Design Change to Thermostat Housing, Thermostat Housing Bolts, and Thermostat Housing O-ring Seal

The purpose of this bulletin is to provide "back service" information regarding thermostat housing, thermostat housing bolts, and thermostat housing O-ring seal. During the 2002 model year, vehicles equipped with V6 (L81) engines with a serial number higher than and including 10ZJ 08577464 were manufactured using a 2nd design thermostat housing, bolts, and O-ring seal.

The illustration below shows how to determine a 1st design housing from 2nd design housing. The 2nd design housing has ribs between the tube and the mounting flange as shown. The casting numbers are also different. The 1st design casting number is 90502201 and the 2nd design casting number is 24420652. The 2nd design thermostat housing will back service all 2000 - 2002 vehicles assembled with 1st design housings. Any time a 1st design housing or O-ring seal needs replacement, a 2nd design thermostat kit (P/N22687712) should be installed.

Notice: When replacing a 1st design housing with a 2nd design housing, longer mounting bolts (P/N24455322) and 2nd design O-ring seal (P/N 24447061) are required. The mounting flange of the 2nd design housing is thicker than the 1st design housing and requires a longer bolt to have the necessary thread engagement. The O-ring seal groove on the 2nd design housing is deeper and wider which requires the 2nd design seal. Use of 1st design (shorter) mounting bolts or 1st design O-ring seal with a 2nd design housing may cause an engine coolant leak.

Important: New thermostat housing bolts have thread sealant pre-applied to prevent coolant leaks. If you are servicing a vehicle equipped with a 2nd design housing and you are reusing the original bolts, apply thread sealant PST 565® (or equivalent) to bolt threads before installing.

22687712 - Thermostat KIT-Eng Cool (2nd Design) Includes 2nd design thermostat housing O-ring seal P/N 24447061

24455322 - Bolt/Screw-Eng Cool Therm HSG (2nd Design)