North American Turbocoupe Organization



Main cooling fan....
Kuch Offline
Member
#1
So my main cooling fan comes on immediately on start up and doesn't seem to shut off, with the smaller secondary coming on intermittently. The temps never get hot, but what is making the fan run like this, the ECT? Thanks
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof, T3/T4 50 trim, 255LPH, BBK AFPR, 3" DP dual 2.5", MGW shifter, K&N, Gillis valve, RR cam
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
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Jeff K Offline
Administrator
#2
Fans are controlled by the PCM. ECT sends coolant temp to PCM. To operate the main (driver side) fan, PCM opens a ground circuit to the IRCM, which energizes the fan via a relay in the IRCM. Low speed fan should come on with coolant around 210 F. If coolant temp goes over 220 F and main fan has been engaged for more than 10 sec, PCM grounds a circuit to the IRCM, energizing a relay which runs the aux (driver side) fan.

Could be a faulty ECT. With engine cold, check ECT voltage by backprobing ECT circuit (esier said than done). Should around 3 V with coolant temp of 68 F . At operating temp of around 200 F, voltage drops to around .5 V.

If the main fan control circuit from the PCM to the IRCM is open for some reason (broken wire, bad contact at PCM, IRCM, etc) main fan will run whenever engine is running, but that doesnt explain the aux fan running intermittently.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Kuch Offline
Member
#3
Did some checking around the fans the other day and found the A/C high pressure switch for the drivers side fan pulled and a jumper installed. That's why the fan comes on with key on, took her out for a ride yesterday and the temps went up to the very upper normal side after about 20 minutes. I also noticed a new thermostat and housing installed on the engine. Previous owner must have had overheating issues and jumped the drivers fan to cool constantly. Now I have to find out why it's running hot. Going to buy a new temp sender to go with the new ECT I bought but haven't installed yet. Also going to try plugging back in the drivers can to the A/C switch to see how it works
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof, T3/T4 50 trim, 255LPH, BBK AFPR, 3" DP dual 2.5", MGW shifter, K&N, Gillis valve, RR cam
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
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Jeff K Offline
Administrator
#4
Aftermarket water neck? Some aftermarket ones are poorly designed and restrict coolant flow. Motorcraft Thermostat? Again, many aftermarket ones are poor quality.

Does the pass side fan start to run when the engine gets hot?

Is it just the temp gauge that reads high, or do the fuel and oil press gauges lso read high?
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Kuch Offline
Member
#5
Not sure of the brand thermostat and housing, but the car was well maintained at a Ford dealer. I have multiple receipts and can check them. I got the car with a full tank of gas showing, with only maybe 35 miles on it, the level did go down. The oil pressure does read on the high side of normal when cold but settles to just about 3/4 when hot. I was thinking of the IVR may need replacement as well. I do notice that the speedo will do a little jumping at idle. Sign of bad IVR? I know the factory gauges are not totally accurate, but I don't really want to buy an aftermarket gauge to check it
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof, T3/T4 50 trim, 255LPH, BBK AFPR, 3" DP dual 2.5", MGW shifter, K&N, Gillis valve, RR cam
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
Reply

Jeff K Offline
Administrator
#6
Out of wack IVR will cause oil, temp and fuel gauges to read high or low, but IVR has nothing to do with the speedo or tach.

Since the gauges are inaccurate, the only way to really know the coolant temp is to monitor the ECT voltage when engine is up to operating temp (assuming the ECT is in calibration) or check temp with another gauge.

Remove the coolant hose that is on the nipple on the lower intake facing the firewall and See if coolant comes out. Also ue a coathanger wire or similar to clean out any crud in the nipple. THe nipple area can clog with crud in poorly maintained cooling systems and restrict flow over the ECT, causing it to read a lower temp than the coolant actually is, which causes fans to come on late, messes up the A/F ratio, closed to open loop fuel control switchover, etc.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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anasazi4st Offline
Senior Member
#7
If you get a temp sender unit I will be most curious to see what results you get.

In the course of a head gasket replacement in 2011 I replaced all the little hoses and parts that are often hidden and sometimes darned near impossible to get at with the intake manifold, etc. in place. One of these was the temp sending unit. I got one from NAPA, and when I test drove the car for the first time after all the work was done, on both city streets and the freeway, after just a few minutes the temp gauge crept up to the very top of the "Normal" range and stayed there. EATC on or off, no effect. Fearful of damaging the engine, I drove back home at between 15-25 MPH.

Next I got a sending unit from Ford. Same result. I recall trying another one from a different parts store, with no change.

Frustrated and trying to get some sense of what was going on, I put back the one I had removed (which it turns out was not the OEM one, I had replaced that in the mid-90s). Temp gauge dropped back down, fans stopped coming on.

Oddly, the cooling system seemed to be the same temp despite which sending unit was in there. I recall carefully opening the radiator cap and there was no cloud of steam as one might expect with such a high temp reading; coolant temp was the same with either unit.

My research showed that there were actually 2 different units available. Thinking I had been sold the wrong one (each time), I purchased and installed the other. Same thing happened--the engine looked like it was going to overheat, but in reality the gauge was wrong.

I'll be curious to see what happens in your case.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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Kuch Offline
Member
#8
Anasazi, that is an interesting story. Tonight driving to work, about a 16 mile drive, I watched all the gauges. Oil press about 7/8 up, Fuel 3/4 tank, water temp, cold. About 10 minutes in the temps came up to about 1/4 in the normal, oil same, fuel same. Then at about 20 minutes the oil went right up to the top of normal, and gas went up to full, and of course the water temp started climbing. I'm thinking my IVR is going, I have a used one from a late 80's Crown Vic cop car, might try swapping it and see. I may end up getting an aftermarket temp gauge to go along with my after market boost gauge just to track it accurately. Thanks for the reply
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof, T3/T4 50 trim, 255LPH, BBK AFPR, 3" DP dual 2.5", MGW shifter, K&N, Gillis valve, RR cam
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
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Pete D Offline
Administrator
#9
With an aftermarket gauge, you will be amazed at the faster response time. The one I installed in one car came with it's own sender unit.

For sure your IVR is fubared.
Pete Dunham


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