B3000 4WD V6-3.0L OHV (1995)
Thermostat Bypass Hose: Customer Interest
Cooling System - Knock/Thump At Operating Temperature
Bulletin No.: 003/96
Issued: 08/10/96
Revised:
Category
E
Applicable Model/s
1994 - 95 B3000
Subject:
"KNOCK" OR "THUMP" NOISE HEARD IN THE PASSENGER COMPARTMENT
NOTE:
This bulletin has been updated to include 1995 models (refer to the change notes). Please make the necessary changes to Cat. E, 001/95 in your 1995
Service Bulletin Book.
APPLICABLE MODELS
All 1994 B3000
1995 B3000 model vehicles built before 6/19/95
NOTE:
Build date is stamped in yellow ink on the radiator support.
DESCRIPTION
A "knocking" or "thumping" noise may be heard from the passenger compartment. The noise is heard mostly when the engine is at normal operating
temperature. Inadequate coolant flow causes steam to form in the cooling system causing this noise. The noise is then transmitted through the heater
hoses and heater core into the passenger compartment.
Coolant bypass kits are available to increase coolant flow and reduce steam formation.
INSPECTION / REPAIR PROCEDURE [Steps 1, 2, 3 have changed]
1.
Confirm customer complaint.
2.
1994 Vehicles Only-Check base timing.
^
Timing should be 10 degrees BTDC with the SPOUT (Spark Output) Shorting Bar disconnected.
3.
Check the vehicle for items that contribute to high engine coolant temperature (i.e. weak coolant cap spring, exhaust system restriction, stuck
thermostat, low coolant level, hose kinks or damage etc.).
4.
Pressure test the cooling system.
^
If leaks are found, repair as necessary.
5.
Run engine to normal operating temperature and inspect the temperature gauge for fluctuation.
^
If the gauge fluctuates, check the gauge and sending unit according to the workshop manual.
6.
Check the coolant
^
Coolant mixture should be 50/50. Confirm the freezing point is -35 +/-5 degrees (F) (-37 +/-3 degrees C)
7.
Check the radiator support for the vehicle build date.
^
If the vehicle was built before 9-20-93 and has a 13 PSI (90 kpa) radiator cap, install a 16 PSI (110 kpa) cap.
NOTE:
Vehicles built after 9-20-93 were produced with 16 PSI radiator caps and replacement is not necessary.
8.
Recheck the vehicle for "thumping" and "knocking".
^
If the concern still exists, proceed to step 9.
^
If the concern is gone, return the vehicle to the customer.
9.
Install the coolant by-pass service kit. Installation instructions are included in the kit.
10.
Test drive vehicle and confirm repair.
