EXHAUST MANIFOLD LEAKS

What NHTSA is examining

Summary:some 1981-86 trucks with 7.4l engines and cast iron exhaustmanifolds may experience a condition where an exhaust leak developsbetween the manifold and the cylinder head mating surface causing a noisecondition. Most of the reports (and all of the injuries and themanifold fire) are from the p30 motorhome chassis.gm states that a warpedor cracked manifold would permit small amounts of exhaust gas leakagegenerally resulting in noticeable noise and fumes.the exhaust manifoldsare susceptible to extreme heat conditions (such as operating under severeengine/vehicular load conditions and high ambient temperatures).themotorhome application is particularly susceptible to this alleged defectsince the vehicle is nearly always at or near the gvwr of the vehicle.thefew number of reports received by odi for a problem which began 8 years agosuggests that the defect either occurs infrequently or is not perceived asa significant safety hazard.the service bulletin was issued to identifythe high temperature problem and provide a remedy against reoccurrence.===

Vehicles under investigation