have u wondered what would happen if the serpentine belt came off while driving..VID

[steven000e]

On my way home from work. (40 mile trip that day). my battery light came on... I was intrigued but the car seemed fine... i figure I'll check when i get home.
then one by one lights kept pooping on in my dashboard and one by one things stop working in the car, from the radio to the brakes to the steering system... so I decided to try to make it to my local shop...
here is a little video of what i was seeing;

vid



It got to a point that the car was on but no matter what i did the car would not respond to the gas pedal. I i would go to 2dn gear 3th gear... nothing ... RPM gauge was stock at 1500 rpms.. so i tried to turn the car off and then on again... nothing . battery drained.. i was rolling maybe at 15 mph by then so i decided to try to turn it on by trowing it in 2nd gear and letting go of the clutch... it worked!! the car turned on but no luck.. still no matter how deep i had the gas pedal the RPMs were at 1500.. finally the car came to a full stop and i had to call a tow truck to get me to a shop....

turned out to be the serpentine belt

so if you ever wondered what would happen.. it will happen!! .. my car has 80k miles

[moyenecorniche]

The gas pedal sends an electronic command, so no juice, no message, thus no response.
There are no cables and wires anymore between the cockpit and the engine room...
99% of the functions are by servo's electronic sensors and computers.

You are lucky that you did not do any damage to your S4.
When lights start flashing, don't try to milk it home.
Pull over look and see if you can detect what is happening.

Nice thing about Audi's is that when something is amiss it lets you know there is a problem starting before a major catastrophe.
However with my FX4 Ford Ranger, The Detroit Idiot Engine Light came on after or just when the engine was self-destructing. As if I needed a warning light when my engine ( 4.0 V6 ) sounded like the silverware in the Cuisinart Blender on the Puree setting.....Catastrophic Failure + the ( Now Comical ) Quote from the Ford Dealership Mechanic ...." We've never seen that before...Gee Ollie..?!?! "

Good Luck and I hope it is a simple and somewhat inexpensive repair.

[redls1bird]

The only real danger you were in was of overheating, but since you were moving, its pretty unlikely. Your description is pretty typical of a failed charging system, as each individual electrical system has its own threshold hold for when it can no longer function. Ive personally had an engine running (fuel injected) with as little as 7 volts being supplied by the battery alone. It wouldnt rev up or anything, but it continued to run.

[dmaxben]

So, before this happened to you, you REALLY wondered what would happen if you drove without a functioning alternator???? Cars need at least ~10.5v of electrical power to function, so big surprise, when your battery started wearing down (because there wasnt any alternator to charge it), various modules on the car start dropping offline due to a low-voltage condition. I dont know what Audi has their various modules' low-voltage cutout/shutdown threshold set at, but I know in my truck the ABS module drops offline at about 11v, airbag module drops out at about 10v, radio/instrument cluster will shut off at about 9.5v and then finally the ECM will shut down the engine at about ~9v.

I mean, did you think it was going to just keep going by itself with no electrical power???

[Cards232323]

This happened to me last month but all I got was the battery light and I was able to get it home, I guess my battery had enough charge luckily

[dmaxben]

The only real danger you were in was of overheating.

why?? You do know that the water pump isnt driven by the serp belt right...?

[BUD-S4]

So, before this happened to you, you REALLY wondered what would happen if you drove without a functioning alternator???? Cars need at least ~10.5v of electrical power to function, so big surprise, when your battery started wearing down (because there wasnt any alternator to charge it), various modules on the car start dropping offline due to a low-voltage condition. I dont know what Audi has their various modules' low-voltage cutout/shutdown threshold set at, but I know in my truck the ABS module drops offline at about 11v, airbag module drops out at about 10v, radio/instrument cluster will shut off at about 9.5v and then finally the ECM will shut down the engine at about ~9v.

I mean, did you think it was going to just keep going by itself with no electrical power???

Hahaha my thoughts exactly.

