Smoking brakes [Update: AC Belt Failure]

[C.J.]

So I was driving at Sonoma raceway last Saturday. In the 4th session, after 3 laps, I noticed heavy white smoke in my rear view mirror after T7, with burning smell. So I immediately pitted.

Initially I was worried if it’s engine issue, like blown gasket. Had some visual check and everything looks normal, no leaks, no spills, oil pressure and oil temperature were within the normal range.

Later the driver behind me came and told me that my brake was smoking, I recalled that the burning smell was indeed brake so I was relieved.

Checked brake pads and rotors today and didn’t see anything suspicious. So I guess it was just overheating. I’m running stock rotors and pads. Has anyone experienced similar issue? Should I be concern about this? Really appreciate your inputs!

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[pilotgore]

So I was driving at Sonoma raceway last Saturday. In the 4th session, after 3 laps, I noticed heavy white smoke in my rear view mirror after T7, with burning smell. So I immediately pitted.

Initially I was worried if it’s engine issue, like blown gasket. Had some visual check and everything looks normal, no leaks, no spills, oil pressure and oil temperature were within the normal range.

Later the driver behind me came and told me that my brake was smoking, I recalled that the burning smell was indeed brake so I was relieved.

Checked brake pads and rotors today and didn’t see anything suspicious. So I guess it was just overheating. I’m running stock rotors and pads. Has anyone experienced similar issue? Should I concern about this? Really appreciate your inputs!

I get brake smoke from time to time, especially in a heavy braking zone where I press the pedal a little too far and get into abs.

You might check all the bleeder screws on the calipers. It’s entirely possible a little brake fluid has leaked onto a rotor and was burning off when it got hot.

Did the car drive and smell alright on the way home?

 

[Egparson202]

Could it be some kind of debris had been captured? Which wheel(s) were smoking?

 

[Tractor Junk]

Did you take the wheels off and check the inside pads? Those run hotter (less airflow) and typically disintegrate faster.

 

[C.J.]

I get brake smoke from time to time, especially in a heavy braking zone where I press the pedal a little too far and get into abs.

You might check all the bleeder screws on the calipers. It’s entirely possible a little brake fluid has leaked onto a rotor and was burning off when it got hot.

Did the car drive and smell alright on the way home?

Thanks for sharing!

Yes I checked caliper and rotors, didn’t see any leakage around bleeding screw.

The car drove well and the smell was gone gradually.

 

[C.J.]

Could it be some kind of debris had been captured? Which wheel(s) were smoking?

Yes that’s also my guess. But didn’t see anything between pads and rotors. The holes of the drilled rotors were all clogged though, not sure if this could cause issues.

I didn’t know which wheels to be honest. I only found some melt rubber inside the wheel barrel.

 

[C.J.]

Did you take the wheels off and check the inside pads? Those run hotter (less airflow) and typically disintegrate faster.

Yes I checked all pads, the inside ones do wear faster and they are thinner than the outside ones.

 

[pilotgore]

So I was driving at Sonoma raceway last Saturday. In the 4th session, after 3 laps, I noticed heavy white smoke in my rear view mirror after T7, with burning smell. So I immediately pitted.

Initially I was worried if it’s engine issue, like blown gasket. Had some visual check and everything looks normal, no leaks, no spills, oil pressure and oil temperature were within the normal range.

Later the driver behind me came and told me that my brake was smoking, I recalled that the burning smell was indeed brake so I was relieved.

Checked brake pads and rotors today and didn’t see anything suspicious. So I guess it was just overheating. I’m running stock rotors and pads. Has anyone experienced similar issue? Should I be concern about this? Really appreciate your inputs!

See any oil drops near the oil plug or belly pan? I’ve had oil blow onto my exhaust pipes causing smoke/smell… although I completely lost my oil plug (long story.)

Edit: the first puff of smoke you see is me locking up the brakes going into ABS. After that, the smoke was coming from the oil. It’s entirely possible the guy behind you that reported seeing smoke was just seeing a brief lockup/abs.

 

[Tomster]

If you overservice your differential, the diff fluid will leak out of the vent line onto your rear brakes. The spec is 9mm below the fill hole. Many fill it to the top.

 

[NoXiDe]

If you overservice your differential, the diff fluid will leak out of the vent line onto your rear brakes. The spec is 9mm below the fill hole. Many fill it to the top.

What's your technique to making sure it's 9mm below?

 

[JAJ]

What's your technique to making sure it's 9mm below?

To measure it, I use a piece of bent wire that goes into the fill hole and hangs straight down 10mm. If there's a drop of oil on the end, then the diff is full.

Of course, having done a diff oil change a bunch of times, I just drain it by pulling the lower cooler line, and then refilling with 52 ounces of fluid.

As for the video of the "smoking" brakes, I have a hard time believing it - nearly 20 years of track experience and I've never seen smoke like that from brakes or from tires when brakes lock up. That smoke, blowing out from under the car, was something else, in my humble opinion.

 

[pilotgore]

To measure it, I use a piece of bent wire that goes into the fill hole and hangs straight down 10mm. If there's a drop of oil on the end, then the diff is full.

Of course, having done a diff oil change a bunch of times, I just drain it by pulling the lower cooler line, and then refilling with 52 ounces of fluid.

As for the video of the "smoking" brakes, I have a hard time believing it - nearly 20 years of track experience and I've never seen smoke like that from brakes or from tires when brakes lock up. That smoke, blowing out from under the car, was something else, in my humble opinion.

In that case I’m happy to add to your 20 years of experience. The first puff of smoke was from locking up after taking a late pass into a big braking zone, but as I mentioned in my previous post the rest of the smoke was from an ejected oil plug and spilling oil over the hot exhaust. I referred to it as “James Bond Mode.”

 

[Tomster]

To measure it, I use a piece of bent wire that goes into the fill hole and hangs straight down 10mm. If there's a drop of oil on the end, then the diff is full.

Of course, having done a diff oil change a bunch of times, I just drain it by pulling the lower cooler line, and then refilling with 52 ounces of fluid.

As for the video of the "smoking" brakes, I have a hard time believing it - nearly 20 years of track experience and I've never seen smoke like that from brakes or from tires when brakes lock up. That smoke, blowing out from under the car, was something else, in my humble opinion.

^^ This

Also, if you start with a known quantity, you can measure what comes out and replace with the same exact amount.

 

[C.J.]

See any oil drops near the oil plug or belly pan? I’ve had oil blow onto my exhaust pipes causing smoke/smell… although I completely lost my oil plug (long story.)

Edit: the first puff of smoke you see is me locking up the brakes going into ABS. After that, the smoke was coming from the oil. It’s entirely possible the guy behind you that reported seeing smoke was just seeing a brief lockup/abs.

Checked oil plug, oil pan and oil filter, no visible leaks. And no obvious change of oil level on the dipstick.

The smoke I saw was not that severe as that in your video, the cars behind me were still be able to see the road. The smoke was transient, and it’s gone after I returned to the paddock. So I agree with you that it’s just a short thing rather than a sustained issue.

And sorry that your oil plug was ejected, hope your car was fine.

 

[C.J.]

If you overservice your differential, the diff fluid will leak out of the vent line onto your rear brakes. The spec is 9mm below the fill hole. Many fill it to the top.

Thanks for bringing it up. I did have the diff rebuilt at dealer recently due to leak. Will keep an eye on it.

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