I’m still working on the heating problem on my 1988 Bronco II 2.9L

When driving the temperature indicator goes up about 4 mm under the red hot line and then drops again slowly at the normal level.
I changed now the Thermostat, temp gauge and radiator pressure cap but nothing changed.
I do not lose any coolant and there is no coolant in the oil that good indicate a cracked head casket. In the coolant I don’t smell exhaust gases so it is not clear to me what is causing this.

Can this have something to do with the water pump or Fan clutch, and how can I test these.
I noticed that when the engine is at working temperature the fan can be easy turned by hand with a minimum force.

Ray

 

Son's 89 ranger had same problem. Found the radiator was plugged about a third way up. Found a radiator at Discount Radiators in Dallas for 120. Works fine now.

Ol yeller

 

Well invested a lot of money today without any success.
Changed the radiator, flushed the system, put in new antifreeze coolant, and cleaned the condenser in front of the radiator and nothing changed.
The only thing improved is that the temp indicator returns quicker to normal level at idle.
Also checked the timing of the engine and pressure tested the coolant system

Ray

 

I have a 99 ranger 4.0. It does the same thing. It heats up to the red line then returns to normal but only when I first start it. I heard of a valve that redirects hot water back to the block before it circulates throught the radiator to help warm it up. I dont know if this causes it but give it a try. If it works let me know.

 

If the temp has a tendancy to go up at idle and come back down on the road and back up if you are stopped in traffic take a look at the water pump. I also have an 88 bII and this was something I went through until I changed the pump( it was leaking). Now it is hard to get enuff heat to keep warm( I plan on checking the thermostat).
just what I have seen from mine,
Jason

 

I had a 94 Ford Explorer with a 4.0, and the temp would go up and down depending on the driving condition (hill, etc). From what I hear, if you replace the thermostat with a non-factory thermostat, the temp goes up and down all the time. Its just something I have heard a lot of techs say, and its common in Fords.

 

Article 99-23-8

FORD: 1995-2000 EXPLORER, RANGER

This TSB article is being republished in its entirety
to include 2000 model year vehicles and to provide
Service Part(s) and Labor Time information

ISSUE
A temperature gauge fluctuation and/or 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
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.htm

DIAGNOSTIC AND SERVICE PROCEDURE
1. Check for excessive exhaust system
restrictions. A restricted exhaust could elevate
cooling system temperatures.
2. If dash-mounted cooling temperature gauge
fluctuates, check that gauge and sending unit
are functioning properly.
3. Check for restrictions or kinks in the radiator or
heater hoses.
4. Pressure check cooling system for leaks.
5. Confirm proper Engine Coolant Temperature
(ECT) sensor signal to EEC-V processor.
6. Check for correct 50/50 coolant mix. Verify that
freezing point is -37°C (±-15°C) or -35°F (±5°F).
7. 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.

APPLICATIONS:
1997-2000 Ranger with automatic or manual
transmission and 1997-2000 Explorer with
automatic transmission.............Part # F8PZ-8522-AA

1995-2000 Explorer with manual transmission
and 1995-1996 Explorer with automatic
transmission.........................Part # F8PZ-8522-BA

1995-1996 Ranger with automatic or manual
transmission.........................Part # F8PZ-8522-CA

 

I would change the temp.sending unit,but what you realy need to do is get a real temp guage,the ones that come from the factory are no more then a fancy idiot light.If you can freely spin your fan I would change the fan clutch too.JMO

 

Hello fellows,

Well after changing almost everything only not the water pump the TEMP meter at this moment in the summer seems to get better, it stays most of the time in the mid level and only driving on highways it goes up until 3 quarter of the measuring range.
Maybe it are air pockets in the coolant system that are finely gone now.

Ray

 

Another way to avoid air pockets in the motor--just like a 400 Chevrolet (gasp, choke, puke)--is to fill the engine with coolant from the TOP first. Fill the radiator secondly. Start the engine and JUST AS SOON AS THE THERMOSTAT OPENS, fill the radiator to the correct level. A few of the 351 M and 400 Fords had the same problem--their coolant flows opposite to a 351 W--and, if filled with coolant like I have described, it alleviates the problem. It is a bit of a hassle, but it surely beats cooking an engine!