[bressen]

I have a 2007 grand caravan with the 3.3 motor and it's being a bear to diagnose.

On Thanksgiving, the water pump failed catastrophically; silently dumped all the coolant without an overtemp warning, so I don't really know how long it was running dry for; the cabin heat was spotty for a few days before this.

We replaced the water pump and thermostat and used the dealer coolant, but it overheats when driven even a short distance, and all the coolant ends up in the overflow reservoir. With the temp gauge maxed, the cabin heat blows cold. It runs rough; with fresh plugs and wires, it sometimes issues check engine codes for misfiring.

But... there's no white smoke, no sign of oil in the coolant, and when my mechanic pressurized the cooling system, it held the pressure.

His current best guess is that the gasket blew somewhere near an exhaust port, and hot exhaust is filling the system and shoving the coolant into the overflow.

Does that make sense? What kinds of tests can be done to make sure?

 

[bressen]

Thanks for all the info!

So, since there is air repeatedly getting into the system, it's almost certainly the head gasket (though we could check to verify flow and look for a leak sucking in air someplace, but that seems unlikely, and could check for CO in the coolant to make sure). A shop I just talked to said if they do the head gaskets on a motor with 155k on it, the bottom end could blow before too long, so I'd be better off just putting in a new engine. Ouch.

 

[bressen]

Did the CO2 test, bad head gasket. (After we took out the test bulb, we noticed we could actually see the bubbles of exhaust coming up the radiator neck with the cap off). I have called five shops, and three of them want to sell me an engine swap.

Price quotes, in case anyone is curious:

• Shop #1: $3500 for a rebuilt motor with a 4 yr/40k mile parts-only (no labor) warranty
• Shop #2: $2500 for a used motor with 80k on it, 6 months warranty, or $5500 for a rebuilt motor
• Shop #3: $1950 for a used motor with 72k on it, 12 month/12k warranty, or $2100 with a lifetime single replacement warranty (it ever goes bad, they'll throw in another motor)
• ebay prices are $350-$1000 plus shipping for a used motor, no rebuilds on offer for my "R" code 3.3, but an "H" code 3.3 rebuilt is $2400.

I've found two shops that are willing to do just the head gaskets; $768 and $900 quotes, though I think that's without resurfacing the heads, and neither of them mentioned that fact, I had to ask.

I'm next to Boston, if anyone has shops to recommend.