BLUE/WHITE SMOKE FROM TAIL- PIPE AFTER EXTENDED IDLE. GMC Truck S15 Pickup - 2WD 1986

For 1990-2009 cars

# BLUE/WHITE SMOKE FROM TAIL- PIPE AFTER EXTENDED IDLE

#### VEHICLES AFFECTED: 1986 S/T WITH THE 2.8L ENGINE

Some 1986 S/T trucks with the 2.8L V6 engine may exhibit a blue/white smoke from the tailpipe after an extended idle. If checking the truck indicates that there is no loss of coolant nor indications of excessive oil consumption, this condition may be caused by excess water (generated by the catalytic converter) accumulating in the rear chamber of the muffler and then being pulled into the exhaust stream and turned into steam.

If this condition is encountered, it can be corrected by drilling a 3/16 inch drain hole in the rear end plate of the muffler and the internal baffle in the muffler. The internal baffle in the muffler is located three inches inboard from the end plate. See Figure 1. The drain hole, which MUST also penetrate the internal baffle, will allow the excess water to drain from the muffler.

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.