Is bench bleeding a MC necessary if using a pressure bleeder (Motive)?

[AR67GTX]

What say you guys on this? I’ve just finished flushing my system with denatured alcohol and getting ready to install new wheel cylinders. I have a bench bleeding set up that I can out on it (MC is on the car - will have to pull the line off - stroke with pedal). It’s a 66 with a single pot MC. Just wondering if it’s really necessary with a Motive pressure bleeder?

 

[themechanic]

Yes, bench bleeding is always a good idea. That's why master cylinders come with the kit to do so and is recommended by the manufacturers.

 

[pnora]

The pressure bleeder may do the job. Myself I would fully bench bleed it first. I believe working the piston will remove all the air where the pressure method may not.

 

[AR67GTX]

Thanks

 

[1 Wild R/T]

I never bench bleed, I either bleed on vehicle with my syringe or I use a pressure bleeder....

 

[padam]

Put me in the always bench bleed camp

 

[Sixpactogo]

Put me in the always bench bleed camp

Me Too.

 

[steve340]

I also never bench bleed but I use a vacuum bleeder. Pressure bleeding should not need to bench bleed as you are "pushing" the air out.
All this assumes the master cylinder piston is in the correct position and the master is not faulty.

 

[Sixpactogo]

I don't assume anything. I just do it because that is the method I learned from the FSM. I'm sure there are a dozen methods that will get the same result even if some take a few attempts. I too use the vacuum bleeder for each wheel cylinder mostly because my wife is busy doing her own thing and I don't want to bother with finding a helper. But then again, I would not be fiddling around with a single pot master cylinder either. I have two cars that came with them but that was the first thing I scrapped. I have never had one fail but I know people that have. Few things on a car more important than brakes IMO.

 

[dadsbee]

I didn't do it and ended up doing this to get the air out of the masters nose !

 

[gkent]

Hmmm, my understanding is that "bench" bleeding doesn't necessarily mean bleeding it on a bench - it just means bleeding the master before hooking up the lines.

 

[padam]

Hmmm, my understanding is that "bench" bleeding doesn't necessarily mean bleeding it on a bench - it just means bleeding the master before hooking up the lines.

But on the bench you can really get after it. In out in out…

 

[pnora]

But on the bench you can really get after it. In out in out…

Plus on the bench you can be sure the piston has traveled to its full direction both ways. Air seems to find its way to be trapped at times. A proper bench bleed eliminates all air.

 

[dadsbee]

Plus on the bench you can be sure the piston has traveled to its full direction both ways. Air seems to find its way to be trapped at times. A proper bench bleed eliminates all air.

Like I showed above. Air wouldn't come out of the masters "nose" for me.Had one good bubble trapped and I had to raise the rear end to get it out..

 

[fesser]

I didn't do it and ended up doing this to get the air out of the masters nose !
View attachment 1814940View attachment 1814942

Is that fluid blueish?

 

[dadsbee]

Is that fluid blueish?

Dot 5, it's a Blueish Purple

 

[AR67GTX]

I’m changing to DOT5 (had enough paint damage to last me) but needed to flush everything out with denatured alcohol so I put the new MC in without bleeding and used my pressure bleeder to run a bunch of alcohol thru the lines to clean them out and pulling the MC back out again is not in the cards except as a very, very last measure.

Once I get the wheel cylinders replaced I’ll bleed the MC on the car with DOT5 and then try to bleed the system. It’s been a toss up as to using my pressure bleeder or install speed bleeders and bleed the system with them. Probably use the speed bleeders as they have worked really well on my other cars. One thing I have working for me is the single bowl MC is usually easier to bleed than a dual bowl MC.

Thanks for all the replies.

 

[gkent]

How do you tell if you have a bubble ... spongy pedal ??

 

[dadsbee]

How do you tell if you have a bubble ... spongy pedal ??

Pretty much, that and it BURPED when it came out! LOL