Hot Stall-No Start

Hello- my wife's 95 Lumina Sedan with the 3.1 and 100,600 miles on it has developed a strange problem. The car loses all power after it heats up. After about 20 minutes of highway driving this morning it started to miss and kept trying to stall. Eventually it did die and when she went to restart there was NO power. It was like the battery was dead. You could hear the soloniod clicking but nothing turning over! I pulled the alternator and had it tested @ AZ and it was good. After I put the alternator back in and jumped it to get it going it ran fine all the way home (15 miles) and now it seems to be alright. When I pulled into the driveway and shut it down it started right back up!! BUT I know as soon as she runs it down the highway it's gonna happen again! I thought maybe the coil paks were bad and breaking down when they got hot but that doesn't explain the dead battery! (at least I don't think it does)

Any thoughts or suggestions would be GREATLY appreciated!

Check the grounds and all power connections, not loose or corroded. Alt. should be checked hot under load on the car.

In addition to Max suggestion on the alternator, the battery should also be load tesed when it is hot. Batteries can dead short when they get hot, and draw so much current that it will cause the car to stall. Once the battery cools down, it will work ok until the next heat cycle. Coil packs and/or ignition modules failing due to heat would have no effect on starter operation or battery state of charge. The starter would crank the engine over, it just wouldn't fire.

In addition to Max suggestion on the alternator, the battery should also be load tesed when it is hot. Batteries can dead short when they get hot, and draw so much current that it will cause the car to stall. Once the battery cools down, it will work ok until the next heat cycle. Coil packs and/or ignition modules failing due to heat would have no effect on starter operation or battery state of charge. The starter would crank the engine over, it just wouldn't fire.

That makes a lot of sense but what would cause the battery to get so hot? And how do you duplicate it-drive until it happens again? Unfortunatley once it dies it won't stay running even with a jump start and I KNOW it won't die somewhere that I can check it!

Thanks for the advise.

Regretfully, it's impossible to recreate the short. It can happen at any time as the plates expand from heat and from the vibration of driving down the road. Since it won't start even with a jump, it could also be a bad starter with a flat spot in the armature or a slightly sticking solenoid that is drawing power, but I've never seen one draw the battery down and cause it to die while driving. A bad spot on the armature will only act up when the starter stops with the brushes on the bad spot. If it stops in another area of the armature, it will work fine.