I have a 1997 Caravan 3.0L.
My wife just reported that the front brakes were harder to work (as in she had to press harder on them to stop).
I got into the car and drove it for a bit and noticed that every time I place my foot on the brake pedal, there is a hissing sound coming from the brake area.
Did notice deteriorated braking for sure. Kind of seemed like power braking was not there or partially there.

Any idea what may be going on? Help will be greatly appreciated.

 

The power brake booster maybe leaking or the vacuum ck valve is leaking. Its not uncommon for the booster being the problem.

 

so do I need to replace the entire booster? Seems to me that if I hear air hissing, there must be some leak. Can you explain how the booster works and how it is integrated into the brake system? Maybe I will then be able to vision what I need to do properly.
Thanks a bunch for the help.


Kind of read what it does now from a manual.
So if I hear hissing sound coming from the end of the booster that sticks into the cabin (where the push rod from brake pedal is), is that a pretty sure sign the booster needs replacement? I still assume the vacuum hose going to the check valve is ok (since I am quite certain I would not be hearing it hissing from across the engine wall).
When I push on the pedal when engine is on, the pedal is really hard to depress and it feels like there are no power brakes for sure (car still moves under normal pressure - you have to really really push to get stopping).
When engine off, the pedal feels spongy (wont get hard after a few pushes with foot - as it normally does when you pump it a few times).
As soon as I press on the brake when engine is off, I can hear the hissing (air escaping) from the booster area nest to the push rod of brake. I can actually hear air escaping without pressing the brake as well (but then it is a small sound which you can only hear with your hear right down there by the brake - pulling on brake with hand helps to stop that minor air leak).

So with above info, booster replace time? or not?

If yes, is it hard to replace the booster? any tricks or advice on it? Do I have to air contaminate the brakes by doing this (bleeding after replace), or is it just a matter of replace of unit without having to bleed brakes after?

Thanks again.

 

You can replace just the booster, and leave the master cylinder in the van. The vacuum for the booster helps you stop the car or van, without pushing so hard down on the pedal. I will post on how to replace the booster in a short time.

 

bought the unit. Had no idea how big the part is - like a flying saucer...lol.
Now, will have to find out how to replace (pretty sure it leaks out of the rear of the unit - due to hissing sound - aka air escaping where the rod from brake pedal goes in).
Hope I get some install tips. Thanks.

 

VACUUM BOOSTER 3.0 LITER ENGINE

REMOVE

CAUTION: Stored vacuum in the vacuum booster must be pumped down (removed) before removing master cylinder from power brake booster. This is necessary to prevent the power brake booster from sucking in any contamination as the master cylinder is removed. This can be done simply by pumping the brake pedal, with the vehicle's engine not running, until a firm feeling brake pedal is achieved.

