HELP - Hot Battery Barfed In My Trunk

KatoKato · 05:32 PM

I'm on my way home from a drive (app. 200 miles) and notice a very slight pungent odour in the car (targa top off). My first thought is that it's the car in front of me but after passing a number of cars still there. About 15 miles later it seems to be getting stronger so I decide to check it out. Opening the trunk reveals the culprit. My battery has heated up so much that the vent cap on the positive end has popped off revealing boiling acid inside. I panic for abit but it does cool down - remove battery, and clean up mess.

So what gives here? I'm hoping all that I need is a new battery. Could it be the alternator? a short somewhere in the system? Any thoughts on how I should proceed would be appreciated.

background:

I've owned the car for three years so the battery is older than that. I've drained it twice - the first time I needed to jump start - the second time the trunk light switch failed and completely drained the battery. Had to trickle charge it back to life.

I removed the A/C fuse and relay last week but can't see why that would be a problem.

Thanks in advance,
Kato

scottb · 07-29-2007, 05:40 PM

Kato: The first thing you MUST do is be sure you have completely flushed the area with a baking soda solution. Acid can get into the nooks and crannies and eat away at the metal, so a good flush is critical.

As to the problem, my money would be on the alternator overcharging the battery, causing the boil-over.

dshepp806 · dshepp806's Garage

Yes,..quantify this thru measurements.

Best

Cooper911SC · 07-29-2007, 06:06 PM

+1 for what scottb says. Clean up area with baking soda/water mix, rinse out well.

Culprit is likely your voltage regulator. (Integral with the alternator on 3.2 cars.) Had this problem on my SC.

Good luck, Cooper

Gogar · 07-29-2007, 06:56 PM

+1 for bad Voltage Regulator. Too high of voltage is getting to your battery and making it boil. Leave it that way for too long, and your alternator will burn up as well.

Vintage914Racer · 07-29-2007, 07:16 PM

I had the same problem last week with my 914-6. It was the regulator

KatoKato · 03:02 AM

Quote:

Originally Posted by scottb

Kato: The first thing you MUST do is be sure you have completely flushed the area with a baking soda solution. Acid can get into the nooks and crannies and eat away at the metal, so a good flush is critical.

As to the problem, my money would be on the alternator overcharging the battery, causing the boil-over.

Luckily it didn't spurt too much acid all over the place. I wiped up the acid with old cloths and then used fresh wet cloths. Will do NaHCO3 rinse today. My fuse panel carpet got a little acid wash - put it in a tub full of water to rinse away the acid.

As for the checking the regulator - can I do this directly? ...

Or should I install the battery and check the terminals while engine is running for high potential difference?

Cheers,
Kato

KatoKato · 07-30-2007, 03:02 AM

Quote:

Originally Posted by Gogar

+1 for bad Voltage Regulator. Too high of voltage is getting to your battery and making it boil. Leave it that way for too long, and your alternator will burn up as well.

Last year when I drained this battery I thought about changing to an Optima Red Top. (I didn't because this one kept charge)

If I would have changed to the red top last year and the voltage regulator went how would I have known? Would the Optima have melted down?

ossiblue · 07-30-2007, 06:54 AM

Quote:

Originally Posted by KatoKato

Last year when I drained this battery I thought about changing to an Optima Red Top. (I didn't because this one kept charge)

If I would have changed to the red top last year and the voltage regulator went how would I have known? Would the Optima have melted down?

Excellent question! Anyone know? This could be helpful to us all.

304065 · 07-30-2007, 07:02 AM

The only test for a regulator out of the car is to hold it up to your nose. If it smells like Talisker, a Single Malt made on the Isle of Skye, it's junk. (Well, Talisker DOES smell like a burning electrical fire if you ask me).

But seriously, given the symptons, its 99% it's your VR. When it fails, it overcharges the battery up to 17 volts and boils the electrolyte. A new one can be purchased from our host here, or bring the entire assembly to an auto electric shop for testing.

Optimas actually like a 15v charge, but much higher than that, my guess is it would have overheated and then shorted out internally.

KatoKato · 07-30-2007, 09:59 AM

Quote:

Originally Posted by john_cramer

The only test for a regulator out of the car is to hold it up to your nose. If it smells like Talisker, a Single Malt made on the Isle of Skye, it's junk. (Well, Talisker DOES smell like a burning electrical fire if you ask me).

