master cylinder

[phils]

I am installing in a new 39-48 ford master cylinder. Should I bench bleed this first before bolting it in?
I only ask because I remember reading somewhere, if it sits level in the car (which it does), bench bleeding the MC is not required...

Also, is DOT 5 fluid the way to go? Seems like I eat up wheel cylinders way too quickly ........

 

[Mitch496]

I allways bench bleed just to be safe.I know there are probably different opinions but ive heard on some vehicles you dont get the full stroke of the master cylinder when its in the car so you would never be able to get all the air out unless you bench bleed

 

[donsrods]

I've been pretty lucky, I'm too lazy to prebleed them but still seem to get all the air out just doing it when installed on the car. As for Dot 5, it is all we run. Main reason is because it doesn't hurt your nicely painted stuff when it drips on it, and a secondary benefit seems to be it is kinder on brake components like wheel cylinders.

On the 27 I am rebuilding, I did the brake system about 20 years ago using what was then called silicone brake fluid, now called DOT 5. I just broke the brake line loose on the rear housing a week or so ago and nice clean fluid came out and the wheel cylinders are still usable, although I am replacing them for safety reasons. The cool part is, in that 20 years I never changed or bled the system one time except for the very first time.

I hear some people say you get spongy pedal and stuff like that with DOT 5, and to that I stick out my tongue............my brakes feel just like normal ones. If you have ever seen what regular brake fluid does to a nicely painted firewall or frame you can understand why I don't use it.

Don

 

[Lightning]

Dot - 5 is the way to go - Just remember not to mix it with 3 - then you will get a spongy peddle !! Dot 3 + Dot 5 = GOO - that's GOO not GOOD

 

[phils]

cleaning out DOT 3

I was in Napa this morning picking up some new crush washers and the guy at the counter was saying I should flush out the system with alcohol first, to fully clean out the DOT-3, before putting in the DOT-5. I am replacing ALL the wheel cylinders too as well as the MC. I just blew out the lines with compressed air. Would you think this would suffice for a cleaning the brake lines? I guess I could pump a little alcohol into the lines and give 'em another shot of compressed air.

 

[Lightning]

I would pump a little alcohol through it just to be safe. 3 & 5 are like water and oil, they don't mix very well and could affect the hydraulics of your brakes.