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Thread: battery boils over, on one side?

  1. #1

    Default battery boils over, on one side?

    okay I'm new to the forum, trying to seek someone out that may have cured a similar problem. I have an 02 d'max completely stock when I bought it a year ago the battery on the passenger side appeared to have boiled over at some point, after a few months I realized that it still was boiling over and eating up the battery tray, I replaced the battery even though both batteries tested fine both with a handheld and w/ a ferrett load tester. the battery continued to boil over on that side. I have since cleaned all of the grounds on both sides of the block and all of the cable ends as well, I also retested both batteries seperately out of the vehicle with the load tester and both are fine. while I was at it I swapped the batteries side to side. wtf the problem continued on the pass. side with the other battery, it's clearly not a battery problem and I can't find any cable problems. I have even talked to a gm field engineer with no help, also the problem was present both with and without the battery insulator in place.

  2. #2
    Join Date
    Jan 2001
    New Hampshire - Live Free or Die


    That's a good one!

    The only reason external to the battery I can think of for a battery to boil is excessive charging current, induced by excessive voltage. This would lead one to deduce that the charging voltage on the passenger's side was higher than on the driver's side, thus there must be some resistance between the two batteries. It could be on either the positive or the negative side. This all would be more plausable if the alternator was connected to the passenger's side battery (is it?) and, somehow, the regulator was seeing the voltage on the driver's side.

    Bottom line, I think you still have a bad cable or connection somewhere.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  3. #3
    Join Date
    Apr 2001


    Welcome to the Forums!

    I've seen this many times when only one battery is replaced. They must be replaced in pairs if the good battery has any significant time on it.

    At the same time, I agree with John. You must have a cable in poor shape creating resistance between them. If you have the ability to load test the batteries, test them at the cable ends (where they connect downstream at the ground points, starter, and crossover cable), not the battery terminals. Just checking voltage won't reliably indicate the resistance at low load. Many times, it's the crossover cable connection (stacked connectors at the passenger side battery) where poor contact is found. If so, it should be disassembled and cleaned, or the cables replaced.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A

  4. #4


    I completely agree with both of you, problem is number one the charging system comes in at the drivers side cable halfway between the battery and the starter where the pass. side battery meets it, number two the batteries were both replaced right before I bought the truck and if it was the battery it would have followed it when I swapped them side to side. number three the cable connections on mine aren't stacked like the older truck at the battery like the older ones were they are crimped and I have pulled the boots off and cleaned the cable ends itself. I am really at a loss here I have voltage dropped the cables under load countless times without finding anything, the only thing I have left to try is to run some heavy gauge cables between the positive and negative terminals of both batteries to try and equalize any voltage differences. the acid is wreaking havoc on my battery tray and inner fender I have to get this fixed.

  5. #5
    Join Date
    Dec 2007
    Enfield, NC


    I have the same problem with my 2001. Three years ago I replaced both stock batteries, and everything was fine until I started having the right side battery leaking acid. In addition to that, every once in a while when I would turn the key to start the truck, everything would go dead (as if both batteries were disconnected, eventually power would come back on and I could start truck at that point). Also, sometimes when I would start the truck, the clock on the radio would reset. Took truck to dealer and they replaced the ignition switch ( of course this did not fix the problem). This past May I found that the left side battery neg. post was broken on the inside causing the loss of power. I again replaced both batteries (May 2007). About three months ago the right side battery started leaking acid again. Today my clock reset on the radio. It appears to be doing the same thing as before, except totally going dead when I start the truck. Note: Checked batteries, both read 14.6 Volts. I will try some of the ideas posted here to remedy the problem. Also, I would welcome new ideas for a permanent fix.
    2001 GMC 4x4 Crew Cab Duallie 95,000 Miles, Injectors replaced @ 87,000 Miles.
    2003 Carriage 34' Fifth Wheel
    2006 HD Night Train

  6. #6


    I observed this happening with my '05, passenger side battery, when the truck was in its first year of service and <40K miles. Didn't own the truck long enough to replace batteries, I thought it was from excessive heat in that location - it happened in the summer time while towing heavy.

    Could this be a factor?
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  7. #7
    NutNbutGMC Guest


    I had an OEM side post to leak out of the post connection (corroded inside of the battery casing). Not an uncommon thing, the more I read here.

  8. #8
    Join Date
    Mar 2002
    Kanata Ont.

    Default Boiling battery...

    Same issue on my '02. Had 2 separate sets of new batteries. Checked everything from top to bottom and no problems. However, I had installed a windshield washer heater that apparently is a very high wattage device. It started leaking after 6-7 months and I never replaced it, just disconnected it. The instant I did that, no more battery issues. There was clearly an issue there, but I have no idea what it was.

    2002 2500HD Crew Cab 4X2 D/A

  9. #9
    Join Date
    Jan 2005


    I had same problem after replacing stock batteries with Champion. Did both at same time. Shortly afterwards, both began leaking out the top caps creating a mess on battery trays.
    Returned batteries and installed replacement Champions. Then had batteries and charging system tested. Problem continued. I gave up, pulled both batteries and trays, cleaned and repainted the trays,then installled Optima red top batteries. Problem gone.
    2002 Duramax LB7 Crew Cab Long Bed 4wd LT

  10. #10
    Join Date
    Mar 2002


    I haven't experienced the boil over as I have Optima redtops but can see where intermittant/unbalanced condition could cause it.