But seriously, given the symptons, its 99% it's your VR.

Just wondering where the Voltage Reg is located. Is it behind the fan? I've read in another thread that sometimes they are removed when replaced...

304065 · 07-30-2007, 10:49 AM

It's integral with the alternator. Search here for details on how to remove. Disconnect the battery before doing any electrical work.

Wil Ferch · 07-30-2007, 10:53 AM

This article might be of some help for 84-89 owners...

http://www.pelicanparts.com/techarticles/911_volt_reg_replace/911_volt_reg_replace.htm

- Wil

KatoKato · 07-30-2007, 01:03 PM

Quote:

Originally Posted by Wil Ferch

This article might be of some help for 84-89 owners...

http://www.pelicanparts.com/techarticles/911_volt_reg_replace/911_volt_reg_replace.htm

- Wil

Thanks Will & John ...

glenncof · 07-30-2007, 01:06 PM

Last spring I saw a car at my kids school with the hood up. Some young guys were in it, and I thought I may help out.

There was no lights on in passenger compartment and car was dead.

They said the day before they had the battery fail and was replaced, so it was new. They said "I hope the guy has a new battery like yesterday."

I had a volt meter in my 911 trunk and put it on the battery. 0 volts or near that.

I put my hand on the battery and it was hotter than the engine compartment.

My guess it over-charging killed the first battery, then second. I think it blew a cell.

My 911 was previously showing signs of over charge; acid burn spots, loss of fluid, white powder on + terminal, flickering lights...

Live and learn.

KatoKato · 03:26 PM

Quote:

Originally Posted by john_cramer

....Optimas actually like a 15v charge, but much higher than that, my guess is it would have overheated and then shorted out internally.

I've been thinking about this and wouldn't a sealed battery like an Optima be more dangerous than a vented acid battery?

This VR problem I haven't ran into but I would think that the vented acid battery is safest in this situation. Vented would mean that it's less likely to explode.

(I called Optima customer service and they told me that under those circumstances Optima batteries will vent)

If the alternator dies either battery would be safe.

Any other situations where the battery could be compromised? And which would be better?

Any thoughts?

Wil Ferch · 07-31-2007, 08:59 AM

Optima batteries don't have a normal vent as such...but you can see the small grey diameter circles on the top that are like "relief valves" for instances such as this...they look like porous ceramic discs, as I recall ( I'm not staring at the battery as I write)...

- Wil

KatoKato · 07-31-2007, 11:55 AM

Quote:

Originally Posted by Wil Ferch

O...but you can see the small grey diameter circles on the top that are like "relief valves" for instances such as this...they look like porous ceramic discs, as I recall l

Yes - I see those. Just purchased mine today. Sweet!

disfin · 07-31-2007, 06:44 PM

+1 for the VR. Not too hard to do, but you'll want to read the tech article and also reference the 101 book. Unfortunately the 101 book uses an SC which is a tad different than ours, but it will help you get the idea.

KatoKato · 05:03 PM

Quote:

Originally Posted by disfin

+1 for the VR. Not too hard to do, but you'll want to read the tech article and also reference the 101 book. Unfortunately the 101 book uses an SC which is a tad different than ours, but it will help you get the idea.

Update - due to time constaints (I have two children, ages 2 & 5) and my lack of confidence I had her towed to the wrench.

Thanks to those who have posted on the topic of towing a 911.
Before calling the tow truck I purchased two 15' X 2" nylon? tow lines with hooks. All the guy had were chains so these saved the front valence from being slightly mangled. Secured the rear through the Fuchs as some had suggested.

Diagnosis: VR was shot, alternator brushes worn ... alternator was rebuilt and put back in within a day.

New Optima Battery installed. Thanks Wil for the instructions I found on the battery template.

Optima power!

Luckily I found a nice thick RED cutting board. I used my grinder on one end so it would fit nicely in the lip that comes up from the battery tray. I decided to custom cut the template using my jigsaw .... I just placed the battery on top of the cutting board and traced it's outline.
Sweet!

All is well now - thanks for all of your help .. it is appreciated.