Aerostar Ford Aerostar

Fluctuating Temperature Gauge 94 3.0

Old 04-11-2019, 07:39 PM
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Fluctuating Temperature Gauge 94 3.0

I had a loose coolant hose in the rear of my 94 Aerostar 3.0 so I tightened the clamp and no more leak but since then I am getting weird temperature gauge fluctuations any time the heater or air conditioner is on. It stays rock steady when the heater is off. I am thinking I have air in the system somewhere. I have tried several methods of bleeding air from the system and saw some air bubble out but still have the problem. Why only when the heater is on??? I took it to my mechanic and he could not figure it out. He said the head gasket was good and he changed out the thermostat to be sure it was not an issue but it didn't help. Is there a surefire way to bleed all the air out that anyone knows of? Any other suggestions on what is causing the problem would be appreciated. I found an old thread on this topic and there were tons of theories but no real solution. I was wondering if anyone has any new ideas. Thanks in advance.
Old 04-12-2019, 10:15 AM
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It most likely is air in the system, but I haven't found a sure way to completely purge it on my van. The common method is to point the van up hill and run the engine with the radiator cap in the half-closed position to get the engine hot enough to open the thermostat and circulate the coolant. Turn the heater on full, both front and back if you have a dual system. Good luck.
Old 04-17-2019, 10:55 AM
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Bleeding air is more difficult if your van has the rear system. I replaced my water pump approximately 9-10 days ago and all the air is finally gone. The temp gauge was erratic and reading cooler than the normal operating range. Also after the first few days I heard popping and grumbling from the cooling system after a (hot) drive. Now the gauge goes to ‘N’ and stays within that letter. I noticed an improvement in how the engine ran as soon as things settled down. These cooling systems are very picky! Motorcraft thermostat and radiator cap are a must.

Old 04-18-2019, 06:07 PM
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I've had the symptom in my 4.0 liter and it required wasting coolant to bleed the system of air, until I put a pan under to collect the vomited coolant pushed out by air bubbles and reusing it.

my '97 has the rear system which is a blessing in all weather but by golly what a pain to bleed the air.

when I had the 3 liter '92 it was a piece of cake.

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