I've installed a new master cylinder on my '78 F250 crew. The instructions say to "bench bleed" the MC before bleeding the brake lines. Is this absolutely necessary to get the brakes to be nice and firm after bleeding them? I'm not wanting to put fluid in the cylinder to "bench bleed" it (either on the bench or on the truck) for fear of loosing brake fluid out of the ports onto my nicely painted engine bay parts lol while trying to connect the brake lines. Any advice guys?

 

It is a must! I bought 2 12" pieces of line and bent them over to fit back into the cylinder reservoir. I bled mine on the truck. Much easier than trying to do it on a bench in a vise. Just push the pedal slowly to eliminate spray coming back out.

 

One way or another you need to bleed the the MC, the benifit of putting it in a vice is that you can get all of the air out of all the nooks and crannys a lot easier if the MC is completley level.
IMHO it's a whole lot easier to bleed it on the truck, but unless your planning on bleeding the entire system, which is recomended, you really need to bleed the MC one way or another.

 

The reason "they" recommend BENCH bleeding versus installing it in the vehicle and bleeding it is to keep the MC level in a vise while bleeding the air.

But, I think most people say screw that and do what Ranger showed. Works like a charm.

Josh

 

Ranger has the right idea, I just lay a rag over the top to make sure no splash gets out while pumping and bleeding.

 

The tubes you attach from the MC outlets go into a jar with brake fluid in it.

No fluid leaks anywhere.

 

Johaner, It's good that you are thinking ahead, I had some leaks on the fittings for my new extended front brake lines and by the time I found the leaks it ate right through the chassis saver on my frame. I had to do some touch up.

 

Ok, so i'll bleed the MC......I like Ranger's idea and then cover it with a rag or something. So my concern is that all the fluid (or even one little drop) will come out of the MC when I take the bleeder lines off and try to connect the actual brake lines. I just can't be touching up paint....that will just kill me to see paint get ruined and have to touch up. So will any drop come out of the ports when switching lines?

 

Yes several drops will come out when you swap lines. Get plenty of towels. Just make sure you don't press the pedal to hard when doing it my way or you will have a brake fluid mess.

 

im sure youll get decent pedal if you bleed it in the truck, however its not messy at all and you will NOT get out ALL of the air in the truck as its not level.

 

I've done it both ways numerous times and they both work.
However I got a little bleeder helper syringe (Classic Performance Products pn# CP0105) just to make sure and suck or push any air out.
If you make yourself a little bleed kit it becomes easy as pie.

 

I used clear tubing to see how much air is still in the MC.

 

Just a thought you could also use DOT 5 brake fluid which is a little more gentler to the paint.