Coolant temp is normal while idling, cools off when fans cut in
When vehicle is idling the temp reaches normal, but when vehicle is moving and the fans cut in, the engine temp drops out of normal range, and when this happens, the heater is hardly blowing hot air. This is on a 1995 Ford Windstar, with a 3.8litre engine. the coolant level is right up. Could this be the sensor that regulates the two electric fans?
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Re: Coolant temp is normal while idling, cools off when...
I would check to see if the stat is working right, do you have rear heat on this vech? . if you do you may have a air pocket, the windstars have a metal tube coning from the water pump that gose to the heater core lines for the rear heat and they like to fail. they get a pin hole leak that hard to find, the water pump also likes to fail also, not moving a enough fluid under load the ends of the inmpler wear down
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there is another coolant temp sensor that is a normally open switch. It closes when it reaches a certain temp and turns the fan on. If you are not getting 12 volts at your fan motor and your fuse is good for this circuit than you have a bad "automatic switch". that will need to be replaced
Hi Tommy, Try carrying out the following tests and observe the results. Open the hood (bonnet) and start the engine, let it warm up until it reaches normal operating temperature. Observe if the electric cooling fan cuts in at the required setting. If the fan fails to start you have your problem. The failure may be due to a defective sender unit, a defective relay or a defective fan motor. If it starts but rotates slowly it may not have sufficient cooling action. If it runs normally check to see if the radiator cap is emitting steam (leaking) If it is, replace it. If the vehicle has been in use for some time, a cooling system flush may be required. It is unlikely to be a problem connected with the thermostat as the thermostat is a thermo mechanical devise, which either allows sufficient coolant to pass or does not. It is not impossible that it is defective but unlikely. Other causes for changes in coolant temperature can be caused by incorrect ignition or valve timing. Valve timing can have changed because of stretched timing belt or chain or a gear which has jumped. It could also be a fault with the gauge circuitry. I hope that this info has been of help. Regards John
Try this for a diagnostic:
Check coolant level. Fill if necessary. Check for leaks.
Start vehicle. Allow to run.
Observe coolant temp gauge. It should slowly climb to center.
Once coolant temp gauge reaches the middle, the coolant fan is triggered to activate by the vehicle's computer (ecm). Fan should come on until temp drops slightly then cycle off.
If fan is working, move to next step. If fan isn't working, possible causes:blown fuse, faulty fan relay, coolant fan switch, faulty cooling fan.
If there are no leaks, and the fan works properly as described above, have a compression test performed. This test will basically measure the compression power (in PSI) in each cylinder by screwing a device into the spark plug hole of each cylinder cranking the vehicle (with ignition disabled) and observing the gauge. Each cylinder reading should be significantly close to its next one. If not, suspect a faulty cylinder head gasket.
The radiator fan should come on when car reaches normal operating temp,With engine at Idle and temp normal feel the top radiator Hose ,it should be hot,If no then Engine coolant is not moving-cause could be an "Air lock" if that is the case,turn key off until it cools then disconnect top Hose and start engine,at normal temp,you should have Engine Coolant coming out,turn key off let engine cool;reconnect and refill with a 50/50 mix;
Back to the Fan problem;the Fan should come on when engine temp is normal,if not turn the Air-Conditioner on,radiator Fan should come on at any temp;two checks ,one is the Fan Relay ,located in the under Hood main power supply box;There will be 3 or 4 relays for different systems since they are of the same part number swap and see if problem is fixed;if no check the Fuse in same power supply box;You said fans spin so they are not locked up;Take an eight dollar D.C. circuit tester,they look like an ice pick with a clamp for ground attach,to ground and with the fan plug disconnected see if you have voltage; ,You can have a continuous fan by finding a wire close to the fan that has power when the key is in the on position,take a wire and attach to that wire;
Check your coolant levels. If the temperature isn't much higher than normal, you may be fine, or you may have a Coolant Temperature Sensor going bad, and reporting the incorrect temperature. Even though the thermostat was replaced 8 months ago, it is possible it is already going bad again. I believe this is more of a Coolant Temp. Sensor fault though. The cooling fans are On when the AC is on. With the AC off, the cooling fans come on when the engine reaches a certain temperature, and cut off once the temperature is back in range. The Coolant Temperature sensor shouldn't cost much, and is easy to replace. I would start with that, top it off with coolant, and then maybe change the thermostat.
You probably need to bleed the cooling system properly.
Open the cooling system bleeder screws.
Slowly fill the cooling system with a 50/50 coolant mixture until coolant runs freely out of bleeder screws. Close the cooling system bleeder screws Install the coolant pressure cap Start the engine. Run the engine at 2,000 - 2,500 RPM until the engine reaches normal operating temperature. (midway on gauge) Allow the engine to idle for 3 minutes. Shut the engine off. Allow the engine to completely cool. Top off the coolant as necessary.
Run engine again at 2000 - 2500 RPM until the engine reaches normal operating temperature.
Allow engine to idle until cooling fans come on. It should come on with the gauge about 3/4 of the way to red. - if it gets to where is touches the red, shut down immediately.
When the fan comes on, put your hand behind the fan and observe the temperature of the air coming from the fan. It should feel hot. If it is blowing cold air, the coolant is not circulating through the radiator like it should. This could be caused by lots of things including an improper/defective thermostat, corroded water pump impeller, or a blown head gasket.
You have two fan's on your truck, 1 is a fan clutch runs with the drive belt, 2 elec fan motor, with test light and engine running at normal temp, just a little bit above 1/2 way on your temp gauge check voltage at elec. cooling fan harness if you have voltage at one of the two wire's and fan don't turn on, bad cooling fan motor, on the fan clutch after you check voltage at elec. fan motor turn engine off, with your hand spin drive belt fan if it spin's freely bad fan clutch, replace it.Also check cooling level.Hope this was very helpful
Make sure the cooling fans are working when the engine reaches above normal temp,if they are not ,turn the ac on,and see if the cooling fans come on,if so,replace the coolant temp sensor,if it has a clutch fan,then replace it,for it is not staying engaged ,and is not turning fast enough to cool the radiator.