This my first post. My 2000 G. Caravan 3.3L overheated coming up a mountain going home with temp warning light and audio alarm. Had to stop at top to let engine cool off. Rad fluid was boiling out of res. Had to lemp home at low speed with heat on, with a couple of other stops. I had the engine replaced 11 months ago, with new t. stat, new pump, and hoses. Replaced rad. 2 years ago. Had not overheated till now. I have press tested rad. with no leaks, replaced stat with superstat-fail open, took off and checked pump / metal impeller still tight, changed fluid and cap. Hoses good, fans come on when temp is reached at idle, and when a/c is turned on. Has also had slight miss detected at all rps's for a couple of months. Still overheats after a few minutes at driving speed. I don't Know of any other simple fixes. Any Guru's out there?

 

Maybe exhaust is leaking past head gasket and into coolant. Get a loaner test kit from Autozone or the like.

 

Took van to local shop to have exhaust in rad. fluid tested, came up negative. Called local rad. shop, they said to disconect coil and turn over engine and watch rad. level. Tried twice at about 20 to 30 revs. with no change in fliud level, either up or down. They suggested taking out new t. stat and driving. This I will do after work today. Stil no cause.

 

Today also took out t. stat to test overheating. After reaching operating temp, reved engine up to 2500 for a couple of min. untill it started to overheat again. Still at a loss for the cause.

 

The engine then has a coolant flow problem, weather a water pump, radiator, or engine block. Also by any chance is the cooling fan coming on at anytime it is overheating?

 

Hows the temperature on Upper and lower Radiator hose when over heating? and is Fan coming on when over heat?
what about heats from HVAC?
Master is probably right on coolant restriction. Try disconnect the Upper and lower Rad Hose, shove a Garden hose into the Rad Hose and into the Engine, see if water flows out freely.

 

Fans work when engine gets to operating temp, also work when a/c is turned on when cold or hot. Top hose gets hot as temp is rising, and is super hot when it gets toward overheating. Also as I stated yesterday, van went past center heat and climbing while in idle with RPM to 2500 with no thermostat in the van.

 

what about the bottom Hose? you could be a plug up radiator. check radiator flow.