Dodge Nitro. Manual — part 367

7. If original master cylinder is being installed, check condition of seal at rear of master cylinder. Replace

seal if cut, or torn.

8. Clean cylinder mounting surface of brake booster. Use shop towel wetted with brake cleaner for this

purpose. Dirt, grease, or similar materials will prevent proper cylinder seating and could result in vacuum
leak.

9. Align and install master cylinder on the booster studs. Install mounting nuts and tighten to 25 N.m (220

in. lbs.).

10. Connect vacuum hose to booster check valve (1).

11. Remount the HCU. Tighten bracket mounting nuts to 14 N.m (125 in. lbs.).

12. Connect and secure the brake lines (4) to HCU or junction block and master cylinder. Start all brake line

fittings by hand to avoid cross threading.

13. Connect the wire to fluid level switch (3) at the bottom of the reservoir (2).

14. Fill and bleed base brake system, see STANDARD PROCEDURE.

15. Verify proper brake operation before moving vehicle.

POWER BRAKE BOOSTER - RHD

Fig. 59: Identifying Retainer Clip, Pedal & Booster Mounting Nuts
Courtesy of CHRYSLER LLC

1. Align and position booster on the dash panel.

2. Install booster mounting nuts (1). Tighten nuts just enough to hold booster in place.

3. Slide booster push rod onto the brake pedal (2). Then secure push rod to pedal pin with retaining clip (3).

4. Tighten booster mounting nuts (1) to 39 N.m (29 ft. lbs.).

5. Install a new brake lamp switch and reconnect the electrical connector.

NOTE:

Lubricate the pedal pin with Mopar multi-mileage grease before
installation.

2007 Dodge Nitro R/T

2007 BRAKES Base - Service Information - Nitro

6. Install the knee blocker, refer to INSTALLATION .

Fig. 60: Brake Booster
Courtesy of CHRYSLER LLC

7. If original master cylinder is being installed, check condition of seal at rear of master cylinder. Replace

seal if cut, or torn.

8. Clean cylinder mounting surface of brake booster. Use shop towel wetted with brake cleaner for this

purpose. Dirt, grease, or similar materials will prevent proper cylinder seating and could result in vacuum
leak.

9. Align and install master cylinder on the booster studs (2). Install mounting nuts and tighten to 17.5 N.m

(155 in. lbs.). See INSTALLATION.

10. Connect vacuum hose to booster check valve (1).

11. Connect and secure the brake lines to master cylinder. Start all brake line fittings by hand to avoid cross

threading.

12. Connect the wire to fluid reservoir.

13. Install the air box.

14. Fill and bleed base brake system, see STANDARD PROCEDURE.

15. Verify proper brake operation before moving vehicle.

MASTER CYLINDER

DESCRIPTION

MASTER CYLINDER

The master cylinder has a removable plastic reservoir. The cylinder body is made of aluminum and contains a
primary and secondary piston assembly. The cylinder body including the piston assemblies are not serviceable.
If diagnosis indicates an internal problem with the cylinder body, it must be replaced as an assembly. The
reservoir and grommets are the only replaceable parts on the master cylinder.

2007 Dodge Nitro R/T

2007 BRAKES Base - Service Information - Nitro

OPERATION

MASTER CYLINDER

The master cylinder bore contains a primary and secondary piston. The primary piston supplies hydraulic
pressure to the front brakes. The secondary piston supplies hydraulic pressure to the rear brakes. The master
cylinder reservoir stores reserve brake fluid for the hydraulic brake circuits.

DIAGNOSIS AND TESTING

MASTER CYLINDER/POWER BOOSTER

1. Start engine and check booster vacuum hose connections. A hissing noise indicates vacuum leak. Correct

any vacuum leak before proceeding, also ensure booster mounting nuts are torqued correctly.

2. Stop engine and shift transmission into Neutral.

3. Pump brake pedal until all vacuum reserve in booster is depleted.

4. Press and hold brake pedal under light foot pressure. The pedal should hold firm, if the pedal falls away

master cylinder is faulty (internal leakage). This could also indicate an external leak, such as at fittings,
hoses, HCU, etc., or a symptom of an internal leak in the HCU

5. Start engine and note pedal action. It should fall away slightly under light foot pressure then hold firm. If

no pedal action is discernible, power booster, vacuum supply, or vacuum check valve is faulty. Proceed to
the POWER BOOSTER VACUUM TEST.

6. If the POWER BOOSTER VACUUM TEST passes, rebuild booster vacuum reserve as follows: Release

brake pedal. Increase engine speed to 1500 RPM, close the throttle and immediately turn off ignition to
stop engine.

7. Wait a minimum of 90 seconds and try brake action again. Booster should provide two or more vacuum

assisted pedal applications. If vacuum assist is not provided, booster is faulty.

POWER BOOSTER VACUUM TEST

1. Connect vacuum gauge to booster check valve with short length of hose and T-fitting. See Fig. 51.

2. Start and run engine at curb idle speed for one minute.

3. Observe the vacuum supply. If vacuum supply is not adequate, repair vacuum supply.

4. Clamp hose shut between vacuum source and check valve.

5. Stop engine and observe vacuum gauge.

6. If vacuum drops more than one inch Hg (33 millibars) within 15 seconds, booster diaphragm or check

valve is faulty.

2007 Dodge Nitro R/T

2007 BRAKES Base - Service Information - Nitro

Fig. 61: Typical Booster Vacuum Test Connections
Courtesy of CHRYSLER LLC

1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE

2007 Dodge Nitro R/T

2007 BRAKES Base - Service Information - Nitro