1. With engine not running, pump the brake pedal until a firm pedal is achieved (4-5 strokes)
2. Remove both battery cables from battery.
3. Remove the battery thermal guard and the battery from the battery tray.
4. Remove the air inlet resonator and hoses as an assembly from the throttle body and air cleaner housing If vehicle is equipped with speed control, unplug wiring harness connector from the speed control servo. Then disconnect vacuum lines from the speed control servo and vacuum reservoir on battery tray.
5. Remove bolt attaching the speed control servo bracket to the battery tray. Slide the bracket forward to unhook it from the battery tray and remove.
6. Remove the 2 bolts and the nut attaching the battery tray to the body of the vehicle.
7. Remove wiring harness connector from brake fluid level sensor in master cylinder fluid reservoir
8. Clean the area where the master cylinder assembly attaches to the power brake booster. Use only a solvent such as Mopar Brake Parts Cleaner or an equivalent.
9. Remove clip attaching drain hose to brake tube at master cylinder. Remove drain hose from wiper module. Remove the 2 nuts attaching the master cylinder assembly to the power brake vacuum booster NOTE: It is not necessary to remove the brake tubes from the master cylinder when removing the master cylinder from the power brake vacuum booster.
10. Remove the master cylinder and the brake tubes as an assembly from power brake vacuum booster. When master cylinder is removed, lay it out of the way on top of the left motor mount
11. Disconnect vacuum hose from check valve located on power brake vacuum booster. DO NOT REMOVE CHECK VALVE FROM POWER BRAKE BOOSTER.
12. Locate the power brake vacuum booster input rod to brake pedal attachment under instrument panel. Position a small screwdriver between the center tang on the power brake booster input rod to brake pedal pin retaining clip
13. Rotate screwdriver enough to allow retaining clip center tang to pass over end of brake pedal pin. Then pull retaining clip off brake pedal pin. Discard retaining clip. It is not to be reused. Replace only with a new retaining clip when assembled.
14. Remove the 4 nuts attaching the vacuum booster to the dash panel. Nuts are accessible from under dash panel in area of the steering column and pedal bracket assembly.
15. From outside the vehicle, slide power brake vacuum booster forward until its mounting studs clear dash panel. Then tilt the booster up and toward the center of vehicle to remove CAUTION: Do not attempt to disassemble the power brake vacuum booster it is to be serviced ONLY as a complete assembly.

INSTALL

CAUTION: When installing the power brake vacuum booster in the vehicle be sure the heater hoses do not become trapped between the booster and the dash panel of the vehicle.

1. Position power brake booster onto dash panel using the reverse procedure for its removal.
2. Install the 4 power brake vacuum booster mounting nuts. Tighten the 4 mounting nuts to a torque of 29 N·m (250 in. lbs.)
3. Using lubriplate, or an equivalent, coat the surface of the brake pedal pin where it contacts the brake vacuum booster input rod CAUTION: When installing the brake pedal pin on the power brake vacuum booster input rod, do not re-use the old retaining clip.
4. Connect power brake vacuum booster input rod on the brake pedal pin and install a NEW retaining clip
5. Connect the vacuum hose on the check valve in the power brake vacuum booster CAUTION: The master cylinder is used to create the seal for holding vacuum in the power brake vacuum booster. The vacuum seal on the master cylinder MUST be replaced with a NEW seal whenever the master cylinder is removed from the power brake vacuum booster.
   CAUTION: When removing the vacuum seal from the master cylinder do not use a sharp tool.
6. Using a soft tool such as a trim stick, remove the vacuum seal from the master cylinder mounting flange.
7. Install a NEW vacuum seal on mounting flange of master cylinder assembly
8. Position master cylinder on studs of power brake booster, aligning push rod on power brake vacuum booster with master cylinder push rod.
9. Install the 2 master cylinder to power brake unit mounting nuts. Tighten both mounting nuts to a torque of 25 N·m (225 in. lbs.)
10. Install the wiper module drain hose on the wiper module. Install the tie strap attaching the wiper module drain hose to brake tube at the master cylinder. Tie strap should be loosely tightened so as not to collapse the wiper module drain hose.
11. Install the wiring harness connector on the brake fluid level sensor in the master cylinder fluid reservoir
12. Install the battery tray in the vehicle. Install the 2 bolts and the nut attaching the battery tray to the vehicle. Tighten the 2 bolts and the nut to a torque of 14 N·m (125 in lbs.)
13. If vehicle is equipped with speed control, install the speed control servo and bracket on the battery tray. Install and securely tighten bolt attaching bracket to battery tray.
14. If vehicle is equipped with speed control, install the wiring harness connector on the speed control servo. Then connect the vacuum lines onto the speed control servo and vacuum reservoir on battery tray.
15. Install the air inlet resonator and hoses as an assembly on the throttle body and air cleaner housing. Securely tighten the hose clamp at the air cleaner housing and throttle body.
16. Install the battery and the battery thermal guard.
17. Install the battery cables on the battery.
18. Check the operation of the stop lamp switch and adjust if necessary.