1995 Caravan (3.0L)... overheating?

[Flashfox]

Over the past couple of weeks, the engine "seems" to be running hot.

When I start the minivan and drive off, the temp gauge increases... all the way to HOT ("Check Gauges" light and alarm turns on).

However, 20-30 seconds later, and within a 5-6 second period, the gauge's needle drops back to the middle (Normal) and I noticed that the engine's fan is running full-tilt. The temp gauge stays there from that point on during my drive, but the fan keeps on running.

Based on the coolant expansion container, the level is OK. Now maybe I am wrong, but I assume that a "HOT" engine cannot drop to "NORMAL" within 5-6 seconds (or can it?)

One note: Since I have had this Caravan, the temp gauge never really went above 1/3. Dealer said all was OK. However now that it's mid-range, I am concerned that it might be higher than normal, based on experience with this vehicle. In any event, what is happening is definitely not normal.

Not being a mechanic, I would like to have an idea as to what might be wrong BEFORE bringing it to the shop.

Thermostat? Engine Temperature Sending unit? Radiator, etc.

[Deniz]

my 95 3.0L was running too cold. so i checked the thermostate which was stuck open letting the coolent flow through the motor and not letting it warm up. i replaced it for $10 and it works perfectly fine now and the temp does not go over half way, which seems to be the optimum temp.
maybe your termostate is stuck closed thus not letting coolent flow in the engine so the fan is going crazy to cool the engine.

but you say check guages light come on so maybe there is something wrong in the temp guage or the sensor. i would replace that first.

i would run a little test by warming up the engine and let the fan kick in, then shut off the engine and wait a min, start the van again and see if fan kicks in right away or the temp guage goes nuts. if thats the case, fan might be the only thing thats cooling the engine..
good luck.. i hope its not something serious..

[daveyhouse]

definitly change you thermostat before you warp you head

[Flashfox]

Originally Posted by Deniz

i would run a little test by warming up the engine and let the fan kick in, then shut off the engine and wait a min, start the van again and see if fan kicks in right away or the temp guage goes nuts. if thats the case, fan might be the only thing thats cooling the engine..
good luck.. i hope its not something serious..

Thanks... I will check it out.

My "confusion" stems from the fact that when the engine reaches "HOT", it only takes 5-6 seconds for the temp to return to mid-range (NORMAL).

IF the FAN was the ONLY item cooling the engine, wouldn't it take a lot more than 5-6 seconds to bring it down to normal?

I will try the thermostat and hope that it resolves the problem. I will post the results over here as an "FYI".

[gforster]

Originally Posted by Flashfox

Thanks... I will check it out.

My "confusion" stems from the fact that when the engine reaches "HOT", it only takes 5-6 seconds for the temp to return to mid-range (NORMAL).

IF the FAN was the ONLY item cooling the engine, wouldn't it take a lot more than 5-6 seconds to bring it down to normal?

I will try the thermostat and hope that it resolves the problem. I will post the results over here as an "FYI".

It sounds very much to me like your thermostat is sticky - that is that it does not open gradually as coolant reaches it's threshold opening temp - instead it responds too late and "snaps" open very quickly causing the rapid gush of hot coolant being cooled by the rad and thus the gauge dropping off so fast. The only other possibility I know of with the 3.0 is that you could have an air pocket. The 3.0 is suseptable to "hot spots" in the head, and proper purging of air is crucial to it. I hope this helps you out,

Geoff

[daveyhouse]

Originally Posted by gforster

It sounds very much to me like your thermostat is sticky - that is that it does not open gradually as coolant reaches it's threshold opening temp - instead it responds too late and "snaps" open very quickly causing the rapid gush of hot coolant being cooled by the rad and thus the gauge dropping off so fast. The only other possibility I know of with the 3.0 is that you could have an air pocket. The 3.0 is suseptable to "hot spots" in the head, and proper purging of air is crucial to it. I hope this helps you out,

Geoff

Very well put gforster

[Flashfox]

FYI... the problem is resolved. It WAS the thermostat and all is well. Thanks to all who provided me with some help ;-)

Happy Holidays... from Oceanside, California

[daveyhouse]

Thats great to hear it was a cheap fix that could have gotten very expensive.