New and Restored Boosters

A brake booster gets all the air sucked out of it by the running engine. When you apply the brake pedal, a valve in the booster allows air at atmospheric pressure back into ONE side of the big chamber. The unequal air pressure moves a diaphragm and pushrod inside the chamber. This adds to your foot pressure on the brake pedal, and you stop with less effort.

There are essentially only two types: HYDROVACS and MASTERVACS (see images above)

We need some history here. Hydrovacs were the early type of brake booster, like the PBR VH44, that were fitted as original or aftermarket around 1954 on some cars of that period. They were plumbed into the brake line immediately after the master cylinder, effectively boosting the pressure to all four wheels.

Sadly, these early hydrovacs are very complicated in that they combine several vacuum and hydraulic valves and cylinders which, over the years, have aged, are worn and corroded.

Proper restoration involves machining the body and fitting special stainless or bronze sleeves in the damaged bores. Check the left and middle photos above.

Now check the right-side photo above. You will see a Mastervac is a much simpler unit. This is because it is a stand-alone unit, it bolts to the master cylinder, and is NOT a part of the hydraulic system.

Bottom line, HYDROVACS cost more to restore to good working order. They are older and more delicate. Their hydraulic cylinders are almost always corroded and require precision sleeving.

Yes we are. This includes Mastervacs, Hydrovacs, Treadlevacs and remote boosters. Power Brakes been in the brake business since 1956 and we have seen them all.

Here's a list of the makes you may find: Aisin; ATE; Bendix; Clayton Dewandre; Delco; Girling; Girlock; JKC; Knorr; Lockheed; Midlands and PBR just to name a few.

We can restore most boosters, even some sealed units that come crimped together and which were never intended to be serviced. Power Brakes keeps a comprehensive range of brake booster parts that are sourced worldwide to ensure the overhauling of as many boosters as possible.

This includes boosters for American vehicles such as Cadillacs, GMs, Mustangs and Galaxies; English vehicles including Jaguar, Aston Martin and Bristol; and European vehicles like BMW, Alfa Romeo and Mercedes.

Yes they are all tested on a dedicated test rig for output, vacuum and hydraulic performance.

If your booster is a Mastervac, we can quote with confidence.

If it’s an older Hydrovac, we can give you a worst-case scenario, with a promise to do only that which is necessary for a guaranteed job. Just putting a repair kit in one of these units with worn, corroded or oversize bores is futile.

So the cost is ultimately determined by the number of cylinders bores that need to be sleeved, which is only apparent upon inspection.

In most cases we can, but for everybody's safety we prefer not to

The four main reasons are:      

1. Some boosters or power brakes were designed as a sealed unit, never to come apart. Special tools and equipment are needed to dismantle them.  
2. New seals will fail prematurely if fitted to corroded or scored slave and control cylinders in need of sleeving.   
3. Kits only cover major components. You may not recognise other critical worn, damaged or missing parts.      
4. Your best efforts may be in vain if you can't test the unit for vacuum and hydraulic leaks, and overall performance, before refitting to your vehicle. For these reasons, we suggest you send your unit to us for a professional tested outcome.

Here's a simple test. With the motor not running apply the brakes 5 times and wait one minute. Then apply the brakes as normal holding your foot on the pedal. Now start the engine.If the booster is working properly, the brake pedal will sink a little as the booster applies extra pressure. Now turn the engine off. Your brake pedal should stay down. If your pedal slowly comes back, you have a vacuum leak.

• Fault 1...Ruptured Diaphragms in both Hydrovacs and Mastervacs.
  Result...Engine will idle faster and may stop when applying the brakes.
  
  
• Fault 2...Seal failure in Hydrovacs only, causing an internal fluid leak. Result...Fluid will be sucked out of the booster and into the motor and will burn and cause eventual brake failure once the master cylinder is empty of brake fluid
  
  
• Fault 3...Reduction, or loss, of vacuum supply in both Hydrovacs and Mastervacs. Result...The reduction or loss of vacuum supply will result in a hard pedal and poor braking.      
  

To test, remove the vacuum hose from the booster and start the engine.
A vacuum gauge should read 20Hg on the overrun. Just putting a finger over the hose end is not conclusive. Depending on age and condition, the hose may be heat and fuel affected and could collapse when the air gets sucked out of it.
If you have any doubts, replace the vacuum hose and examine the external check valve. You should be able to suck air in through the valve, but not out. 

Power Brakes' facilities and collective experience are available to identify and correct all these problems.

Yes we do...for more information visit the Your Guarantee page for details.