Brakes - Hard Pedal Feel
88chevy16Number: 88-311-5
Section: 5
Date: JULY, 1988
Subject IMPROVED BRAKE PEDAL FEEL -
COLD ENGINE/QUICK BRAKE REAPPLY
Model and Year 1984-86 C/K WITH 5.7L OR 7.4L ENGINE AND JB7 BRAKES
1987-88 R/V WITH 5.7L OR 7.4L ENGINE AND JB7 BRAKES
TO: ALL CHEVROLET DEALERS
A condition described as a hard brake pedal feel with a cold engine or upon quick reapply of the brakes may be caused by reduced vacuum at the brake booster. Vehicles with the condition can be improved by installing a high flow vacuum brake kit.
SERVICE PROCEDURE
REMOVAL
1. Remove battery ground cable.
2. Remove air cleaner.
3. Remove existing vacuum check valve and grommet from booster. Disconnect vacuum pipe at TBI adapter and remove pipe and hose assembly from vehicle.
4. Remove vacuum pipe fitting from TBI adapter.
5. Remove vacuum fitting for transmission modulator, heating/ventilating and cruise control from inlet manifold in front of distributor.
t��0FIGURE NO. 1 VACUUM HOSES AND FITTINGS INSTALLATION (7.4 LITER ENGINE):
FIGURE NO. 2 VACUUM HOSES AND FITTINGS INSTALLATION (5.7 LITER ENGINE):
INSTALLATION
Note: Apply pipe thread sealer or tape to all fittings.
1. Install pipe plug (1) in TBI adapter (See Figure 1 for the 7.4L engine and Figure 2 for the 5.7L engine.) Torque to 11-14 N-m.
2. Install pipe tee (2) in inlet manifold. Torque to 11 N-m minimum (See Figure 1 or Figure 2.)
3. Install nipple (3) in horizontal side of tee. Torque to 11-14 Nm.
4. Install vacuum fitting (6) into vacuum tee. Torque to 11 N-m minimum.
5. Install heater/vent vacuum hose to side nipple on fitting and transmission modulator pipe onto top nipple of fitting. If vehicle is not equipped with cruise control or A/C, plug side nipple on fitting.
6. Check to see that air cleaner clears top of the modulator pipe. It may be necessary to force fitting (6 on Figure 1 and Figure 2), deeper into tee or reshape modulator pipe slightly. If interference still exists, modulator pipe is not fully seated into fitting (6) . Remove hose sleeving from modulator pipe and check alignment of pipe to fitting. Bend pipe slightly to correct alignment. Lubricate hose sleeve with silicone spray and install back on modulator pipe. Push sleeve as high as possible and insert modulator pipe back into fitting. Slide hose sleeve back down to proper position. Recheck for proper clearance.
7. Attach 15/32 ID vacuum hose (4) to nipple on tee (2) and secure with hose clamp (5) about 1/4 inch from hex on nipple.
FIGURE NO. 3 VACUUM HOSES AND CHECK VALVE INSTALL.:
8. Route hose under map sensor and wiring harness and over valve rocker cover. Carefully route hose over distributor and clip (4) in two places on vertical surface of cowl above distributor (see Figure 3). Adjust hose carefully so it will not kink or rub against cowl or other parts with engine movements.
9. It may be necessary to rotate the tee in the inlet manifold to help route hose properly.
10. Install new grommet (2) and check valve (1) in booster. some units may require loosening the master cylinder to install the check valve.
11. Attach 15/32 ID vacuum hose (3) to check valve.
12. Reinstall air cleaner.
13. Reconnect battery ground cable.
Labor Operation: T7515
Labor Time: .7 hr. - 5.7L (RPO L05, LT9) Engine .9 hr. - 7.4L (RPO L19, LE8) Engine
In both cases, use Labor Operation number T7515.
Note: Start engine and check for proper braking action before road testing.
Parts are expected to be available by July 31, 1988.
Parts List Quantity Part Number
Power Brake Kit 1 15624666
Kit Consists of:
Pipe Plug 1 444620
Pipe Tee 1 444150
Nipple 1 443980
Hose Clamp 1 3866998
Fitting Vacuum Hose 1 367174
Check Valve Kit 1 18012017
Clamp Hose 2 3992185
Hose 1 9442360
Instruction 1 15624667