Can I pressure bleed using vent line?

autobonrun · autobonrun's Garage

I'm right in the middle of a rebuild and have gone through the posts on bleeding brakes. Many talk about modifying the reservoir cap to accept a pressure hose.

Can I pressure bleed the system using the overflow vent line? This seems too simple so I'm assuming there's a reason for not doing it.

pwd72s · 12-12-2001, 04:57 PM

Great thought. Why naught? The overflow vent line is made of pretty low pressure capable material. But if you stay under that unknown pressure, what not? Heck, I think gravity alone would do the job..if you gave it the time needed.

tbitz · 12-12-2001, 04:59 PM

I've done it many times. Works great. Check the following post for a picture of my setup.

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=52616

autobonrun · autobonrun's Garage

Thanks for the info and link. I'm off to the hardware store to buy some hose and something to pressure up the system.

pwd72s · 12-12-2001, 05:07 PM

Tony...you got it! Also, if the vent hose line was high enough, don't you think ambient air pressue and gravity would do the job? I mean, as long as somebody was patient enough? After all, fluids do run downhill....

SK · 12-12-2001, 05:14 PM

GP - I was just going to search for the post that tbitz just reposted. Looks like you got me thinking today....

wckrause · wckrause's Garage

I used a pressure bleader, but only pumped it up a little bit, maybe just 10 - 12 psi. Sort of a combination of the gravity and pressure method. The fluid moved through the system a bit faster, but slow enough that I could keep on eye on the caliper that was being bled, and the brake fluid level at the same time.

Using the vent line would work great for that low pressure method.