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I changed out my rubber brake lines for new braided stainless ones on the Triumph GT6 yesterday, so today it was time to bleed them.

I spent about 30 minutes by the passenger rear wheel, pumping the mightyvac like crazy to keep suction in it, and getting nothing but a long stream of bubbles that never improved. I finally gave up and moved over to the other rear wheel, with the same results. This is pretty much what happened last time, where it finally ended up good enough to get it to a shop and pay someone about $100 to bleed the brakes with a pressure bleeder. Wasn't looking forward to that again, but I knew I at least had to finish the 4 wheels to get some sort of brake fluid back in there before I could even consider getting it down and over to the garage.

Forearms hurting from pumping, I took a break, and pulled up Google on my phone and searched "How to bleed brakes with a mightyvac" and got this video:http://www.youtube.com/watch?v=KTY2iBkFeV0

So I'm watching, and he gets to the part about taking the bleeder valve out and putting 4 loops of teflon tape on it and putting it back in, and I'm thinking "Okay, that's probably overengineering, it can't make that much difference, you're just going to be wasting brake fluid while you put the teflon tape on". So I went back to the passenger front wheel, pumped up the mightyvac and cracked the bleed nipple, and same story, bubbles like crazy and no signs of improvement. So I thought "Well, heck, I'll try it, and if the guys at the brake shop laugh that I have teflon tape on my brake nipples, so be it." Stuck a cup under the caliper and pulled the nipple out, wrapped it around 4 times with teflon tape, and threaded it back in. Topped up the master cylinder again, hooked the mightyvac back up and pumped it up to 20 again. Cracked the nipple and a solid wall of clean fluid came through, with just a few microscopic bubbles (which he explained are usually just from sucking air up the threads.)
More telling, now, from the initial pump up to -20, it only got to -15 before I had to top up the master cylinder. Before I would pump to -20, crack the nipple open and run it down to -5 about 7 times before I had to top up. (I counted, because I'm doing this in the garage and it's a pain to get out from between the wall and the car to check the fluid level, but I didn't want to run it dry either.)
After another 2 top ups, I was satisfied I had a totally negligible amount of air in the lines. This is probably the 10th time I've bled brakes on a car and the first time I can really, honestly say that I feel good that I'm sure I got it all, and it took about 5 minutes to do the corner, vs 30 minutes of flailing to no effect.
Re-did the other wheels, with the same result, every time. I went ahead and ran through the rest of the brake fluid on the rear wheels since it goes bad storing it, just to be sure that I got it all, but it was pretty obviously perfectly fine long before I wrapped up.
A quarter's worth of teflon tape, and a minute to pull the nipple and wrap it, to save $100, (or a life, potentially, from dodgy brakes). I'm definitely a believer now.

I also found that bleeding brakes with a Mighty Vac was a PITA. I found what I think is a better and faster way

I discovered Speed Bleeders while fighting the brakes on my Ford Power Stroke F250.

Speed Bleeders are bleed screws that have a check valve in them and also have a coating on the threads to prevent the air intrusion passed the threads.

You slip a piece of tubing over the nipple, into a container, open the bleeder a quarter turn and pump the peddle. It's quick and clean and works.

You can find them by googleing "speed bleeder" or on E-bay the same way. About $7.00 each. Cheap at twice the price, I have them in every vehicle I work on.

John

I have had good results with the various vacuum type bleeders ( my own use a airline so no hand pumping needed). The key prior to even using a vacuum bleeder is to pull the cap on the master cylinder first and crack open the bleeder on the cylinder or caliper that you wish to bleed and let it gravity bleed for a good while. Then close the bleeder top off the fluid. Then attach the vacuum bleeder and just ever so slightly crack the bleeder.

Thanks
James

.If the MC does NOT have a plastic reservoir then obtain a spare cap that will fit the master cylinder. Drill spare cap for common wheel air valve. Use compressed air WITH AN AIR REGULATOR to pressureize the MC and bleed the brakes.

I have yet to find ANY suitable application (bleeding, automotive related or otherwise) for a vacuum pump that is NOT a POWER driven vacuum pump.

A Mityvac is a very useful tool. One among many uses in conjunction with a timing light is to perform a somewhat quantitative (not as precise as a Sun machine) check on the calibration of the distributor vacuum advance unit.

I've used the speed bleeders, pressure bleeders, and vacuum bleeding. I like the pressure bleeder best.

For vacuum bleeding I took old nipples and punched holes in them, bled them using vacuum, and reinstalled the original. I have an assortment of those special bleeders both SAE and Metric.

When using vacuum I only draw around 5 inhg because air can be pulled around the wheel cylinder cups.

However, all of this fancy stuff is not really necessary when the system has a residual check valve. That valve prevents air from entering the system when the brake pedal is released.

Sometimes an air bubble can only be taken care of using pressure bleeding or purge bleeding.

And of course today's cars with stupid government mandated junk ABS brakes are a whole different problem.