You should have done the job yourself and learned something about the car.. Rather then send it to a mechanic Who's going to rape you on labor. $15 belt and two hours of your time and it's done.

[redls1bird]

why?? You do know that the water pump isnt driven by the serp belt right...?

And what do you think runs the cooling fans, hopes and dreams? Think things through before you post.

[steven000e]

So, before this happened to you, you REALLY wondered what would happen if you drove without a functioning alternator???? Cars need at least ~10.5v of electrical power to function, so big surprise, when your battery started wearing down (because there wasnt any alternator to charge it), various modules on the car start dropping offline due to a low-voltage condition. I dont know what Audi has their various modules' low-voltage cutout/shutdown threshold set at, but I know in my truck the ABS module drops offline at about 11v, airbag module drops out at about 10v, radio/instrument cluster will shut off at about 9.5v and then finally the ECM will shut down the engine at about ~9v.

I mean, did you think it was going to just keep going by itself with no electrical power???

Hahaha my thoughts exactly.

You should have done the job yourself and learned something about the car.. Rather then send it to a mechanic Who's going to rape you on labor. $15 belt and two hours of your time and it's done.

i don't go a research how everything works to detail every time i buy something. I mean when you buy a TV or a Cell phone ... do you know how everything works? what chip does what when and how much energy it needs... NO you research the basics... how to make phone calls.. internet..
I dont understand you giving me shit because i didnt know what amount of voltage each system my car uses.. thats stupid.
I knew by common sense that the systems where failing due to a faulty battery.. what i dint know was that afternoon at 545pm the belt would come off... so what choice did i have??? stupid comments i swear...

anyway i shared this video as an experience video.. to anyone that might be interested in what would happen... thats it... you dont need to turn it into an academic class.

[dmaxben]

And what do you think runs the cooling fans, hopes and dreams? Think things through before you post.

unless he is sitting idling in traffic with the AC on, there is enough ram-air to cool the engine until the battery doesnt have enough charge left to run the engine or the fans. Youd be surprised how, most of the time when driving, the cooling fans arent even on.

I dont even run a cooling fan on my truck in the winter. Yes. Thats right, I completely remove the fan. It makes it warm up about 45 minutes sooner (than if the fan was on), and ZOMG the coolant temp gauge doesnt register 1* hotter than normal. Granted Ive never tried running my S4 with no fan, but Id be willing to bet that unless im sitting in traffic in 100* outside air temps with the AC cranked, it woudlnt overheat.

[dmaxben]

I mean when you buy a TV or a Cell phone ... do you know how everything works?.

haha as ridiculous as it sounds, yes, the first thing I do when I buy any mechanical device is take it apart to see how it works...

[BCsniper]

welcome to what driving an S4 with a dieing battery looks like.

I've been in that scenario several times when I kept having alternator issues. Did you not see the giant flashing yellow battery symbol in the DIS before all of your other stuff started to shut down and die?

and this wont hurt your car at all you've just run out of power....it's what happens when you end up running a big V8 on nothing but battery power

[B6JoeS4]

Better hope the belt snapping did not get behind the crank pulley and take out the front main seal. Ask me how I know this is possible

[05 B6 S4]

It is an informative video I just was hitting the brakes and turning my computer to the right to pull over. I would never be able to keep driving with all of those lights flashing at me. I just hear something abnormal or smell something weird and I'am on the side of the road checking things.

[likewater]

And what do you think runs the cooling fans, hopes and dreams? Think things through before you post.

Dude...really? Is this post a joke? You do realize that the serp belt only runs the alternator in these cars right?

[B5 SLPR]

This happened to me, my belt blew up and jacked things up

[dmaxben]

Dude...really? Is this post a joke? You do realize that the serp belt only runs the alternator in these cars right?

well hes probably thinking "the fans are electric, so when the belt snaps, the alternator wont charge the battery, thus the battery will drain and then there wont be any electrical power to run the E-fans"

Of course, DUH, then the car wont be running anyway because the ECM will have died too, so the E-fans being dead is a moot point.

