1998 Plymouth Voyager brake-booster

Tiny
FASTEDDIEV12
  • MEMBER
  • 1998 PLYMOUTH VOYAGER
  • 3.3L
  • V6
  • 170,000 MILES
Please tell me if it is safe to replace the hose connected to the brake booster above the mastercylander, on a '98 Voyager 3.3L
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Friday, August 15th, 2014 AT 7:10 PM

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Tiny
CARADIODOC
  • EXPERT
It would be unsafe to not replace it if it is leaking or dry-rotted. If it leaks bad enough, you'll lose the power assist for the brakes.
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Friday, August 15th, 2014 AT 7:54 PM
Tiny
FASTEDDIEV12
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I'm sorry I ment without introducing air into the brake system. Or do I need to bleed all over again.
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Friday, August 15th, 2014 AT 8:25 PM
Tiny
CARADIODOC
  • EXPERT
You're talking about the 1/2" diameter rubber hose that goes between the plastic check valve in the booster to the intake manifold, right? There's air in that hose now. With the engine off, it's open to atmospheric pressure. That hose has nothing to do with the brake fluid, and there's no need to bleed anything. Just pull the hose off and pop a new one on. Be careful with that check valve. Rough tugging can break the nipple off. If that happens, you'll find hundreds of perfectly fine replacements in any salvage yard. Failure of those is extremely rare so don't waste your money on a new valve.

The new hose can be purchased from a bulk roll at any auto parts store, and it doesn't have to be gas-resistant, but it does need to be for vacuum. Some hoses are made for pressure and will collapse and become blocked when under a vacuum. Just tell the parts people what its purpose is and they'll get you the right stuff. Here again, failure is so rare, I'd be comfortable with an original hose from a salvage yard.

On the topic of bleeding the brake hydraulic system, all brake fluid absorbs moisture from the air through the porous rubber flex hoses and the rubber bladder seal under the reservoir cap. That moisture lowers the boiling point of the fluid considerably which can lead to one form of brake fade, and that moisture contributes to corrosion of metal parts. Very few of us do this, but every manufacturer specifies the intervals at which the fluid should be flushed and replaced. As I recall, that can be as often as every two or three years. If you drive a vehicle like my rusty trusty '88 Grand Caravan in the middle of road salt country, that happens every two years anyway due to rusted steel brake lines!

All of this story assumes you're talking about the vacuum hose. If you have anti-lock brakes and the hose is the rubber high-pressure hose that goes from the pump to the accumulator, depending on the ABS system, that one can have up to 2200 pounds of pressure and you'll want the correct hose from the dealer. Before working on that system, you have to bleed off that pressure that's stored in the accumulator. To do that is real involved. You turn the ignition switch off, them pump the brake pedal a minimum of 40 times. At around 25 to 30 pumps you'll notice that a little more force is needed on the pedal. At around 40 pumps you'll feel the pedal get real hard. That's it; you're done.

When you replace anything in those systems, after adding fresh new brake fluid, you simply turn on the ignition switch. You'll hear the pump run for about 20 seconds as it builds the pressure back up in the accumulator. That pressure is used to reapply each brake during an anti-lock stop in the "block, bleed, apply" sequence that occurs about 15 times per second. That's the buzzing you feel in the pedal and hear when the system activates. That pressure is also used to provide the power assist. As the pump runs, the air will be bled out of the hose and will work its way into the reservoir.

To check the fluid level when you're done, turn the ignition switch off and again pump the pedal at least 40 times. The stored fluid in the accumulator will go into the reservoir and bring it up to the level for checking. Later the level will go down a lot when you turn on the ignition switch, but that's not the time to check it. This applies to the Bendix-10 anti-lock brake system. I have that on a '93 Dynasty and a '95 Grand Caravan. It is a REAL effective system. I can't remember if they still used that system in '98, but regardless, if you pump the pedal 40 times, there will be no danger of getting sprayed with brake fluid under high pressure. Some of the newer ABS system went back to using the standard vacuum power booster and hose. You treat those just like any other power brake system.
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Friday, August 15th, 2014 AT 9:23 PM

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