Running Cold

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TurtleTruck

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I'm new to Broncos and the forum, but seems like there's a lot of good knowledge here! Just got my first Bronco a few months ago (94 with the 351) and need some help. It's running super cold (with no help from the weather here) not warming up at all. I can feel it change slightly when I turn the cab temp control so I don't think it's the blend door... Temp gauge doesn't move at all and "heat" blows very cool...I'm thinking maybe the thermostat?  I know it's not much to go on, but any thoughts? 

 

miesk5

96 Bronco 5.0
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Yo,

Main suspect is the thermostat.

Following by Ford in 96 Bronco Workshop Manual, partial.  Same for your 94, 

except for:

92 through 95 uses the Electronic Engine Control, version Four (EEC-IV, aka On Board Diagnostics (OBD-I)) engine management computer.

96 uses the OBD-II (EEC-V) engine management computer;

4WABS (93-96);

RABS (87-92);

Air Bag (94-96);

3 ***** Automatic Locking Hubs (Built from May 95 through 96); Spark Plug Wire Routing & Firing Order (The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. The firing order for 1994- 96 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8.);

R134a in 94-96;

2-piece Spindle Rolling Diaphragm Seal (RDS) used on 5/95 to 96 Broncos & F Series 1/2-ton 4WD;

Speed density EFI uses a Manifold Absolute Pressure Sensor (MAP), a Throttle Position Sensor (TPS), an Air Intake Temperature Sender (ACT) that gives the engine certain volumetric efficiencies over it's RPM range. Speed density EFI also uses what is called bank fire injection. 4 injectors are fired at one time on each side of the engine (only 2 wires for firing injectors from EEC-IV).

Mass Air Electronic Fuel Injection (EFI), aka Sequential Electronic Fuel Injection (SEFI) in 95 5.8 California models and in all 96s. Mass Air directly reads the mass of air (or number of molecules of air). By doing this, it can detect the changes in the volume of air, in addition to it's pressure & temperature. Mass air has one separate wire for each injector & fires them twice for every power stroke of the engine. This makes the injector timing more accurate & will help emissions along with power.

96 5.8 do not have the Air Injection (AIR), Secondary Air Injection; Pump (Smog Pump), Thermactor Air Bypass (TAB) & Thermactor Air Diverter (TAD) Solenoids; Diverter, Check & Bypass Valves, Cross-Over Tube, etc. But 96 5.0 does have the system.

Only 95 5.8L California models & all 96 have the Differential Pressure Feedback (DPFE) Sensor instead of EGR Valve Position (EVP) Sensor.

The 96, Vapor Management Valve (VMV) replaces the canister purge valve (CanP valve) used in EEC IV. But the 96 manual still shows CanP valve probably because it was a late addition to the 96 production line.

The Speed Control Deactivation Switch (SCDS) in a 93 Bronco is located on the driver side frame rail, but in 94 through 96 it is on the master cylinder.

Still researching other differences.


  • Engine Does Not Reach Normal Operating Temperature


  • Damaged water thermostat.
  • Cooling fan.




PINPOINT TEST C: ENGINE DOES NOT REACH NORMAL OPERATING TEMPERATURE



C1 CHECK FOR FROZEN FAN CLUTCH


Did fan clutch pass test?

Yes


No


GO to C2.


REPLACE fan clutch. REFER to Cooling Fan Blade and Fan Clutch in the Removal and Installation portion of this section.h



CHECK THERMOSTAT OPERATION


Does thermostat begin to open and become fully open at temperatures in the specifications at the end of this section?  See http://www.diesel-dave.com/vehic/manual/stj/stj33040.htm

Yes


No


REINSTALL water thermostat and CHECK temperature gauge operation as outlined in Section 13-01.


REPLACE thermostat.

 


Symptom Chart — Climate Control System



CLIMATE CONTROL SYSTEM


Condition


Possible Source


Action


  • Insufficient, Erratic, or No Heat


  • Low radiator coolant due to coolant leaks.


