Bench Bleeding Mess
 

Bench bled my master cylinder, but when I remove the temporary tubes to attach the hard lines to my combination valve, all the brake fluid flows out the ports all over everything. I can't possibly get both ends of the brake lines tightened in time to prevent a big mess. Any suggestions?

I have a setup like this:

Re: Bench Bleeding Mess
 

are you putting the cap on the master cylinder reservoir? having the cap on makes the leakage slower, it doesnt stop it.

if the cap is on and you have the ports blocked (it came with port blocking plastic caps right?) you dont have to get the lines on without losing any fluid, you just have to get the lines on before the reservoir loses ALL the fluid. so a rag will help.

Re: Bench Bleeding Mess
 

Just capping the fitting holes off with the little plastic caps the new master came with seems to work for me.

Brian

Re: Bench Bleeding Mess
 

i do it the way joedoh suggested.....put the lid on and the seal will hold fluid in giving you time to hook up lines before it drains dry....

Re: Bench Bleeding Mess
 

You are right, sorry I thought putting the lid on was a given. I do that as well but put the little plastic cap plugs that come with the master cyl in the holes too.

Brian

Re: Bench Bleeding Mess
 

You can see that to connect the lines, I have two ends to screw in on each port. By the time I get both ends attached and tightened, I've lost virtually everything in the reservoir and now introduced a bunch more air in the system.

Is the any way to connect everything and THEN bleed the MC? Would a Mity-vac unit bleed the entire system including MC?

Re: Bench Bleeding Mess
 

you may have a problem with the check valves in your master cylinder, with the cap on and the port open (no plug. hose or line installed) it leaks very slowly on the ones I have done. I have plenty of time to remove the hose fittings, install the plastic plugs, check the level, add if necessary, take it to the truck, install it, remove the plastic plugs one at a time, install the brake lines one at a time, check the level again. if your lines are hard to line up, install the lines before installing the master. dual circuit systems usually have a dam in the reservoir so one side going down doesnt totally affect the other.


bench bleeding saves time over normal bleeding but if you have a vacuum bleeder you wont need to bench bleed. sometimes with a new master I will gravity bleed the fronts (just leave the bleeders open with a hose to a pan) and vacuum bleed the rears, which can be a giant pain anyway with an empty system. on this last one I did the bleeder hose to a bottle of brake fluid and pump the brakes trick, no amount of vacuum was pulling that fluid from the master.

Re: Bench Bleeding Mess
 

Yes, there is. Bench bleeding is a time and labor saver. You can bleed the master on the vehicle. It works best with a pressure bleeder attached but it can be done without. The difference is that you will usually have to spend more time. When I have to bleed a master that has been completely emptied I pump the ever living snot outta the pedal using a bunch of short and quick pedal presses letting the pedal come all the way back each time. On the final press hold the pedal down as always and open a bleeder.

The challenge to doing this comes when you have a system with an isolation valve that locks out 1/2 of the brakes if there's a pressure mismatch. Getting the valve to unlock sometimes means waiting overnight for pressure to equalize.

FWIW I never seem to have good luck vacuum bleeding.

Re: Bench Bleeding Mess
 

Bolt master cylinder in place ,make up two short lines install on master put other end in master (where you fill it ) fill with fluid and keep the two lines in fluid at all times. Pump the pedal keep pumping 5 or six times ,then check fluid ,fill if needed . Pump again until all air is gone , Now put your lines on and bleed system. Done one line at a time .:devil:

Re: Bench Bleeding Mess
 

X2. I think cpp even has a small kit like this that comes with their master cylinders.

Re: Bench Bleeding Mess
 

Get a bench bleeding.kit, they are cheap and you will have almost no spillage. Take the fittings off the mc and screw in the adapters and stick the other end of the hoses back in the fluid and stroke away. It makes the job very easy...

Re: Bench Bleeding Mess
 

I did not have the lid tightened down with the bales, so maybe that will slow the outflow while I attach my hard lines. I'll try again and let you know.

Re: Bench Bleeding Mess
 

Follow up:

I re-bled my MC on the car and this time secured the lid by snapping down the bales while I removed the bench bleed tubes and attached the permanent hard lines, as recommended by astute members of this forum. Only about a teaspoon came out of each port while they were open, which was easy to contain. I had been avoiding closing the bales because they are EXTREMELY hard to snap down, but evidently just setting the lid on the top doesn't provide adequate vacuum to prevent fluid draining out. I've bench bled many systems, but never encountered this before. Evidently I'd always closed the lid before. Thanks for the suggestions gentlemen!

Now the next problem: I can't get any fluid to the rear brakes, no matter how much I pump the pedal. Why not? Would a vacuum bleeder pull it through?

Re: Bench Bleeding Mess
 

sometimes I cant get fluid to the rear no matter WHAT I do, especially on a totally empty system. what always works for me is to attach a hose to the bleeder and sink it in a bottle of brake fluid, then pump pump pump and after 4-5 pumps bam, fluid is coming out. on those trucks I NEVER get it with a vacuum bleeder, I have spent a half hour before pulling vacuum on it with no luck.

Re: Bench Bleeding Mess
 

How is your system designed? Do you have an isolation / combination valve in the system? Do you have a decent pedal even though the rear brakes will not bleed?

Re: Bench Bleeding Mess
 

Yes. Apparently I may have triggered the pressure differential valve and will have to figure out how to reset it.

Re: Bench Bleeding Mess
 

as I was reading this I was thinking proportioning valve tripped...sounds like you already know it....on some you can reset it with a small screwdriver by sticking it in the end...you can also loosen the front brake line and make it trip by pressing the brake pedal...they make a little tool you can screw in the center to keep it from moving while your bleeding once you get it recentered...

Re: Bench Bleeding Mess
 

Thanks Mongo Greg. I have built many brake systems but this is my first time using the OEM style brass block combo valves, so I didn't know about that trick. I couldn't find the tool locally so I'll order it now.

Re: Bench Bleeding Mess
 

Sometimes it's possible to trick the valve into moving with a shot of air applied to a bleeder. Sometimes letting the vehicle sit overnight is enough to cause it to move off its seat. Either way, if the valve moves the next step is to gravity bleed. Applying pedal pressure will only re-seat the valve and you will end up right back to where you started.

The tool is nice. I've never owned one.

Re: Bench Bleeding Mess
 

Evidently the valve must be spring-loaded because it did reset itself overnight. At least that's what I guess by hooking a test light to it: no light = no ground. So now I'll do what you suggested and gravity bleed to equalize fluid in the front and rear. But I'll probably also use the trick little tool. Thanks!

Re: Bench Bleeding Mess
 

Nice! Good luck.