Smoking brakes?

[Pegasus]

I have noticed that when pushing hard on the brakes of my E36 318is (25000 miles), smoke comes out of my rear brakes (I think...). It also smells like something is burning or hot in there.
The brakes feel fine, the car stops well and no warning light is on. When I bought the car (last week), I had to add some brake fluid because the level was too low. I used Castrol DOT 4 brake fluid.
Is this normal? I am new to BMWs but I have not experienced this with other cars.
Thanks.

[El Presidente]

Have you visually inspected the pads and rotors?

[ZoomZoomBeauty416]

When he speaks of "smoke" think it might be a large amount of break dust or something??

~*Teg*~

[nycbmw325is]

Originally posted by Pegasus@Sep 15 2004, 12:22 PM
I have noticed that when pushing hard on the brakes of my E36 318is (25000 miles), smoke comes out of my rear brakes (I think...). It also smells like something is burning or hot in there.
The brakes feel fine, the car stops well and no warning light is on. When I bought the car (last week), I had to add some brake fluid because the level was too low. I used Castrol DOT 4 brake fluid.
Is this normal? I am new to BMWs but I have not experienced this with other cars.
Thanks.

left and right side? does it happen when you use the brakes softly or moderately? could be a sticking caliper and the pad is rubbing against the rotor generating a lot of heat and cooking the rotor and pad. or if could be that you have a leak in the brake line and it is getting on the pad or rotor, or it could be your parking brake not releasing due to a frozen mechanism or sticking cable or even overtightned adjustment.

as pres said... pull a wheel and look at those rotors first, see any blue spots or blue or rainbow discoloroation on the rotor? then you have something dragging and have cooked your rotor and need to replace at fix the offending mechanism.

[bitcore]

Yah, That's definately not good.
Check what NYCBMW said.

Does the fluid level decline any?

[Pegasus]

I haven't checked the pads and rotors yet. I noticed the smoke today in the morning. I was driving at 70 mph and had to break relatively hard because of a traffic jam ahead (it wasn't a hard, ABS assisted stop). I saw the white smoke when I checked the cars that were stopping behind me, as the traffic slowed down. I think the smoke was coming from both the right and left sides.
So, I should look for some blue spots / rainbow discoloration on the rotors? Do I need to have a mechanic check this or is this a simple thing that I can fix myself?
Otherwise, the car is braking ok. I don't feel anything unusual.
Thanks.

[bitcore]

Burning rubber? rear wheels will lock up MUCH quicker than front due to weight transfer, some tires have a tendancy to start smoking like a B without much sliding going on.
Maybe you locked the rear wheels, but since ABS kicked in, you stayed in controll and didn't feel any rear swaying.

[nycbmw325is]

Originally posted by bitcore@Sep 15 2004, 02:39 PM
Burning rubber? rear wheels will lock up MUCH quicker than front due to weight transfer, some tires have a tendancy to start smoking like a B without much sliding going on.
Maybe you locked the rear wheels, but since ABS kicked in, you stayed in controll and didn't feel any rear swaying.

Nope ... If ABS is functioning correctly, no wheel will lock up for more than a few milliseconds, that is how ABS works. Yes there is weight transfer, but there is also something called a proportioning valve that "dispenses" the pressure differently front to back so that there rears dont lock up.... That is how pre-ABS cars managed to brake so well without locking th rears up.

[bitcore]

I didn't mean locked up like.. REALLY locked up :P
I've said all that I can sugest in this thread.

[Pegasus]

Well, I checked all pads and rotors. They are fine. Pads are like 60% and rotors do not have any blue / rainbow spots or scratches. Also, I found no leaks. I am really puzzled. What do you think?

[Pegasus]

I was just wondering whether the smoke could be related to the clutch. When I saw the smoke (it happened twice today), I downshifted in order to slow down the car. On the other hand, note that I do not feel anything strange with the clutch. It seems fine.

[Pegasus]

BTW, my tires are 15" Dunlops. They only have like 5000 miles on them. When the smoke appeared, I didn't feel anything weird with the car, so I don't think that the rear wheels locked up. Again, it was not a hard ABS assisted stop.

[El Presidente]

a burnt clutch wouldn't produce the smoke you describe.

Also, how did you check for leaks? To be sure you should have someone apply the brake while inspecting the line. A small enough leak would only manifest itself under pressure.

[Pegasus]

I didn't have someone apply the brake, as you suggest. I visually checked the condition of the hoses, rotors and pads. I didn't found any evidence of leaks. If I had a leak I should probably have seen traces of fluid around, don't you think? Also, the fluid level has not decreased so far. I will keep checking it regularly anyway. On the other hand, I think that if I had a leak I would be feeling it when applying the brakes ("spongy" brakes), because I would be getting air into the system, right?

[El Presidente]

That all depends on the size of a leak. A small enough leak would be able to force fluid out but not draw air back in.