Dear Tom and Ray:
My wife's car is an '08 Toyota Sienna all-wheel-drive van with almost 70,000 miles on it. In the past few months, the whole garage has been stinking like rotten eggs. At first I thought it was catalytic converter smell, but the odor was coming from under the hood, not out the tailpipe. I traced down the smell to the battery and noticed that the positive terminal had aqua-colored gunk on it, but the negative terminal was clean. So I took it to the shop and had the battery terminals cleaned. Two days ago, the van failed to start. I opened the hood and noticed that the deposits on the battery terminal were back and that the clamp on the positive terminal actually had corroded through and was loose on the post. The sulfur smell is still around, but not nearly as pungent as it had been. I removed the battery from the car and cleaned off the deposits. I thoroughly washed the outside of the battery and dried it. I replaced the positive battery clamp with a Toyota OEM clamp ($26 and a family-size jar of Vaseline!). I brushed both battery poles and the negative terminal clamp with a steel-wire brush and reinstalled the battery. For good measure, I doused both battery terminals with WD-40. I don't ever recall having a car battery produce so much odor that it stunk up a two-car garage. What would cause these symptoms to occur? The battery is Toyota OEM and is labeled an "84-month" battery. Should I insist that Toyota replace it?
Ray: Yes. You need a new battery. Yours is junk.
Tom: Your battery is out-gassing. It's emitting hydrogen sulfide (H2S), a gas best known by the question it usually prompts about who's been eating bean burritos.
Ray: ... unless my brother is nearby, in which case the question is unnecessary.
Tom: That hydrogen sulfide is what's corroding your battery terminals and leaving that white (or, in your case, aqua), chalky residue.
Ray: You've cleaned and replaced everything, but you keep putting the bad battery back in there. So unless you change it out, I have no doubt the outgassing and corrosion will continue.
Tom: Then -- and this is very important -- after your dealer replaces the battery, he has to check your whole charging system. The problem could be in the battery itself, or it could be that the battery is getting overcharged.
Ray: That's what we do to our customers. But in your case, it means that your alternator or voltage regulator may be faulty. So the battery is continually getting charged, even after it's already fully charged. That's making the battery fluid boil over and causing the battery to out-gas.
Tom: So Toyota owes you a battery, or at least the pro-rated portion of that 84-month battery you didn't get to use. And depending on how your charging system checks out, it may owe you an alternator, too, Paul. The jar of Vaseline's on you, though.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk website.)