    Had it serviced in TX while visiting family last yr and the tech stripped the term threads ~ on both batts. Sometimes no start, sometimes okay. If one batt is not making the connection, the other does the work (charging/discharging). If both batts not making contact then ~ dead. Dealers can have some real pinheads working for them.

    The batts were new (read expensive) so I went down to the hw store and got some heli (helix) coils and prob resolved.
    \'02 \'Rado EC Shorty w/some stuff

  11. #11


    I also have the same problem going on right now. I replaced both batteries in Nov. I have a 2002 Duramax, and the passenger side battery is leaking through the caps. I have checked the voltage running and sitting not running. Both batteries test the same 14.6 running, 12.5 sitting.
    I'm at a lost to what to do next. I had problem with the positive side corroding not making good contact, cleaned and that is when the leaking started. If any of you come up with a solution I would like to know. Will keep an eye on the thread.

  12. #12


    Went back to Walmart where I had bought the new battery's, they checked both battery's showed that they were good. The manager told me that I had a electrical problem, so went the Chevy garage and they tested both battery's with a different tester and guess what the battery that had been boiling over tested bad, but what was funny about the whole thing was that chevy was testing with a handheld tester first and the battery showed that it was good, that is when he got the different tester. It done a much more detailed testing than the handheld did. So away I went back to Walmart and showed the testing that Chevy had done, and no problem he gave me a new battery.
    Now I have got an appointment to go back to Chevy tomorrow because when we were hooking the battery's back up there some sparking going on when hooking up the cables. So I guss we better try and find if everything is good to go. I do think we may have a cable that is going to be replaced. We'll see.

  13. #13
    Join Date
    Jun 2000
    Morrisville, VT, USA


    Don't know if you have done this already, but here's the first thing I do when I get a rig with side-post batteries. I buy four SS 3/8-16 X 2" bolts and 8 SS nuts to fit. Pare away the GM rubber shields on the cable ends and bolt everything back by putting a nut on each, followed by a cable end, then another nut and bottoming out each bolt in the battery, then backing it off a fraction, then tightening the bottom nut, then clamping the turminals between the two nuts. This is an old DP fix from way back. It may not help in your case, but it sure has elliminated any battery problems that I have ever had.
    You may be getting a big drag on your system (switch off). I always get a very slight spark with everything off, but not enough to make noise. The local starter/altinater guy at home told me that there's usually up to about 250 MA draw on a normal system, but a battery should hold up for at least a couple of weeks without going too dead to start.
    Be sure your bottom nut is tight, and that you don't loosen it while tightening the second nut. Always use two wrenches to keep from stripping the internal battery threads. I found one lose on my 04 while home at Christmas. One cold glow cycle was enough to kill my batteries at 0 deg. Just tightened her up and boosted it, and no problems since.
    Hope you get resolution right away.
    Dick Wells
    2008 Jaco Seneca 35' motor home (Kodiak 5500 chassis). Pulling 18' Wells Cargo enclosed trailer, with 2016 Miata in it.

  14. #14
    Join Date
    Dec 2004


    I know you've already changed the batteries, but here's what I found on mine. The passenger battery was found boiling the fluid after an engine shut down and I popped the hood right away to check on something else. I assumed the battery that was boiling was the bad one so I disconnected the drivers side and drove a few days to work using only the passenger side battery, no problem. Then I unhooked the passenger side and hooked up the drivers side and tried to do the same thing. It wouldn't start the truck, that battery was almost dead. So it appears to me the driver side battery was weak and the alternator was charging full bore to try and charge the weak battery, meanwhile the passenger side was getting way overcharged, because of no isolator between the two batteries. I put a new battery on the driver side and drove it a couple of months and kept checking and the passenger side never boiled again, so just to be safe I put a new battery on that side too to keep everyting as even as possible. I always recommend once a year you pull the cables and clean up everything just to be sure your getting the best connectiion. My original batteries went 6 years, but I don't live in cold country either. Fortunately for me the boiling fluid stayed in the battery, never came out onto the battery tray. It pays to pay attention to everything on a vehicle, I check constantly to see if I can find something wrong before it becomes a problem. Just my own personal maintainence habit, but it works.
    02 2500HD LT D/A SB CC 4X4 BLACK, Westin stainless nerf bars, BW GN Hitch,Racor 60S post oem fuel filter, Oil Guard bypass engine oil Filter. All synthetic fluids. Kennedy boost valve, edge, Modified air intake,EGT & Boost digital gauge,TransferFlow combo fuel & tool box, Air Lift Suspesion Bags Rear & compressor with remote, Bilsteins front & rear, Frontier front replacement bumper.

  15. #15
    Join Date
    Jun 2024
    Alberta, Canada


    Only the pass side battery?? I'm willing to bet that your issue is that your windshield drains directly onto the top of that battery. If it is a flat top maintenance free battery, the drainage gradually overfills the battery. Poor some water on the pass side windshield and I guarantee that it drains directly onto that battery. I had the same issue. I put some duct tape on the top of the battery where it drips and built a little duct tape dam so it drains off and I've had no issues since.

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