It's the charging system you need to check instead of just replacing batteries. The generator keeps the battery charged and runs the car's electrical system. GM has had a big problem with their generators since they redesigned them for the 1987 model year. Because of their design, they develop huge voltage spikes that can damage the internal diodes and voltage regulator. To prevent those spikes, replace the battery at the same time you replace the generator, unless, like yours, it's less than about two years old. As they age, they lose their ability to dampen and absorb those spikes.
Since your battery lasts more than a day or two, most likely one of the six diodes has been damaged already. That cuts the maximum output current you can get to exactly one third of the generator's rated capacity. 30 amps from the common 90 amp generator is not enough to run the entire electrical system under all conditions. The battery will have to make up the difference until it slowly runs down over days or weeks.
There are tests you can do yourself to start the diagnosis of the charging system, but for this problem you'll need a professional load tester to measure full-load output current.
No engine can get hot enough to overheat in just ten blocks. Depending on what the symptom is, most likely the thermostat is not opening due to combustion gases pooling under it. Thermostats have to be hit with hot liquid to open. Hot air won't do it. The second symptom of white smoke makes a leaking cylinder head gasket the main suspect. That's assuming it's coming from the tail pipe. You didn't say where the smoke is coming from. Your mechanic can perform a chemical test at the coolant reservoir to verify that.
Sunday, September 28th, 2014 AT 11:04 PM