Basically, yeah, I HOPE the guy was joking in that post.

either that or he doesnt know that the fans are electric...

[likewater]

well hes probably thinking "the fans are electric, so when the belt snaps, the alternator wont charge the battery, thus the battery will drain and then there wont be any electrical power to run the E-fans"

Of course, DUH, then the car wont be running anyway because the ECM will have died too, so the E-fans being dead is a moot point.

Basically, yeah, I HOPE the guy was joking in that post.

either that or he doesnt know that the fans are electric...

Yeah could be. Just the way he posted it made it seem like he thought the fans were run off the serp belt. Anyway it's all good.

[redls1bird]

Hey, I aee a lot of people are misunderstanding my posts. I'm not looking to get into a war about it, I just want to clarify my stance.

In my original post, I said op was in most danger of overheating, but was unlikely since he was still moving. This is due to two things, the fans are electric, so no or minimal cooling while not in motion. 2, the engine is running leaner. Less voltage to the fuel pump means less fuel delivered means higher engine temps.

How many posts have we seen where people are concerned about the amount of heat enters the cabin, or the amount of time these cars take to cool off. Combine the heat retention with high summer temps, no cooling fans and lean running of the engine and you've got a recipe for overheating.

/clarification

[Mr. Goodwood]

Had that happen to me in my A6. The scariest part is the loss of power steering and trying to turn a 4000lb car with 235 tires.
The belt end up whiping around and broke a bunch of stuff as well. So if your car is at 100,000km get your belt changed ASAP.

[ringsroc]

Thanks for the video. It is nice to see what might happen if you take it that far.
I would have to pull over at least to check things out unless I was very close to my destination.

[dmaxben]

In my original post, I said op was in most danger of overheating, but was unlikely since he was still moving. This is due to two things, the fans are electric, so no or minimal cooling while not in motion. 2, the engine is running leaner. Less voltage to the fuel pump means less fuel delivered means higher engine temps.

When the fans die (due to the battery running down low enough), the engine is going to die also...its not like the engine will continue to run with no fans.

And the whole "less voltage to the fuel pump making the engine run leaner"?? Come on, really??? The ECM will correct for that just fine...there are tables in the ECM that reference battery voltage vs. injector pulse width modifier, SPECIFICALLY for this reason....to keep the engine running at stoich regardless of battery/system voltage....or at least keep it running at stoich as long as there is enough power to run the ECM...and when battery voltage drops that low, the ECM will simply power down and shut off the engine....

[redls1bird]

When the fans die (due to the battery running down low enough), the engine is going to die also...its not like the engine will continue to run with no fans.

And the whole "less voltage to the fuel pump making the engine run leaner"?? Come on, really??? The ECM will correct for that just fine...there are tables in the ECM that reference battery voltage vs. injector pulse width modifier, SPECIFICALLY for this reason....to keep the engine running at stoich regardless of battery/system voltage....or at least keep it running at stoich as long as there is enough power to run the ECM...and when battery voltage drops that low, the ECM will simply power down and shut off the engine....

The ecm is not aware of the volume, whether or not its based on battery voltage showing the in ecm. This is why later cars have fuel pressure sensors, and also why a clogged fuel filter can cause self adaptations codes in the partial load range without any other fault codes.

[Fade2Black]

I had this happen to me on the way to have it replaced. I drove about 35 miles with out the belt, not smart but I made it and when we pulled the bumper it was laying in there.

[dmaxben]

The ecm is not aware of the volume.

no but it has fucking O2 sensors for closed-loop feedback.

[redls1bird]

Why are you getting so upset? You cant discuss things without cursing?

Being in closed loop and depending on the o2 sensors would work for a very short time since the ecm's adjustment ability is not infinite. Also, the coolant temp sensors signal needed to enter and stay in closed lop would be off since its reference voltage would not be correct anymore.

[dmaxben]

omg fine im done, you win. :rolleyes: