Cooling System - Knocking/Thumping Sound

Article No.
96-21-12

10/07/96

^ COOLING SYSTEM - PULSATING COOLANT FLOW - NOISE - "KNOCK/THUMP" - AUDIBLE IN PASSENGER COMPARTMENT - 3.0L ENGINE

^ NOISE - "KNOCK/THUMP" - COOLING SYSTEM - AUDIBLE IN PASSENGER COMPARTMENT - 3.0L ENGINE

LIGHT TRUCK:
1991-95 RANGER
1995 AEROSTAR

This TSB is being republished in its entirety to include the 1995 model year and to add Aerostar to the list of affected vehicles.

ISSUE:
A "knocking/thumping" noise may be audible in the passenger compartment on some vehicles. This noise is most pronounced with the engine at normal operating temperature. The noise is caused by steam formation in the cooling system. The noise is then transmitted through the heater hoses and heater core.

ACTION:
Install a Coolant By-Pass Kit. This increases coolant flow which reduces steam formation. Refer to the following Diagnostic and Service Procedure for details.

DIAGNOSTIC AND SERVICE PROCEDURE

1. Check that base timing is at 10° BTDC with SPOUT disconnected.

2. Check for excessive exhaust system restrictions. A restricted exhaust could elevate cooling system temperatures.

3. If dash-mounted cooling temperature gauge fluctuates, check that gauge and sending unit are functioning properly.

4. Check for restrictions or kinks in the radiator or heater hoses.

5. Pressure check cooling system for leaks.

6. Confirm proper Engine Coolant Temperature (ECT) sensor signal to EEC-IV processor. Refer to TSB Article 93-24-8 (Cooling System - Thermostat Diagnosis) for tool and procedure to check thermostat.

7. Check for correct 50/50 coolant mix. Verify that freezing point is -37°C (+/- -3°C) or -35°F (+/- 5°F).

8. For 1991-93 Rangers, install a 110 kPa (16 psi) Radiator Cap (F4TZ-8100-B). These model year vehicles originally came with a 90 kPa (13 psi) radiator cap.








9. If concern still exists, install service Coolant By-Pass Kit and verify that concern has been resolved. Refer to the Application Chart in this article.





Parts Block

OTHER APPLICABLE ARTICLES: 93-24-8

SUPERSEDES: 95-12-8

WARRANTY STATUS: Eligible Under the Provisions Of Bumper To Bumper Warranty Coverage For 1992-95 Model Year Vehicles, Basic Warranty Coverage For 1991 Model Year Vehicles

OPERATION DESCRIPTION TIME

962112A Install Kit - 1991 Ranger 1.2 Hrs.

962112B Install Kit - 1992-94 0.7 Hr.
Ranger

962112C Install Kit - 1995 Ranger 1.1 Hr.

962112D Install Kit - 1995 Aerostar 1.0 Hr.

DEALER CODING
CONDITION
BASIC PART NO. CODE
8522 11

OASIS CODES: 111000, 208000, 402000, 497000, 702000, 702100, 70230