jstluise

'87 22RE, battery is a Optima red top (4 years old), age of alt unknown.

After the drive home from work I noticed an odd noise coming from under the hood. Upon closer inspection, I found the battery to be hissing from around the positive terminal post. The battery was also hot, but I'm not sure if that was from being in the hot engine bay (hot day today, also). But, if the batt was hissing I'm sure it was pretty hot.

My volt meter in the dash looked normal, but I hooked up the dmm anyways. Engine off, battery was at the normal 12.6V. At idle, I was at 14.3V and at higher RPMs the voltage stayed at 14.3V.

14.3V doesn't seem too high, does it? From a quick search, 14.3V looks to be at the upper end of the normal range (13.8V-14.2V). I'll be taking in the batt and alt to get checked, but at this point I'm not sure what is the culprit. Any thoughts?

wyoming9

iTrader: (1)

Well seems the Optima Batteries just seem to have all kinds of interesting problems.

As it is a AGM battery I am not sure just how it could be hissing . Which means it is pushing gas out.

Has the plastic cracked around the positive terminal??

When you checked the voltage how much of a load did you have on ??

jstluise

There are vents built into the top of the Optima but I guess the seal between the case and the post failed. The battery was a reman when I got it so I can see how that could be the case. Anyways, it was definitely bubbling/hissing out of the post and the battery was pretty hot.

When I checked the voltage I didn't have any load on it (i.e. no headlights, heater, etc).

I did the check again this morning. 12.4v before starting, and 14.4v at idle and higher RPMs. I disconnected the positive terminal while it was running and it stayed running, indicated the alternator was at least supplying power; however, checking the voltage on the alt (with battery disconnect) I was getting 14.8v at idle and while revving it jumped around with a max of 15.5v. So, not quite regulating like it should.

I thought about driving it to work with the battery disconnected so I could avoid stress on the battery, but while driving it I was getting intermittent charge lights indicating the alternator wasn't acting normal. I also couldn't turn my lights on or any load without stalling the truck, another indicator the alt is having issues.

So, I picked up a reman'd alt and swapped it in this morning before work. Did the same tests and the voltage on the alt stayed constant at 14.6v (battery disconnected) at all RPMs. Could even turn my lights on without problems. Looking good. Hooked up my battery and drove an hour to work. When I got there I checked the battery and it was nice and cool. I think the problem is solved!

mwisham

Disconnecting the battery cable while the engine is running is a very good way to blow your alternator. Fifty years ago, that might have been an old mechanics trick to see if the alternator was charging, but these days, you should never ever do that. 14.5
is a little bit, not much on the high end. Probably a combination of hot day hot engine compartment and bad seal on positive post.