Went to start my 2008 SR5 V8 last night, and dead battery. I got someone to give me a jump, and started home. The battery light was flashing, but then the whole dash started lighting up. Eventually, the car died and couldn't get it restarted. Had to have my wife buy a battery and delivery it to me to get it home.

I have never experienced this in any car before. Usually, after you jump it, you can drive it just fine until you need to stop and put in the new battery. I was completely surprised that this 4Runner completely freaked out, and quit running. The dash was like a christmas tree.

I was driving around with very low rpm's much of the time through residential streets. Thinking that maybe if I made it to the highway or kept the rev's up that enough voltage would be coming out of the alternator to keep the car going?

Anyways, was a huge surprise to me, and was happy/lucky that it happened close to home and when a local auto parts store was still open!

I would say you most likely answered your own question

I can see the alternator showing its tail when a new battery is installed. I have seen starters do this also before. Sometimes when a new device is introduced to an old situation the older stuff doesn't want to cooperate. All 3 items are directly connected.

You can have it tested for free at autozone to confirm, but that definitely sounds like the alternator to me.

Usually, after you jump it, you can drive it just fine until you need to stop and put in the new battery.

IF the battery is really "shot" that will happen. Car idle drops and the car stalls and won't restart.

I replace a battery every 4 years. I have a 2005 4runner with 150,000 miles.
Alternator is 15 years old and still charges my batteries fine.

New alternator replacement for Toyota 4runners at Amazon under $100. Seems crazy to me to rebuild one when you can buy one with new parts and warantee for cheap!


Amazon.com: New Alternator Replacement For 99-04 TOYOTA 4RUNNER TACOMA T-100 3.4L 27060-65160 101211-9590: Automotive

Was your battery light on the last time you drove it, before the dead battery episode? It sounds like your alternator died, thus eventually resulting in a dead battery. In that case a jump will get the engine started, but without a working alternator there's no power source to recharge the battery or to supply power to the vehicle systems. Eventually your discharged battery can't supply enough juice and the engine dies.

The new battery was fresh enough to get you going again, but if the alternator is still sick you're going to have a repeat experience. Best get the alternator checked, as suggested above. Or, if you have a multimeter, measure the battery voltage with the engine running. If it's below about 12.8 volts your alternator is not getting the job done.

(A healthy alternator will supply adequate voltage and current for basic vehicle systems even at idle.)

Well, the same thing happened today. Once I put the new battery in all seemed fine, and drove it for several days. Then today the car died just like it did last time before I put the new battery in. I guess it’s likely the alternator that’s the problem.

Check it with a volt meter when it's running and see if the alternator is charging the batt. You should see around 14 volts if the alternator is charging the batt.

Will do, hope I can get it to start with a jump!

There's plenty of info and posts on here about replacing the alternator brushes, which is likely your problem. They're $20 or so, and if you already have the alternator out, it takes an additional 10 minutes to swap out the brush assembly. Tapping the alternator a few times lightly with a hammer may get your current brushes to seat down enough to charge the battery for a few days, while you wait for replacement brushes to arrive.

It was the alternator as suggested. I researched the method of replacement here and did the job in about three hours. All is good now.

This was me this weekend!

Jumped it and was letting it "charge" before running out to AutoZone to get the battery tested. Had a multi-meter on the battery showing ~14V @ cold startup, and slow decreased to 11.4V after about 10 min.
Walked away for another 10 min and returned to a silent V8. No juice. Only light on my dash was the barely lit "door ajar".

I'm guessing the engine-bay whine is also a symptom of my dying alternator. TBD!

Since about 1968 cars need the battery to get started. After that the alternator provides the needed electricity for everything and keeps the battery charged up. If the alternator goes bad the car can still run off the battery until it is depleted, somewhere at or below 11 volts. If the battery AND the alternator are both bad then you're stuck. (I had a '69 Plymouth Barracuda 318 V8. I took the battery out after it was started and it continued to run. I was later told this isn't a good thing to do because the electrical circuit expects the battery to be there, even if it's dead. Otherwise it can cause damage.)

Instead of buying a new battery each time you can just charge up the battery again and use that until you get the alternator replaced. On old alternators it could be the brushes but I had an alternator go out on a brand new Oldsmobile. Mechanic said it was a diode, so you never know. I replaced the alternator in my '91 Camry when it was 27 years old. I rebuilt the starter myself about the same time and it was working fine when I donated it to Goodwill in it's 29th year. I hated to see that car go. (Brake and fuel lines rusted out and it was going to be an expensive repair.)

My 2004 T4R is going strong on its second battery, installed in 2015. Everything else is pretty much OEM.