DIESEL-BRAKE LIGHT COMES ON POSSIBLE VACUUM HOSE LEAK

VEHICLES AFFECTED: 1984 'A' Series Vehicles Equipped with 4.3L V-6 Diesel Engine (LT7)-Federal Emissions Only (NA5&NM1)

Some 1984 'A' series vehicles with 4.3L V-6 (LT7) diesel engines equipped with Federal emission (NA5&NM1) may experience a slight vacuum leak which may be due to abrasion/puncturing of a section of a rubber hose, causing the brake light to come on. The leak is a result of a hole being worn in the vacuum hose between the vacuum regulator valve and the 'T'. If the brake light comes on, particularly if it is on only at idle, examine the vacuum hose for abrasion and a hole. If worn through, replace and reroute as shown below. If not worn, check out the system as outlined in Section 5 of the Chassis Service Manual.

SERVICE PROCEDURE

Rotate the 'T' in the vacuum line until it is aimed at the left front headlamp. Use a 343mm (13-1/2 in) length of 5.6mm (7/32 in) I.D. vacuum hose cut from bulk hose, part no. 3987364.

Route the hose in front of the EGR solenoids as shown in Figure 1.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.