The Scary experiences thread

anupmathur

Super Moderator
Staff member
If alternator bearing jams leading to belt breakage, all power to brakes goes, but brakes still work, all you need to do is stand on the brake pedal as hard as you can.
I'm a little confused about this failure of brakes!
What has the alternator got to do with brakes?
What has a 'fan-belt' got to do with brakes?
 

tsk1979

Reclaimed and Recycled
In many cars, the power to Power steering, brakes, AC is given by a single belt. This is often known as the fan belt(a term carried over from the days of mechanical fans).
Now many cars esp in winters give that screeching sound in morning due to slightly loose belt. Some overzealous mechanics tighten the belt too much, and this puts load on the alternator bearing.
After a few thousand kms, the alternator bearing jams, which mean with 100 horses from the engine, the rubber belt simply snaps(I have had this happen to me).
So voila, no power to AC/Power steering or Brakes.

Now why is it the alternator bearing which goes first with an overtight belt, I have no idea, but I suspect the reason is that power steering system gets load only when turning the car, but alternator is always "loaded".
Moreover power steering system bearings are larger and more robust, and as always the weakest link in the chain goes first.
 

akshay4384

THE LONE RIDER
If alternator bearing jams leading to belt breakage, all power to brakes goes, but brakes still work, all you need to do is stand on the brake pedal as hard as you can. In a car, you can still get some braking, in a heavy vehicle you need a lead foot. After you slow down to 20-30, pull the hand brake, as it will still work, pressure or no pressure.
i agree i had faced this thing in 2003 in my Bolero while coming from Dehradun and the alternator Belt snapped(later diagnosed at mahindra A.S.S as i had only one clue that brakes were not working apart from the battery not charging light glowing in instrument cluster) and brakes were not working,i panicked and later realised they are working but after applying lot of force
 
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anupmathur

Super Moderator
Staff member
Nope! You are talking vehicles with air brakes. Most modern vehicles(cars or SUVs) have belt powered brakes.
Belt powered as hydraulic or pneumatic?
Have you topped up a brake POWER reservoir in your car?
Please show me.
 

tsk1979

Reclaimed and Recycled
Yes, there is brake fluid reservoir in the car. Brake fluid needs to be changed every 20K kms or so.
Safari has 2 brake fluid reservoirs.
However most cars including safari/indica/safari have hydraulic brakes.
Ambassador some versions have Air brakes, and you can also see the sticker "Caution, Air Brake"

But I guess even air brakes can be belt powered, with belt driving a motor to create vaccum..?

Anyways I found some articles explaining how it works
http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake.htm

Indica also has a master cylinder, and the energy to create vaccum comes from the belt.
For example when in my car the master cylinder seal went kaput, I lost pressure, I had to keep topping up the brake fluid every 10-15kms, and take her to the mechanic
 
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sandeep9868

Sirfira Trekker
oppps...silly mistake...i admit that my grammer is bad...but never thought that its now getting poor to poorest:rolleyes:.
 

sandeep9868

Sirfira Trekker
I don’t know about other car, but yes Scorpio (old one) having the electronic breaks and power steering system and they get their power from belt system.
Actually belt rotates the alternator which in turn charges the battery (as in our case the battery sign on the dashboard console started blinking). This means there was some problem with the battery power, and as I told earlier the alternator come off from the belt and battery loosen its power.
We later on replaced the ball bearing set and fixed the alternator and then everything going smooth.

Yes, Akshay is also right; actually the breaks went very hard and impossible to apply. My friend had putted lots of effort to push them down but all went useless that time.
 

popsha

Incredible Bulk
If my guess is right, the old Scorpio had rear drum brakes. Power or no power drum brakes work fine. Just a lil more pressure is what is needed. All disc setup needs a lil extra effort than drum brakes.

The power "assisted" setup only "assists" you in braking, this doesn't mean that if there was no assist there will be no brake pressure. They just help in reducing the pressure needed on the brake pedals. If there is sufficient brake fluid with no bubbles in the brake lines the brakes should work just fine engine/alternator/radio or whatever running or not running.

This holds true for most of the cars unless its one of those prototypic drive-by-wire thingys

PS: Electro-Hydraulicaly assisted brakes maybe used in vehicles with ABS systems but still electrical failure would not result in brake efficiency reduction.
 
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