Hi guys,

My dad's owns a 2005 4Runner Sport (8 cyl.) with about 50,000km (30,000mi) on it which he owned since new. My dad took it to work last Winter (always plugs in the block heater) and one day when he wanted to leave work, the 4Runner wouldn't start as the battery was dead. He got a jump and the vehicle started fine. He charged the battery and everything seemed to work fine afterwards. Fast forward to March/April of this year. My whole family went to Germany for about 4 weeks. After we came home, my dad tried to start the 4Runner and the battery was completely dead. Assuming the battery was done for, we replaced it with one of those dry/gel cell batteries. Everything worked fine again for a while, however started to have starting issues more and more frequently in the last few weeks. My dad got the battery checked, and it tested fine. He went to a shop to see if the vehicle draws power when the engine is switched off, and according to the shop, the draw was in spec. I thought it might be the alternator, but even if you charge the battery and let the vehicle sit for a week, it won't start. The battery isn't completely dead at that point, but apparently doesn't have enough power to turn over the engine. Has anybody had any similar problems or know what the problem could be? We live in a small town and the nearest Toyota dealer is about 80 miles away. My family has owned 10 Toyota's in the past 18 years (still own 5 of them) and never had any issues like this before. Please help! Thanks in advance.

If the shop tested parasitic draw and found it to be within specs, then I'd take a good look at the alternator. Sometimes a faulty alternator diode can drain the battery with the key/ignition off. Other than that, I can't think of anything that would cause the problem you have described (assuming that the battery is in good shape and doesn't have any type of internal shorts).

If Jed's suggestion also fails, here is my guess:

The original battery may have just died of old age (4 to 5 years which is not uncommon) and there may not be any drainage issue at all (parasitic draw is fine). In fact, it's your replacement battery that may be faulty.

Thanks for the reply guys. We returned the Optima battery and got a conventinal instead. We fully charged it and are going to monitor it in the next few days. I'll keep you updated.

if the vec. sits for a week or more without starting it, IMO, i would get a deep discharge battery, at least it can be recharged many times if it drops too low to start. most reg. batteries lose they're ability to hold a charge after its dropped too low.

Alright it's been a while and I figured I'd post an update. We replaced the Optima battery with a regular kind and that seemed to fix the issue. No more starting issues after sitting for a week. The battery still discharges slightly after sitting for a week (85-80% of charge after sitting for about a week - according to our battery charger), but not as significantly as it did with the Optima battery. Thanks again for the replies.

I would be curious to hear of your report in about 6 months. I have a 2004 4Runner and am on my third battery. I went from the original Panasonic, which lasted about three years to an Optima (junk), which lasted about 9 months, to a Sears Platinum which is about a 1 1/2 years old.

I spent about $200 on the Sears Platinum battery thinking I would get the beast, but something is clearly wrong with my 4Runner. I've noticed the vehicle turning over more slowly over the past few weeks. And then my car was dead this morning following one day I did not use my vehicle.

In the past I had the dealer check for parasitic draw along with an electrical check and everything checked out okay.

But something is wrong with my 4Runner.

I would be interested to hear about your experience in the next 6 months or so -- especially with winter coming.

I am on my original battery.

Went back to the shop with my '04 4Runner, 94k miles, with a battery discharge light on. Stealer said alternator failed and $750+ to replace. Talked them into an aftermarket, but honestly, my first experience with Toyota will be my last. 8 year old vehicle with 94k miles, 2 new rotors, 2 new calipers (frozen at 40k miles), 3 new oxygen sensors (2 out of warranty), new radiator, new alternator... The odd thing is that I was still on the original battery! Now almost 4k into repairs and I am not convinced of Toyota's reliability. My wife's old 2000 Yukon with 160k miles and over 8 years old took less repairs over it's lifetime, and it was a first model year. I will not buy another Toy again, nor would I recommend them. Maybe I got a lemon, but at this point, I am just ticked off that this vehicle is sooo unreliable...