I have a 2008 Grand Caravan SXT with the 3.8L. Purchased used, was losing coolant and overheating, had several problems. I have since replaced the head gaskets, radiator, water pump, thermostat, upper and lower hoses, and the bypass tube from the water pump to the lower hose, (and radiator cap, duh) but the system is still losing coolant. I'm not seeing anything on the ground, but do see steam occasionally from the exhaust, and a cool surface placed near the exhaust collects water. I'm not getting any codes, but when I stress the motor by running the ac compressor, I start getting an intermittent misfire in cylinder 4 at certain engine speeds and throttles, which sounds to me like a small amount of coolant getting into the cylinder, changing the atomization ratio. I'm at my wits end here. The heat blows nice and strong, although it does have a faint antifreeze smell(even though I've been using water in it until I can fix this, antifreeze isn't cheap). I haven't noticed any evidence of coolant leaking inside the vehicle, so I *think* the front heater core is good, and assume the rear is, although I'm not sure where it's at, or how to check it. Am I missing something, or does this sound like a cracked head? I'd hate to pay for reman heads, just to find that it's something else. Any help would be appreciated.

Edit: Also, how likely is it(percentage-wise) that the head gasket(s) blew almost immediately after replacing it(them), being that I didn't have a torque wrench? I used new bolts, and tried to maintain the same amount of torque across all of them, followed the correct torque pattern, but may not have hit the right numbers. I should also add that during a compression test, all cylinders reported 180psi+ except cylinder 4, which read just over 170. Is that enough variance to suggest a problem with the head seal?

 

head bolts are a critical torque...you can't install them without a torque wrench. The heads and block should be measured for warpage. They must be torqued in sequence in 4 steps. head bolts are reusable but must be inspected for bolt stretch.

remove the plugs and rent a boroscope and look into each cylinder fo r signs of coolant. chemical testers are available for testing for headgasket leaks.

 

It very well could be the head gasket since it was not properly torqued, but there is a common place for coolant leaks that I didn't see you mention, the two plastic Y's in the heater hoses. The most common leak is in the Y just behind and below the coil pack, the leak tends to be small and drip (or spray) onto the crossover pipe so the only evidence of the leak is dried coolant residue on the crossover pipe. The second Y on the firewall just above the ABS module.

There is a thread about the Y connector here: 2008 Grand Caravan coolant leak

 

Thanks for the replies, guys. I've checked both Y connectors with the engine at operating temp and found no evidence of any leaking, as common as it seems to be. I have new head bolts and gaskets on the way, and I'm going to get my hands on a torque wrench(need to have one anyway, any self-respecting mechanic would) so that I can do this properly. Once I have the heads off, how would I go about checking them for flatness?