Vacuum bleeding

[SHOZ]

I have a hand vacuum pump and tried to vacuum bleed the brakes on my Accent. But all it does is suck air though the threads of the bleeder screw. It can make over 25" Hg of vacuum. I tried grease, thread sealant, oil and they all let air in.

Help me out.

 

[JMJNet]

Smaller hose connector.

 

[SHOZ]

It's not leaking at the hose. at least I don't think it is. New vacuum hose that is a tight fit and I have a clamp on it too.

 

[Dave Sherman]

I'd be very careful about using grease or oil on the threads; contaminating the brake fluid with anything petroleum based can cause the seals to swell and ruin them.

I've used a vacuum bleeder lots of times, and yes, you get some bubbles from around the threads, but you do get fluid out of it. I just relieve the vacuum and bleed by gravity to get the last of the bubbles out before closing the bleeder.

 

[cpayne5]

I've used teflon tape to seal bleeder threads when this happens.

 

[wings&wheels]

You learn to 'read' the bubbles; what is air coming past the threads vs. coming through the system. I mostly pressure bleed, but have always had some air leakage through the threads on cars I have to vac bleed.

 

[atikovi]

Using a hand vac pump to bleed brakes is a pain. If you don't have an air compressor, at least get one of those vacuum bleeders that you pump up with your arm.

 

[JamesBond]

I have the same problem with my vacuum bleeder. I've gone back to gravity bleeding with a few pumps doing the 2 person method at the end.

 

[Jethro_Bob]

A very easy thing to overlook if your in a hurry or don't do it very often is failure to remove the lid/cap from the brake fluid reservoir.

 

[Cdn17Sport6MT]

Originally Posted by cpayne5
I've used teflon tape to seal bleeder threads when this happens.

I use 2 turns of teflon tape, turned-over on itself. I get SOME bubbles, but pretty minor. Believe me, 25" of Hg of vacuum really courses the brake fluid into my Mason's jar... Also, I too remove the brake reservoir cap.

 

[Traction]

It does not matter if you get bubbles at the bleeder valve, as long as you are moving fluid, which is what it's about. Bubbles at the threads are not in the line. Although I use a OTC air-powered vac bleeder that moves fluid quickly, I always have bubbles at the bleeder valve, but all the air comes out of the lines. Yes, a tighter seal helps move the fluid quicker, but don't worry about the bubbles after you have moved at least a 1/2 pint of fluid, or whatever it takes to fill the line, and cylinder, which shouldn't take quarts of fluid to bleed. I usually just suck a quart, or about a pint on each corner, and finish with a pint on a complete bleed. I do it all by myself, with no helper needed, and it has worked many times now.

 

[Hall]

Originally Posted by wings&wheels
You learn to 'read' the bubbles; what is air coming past the threads vs. coming through the system.

This is very true. I think the Mityvac instructions even refer to this. If the bubbles are very small and consistent (number of bubbles, spacing between them, etc), it's almost certainly air coming in through the threads and can be ignored. It's when you get a large bubble or bubbles and in inconsistent patterns that you need to watch for as they will be presumed to be coming from the actual line, caliper, etc.

 

[Cdn17Sport6MT]

Originally Posted by Traction
It does not matter if you get bubbles at the bleeder valve, as long as you are moving fluid, which is what it's about. Bubbles at the threads are not in the line. ...

100%

 

[Cdn17Sport6MT]

For ea. new car I buy, I buy one additional bleedscrew... in the case of my Mazda6 - one frt bleedscrew, and one rear bleedscrew (cuz they are differnt). I tape it up with teflon tape (not on the seat, just on the threads) so I can have one such screw "at the ready", ready to replace the one I take out. This minimizes fluid leakage... and I then rotate it to very lightly seated by hand. I slip the vac. hose over the nipple, and then I release the "haemostat" (or open the valve) that admits vacuum into the hose. Then I open the bleed screw, oh, about a turn or so (only). Some air bypass goes into the bleed hose... but 'boy does the brake fluid course into the vacuum jar. I have a one quart Mason's jar on a wooden base so as to prevent said glass jar from falling over. This set up has served me for years...

 

[Kestas]

I had the same problem during vacuum bleeding, where air would get past the threads. I abandoned the idea of vacuum bleeding and relegated the vacuum system to removing the fluid in the master cylinder.

 

[Cdn17Sport6MT]

For me the vacuum method is very convenient, the least messy, requires no special adapter for the master cylinder reservoir, and most importantly does NOT require you to stroke the master cylinder. Therein lies the worst: if you stroke the Master beyond the limits it normally sees in regular braking operation - the seals, the rubbers, traverse portions of the bore of the Master that are potentially rough due to rust, dirt, etc. You very likely will have a master cylinder failure shortly thereafter. If you do not stroke the master beyond normal limits and if you change brake fluid every two years with this Vacuum method, you will get great life expectancy out of all hydraulic components.

 

[Cdn17Sport6MT]

 

[double vanos]

Air at the bleed screw is normal. Just watch to see if the master cylinder fluid is dropping. If it is, you're good to go.

 

[wtd]

My Mityvak vacuum bleeder will not pull a vacuum with the hose attached to the bleeder but it will if I put the hose to my hand. I even used a new rubber piece that goes on the bleeder with no results. I had to do the two man method this last time because I could not build up enough pressure to pull brake fluid through the hose with the vacuum pump.

I will have to figure out another way. Gravity bleed would not work on this last vehicle.

I used to get bubbles all of the time using the vacuum pump method and you learn what the bubbles look like when it's air in the line vs coming through the threads.

 

[slacktide_bitog]

Speed bleeders are awesome