2000 Caravan NOT Overheating?


Drove over an hour this morning, turned off the engine and heard gurgling. What gives?

I open the hood and the coolant is bubbling & overflowing in the plastic overflow reservoir.

Started the Caravan back up and turned on the heat on high - watched as the coolant in the overflow went back down, below Max, below Min, then stopped halfway between Min & the bottom of the reservoir.

Turned the heat off, let sit running for a couple more minutes, but no change. The Temperature gauge was at its normal (for me) halfway point.

What’s going on?

PS: I did hear some gurgling last week - but it didn’t last more than a couple of seconds. Today’s gurgling - including coolant escaping from reservoir - lasted long enough for me to (a) turn off the car, hear it, ponder it; (b) pop the hood, walk to the front and open the hood, wonder why the coolant is bubbling in the reservoir; © get back in the car, turn it on, turn on the heat. As the coolant level in the reservoir fell, the bubbling stopped.

My GUESS is there is air in the system. Check coolant level after the car sits for 8 or more hours, coolant level in recovery tank should be at or above minimum level.
If you haven’t had the system serviced within 3 years now is the time to do it.
Just read your update, yes you need the coolant system serviced.

The cooling system is not holding pressure properly, replace the radiator cap.

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You have air in the system. Typically this happens when a leak allows not only coolant to be released when the system is hot and under pressure, but also air to be drawn in when the engine cools down, often after the coolant in the reservoir is blown out to where it’s low and air is drawn back in.

You cannot trust the temp sensor once the coolant level drops to where the sensor is in an air pocket. It’ll often read okay even when the engine is overheated.

You need to have the system pressure checked, repair the leak, and then pressure test again, check for fluid retention when hot, and check for operation of the thermostat (which can be removed and bench tested if you like).

NOTE: you MIGHT end up having to check for a headgasket leak, but I won’t go there until the cooling system is addressed as a first possible cause. Post back.

By the way, the radiator cap if it’s not holding pressure could be the culprit, but it can be tested, and my gut tells me you have more going on here. There are a lot more common causes of your symptom than a failed radiator cap.

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When my truck does that, it is usually the radiator pressure cap isn’t sealing tightly.

It could turn out to be that too, but when a problem exists that could manifest itself as a destroyed engine I believe prudence dictates checking every reasonable possible cause out thoroughly and not just assuming it’s one easy part. Worst case by going through all the possibilities, he discovers it was only the cap. Best case, he discovers he has other cooling system problems and saves the engine.

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I have been running errands around town. Still no overheating, no more gurgling or coolant coming out of the reservoir.

Will top up the coolant and keep watch on this. And it is a good idea to flush the coolant, too. Maybe next week/end.

Good cap, bad cap: So what does the cap do that can go bad? It wasn’t flowing out through the radiator cap.

The cap does three things:

  1. it allows the cooling system to pressurize to a set point, typically 16psi, to allow the coolant to get hotter without boiling. Fluid under pressure has a higher boiling point.

  2. it allows excess pressure to push the coolant into the reservoir without exposing the system to the outside world.

  3. it allows the engine as it cools to draw coolant back into the engine rather than air.


By the virtues of a mechanical spring.

Through the radiator cap is the only path to the reservoir. Coolant boils at 215 to 220 F when not pressurized/no functioning cap. With a proper radiator cap the coolant won’t boil until 260 F plus. What you observed was likely just the coolant boiling after you shut off the engine.

Quick reply to say thanks.

More recently, there is a ‘mysterious’ leak and I see a coolant leak where the fluid dripping off the oil pan. I need more room to get under safely to see what’s what. Have moved this yes-overheating to: 2000 Caravan 3.0 V6 leaking coolant, overheating