HEAT PROBLEM ON 3Y TOYOTA ENGINE

check that the wire to the temp sender unit has not fallen off and is shorting out on the head/block. The power comes from the ignition switch through the gauge down to the sender unit and because the sender is a temperature controlled resistance unit the voltage is very low and so the gauge reads cold . as the temperature heats up , the resistance is decreased and so the voltage is increased though the gauge and the needle reads higher.. Hench if the gauge goes directly to hot on start up the wire is shorting out or the sender unit is faulty.

.002 is fine. You need that clearance for oil to fill in between the crankshaft and the bearing.

Hi Aaron, I am not familiar with the engine type you record? I know of the 21R and 22R, the 'Y' series being the 2Y 3Y and 4Y. I also know of the L series diesel engines. If you could be more specific about the problem you're facing we may be able to give some help. If you would like to fit an oil pressure gauge, I suggest the electrical units found in the Land Cruise and other similar vehicles. The sender units for these units have leak proof very fine threading but I cannot remember the gauge or the pitch. Regards John

The temperature you see on the dash board gauge is not necessarily the actual temperature of the coolant. The engine has a 'coolant sensor' which sends information to the electronic control unit (ECU /PCM) and there is a separate 'sender' which governs the gauge reading you see on the dash board. The sender usually has just one wire connected to the top of it. The sender is basically a heat dependent resistor and the temperature gauge simply reads this resistance. Sometimes corrosion in the electrical connector can inhibit the correct readings, so first disconnect the sender and inspect/clean the pin with a little wire wool. Now check the coolant. First put the interior heater on maximum heat. Run the engine up to working temperature and then squeeze all rubber hoses to help shift any trapped air. Top up the coolant if the level drops when air pockets have been shifted. The following sequence should occur when the engine is warming up. 1) When cold the engine has higher then normal revs. This is due to the coolant sensor (not sender) telling the ECU that the engine is cold and that the injectors should add more fuel to compensate for the cold condition of the engine. 2) Within about a minute the idle revs begin to drop as the coolant sensor detects the engine warming up 3) After about 5 minutes the thermostat should open. You can detect yourself this by feeling the top rubber radiator hose getting hot. 4) If you have an electric cooling fan on the radiator this should switch on about now. If you have a fan driven by a viscous clutch this will engage a little later. 5) after about 2 more minutes the face of the radiator should be becoming hot and the bottom rubber radiator return hose should become warm, then hot.
If you have an electric fan and it fails to come on then check the electric relay and fuse for it. Viscous clutch fans should always show some resistance when turned over by hand when the engine is off, if it spins freely then the clutch coupling is faulty and it will need to be replaced. A sign of faulty fan related over-heating is a car than runs at normal temperature when cruising on the freeway but overheats when standing at the lights; fan engagement is to compensate for the lack of air flow across the radiator core when the vehicle is stationary.
I hope the above helps

Keep in mind the temperature sender that indicates on the dash board is quite separate to the temperature sensor used by the cars power control module to set injection parameters etc. The dash board is to keep you happy the sensor keeps the engine happy. The thermometer sender is just a heat sensitive resistor (thermistor) and only as two wires to it. One wire is from the voltage supply and the other is to the dash board gauge (effectively a voltmeter) which monitor temperature by monitoring the voltage output due to the resistance of the thermistor in accord with the coolant temperature. First check that the connection with the sender is clean and free of corrosion. Put a voltmeter across the sender pins and turn the engine on. Measure the voltage change with temperature. If the voltage does change as the engine warms but the gauge on the dash is stubborn then it is likely that there is something wrong at the gauge. If there is not voltage change with engine warming then the sender is faulty.

.if your truck is over heating with a temp. higher than the normal whicjh supposedly, then the fan keeps on. but if the temperature of your engine is normal when you look at the gauge, then the thermostat attached to the engine below it is fine.
The problem as we go back that your fan keeps on turning, even though your getting a normal temperature., probably get new coolant temperature sender sensor.
To check your temperature sender disconnect the plug from the sender and test it using an ohm meter. When the engine is cold you should have infinite resistance. Then run the engine untill it gets warm. Shut off the motor. Disconnect the plug from your temperature sender and check the resistance again. It should no longer be infinite ( see your repair manual for the correct reading).

It might not be the fan but the strain on the engine with the AC on the makes the engine heat up.
So a possible timing tuning of the engine is necessary to keep the engine in trim mode. Nomally the heat will also be related to the external temperature as it could make it worse.
An opinion from Toyota will be good to concur and decide.

Coolant Temperature Sender TESTING a coolant temperature sensor: Using an ohmmeter, measure the resistance between the terminals. Refer to the appropriate chart for your engine. If the resistance is not as specified, replace the sender. Fig. 1: Coolant temperature sender chart — gasoline engines
Fig. 2: Coolant temperature sensor chart — deisel engines
Fig. 3: Inspecting the coolant temperature sender for resistance

Possible your radiator must have gone bad.
Or consider a radiator flush.

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The Engine Coolant Temperature (ECT) sensor is mounted in the intake manifold and sends engine temperature information to the ECM. The ECM supplies 5 volts to the coolant temperature sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the ECM monitors a high signal voltage which it interprets as a cold engine. As the sensor warms (internal resistance low), the ECM monitors a low signal voltage which it interprets as warm engine.
Fig. 1: View of the Engine Coolant Temperature (ECT) sensor Fig. 2: Engine Coolant Temperature (ECT) sensor locationTESTING
See Figures 3 and 4

1. Remove the ECT sensor from the vehicle.
2. Immerse the tip of the sensor in container of water.
3. Connect a digital ohmmeter to the two terminals of the sensor.
4. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the engine coolant sensor temperature vs. resistance illustration.
5. Repeat the test at two other temperature points, heating or cooling the water as necessary.
6. If the sensor does not meet specification, it must be replaced.

Fig. 3: Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensor wiring diagram Fig. 4: ECT sensor temperature vs. resistance values