  • CHECK radiator cap pressure. REPLACE if below minimum pressure. FILL to specified coolant level. PRESSURE TEST for engine cooling system and heating system leaks. SERVICE as required.


 


  • Engine overheating.


  • REMOVE bugs, leaves, etc. from radiator and support or A/C condenser core fins. CHECK for:

    Operation of engine fan clutchLoose drive beltSticking thermostatIncorrect ignition timingWater pump impeller damageRestricted cooling system
  • SERVICE as required.



 


  • Loose drive belt.


  • REPLACE drive belt if cracked or worn and ADJUST drive belt tension.


 


  • Thermostat.


  • FEEL heater water hoses. If the heater water hoses are too hot to hold, the thermostat is OK. If the heater water hoses do not get too hot to hold, REPLACE the thermostat. If only one heater water hose gets hot while the other remains cool, a plugged heater water hose or heater core is indicated.


 


  • Heater water hoses.


  • CHECK condition of hoses. 

 

miesk5

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Yo,

It was 4 deg F here this morning ... with blizzard yesterday. if I started our Bronco now, I probably wouldn't have heat for first 2 miles while at 25 mph, and maybe longer if driving into the wind.  

Try driving at 25 mph and see if you get heat like I would.

 

Skitter302

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I'm wondering if flushing the heater core is a smart move while you swapping in a new thermostat.

 

miesk5

96 Bronco 5.0
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Yo,

YW!

As our friend Skitter302 suggested about the core;

 Heater Core; Plugged Heater Core:

Check to ensure the engine coolant is at the proper level, then start the engine and let it run until it is warmed to operating temperature. Turn on the heater and feel the inlet and outlet heater water hoses (18472) to the heater core (18476). If the inlet heater water hose is hot and outlet heater water hose is cooler, the heater core may be plugged.

NOTE: Make sure that an appropriate container is used to collect any coolant that is lost during the heater core bleed procedure.

To bleed air from heater core, remove the hose at the outlet connection of the heater core (hose leading to the water pump). Allow any trapped air to flow out. When a continuous flow of coolant is obtained, connect the hose to the core. Do not overtighten heater hose clamps.

Pressure Test; mieskk5 note, most shops just run flusher solution through heater core by placing temp at hot, to floor and fan on med.  Some just force a small garden hose nozzle into one heater hose to flush out through the other hose.

  1. Drain the cooling system.
  1. Disconnect the heater water hoses from the heater core. If constant tension clamps are used, be sure they are properly positioned.
  1. Install a short piece of heater water hose (approximately 100mm [4 inches] long) onto each tube of the heater core.

    m4111b.gif
     
  1. Fill the heater core and heater water hoses with water and install Plug BT-7422-B and Adapter BT-7422-A from Radiator/Heater Core Pressure Tester 014-R1052 or equivalent in the ends of the heater water hoses. Secure the heater water hoses to the heater core, plug and adapter with clamps.

    m4108a.gif

     

    Item


    Part Number


    Description


    1





    Bleed Valve (Part of 014-R1052)


    2


    014-R1052


    Radiator/Heater Core Pressure Tester


    3


    7422


    Adapter B


    4


    7422


    Plug


    5


    8287


    Hose Clamp


    6


    18C266


    Heater Hose (4 Inches Long)

  1. Attach Radiator/Heater Core Pressure Tester 014-R1052 or equivalent to the adapter. Close the bleed valve at the base of the gauge and pump 207 kPa (30 psi) of air pressure into the heater core.

    m4109d.gif
     
  1. Observe the pressure gauge for a minimum of three minutes. The pressure should not drop.
  1. If the pressure does not drop, no leaks are indicated.
  1. If the pressure drops, check the connections at the core for leaks. If the heater water hoses do not leak, remove the heater core from the vehicle and test the heater core as described in this section. Refer to Section 12-02 for removal and installation procedures for the heater core.
 
 

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