Normally I don't second guess mechanics because it's common for details to get lost in translation between mechanic, service adviser, customer, and me, plus, I can't actually see and hear the vehicle. Mechanics also are not very good at explaining things in layman's terms without sounding like they're talking down to you. In this case, however, I think I'd recommend a second opinion.
My first question is why the engine stopped running originally and if you got it restarted. There are two serious possibilities I can think of. The first would be the engine got so hot that the oil broke down and lost its lubricating properties. The weakest link in the chain is the lower end of the 3.0L engine. (I didn't say weak; I said weakest). The first thing to go would have been the crankshaft and connecting rod bearings, but that would not cause the engine to stop running. You would have noticed severely decreased power and a loud banging noise. This happened to me a few years ago, but I was still able to slowly nurse it over 30 miles to get back home.
The second problem could be an overheated and warped cylinder head. They are made from aluminum and do warp easily from overheating. Also, a leaking head gasket could be responsible for your comment about losing coolant and not finding any leaks. If your mechanic suspects the head gaskets are leaking, he could be worried one or both of the heads are warped too. There is no way to tell until the engine is disassembled. If two heads are needed, it would cost less to install a used engine. If just head gaskets are needed, the total job will likely cost less than $400.00.
Those are the bad scenarios. The first thing to do is to get the engine running and listen to it. A little clicking is normal when you're standing next to it with the hood open. If you see air bubbles gurgling into the coolant overflow reservoir, that's a good sign of a blown head gasket. Your mechanic can also use a special tool over the neck of the radiator to check for head gasket leakage. It's a clear plastic tube with two vials of dark blue liquid. He will draw air from the radiator through the tube. If a head gasket is leaking, the fluid will turn bright yellow. That test can detect a leak small enough to not affect engine performance.
The sensor for the temperature gauge is very close to the bypass hose. When the hose popped, the coolant was still circulating past the sensor. When the coolant level dropped enough to stop circulation, the heat buildup took place away from the sensor. That heat could only reach the sensor by way of hot air which is very ineffective. In addition, the coolant on the sensor evaporates off which is a cooling process. As soon as the cooling system lost pressure, the water in the system began to boil and left as steam at 212 degrees. That is not a damaging temperature to the engine, but as the temperature rose, there was no way for it to reach the sensor. That's why you didn't see the gauge rise.
As far as repairing or junking the van, I'm the wrong person to ask. After working in the industry for many years, I am so frustrated with the engineers' insane need to add dozens of unnecessary, unreliable computers to every imaginable system. I will never own anything newer than a '95. I have one now that will be sold when I have time to make repairs. My daily driver is a 1988 Grand Caravan with only an engine computer. On occasion, I use it to pull an enclosed trailer that's bigger than the van, and it never complains.
The '96 and newer Caravans have a lot of trouble with body computers and heater / ac computers. The first time I worked on one, I knew I never wanted to own one. Sad comment from a life-long Chrysler fan. The only thing I find in their favor is GM's cars and trucks are infinitely worse. Their vehicles guarantee very expensive repair bills. You must remember too that car manufacturers sell cars that are in their best interest. They do not make money when we fix a car and keep it on the road. They make money by "selling product". They benefit when we decide it's too expensive to fix our cars.
I know from talking with people at car shows there would be a lot more new car sales if the cars were not so ridiculously over-engineered. Unfortunately, Detroit isn't listening, and they can't figure out why sales have been slipping for more than a decade. People are fed up with $700.00 repair bills because their power locks or wipers didn't work. And $700.00 repairs are a given now. You know they're in your future when you buy a new car.
So now you see why I'm the wrong person to ask. Personally, I get the last ounce of life out of everything I own. Heck, I'm still driving my first new car, a 1980 Volare / Road Runner.
Sunday, December 13th, 2009 AT 11:28 AM