Brake Booster


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By oldgasser - 11 Years Ago
Can someone shed so light on the brake situation that I have.I installed a re built power booster from Mac's last fall in my 55 Ford with totally new brake system throughout the car I had great brakes last fall being the car sat until today when I started it & discovered I had no brakes so I checked the Master cylinder & it was dry ( of the Dot 5 silicone fluid) so I inturn checked for leaks & found none. I was bleeding the power brake Booster & seen that the fluid was coming out the booster screen area< do you think it is the booster or the MC bleeding into the booster or what?? I did phone the teck guy at Mac's & he said the Dot 5 silicone was the problem just switch back. I'm am hesident on this for I have two other 55/57 Fords that has P/booster with no problems.
Need your input please.
Old Gasser email address ronandjen@xplornet.com
By lyonroad - 11 Years Ago
You might want to research the swapping of brake fluids. I seem to recall that silicone and conventional brake fluid (DOT 3) don't like each other. Contaminating one with the other can cause a real gummy mess. I could be wrong but it wouldn't hurt to check.
By Ted - 11 Years Ago

Mark is right in that the incompatibility between between Dot 5 and the other brake fluids prevents switching without thoroughly flushing the whole system. The credibility of the guy at Mac’s just dropped several notches in saying to simply switch out the fluids without mentioning a system flush. I use the Dot 5 Silicone based brake fluids in all my race cars and in some of my street drivers including my ’55 Ford without issue. The ’55 has had the Dot 5 fluid in it since 1990 and it was nice to tear into the wheel cylinders a couple of years ago and not find that prerequisite‘mud’ in them that is common when using Dot 3 & 4 fluids. Just my personal opinion but as far as I’m concerned, Dot 5 brake fluid being non-hydroscopic makes it far superior to the other fluids and especially in a drum brake application. I am aware of some the foaming or air issues associated with the Dot 5 fluids when used in anti-lock brake systems but for my vintage cars and race cars, that’s not an issue.
By lyonroad - 11 Years Ago
Ted, its good to learn that you have not had any problems with the DOT 5 brake fluid. Years ago when I was installing a new braking system on my 56 Merc pickup I considered DOT 5 but read some reports about performance issues. Ultimately, after considerable dithering, I went with DOT 3 and have been dealing with the mess it makes when there is a leak or spill ,especially when you have an under the floor master cylinder. Just this spring when I put the truck back on the road there was a puddle of brake fluid in the bottom of the rear wheel dolly. The left rear wheel cylinder had failed and there was dissolved paint and rust all over the backing plate, brake drum and running down the brake line and all over the rear axle housing. It would be nice to use something that works and doesn't destroy paint,or cause metal to rust. Perhaps I will try DOT5 on the car.
Thanks
By oldgasser - 11 Years Ago
Thank you fellows for your comments & opinions much appreciated. I have been trying to touch base with the company that re-builds these units for the 55/56 Ford ( power brake) boosters but no luck.Would anyone know of a company that re-builds these units?
Thank you for your time.
Cheers Old Gasser.
(Ron)
By paul2748 - 11 Years Ago
One place to loook is in Hemmings under "Services Offered".

It's not the dot 5 fluid. I use this in two cars, one a 56 Bird (power brakes)and did not have the problem you have. The internal seal in the booster has failed. It seems to me Mac's should replace it.