Has anyone ever heard of this?

Yesterday, I started smelling something throught the air vents...like a burning smell. So I stopped the car and went hunting. I found the battery was sizzling and venting some fluid out the side. So I replaced the battery right away.

This moring after driving it last night I find a similar situation with the new battery. There was a little adapter and a hose with the battery. The guy at the parts store said that this hose is to attach to some kind of drain that some cars have to vent the battey!

What the heck are they talking about? I have never heard of "venting a battery". But I do know I dont want battery acid spitting on the inside of the engine compartment!

Any clues?

Steve

I would guess that your alternator/voltage regulator has problems and the battery is possibly overcharging , heating up, and venting fluid. I would have the alternator/regulator checked ASAP

My understanding is that the vent tube you are talking about is normally for venting hydrogen gas which may be produced by batteries under certain conditions. My C230 has a vent tube as it is inside the trunk, and H2 gas could get into the car. My 300E has the battery in a "traditional" under hood location, and doesn't use a tube. Instead, it sits on a tray to catch spills.

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John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E

Hi again Steve! Don't drive the car until you straighten out the battery problem! The vent hose you mentioned is only for vehicles with the battery in the trunk or under the back seat. It vents the gasses to the outside of the vehicle. Your battery is under the hood so it can vent safely without the hose attached. Your problem sounds like the alternator is overcharging. This could lead to a battery exploding! Have this looked at immediately! The most likely cause is a bad voltage regulator. It's easy to replace and it's cheap too, however there's a small chance the alternator is the culprit. Keep in mind that the acid and gas escaping from the battery is very harmful to the surrounding area. There are several expensive components just inches away from the battery( behind the black plastic cover to the rear ). Get this fixed ASAP! Keep me posted.

Sounds like some sort of overcharging problem. Yes, batteries do emit a gas (a friend of mine pointed out on the top of the battery that the gas was hydrogen - READ 'hydrogen bomb'!!??) I like to connect a long hose from the vent hole in the battery (if it has a single one) and snake it safely through the body & frame and hang it out the bottom of the car to positively vent the battery. I don't know if this helps anything, it's just a theory of mine that if the combustible fumes are far away from any spark, the better (such as a spark that might occur when a battery terminal is loose or slightly corroded and you hit the key and an arc occurs). It is also important to keep the battery full of water to allow less space for gas to accumulate. Soooo... ...in my opinion, connect a good long vent hose and feel safer. Besides possibly averting a bad situation, (an exploding battery) it will save your battery tray, inner fender, etc. from rusting/rotting. First thing I would do is establish that the charging system is not overcharging as I suspect, and remedy that situation.
Does any body agree/disagree with this reasoning. Respond if you think this is bunk, I enjoy learning new things, especially when substantiated by fact, rather than theory; as I have presented above.

Thanks for the info guys,

This little problem sound serious. However, unlike my old corvette where the alernator was 38 buck and took me 1/2 to change, I think I'm in deeper water here!

Interestingly, I get to warning light on the dash to mention anything is wrong, (not that that is the difinitive answer to problems) however, If it was over-charging, which it might be, I would have thought that would trigger the indicator too.

A couple of questions come to mind...

Where is the voltage regulator?
and
My shop is about 5 miles away...The battery in brand new I think I should make it that far, don't you?

I think I'll check on parts prices tonight.

Man, I'll be glad to get this thing straightened out for a while.

This is starting to become annoying and expensive!

Steve

On my 87 300E the voltage regulator is part of the replacable alternator brush assembly. About 5-10 minutes work and probably about $35 - $50 for the part. Enter your year model in Fastlane and see what they charge. Fast shipping and decent prices. (For example, on my 300E, the Bosch unit is $52, while the German aftermarket unit is $14: For my 98 C230, the Bosch unit is $40) They often have a pic of the part as well.

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John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E

Hey Guys,
Listen to this..

I had a brain wave and finally thought of something. I took my volt meter and went out to my car. Turned it on and thouched the battery leads.

12.57 Volts .. not bad

Then I Started the engine, touched the battery terminals

18.77 Volts .. woah!

So I stopped the engine and went and checked the battery again and :

16.35 Volts .. and I kept the contacts on and watched the number descend...

I think overcharging may the correct diagnosis.

I looked down past the exhaust manifod and saw the alternator easliy but getting to it....It looks as though from the bottom qould be better if I removed the panel covering the bottom of the engine.

Am I on the right track? It feels right.

Steve

Had this happen on my W124 last year!

Had windows down and could smell (as well as see) battery vapors being emitted.

Did the voltmeter check and found 17.5 volts with the engine running!

Ended up replacing the alternator on mine...the regulator is internal...

You do have to remove the lower panel to get to the alternator.

The 2 19mm bolts that anchor the alternator can be a bit stubborn, and there is little room to move around for the top bolt. Good time to replace the serpentine belt if it's looking aged in any way.

Sorry...I'm talking as if I know what model car you own?

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

It is a 90 300e.

I am getting 18.77 volts running. I would like to replace the regulator first and see what I get, but we'll see.

If I have to go the entire alternator route, does anyone know off hand if it is a 70 or 80 Amp Alternator?

Steve

Oh by the way G-Benz...If you have experience in changing that alternator out...please please...feel free!!!

Here's my post back when it actually occurred...

Battery venting excessively in 300E.

and my repair progress (sorry, no pics)

Alternator and serpentine belt install..Success!!!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Hi guys! Had the same problem when I just bought my C180 1994 Euro version early this year. The battery in the rear boot was venting acid and gas out of the tube and through the hole in the floor under the spare. The tube was ruptured and the stuff spewed around the back and rusted up the steel in the weaker joints and scratched spots which have been fixed now. Got the electrics checked and it was ok and a new battery was installed and it runs very well now. Only use the car once a week and it is still almost fully charged.

Well, Ive gone and done it now!

I don't have my parts yet but I was curious (you know what that leads to) about the Voltage regulator.

So.. I reached down and undid the two screws that held it in place. No big deal it just fell out in my hand. So, I thought I get a head start and see how it went back in so that I would know when the new parts showed up.

I CAN"T GET THE STUPID THIG TO GO BACK IN!!!!

Ok, calmer now. The part has two contacts on it that touch a spindle on the alternator, I can see that but it wont fit back in.

Q...Are the two contacts on the Voltage Regulator supposed to be different lengths? These are. And when you put these back into the alternator they point towards the center right?

If you have done this and if there are any tricks, please help.

Steve

Sounds like the carbon brushes. These are spring loaded. You have to hold these back to clear the armature (spindle inside the alternator). I usually use sewing cotton to tie these back, and then cut the cotton and draw it out when assembled.

They can wear unevenly, don't worry about it.

You may need to clean up the armauture (the copper bit), if it is worn or dirty. Use very fine glass paper and clean off all the dust. Do not use emery paper or carborundum paper, or whatever it's called in the States. The dust off this is electrically conductive and may cause you problems!

I hope you aren't going to put the alternator back on when it is clearly overcharging. Spraying boiling hot acid around the inside of your car is not part of the maintenance schedule!

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Cheers, Neil

I will use that tip to put the new VR back into the alternator.

The alternator is still mounted on the car and it won't be driven until it's fixed.

I was just trying a "test fit" to make sure I understood how the new VR would go back it - thats when I was having troubles.

You mentioned "sewing cotton" sorry for the differences in English, but do you mean thread?

Thanks
steve

Yes, sewing cotton=thread.

Have fun!

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Cheers, Neil