeder when you get halfway down. Let me know. OK Check the reservoir again. It looks nearly full. OK one or two more times of this. We hope to see clear, clean fluid without bubbles and get a firm pedal and a full reservoir. You said the fluid in the tube was clean and without bubbles when you last closed the bleeder., but the pedal still feels a bit mushy. That's because we only did one wheel. This is a Chevy and we did the right rear first because it is furthest from the master cylinder. We'll do the left rear now. When we do the VW we'll do them in a different order. Don't know why but that's what the Bentley says. What's a Bentley? That's the big green book that you used to sit on when you started eating at the dinner table. Awesome, I'll bet we saved some money by doing this ourselves and not buying fancy tools. Yes son.


Aloha
tp

[Merian]

Bubble, Bubble
Toil and Trouble
Brakes Smoke and Rotor Rubble
Round about the wheel hub go
In the poison'd disc pads throw
Crash into the Fog and Filthy Air

[Syncroweekender]

Thanks for all the replies. I rounded up an assistant and did some of the old fashioned brake bleeding. No bubbles out of any brake, the pedal is nice and firm, and I double checked the brake lines from front to back and I found no leaks.

This is the first time I've used a pressure bleeder, always done it with a helper pushing the brakes . I wouldn't have guessed that the bleeder screw threads could introduce air while the brake line is under pressure. Since the front brakes didn't bubble but both the rears did, I was worried that there was something unique about the rear brake circuit that I was missing.

I figure if the pedal is still firm, reservoir is still full and no drips by the time I get the rest of the van put back together, I'll be ready for a test drive.

[IdahoDoug]

Tom,

That was a great share about your son and you if I read it right. Bravo.
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Tom Powell]

[Abscate]

Adding to Toms dialogue...

"You silly fool. Why don't you just pay the dealer to do this?"

......then I have nothing to write on the Internet....

My long suffering partner has many brake bleed assistant jobs on her resume, but using the right tension on the bleeder, and a big loop of PVC tubing to keep air out of the system, one can bleed brakes single handed without a pressure bleeder.

I have observed air leaking into the bleed tube from the threads many times.
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.ssS!

[djkeev]

[nocreditnodebt]

My last brake bleed, not on a VW, had this issue. I went through a quart of fluid but the micro bubbles kept exiting the rear drums, and then the master cylinder went dry as my assistant agreed only to press the brake pedal, not refill the reservoir.

Then the curses flew, and some tools reached low earth orbit.

After re bench bleeding the MC, I kept getting the micro bubbles out the rear. I had done these brakes before with no bubbles, but this time micro bubbles every time. Eventually I thought air was being sucked in past the threads as the fluid was pushed past, and wrapped the bleeders exposed threads with ptfe tape and it was reduced so much, that I knew it was the source of the micro bubbles, and ended the bleeding then and there.

Brakes never felt better.