89 Toyota Supra Turbo

Electric Cooling Fan Upgrade

November 2001

The sound of the engine seemed too loud after the wastegate modification - at low RPM the engine was noisier, and when cold, at 3000 - 3500 RPM a high pitched screeching was developing. At first I thought the turbo wasn't in good shape and the additional boost was messing with it. A bit of test driving revealed that the turbo still spooled up quietly and maintained a good boost level.

It then seemed like a pulley was failing either the A/C compressor or the air injection unit. Neither. It was the idler pulley for the A/C compressor belt. The pulley was replaced by the local mechanic ( I had neither tools nor time ). That solved the screeching noise.

At idle, and at low RPM the engine noise seemed to mostly be fan noise. I checked the fan clutch, and it was not turning freely when cold. I figured it must be jammed. I removed the fan and clutch and it was very difficult to turn independently. Time to replace it.

 

I decided to replace the unit with an electric fan unit. Here's the stock fan and fan clutch out of the car, plus the portion of the fan shroud that I removed to make way for the electric fan.

The electric fan unit and thermostat are rated at 1300 CFM (open) and derated to about 1100 CFM in a typical radiator application. The electric fan unit is an Imperial 226116 with a 226203 thermal controller. The manufacturer lists that unit as appropriate for engines in the 3.2L to 4.0L range. That seems sufficient for the Toyota 7M-GTE at 3.0L

Here is the completed electric fan installation.

The stock fan and fan clutch were removed, preserving the stock water pump pulley and threaded studs.

The thermal control uses a temperature sensor that is located against the top of the radiator by a small clip. The control receives the temperature level signal from the sensor and switches the fan on and off accordingly.

The thermal control is adjustable, with the lowest setting providing for constant fan operation. The temperature range is listed as 32C to 120C. I found the halfway setting to work well at this time, winter in California. The fan runs briefly when the engine us shutoff for a few cycles, then remains off.

The electric fan is mounted using spring loaded locking clips that push the fan shroud and motor frame against the radiator. The fan can be installed either side of the radiator, pushing or pulling air through the radiator, depending on the wiring polarity.

Note the generous amount of air clearance that this retrofit creates by removing the bulky stock fan assembly. Plus, the electric fan, even when running, is very quiet.

Test driving the car for a few days, both in highway and street conditions has revealed significant improvements to the car:

  1. Better cold-start warm up, because the fan does not start until the engine is at operating temperature
  2. Better cold engine performance at low speed
  3. Engine feels more responsive without the added inertia and drag of the stock fan and fan clutch
  4. Engine runs quieter and sounds smoother, less vibration.
  5. Running the fan after engine shutoff seems to reduce the heat buildup ("heat soak condition")

I'm expecting that my gas mileage will increase slightly as a result of the fan upgrade. If I see something significant there, I'll update this posting.

One concern is regarding "knocking" in the engine. I recently tried a less expensive gasoline and I've noticed some low RPM knocking when the engine is fully at operating temperature. Whether this is a result of chaging the cooling system, or simple bad gasoline should be easy to determine. Also, because the remaining engine noises are not masked by the fan noise, I probably am noticing more of these - including the low speed gasoline knocking. More later...

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