Hi, I have 2005 caravan that is loosing coolant very often.
Different shops tell me different stories, some of them very expensive to try. One of them already made me change the radiator, the radiator cap, I even replaced the thermostat, but the symptoms remain: once the engine gets hot, if I stop the car, the coolant starts gurgling, the reservoir tank fills up and starts spilling coolant on the ground, I can see the coolant going beyond the MAX mark in the reservoir tank.
If a start the AC, which starts the radiator fans, I can see the coolant level going down in the reservoir tank until it goes closer to the MIN level.
This happens in just seconds, it is like once the fans start working, something is sucking the coolant into the engine. If I turn the engine off at this point, everything is fine, no coolant gets lost.
But I don't want to be doing this every time I drive the car, Anybody has any idea, suggestion as to what might be wrong with the cooling system?

(oil looks fine, the only thing left to test in the system is the water pump, but, given the symptoms, Could it be that?)

 

I'ma guessing head gasket, small leak which only goes when the piston stops near the top of the compression stroke.

 

You may have a head gasket leaking exhaust into the cooling system making it boil over. A shop can test for this. Have they? They would use something like these: http://www.amazon.com/s/ref=nb_sb_ss...on+leak+tester

 

Do you have a lot of smoke coming out of your tailpipe, perhaps with a slight blue color? Also check your oil dipstick and the underside of the oil cap. Does the oil look like chocolate milkshake? If the answer to either is yes you have a blown head gasket.

The tester Cougar41 mentioned is a really good way to check for a blown HG as well, as depending on where the break is you may or may not get either of the above symptoms. I know AutoZone loans out that tool for free with a deposit; the only thing is you have to buy the testing fluid which costs like $8. It's not difficult to use the tester if you know how to follow directions, remove a radiator cap, and use a turkey baster. If you don't have an AutoZone near you check with your local major chain auto parts store.

 

Thanks for the suggestions, no there is no white or any other color of smoke coming out of the tailpipe, the oil looks fine to me, and I'm pretty sure where the coolant is going: to the ground when it overflows the recovery tank. If I keep doing the thing of waiting couple of minutes until I see the coolant returning to a normal level in the recovery tank and then turn the engine off, nothing gets lost. But it was not like that before.
I'm gonna go ahead and contact my local AutoZone to get the kit for testing for a head gasket leak, I'll post the results
Thank you all.

 

I had a '93. It got overheated (slightly) a couple of times b/c of the plastic radiator & a dripping drain valve. Eventually, it would keep puking out the contents of the reservoir. It wouldn't do it every time, about once a week IIRC. Eventually, it looked like a steam engine. Never saw anything in the oil; and until the end, never saw anything in the exhaust. Just my experience, YMMV.

 

Did you check the pressure cap first.

 

Went to my local autozone, they don't lend tools out, and they don't have the tool for sale either (I'm in méxico city), so probably I'm going to have to order it online.
Meanwhile I made some more experiments and this is what I've observed: if the fans are working most of the time (when the AC is on), the coolant level is between the min/max marks at all times. If I turn the AC off, the fans start working but for a very short period of time, so short, that the coolant level starts going above the MAX mark.
So, Could it be that I have a faulty coolant temperature sensor?

 

If the fans don't come on when the A/C is not switched on but they come on when the A/C is switched on, then you could either have a bad fan relay or a bad ECT sensor. I'm not familiar with the '93 fan setup. Judging from your comments it sounds like there are 2 fans, but I don't know if there is one fan for the A/C condenser and one fan for engine cooling, or if the two fans work in unison (like on the 2001-2007). If you can get your hands on a Haynes or Chilton manual, there should be instructions on how to test the ECT sensor and fan relay(s).

 

The coolant sensor or relay, but likely the sensor is the first thing that came to mind. It's over heating because it's not being cooled, as soon as the fan kicks in (the a/c automatically turns it on) the engine calms right down. Fan sensor would be the first thing I'd try.

Be well,
Larry