TSB 96-21-12 addresses that but is for Ranger & Aerostar with 3.0L engines. I see nothing to include Explorer. The "Bulletin" numbers aren't TSB numbers. There are 137 TSB's for the 1993 Explorer and I didn't see a reference to the "thumping" subject you state. There is a temp gauge TSB for the Explorer and a thumping TSB for the Ranger......
Component Description:
67. ENGINE AND ENGINE COOLING:COOLING SYSTEM:HOSE
Bulletin Number: BC1019997230
Bulletin Date: Jan 1997
Vehicle: 1,993 Ford Ranger
Summary:
4.0L EQUIPPED VEHICLES MAY EXPERIENCE TEMPERATURE GAUGE FLUCTUATION THAT MAY BE ACCOMPNIED WITH A THUMPING NOISE OR FEEL IN THE COOLANT HOSES WITH THE ENGINE AT NORMAL OPERATING TEMPERATURE. ( NHTSA ITEM NUMBER - 51559 )
Component Description:
69. ENGINE AND ENGINE COOLING:COOLING SYSTEM:HOSE
Bulletin Number: BC3485972301
Bulletin Date: Jan 1997
Vehicle: 1,993 Ford Ranger
Summary:
4.0L EQUIPPED VEHICLES MAY EXPERIENCE TEMPERATURE GAUGE FLUCTUATION THAT MAY BE ACCOMPANIED WITH A THUMPING NOISE OR FEEL IN THE COOLANT HOSE WITH THE ENGINE AT NORMAL OPERATING TEMPERATURE. ( NHTSA ITEM NUMBER - 51482 )
TSB
95-18-5 TEMPERATURE GAUGE - FLUCTUATING AND/OR INACCURATE HIGH READINGS
Publication Date: SEPTEMBER 11, 1995
FORD: 1990-1994 TAURUS, THUNDERBIRD
1991-1993 TEMPO
1991-1994 ESCORT
LINCOLN-MERCURY: 1990-1994 COUGAR, SABLE
1991-1993 TOPAZ
1991-1994 TRACER
LIGHT TRUCK: 1990-1991 AEROSTAR
1990-1994 RANGER
1991-1994 EXPLORER
This TSB article is being republished in its entirety to correct model year application and revise the part descriptions.
ISSUE:
Some vehicles may show temperature gauge fluctuations and/or inaccurate (high) readings (affected engines are 3.0L/4.0L Ranger, 4.0L Explore and 1.9L Escort/Tracer). The inaccurate (high) readings may result in a customer concern with the perception of engine overheating. This is caused by Gauge/Sender design characteristics which create a sensitive gauge indication.
ACTION:
Replace the gauge and sender with a new Temperature Indication Service Kit. Refer to the following for Additional Concerns and Service Procedure for details.
ADDITIONAL CONCERNS
Please verify the following two (2) concerns before implementing the fix for the above concern.
Perform cooling system diagnosis per TSB 93-24-8.
Vehicles built from 1/1/93 to 4/1/93 may experience high temperature gauge indications which may have been due to the installation of improperly manufactured temperature sending units. The customer concern is that the gauge indication is beyond the letter "L" in the word "NORMAL". If this condition occurs, inspect the temperature sender for an "A3" stamped date code on the hex of the sending unit. If an "A3" unit is found, replace with "NON-A3" service stock.
1993 Taurus/Sable 3.8L vehicles built 8/16/93 to 8/31/93 may have high temperature gauge readings caused by an incorrect temperature sending unit installed at the assembly plant. The incorrect temperature sending unit can be identified by a blue insulator around the terminal. The correct temperature sending unit has a green insulator. If a temperature sending unit with a blue insulator is found, replace it with an F1SZ-10884-A.
Explorer 4.0L vehicles with date code 2204 to 2274 should not be used. Any other date code outside this is acceptable even with an "A3" stamp.
NOTE: DATE CODES ARE BASED ON THE JULIAN DATE CODE SYSTEM. THE LAST NUMBER DENOTES THE YEAR THAT THE PART WAS MANUFACTURED. FOR EXAMPLE, 2274 (1994 PART) AND 2275 (1995 PART). ANY 1995 PART MAY BE USED.
TEMPERATURE INDICATION SERVICE KIT PROCEDURE
NOTE: THIS PROCEDURE IS PERFORMED AFTER THE ABOVE TWO (2) STEPS HAVE BEEN DONE.
The installation of the service kit will result in a pointer indicating in the approximate center of the "NORMAL" band while providing protection for a boil-over condition.
The service kit consists of:
Instructions
Temperature Gauge
Temperature Sender
The instructions will contain the following steps:
Remove BOTH existing temperature sender and temperature gauge from the vehicle.
NOTE: REFER TO SECTION 13, CONVENTIONAL INSTRUMENT CLUSTER, OF THE APPROPRIATE SERVICE MANUAL FOR TEMPERATURE GAUGE REMOVAL AND INSTALLATION INSTRUCTIONS. REFER TO SECTION 03-03, COOLING SYSTEM, OF THE APPROPRIATE SERVICE MANUAL FOR TEMPERATURE SENDER REMOVAL AND INSTALLATION PROCEDURES.
Install BOTH service kit temperature sender and temperature gauge into the vehicle.
NOTE: THE SERVICE KIT TEMPERATURE SENDER AND TEMPERATURE GAUGE MUST BE USED TOGETHER.
F47Z-10E922-B Temperature Indication Kit - With Tachometer (Explorer - 4.0L, Ranger - 3.0L And 4.0L Engines)
TSB
96-21-12 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
Publication Date: OCTOBER 7, 1996
LIGHT TRUCK: 1991-1995 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
Check that base timing is at 10° BTDC with SPOUT disconnected.
Check for excessive exhaust system restrictions. A restricted exhaust could elevate cooling system temperatures.
If dash-mounted cooling temperature gauge fluctuates, check that gauge and sending unit are functioning properly.
Check for restrictions or kinks in the radiator or heater hoses.
Pressure check cooling system for leaks.
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.
Check for correct 50/50 coolant mix. Verify that freezing point is -37°C (±-3°C) or -35°F (±5°F).
For 1991-93 Rangers, install a 110 kPa (16 psi) Radiator Cap (F4TZ-8100-B).
NOTE: These model year vehicles originally came with a 90 kPa (13 psi) radiator cap.
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.
