Engine - Squeak/Squeal Noise After Cold Start

Bulletin No.:
T-93-57

File in Group:
6

Number:
36

Corp.Ref.No.:
316101R

Date:
Jan. 1993



SUBJECT:
SQUEAK/SQUEAL NOISE AFTER COLD START


MODELS AFFECTED:
1991-1993 MODELS WITH 4.5L, 4.9L V8 ENGINE (VIN 8 OR VIN B)


Some 1991-1993 vehicles equipped with either the 4.5L or 4.9L V8 engine may experience a squeak or squeal type noise as started from a cold condition (sometimes misdiagnosed as belt squeal.) The noise lasts for a few minutes then disappears and may or may not return during the next cold start. This noise is not exhibited once the engine is warm and may be more frequent and longer lasting during colder ambient temperatures.

The source of this noise is a rapid oscillation of the pressure relief valve (non-serviceable) inside the oil pump. An oil pump with a redesigned relief valve has been developed to alleviate this condition. The new pump, P/N 3535211, went into production in October, 1992 effective with EUN T10L520897 located on the inside of the rear valve cover and is currently available from GMSPO to address complaint vehicles. The revised pump supersedes the previous design part number 1649416. For 1991-1993 vehicles only.

Parts are currently available from GMSPO.





Warranty Information