Classic/Antique Car Repair: Power Brake Booster - Test?, power brake booster, vacuum hose

Question
Hello,
I have a 1970 Dodge that I am saving in storage. This year, I noticed the Master Cylinder had started leaking down the front of the power brake booster - which sits behind it.  I had the Master Cylinder replaced and now the leak is gone.

But, now I am not sure if my Power Brake Booster is still ok. I had heard that sometimes the brake fluid enters this unit and destroys it.  My brakes still work - but I seem to recall better stopping power.  

Are there ways to test the power booster to see if it needs to be rebuilt/replaced?

Thanks very much!

Answer
The little bit of brake fluid that got into the front of the booster isn't likely to have caused any damage.

There is a way to test the booster, though.  Find a place to test drive the car where you have a lot of room in case the brakes don't work too well.  When you get there, do a test stop from about 30 MPH with the booster hooked up, then unplug the vacuum hose that goes to the side of the booster from the intake manifold, and plug that hose so the engine isn't aware that you have disconnected it. Be careful taking the hose off the booster, those fittings are delicate!  

Now repeat the stop test.  The difference in pedal force that you experience tells you what the booster is doing for you.

Also, if you hear a "hissing" noise from the booster when you step on the brakes (with it hooked up again), that is a warning that it is leaking and should be replaced.

The booster is readily available from NAPA stores and other parts places - but usually it is cheaper to buy the complete master cylinder and booster as a unit, and also less work!

Dick