North American Turbocoupe Organization



Radiator Fans not coming on
GrandeDan Offline
Junior Member
#1
So here’s the issue and what I’ve done so far.

The car, a 1988 thunderbird turbo coupe, is completely stock, I was driving the car around and noticed the temperature gauge was getting very high. The gauge at one point, while sitting at a stop light, went to the very top of the normal range. When the car is moving the temp goes down but that’s expected because air is moving through the radiator. From what I’ve read, the car should stay in the middle of that normal range.

So what I’ve seen so far when trying to diagnose this.
When looking at the fans, I turned the key on, and the passenger side fan starts but turns off without me moving the key from the key on position.

To see if the driver side fan turns on, I poked the pink wire in the IRCM in spot 17 I believe and attached it to ground on the battery. That fan also turned on. So I know the wiring harnesses are still intact and the IRCM and relay for the driver side fan are okay. I’m not sure what the next thing to test is or how to test it. My thought is the ECT sensor is bad but that’s just an educated guess. I’d like to figure this out for sure.
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Kuch Offline
Senior Member
#2
Grande,
It sounds like your fans are being controlled by the IRCM correctly as it turns on with the ignition switch, good there. The fans are thermally turned on by the ECT sensor located on the intake in between injectors 2-3. It is a pain to change as you have to drain some coolant and try to get your hands and socket in there to remove. It may be easier to remove the upper intake, but that involves a little more work with all of the wire, brackets, hoses, and such. Also, the coolant flow through the intake goes through the small coolant hose on the lower intake, this hose nipple in the intake is probably all corroded closed limiting coolant flow over the ECT sensor. You can remove the small hose and run a small screwdriver or pick or scribe into the intake to see if any coolant flows out. My car had the same issues, I also suggest getting a FACTORY FORD ECT from a junkyard as opposed to the available aftermarket ones. I tried some aftermarket ones and it always seemed to be turning the fans on hotter than it should be, put a used one from a late 80's Crown Vic with a 5.0 in and they turned on when the temp gauge just broke the normal into the hot range. That ECT is still in the car 4 years later. You will probably get a lot of responses from others that have the same issue as you as this is fairly common on these cars, but mostly simple to fix, just tedious.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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Jeff K Offline
Administrator
#3
You can run the KOEO EEC self test to check fan operation. As part of the test, the PCM will briefly operate the main fan (pass side fan) and the secondary (driver side) fan. PCM picks up the system voltage drop to determine if the fans are running. Failure to detect the voltage drop will set codes.

ECT gets its temp info from coolant flowing thru the small hose coming out of the intake pointing toward the pass side. Not uncommon for the small bung the small coolant hose is attached to getting plugged with "goo" if the cooling system wasnt maintained. If plugged, the ECT will read a lower temp due to little to no flow past the ECT, causing fans to turn on late or not at all.

When I got my TC, that bung was almost completely plugged and fans turned on at too high a temp. Cleaned out the bung, and all was well.
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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GrandeDan Offline
Junior Member
#4
Jeff, could you explain how to do the KOEO EEC test for an 88 turbo coupe?
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GrandeDan Offline
Junior Member
#5
Also, could one of you post a picture of what the coolant hose looks like or it’s place in the intake that I should clean out?
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Jeff K Offline
Administrator
#6
You can do the EEC self tests (KOEO, CM, KOER) by jumping some terminals on the EEC IV TEST connector under the hood and watching the CEL flash out the codes. Our tech articles have info on how to do this. There are also lots of articles on the web on how to do this. Google is your friend.
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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Jeff K Offline
Administrator
#7
For the coolant hose and bung that tend to get plugged..... locate the ECT, which sticks straight up from the intake between cyllinders 2 and 3. Look down several inches directly below the ECT and you will see the small coolant hose and its bung.
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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