Battery overflowing. - PeachParts Mercedes-Benz Forum

alfa 75 · #1 08-20-2010, 05:05 PM

Hi, I've got a 1984 300D with approximately 205,000 miles. Last week I noticed a terrible smell from under the hood that turned out to be the battery overflowing. The battery was ancient so I changed it, it was okay for a few days but today it started again. It is fairly hot outside (in the upper 90s, I think) and the car gets hot but it has never been overheated, it never goes up past the next bar after 80 degrees.

Could my alternator be overcharging the battery? If not, what could be causing this?

Thanks.

whunter · #2 08-20-2010, 05:07 PM

The alternator is over charging...

battery blew up - attention PEH
http://www.peachparts.com/shopforum/showthread.php?p=445147

Better take a peek under battery tray! : (
http://www.peachparts.com/shopforum/showthread.php?p=1633733

I found my battery problem, but how do I clean this?
http://www.peachparts.com/shopforum/showthread.php?p=1927470

Spewing Battery !
http://www.peachparts.com/shopforum/showthread.php?p=280541

"Alternator" 115 Amp Bosch AL129X works in 123s!
http://www.peachparts.com/shopforum/showthread.php?t=93569

Pictorial on Installing the Voltage Regulator
http://www.peachparts.com/shopforum/showthread.php?t=166105

Battery Safety
http://www.peachparts.com/shopforum/showthread.php?p=1057827

Starter health is important to your diesel!!!
http://www.peachparts.com/shopforum/showthread.php?p=739798

Tackling a starter, need suggestions (and sympathy)
http://www.peachparts.com/shopforum/showthread.php?p=1001659

Reasons to change the W124 Alternator brushes/V regulator!
http://www.peachparts.com/shopforum/showthread.php?t=121404

Battery selection / Charging System / jump starting / cold weather battery issues
http://www.peachparts.com/shopforum/showthread.php?p=1058189

Have a great day.

.

alfa 75 · #3 08-20-2010, 05:08 PM

Guess a replacement is in order then, thanks.

barry123400 · #4 08-20-2010, 05:11 PM

Check the voltage with the motor running at the battery terminals. No more than 14 volts should be present. Sounds like your voltage regulator on the alternator may have failed.

You could be boiling the battery acid out of the battery. Clean up the corrosive spillage and neutralise the acid.. Do not keep driving with this condition as it could total your new battery.

Plus the alternator was not really designed to put out constant high current like your indications seem to indicate it might be doing. Usually again it is a failed voltage regulator and the voltage test indicates it. The voltage regulator can be changed with the alternator on the car.

rrgrassi · #5 08-20-2010, 05:44 PM

I hope you neutralized the acid from the boilover.

alfa 75 · #6 08-20-2010, 06:07 PM

I just tested it, I am getting 15.8 volts at the battery with the engine idling. How do I determine if it's the regulator or the alternator itself? I'm tempted to change the regulator and go from there.

alfa 75 · #7 08-20-2010, 06:29 PM

Quote:

Originally Posted by rrgrassi

I hope you neutralized the acid from the boilover.

Yeah, with baking soda and water - is that strong enough?

compress ignite · #8 08-20-2010, 06:33 PM

Obtain a New one and R+R.

Problem will be fixed.

14.5 Volts is the Max you should see,Regardless.

Yes , a nice strong Basic solution of Baking Soda and Water,will do the Neutralization.Rinse well and then inspect for potential rust toeholds.

vstech · #9 08-20-2010, 10:43 PM

Quote:

Originally Posted by compress ignite

Obtain a New one and R+R.

Problem will be fixed.

14.5 Volts is the Max you should see,Regardless.

Yes , a nice strong Basic solution of Baking Soda and Water,will do the Neutralization.Rinse well and then inspect for potential rust toeholds!!!

I fixed your statement for you.
I'll now elaborate.
PULL YOUR BATTERY TRAY OUT AND CLEAN ALL TRACES OF ACID AND GUNK FROM THE FENDER AND THE OVERFLOW AREA!!!!!!!!!
get all traces of leaves out of the spring pockets while you are in there. if there is any paint damage, clean it out really really well, and treat it with por-15 black, and then paint to match, and seal well all seams damaged by the acid.
you want pics of the mess I am working on fixing for a customer? it's not pretty.

compress ignite · #10 08-20-2010, 11:12 PM

Vstech,

Would it be going too far to suggest pulling the Plastic Fender-Well Liner from
Underneath and inspecting there also?

vstech · #11 08-20-2010, 11:51 PM

the car I'm working on, had a 3" hole in the area under the battery, and another 2" hole under the plastic liner... nothing is too far if you want the car to last.

alfa 75 · #12 08-21-2010, 02:11 PM

Quote:

Originally Posted by vstech

I fixed your statement for you.
I'll now elaborate.
PULL YOUR BATTERY TRAY OUT AND CLEAN ALL TRACES OF ACID AND GUNK FROM THE FENDER AND THE OVERFLOW AREA!!!!!!!!!
get all traces of leaves out of the spring pockets while you are in there. if there is any paint damage, clean it out really really well, and treat it with por-15 black, and then paint to match, and seal well all seams damaged by the acid.
you want pics of the mess I am working on fixing for a customer? it's not pretty.

I'll clean it again today, though I thought I did a decent job of it. And sure, post pictures, it'll serve as a good warning to others who find this thread one day.

Jeremy5848 · #13 08-21-2010, 02:51 PM

Step one is always to replace the regulator. It's the primary failure mode, especially for your symptoms. It's also an easier job and much less expensive than replacing the entire alternator. [If you replace the regulator, be sure to keep the old regulator for awhile.] If that fixes the problem, fine. If not, go on to step two.

Step two is to get a new (rebuilt?) alternator, which will come with a new regulator, but there will be a core charge that you'll get back when you turn in your old alternator. Before you do that, remove the new regulator that you bought in step one and put back the old regulator that you removed and kept.

Even if the old regulator is good, its brushes will be worn down. Keep the new regulator as a spare. Put it away in the car's spare tire well with the other parts and tools you carry. Then you'll be prepared to do an on-the-road repair should the need ever arise.

Jeremy

vstech · #14 08-22-2010, 09:14 AM

if your car is intact, it's hard to tell what you are looking at in the pics.
the metal below the battry tray is gone, the metal on the firewall below the tray metal has been eaten through in 2 places.
the metal under the fender liner where the doorsill meets the firewall has a heavy coat of rust.

layback40 · #15 08-22-2010, 09:57 AM

It wont hurt to use too much baking soda. If you are not painting, you dont need to rise the baking soda away with clean water. The white residue will help keep everything from going acidic.