Bench Bleeding you M/C

[rflud]

Here's an old post I ran across and I would like to get some more info -<br><br>http://classicbroncos.com/forums/index.php?board=5;action=display;threadid=4343;start=0<br><br>If you plug the brake line hold in the M/C and bench bleed it as mentioned in the thread above, how do you connect the brake lines with out fluid getting everywhere?<br><br>My first thought would be the fluid doesn't just ooze out of the M/C. You have to "force" it out by pressing the brake pedal (or using something to pump the piston). Am I thinking correctly here? <br><br>TIA

 

[Allen_69]

You're correct, in addition you have to think of the brake system as a closed system If air can't enter the system fluid can't leak out

 

[lars]

[quote author=rflud link=board=5;threadid=12253;start=0#90841 date=1039721439]<br>Here's an old post I ran across and I would like to get some more info -<br><br>http://classicbroncos.com/forums/index.php?board=5;action=display;threadid=4343;start=0<br><br>If you plug the brake line hold in the M/C and bench bleed it as mentioned in the thread above, how do you connect the brake lines with out fluid getting everywhere?<br><br>My first thought would be the fluid doesn't just ooze out of the M/C. You have to "force" it out by pressing the brake pedal (or using something to pump the piston). Am I thinking correctly here? <br><br>TIA<br>[/quote]<br><br>Well, I hate brake fluid and it knows it. The stuff will defy gravity to get on me. But generally when I bench bleed the master cylinder it stays put. I've got some of the plastic caps that are usually in the ports of new/rebuilt master cylinders. I put those in loosely while bench bleeding so fluid doesn't squirt everywhere, then leave them in until I hook the lines up. But even without the plugs not much comes out. I generally lose a little when hooking up the lines but it's taken care of when I bleed the system later.<br><br>HTH,<br><br>Lars

 

[Waverous]

What I have done is use some old brake lines and attach them to the MC and bend them back up into the MC so as to ensure air doesn't reenter thru the port. This also keeps the brake fluid back in the MC

 

[lars]

[quote author=Waverous link=board=5;threadid=12253;start=0#90909 date=1039732871]<br>What I have done is use some old brake lines and attach them to the MC and bend them back up into the MC so as to ensure air doesn't reenter thru the port. This also keeps the brake fluid back in the MC<br>[/quote]<br><br>It would still find a way to spray all over me though...

 

[rflud]

So the "bench" part of the term is not to be taken literally. I mean, you could actually install everything and not hoop up the lines, pop the M/C lid off and pump the brake pedal until you don't have any more bubbles. Right?<br>

 

[lars]

[quote author=rflud link=board=5;threadid=12253;start=0#90955 date=1039740751]<br>So the "bench" part of the term is not to be taken literally. I mean, you could actually install everything and not hoop up the lines, pop the M/C lid off and pump the brake pedal until you don't have any more bubbles. Right?<br><br>[/quote]<br><br>I haven't done it but I know others have. I've found that I always have to "finesse" the piston to get the last bit of air out. That might be tricky with it mounted on the truck. Or not...

 

[brokenhorse]

Do it on the truck it works great!!!!

 

[rflud]

Well, the M/C and PB booster are mounted in the truck along with the pedal assembly. Now all I need to do it put some fluid in and start pressing the pedal.<br><br>Thanks for all the good info.

 

[Waverous]

The important part of bench bleeding is to hyper press the plunger past the extent the plunger rod will. This ensures that there will not be any residual air in the piston/plunger. The best way to accomplish this is to secure the MC in a vise and press the plunger in as far as it will go with a big screw driver.

 

[jr]

Like Waverous said. You can use your new lines and bend them back to the reservoir. Then hook up your lines to the proportion valve and open up the bleeder screws and gravity bleed it for a few minutes. Then close them all up and ask a beer budy to help you bleed starting with the farthest wheel. Your beer budy should be in good shape or will quit on you after your first bleed.

 

[BwoncoHowie]

Re: bench bleeding master cylinders without squirting brake fluid all over the place.<br>There is no clean way of doing this unless you do what I did after making countless messes. I went to the boneyard and cut some master cyl brake tubing off a junker that uses the same size fitting. Take the fitting (inverted flare nut and the flared tubing with about 10")<br>when you get the tubes with the fittings home, clean them and hook them up to the master cyl that you are bench bleeding. Then bend the tubes so that they point back into the resesvoir. you can now bleed the MC without losing the brake fluid. After the MC has been bench bled, with the lines still connected, put the reservior cover in place and bolt it up to the vehicle. you can then disconnect your bleeder tools and connect the vehicle's brake lines to it...<br><br>BH

 

[Explore74]

there is no magic way not to make a mess, but to save time, try bleeding the brakes where the lines connect to the master cyl. just take it slow. like, pump twice, and bleed. this way you wont have to chase bubbles through the brake warning switch, and all 4 cylinders.