Duramax battery fluid grows over time

Snowman9000,

Check out this battery. No caps on top for water to get into.

NAPA BAT 8478

This is the same style that my truck came with and what I installed for replacements. No problems.

I would have someone check the voltage regulator. It may be overcharging your batteries. Not unusual for this part to fail and no sense in putting in new batteries until this is checked out.

Yes, there is acid and rust damage beneath the battery. Not eaten away damage, but needing to be neutralized and painted.

The batteries are weak and not charging well anyway, so I think it's time for two new maintenance free ones.

Snowman9000 wrote:
I first noticed a rusty stain on the gravel where my 2004.5 Duramax is parked every day, under the passenger side battery. So I checked the fluid levels, and darn, it's over-full, did I do that??? I used the hydrometer to suck out the excess. This was a year or two ago.
So today I checked it again, and it's over full again!!!

This battery is partly covered by the sheetmetal edge in front of the windshield wipers and cabin air intake grilles. It keeps gaining fluid level in the rear three cells, which are covered by one big 3-hole cap. Rainwater running off the sheetmetal above could run right onto the cap and the cavity it sits in. That's all I can figure.

Anyone ever run into this?

I ran into the same problem and your right. The water, or worse yet windshield washer fluid, drips directly onto the battery and will overfill a battery with sunken caps. I used a small piece of plastic to redirect the liquid off the top of the battery. I had to remove the battery holder to clean and repaint it. No more problems now.

"Rainwater running off the sheetmetal above could run right onto the cap and the cavity it sits in."

This is right, water runs off the windshield, to the side, and onto the top of the passenger side battery, then it might get into the battery if it has caps. Spray the windshield with a hose and watch where the water goes.

"These original batteries were "maintenance free" without removable caps."
X2

The original batteries had no caps, thus no way for water to get in the battery.

The OEM batteries on my truck were made by Deka. Near me NAPA batteries are made by Deka. That is what I replaced mine with.

I have read of others putting a cover over the top of the battery to divert the water down the side of the battery to solve this problem.

I hope you get it fixed soon. The battery tray and more are getting an acid bath.

I've heard from my very good battery dealer that the Duramax vehicles don't work well with batteries that have removable caps like it seems you're using.
The original batteries in my '05 Duramax lasted about 7 years. I just replaced them then because it seemed like it should be time even though they still started the truck fine. These original batteries were "maintenance free" without removable caps.
Later I installed a separate deep cycle battery for my camper, it had removable caps. In just a few days it boiled over. The dealer said he'd seen that problem many times with these vehicles. He replaced it with a "maintenance free" deep cycle without removable caps. That battery is still going strong now after nearly 4 years.
I don't know why but apparently this is fairly common, according to him.