SN95 cooling system question

[Craig K.]

I was driving home the other day and the car overheated.
The temp gage went up to pass the L (in Normal) I pulled over and the overflow started puking out fluid (brown/grey colored).

So Thursday night I pull the radiator and put the one in from Tommy (mind had a wepping leak (never lost much fluid). I flushed out the engine through the heater hose tubes for the oil heat exchanger.

I refilled the car with about 2 gallons of distilled water and one gallon of antifreeze.
I drove the car Thursday night, and the gage would go to between the A and L then the fan would kick on and the gage would go back to the M.

I drove the car to work this morning, and the gage seemed a little eratict, it would go high to about the A, then drop to the O (perhaps when the T-Stat opened) then is a few second go back to the A, then it settle on the M.

After work today I put in a brand new Napa 180 degree T-stat. I also drilled a 9/32" hole on the top half and a 1/4" hole on the bottom of the T-Stat. I also added Royal Purple Ice Water (a water wetter product).

The car stills preforms the same as this morning.

The questions I have are:
1) Could the Temp. Sending unit have gone bad because it got so hot when it over heated? Also is this sending unit the one at port # 5 (drivers side first cylinder) on the lower intake?

2) Do the SN95 car have veriable fans? Should the fan only come on once it hits only one temperature at full blast power?

3)How do you know if the SN95 fan control unit goes bad, is it that the fan just won't go on anymore?

4) If I were to through in a mechanical gage to check the temps vs. the dash gage, where is a good temporary port to install the sending unti?

Sorry for the long read, it has just gotten to the point where no I don't trust the car anymore.

Craig

[Sendero]

I believe that the 5.0 SN95 fan units have a primary and secondary fan. I know that one comes on a X* and the second one is supposed to kick in with the A/C or X* above the first fan.

Sounds like you might have an air bubble?

[Craig K.]

Originally Posted by Sendero

I believe that the 5.0 SN95 fan units have a primary and secondary fan. I know that one comes on a X* and the second one is supposed to kick in with the A/C or X* above the first fan.

Sounds like you might have an air bubble?

Thats how I thought the fan should work as well, but it only seems to me that it kicks on at one constant speed once the gage gets between the A and L.

I don't think I have an air bubble, since I drilled the two small holes into the T-Stat, that should (in therory) allow for all the aire to get out quicker than normal, I think.

[slvrbullit]

they are 2 speed fans, the temp guage sender is the one above cylinder 5, that is for the guage only. The one for the ECU is located above the Tstat housing in the end of the hard tubes that run down along the intake. The fan kicks on at a pretty high temp from the factory, i think it is like 210* or 215* for the low speed fan, the high speed kicks on at I think 230*.

[Wicked]

Originally Posted by slvrbullit

they are 2 speed fans, the temp guage sender is the one above cylinder 5, that is for the guage only. The one for the ECU is located above the Tstat housing in the end of the hard tubes that run down along the intake. The fan kicks on at a pretty high temp from the factory, i think it is like 210* or 215* for the low speed fan, the high speed kicks on at I think 230*.

Correct. If the SN95's are the same as the new edge cars(I think 94+ is all the same), there is also a thermistor on the backside of the radiator, i believe that controls the speed of the fan.

I checked the elc. diagram when I had my fan go out and there is only one speed commanded by the ecu, but the second speed is dictated by the thermistor, from what I can tell.

[slvrbullit]

The thing that controls the fan speed is the little black box by the overflow tank, it also controls the fuel pump and other things, if that is bad get ready to pay $$$ for it.

[CrimsonRacing]

When I got the '94 from Lee he advised me that the temp gauge would register hot but the engine was not overheating.......He gave me another dash pod that had all the gauges in it.I replaced the existing temp gauge with the newer one and still have the same problem.

Also...when I turn on the lights or increase the fans speed for the a/c the temp gauge moves farther and farther towards hot.......(elec short?).

I am considering just getting a brand new gauge pod from Ford and see if that will correct the problem....You have no idea how stressful it is to be sitting in traffic and see your temp gauge way into the hot zone.

[Craig K.]

I hear you Richard.

I have a mechanical gage, but don't have the right fittings for it.

I did put a thermometer on the outside of the upper rad. hose, and it corralated pretty good to the t-stat openning and the fan going on etc...

change the sending units and see what happens...it sounds like an electrical spike to the guages...possibly cause from getting the sensors too hot...

[Craig K.]

OK
I checked the fan output using a mutilmeter and I get 12V when the AC is on Norm. for the fan motor low speed
I get 12V when the AC is on max on the fan motor high speed.
I verified that the fan will run both low/high using some jumper wires.

How can I trouble shoot the coolant temp sending unit, or the "black box"?