1994 caravan w/3.0 engine, engine is over heating,gauge goes to hot then in a few seconds it returns to normal. When I stopped to to check it the coolant had been expelled thru the coolant expansion tank, at first I thought a hose had ruptured but, that was not the case.After talking to some mechanics they suggested that I change the thermostat so I did that, refilled the coolant, making sure that their was no air in the system. I then took it out for an hour test drive, everything seemed fine then the temp spiked to hot then dropped to normal. When I opened the hood to check the coolant was bubbling in the exp. tank, I fiqured the air was just escaping. Next day my wife drove the van and it spiked again and went back to normal in a few seconds. When she got home she opened the hood and the coolant had been expelled again and the van wouldn't start. I can't figure out what is happening, please help. I purchased van new and have taken very good care of it, it currently has 145,000 miles.
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the temp gauge sends the power from the gauge to the sender unit which is a variable ground. That means that as the coolant heats up , the resistance in the sender is decreased and the current through the gage increases ans so the needle goes up
when that wire is shorting out some where the gauge will go to hot and when that short is removed the needle comes back down to cold
so that means that you will need to trace the wire along for where it is rubbed through or get an accredited auto electrician in to find the fault
If the cooling system is functional, yes. The ac condenser adds heat to the air coming thru the radiator when the ac is on. If the engine cooling system is weak, the extra heat will make the engine run hot. Low coolant flow thru the radiator is a common cause.
This is a sign that the thermostat is sticking shut and then opening after the temp gets past a certain point. If the heat gauge goes to high and then drops down suddenly, this is the likely culprit and you need to replace the thermostat - again.
I have had them arrive from the parts store and be defective.
Does the engine over heat or the gauge goes to hot. Really hot. Since the A/C is on , this puts an extra load on the engine. This is why the fans come on when the A/C is turned on. This is usually low speed fan mode. High speed doesn't come on untilll 220 to 230 degrees. Most vehicles. Cars don't over heat untill the gauge gets in the red, when it starts getting close is time to worry and stop. I guess the question to you would be, What does the temp gauge read?
when the level of coolant drops in the motor the heater core is the first to be without
because it sets up high
so you need to check the level
and check where the coolant is going
to make the level drop
It sounds like your thermostat is broken. The metal retaining tabs that hold the thermostat together can break over time. I would recommend pulling it out and checking it. When installing a thermostat there is an arrow on the edge. Make sure it points up. toward the top of the cylinder head.
Start with engine cool. Remove rad cap, top up coolant, start engine, & turn on heater (not defrost). let it run until up to normal operating temperature & radiator fan comes on, then shuts off. Let it do this about 3 times before you put rad cap back on & top up return bottle to proper level. Every once in a while, rev engine slightly for a few seconds while your doing it, to speed up bleed by increasing flow. Keep an eye on temperature gauge for too hot, and fan not coming on, if so, shut it off.
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