Solved- Rotors thermal cracking already?

[MikeMM]

Just got my car out from under the cover and got her out for the first drive of the year. Of course, I did all the normal preseason checks such as oil, tire pressure, leaks etc. When I got back from my 20 mile drive, I double checked everything and I noticed both of my front rotors have a multiple cracks running down the entire face of the rotor, and the rears are cracking as well. I did check them before my drive, but there was some built up corrosion from sitting so I couldn't really see. I didn't have time to take the wheels off last night and see how deep they go, but it is concerning due to the fact they run from edge to edge on the rotor. My car only has 4,4XX miles on it and I haven't tracked it so I'm not really sure how the brakes would have gotten hot enough to crack that bad that soon into their life. I realize drilled rotors are prone to this, but I wouldn't think street use would cause this that fast.

My 2 main questions are:

1. If the cracks are just superficial, are they ok to run or should they be replaced?
2. Considering the mileage, could this be a warranty item for defective rotors or something along those lines?

EDIT TO SUMMARIZE:

My rotors appeared to be cracked. I called the local ford dealer and determined rotors are covered under 3y/36k warranty as long as the damage isn’t from abuse or external sources. I pulled my rotors this evening and thanks to @DCShelby took some sandpaper to what looked like cracks and the void I was feeling with my fingernail was actually pad material creating 2 tiny ridges and a valley on the rotor face. I was incorrect in my initial assumption, but I suppose it’s better to be wrong and overreact than not and have a rotor let loose on the interstate. Thanks for all the help and responses.

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[Grimace427]

Photos?

 

[MikeMM]

Photos?

I'll post some up tonight when I can get the wheels off.

 

[Tank]

Pics would help.

Like you said, you don’t know how deep they go but I would definitely bring it in for a check, possible warranty replacement.

Google it.

 

[MikeMM]

Pics would help.

Like you said, you don’t know how deep they go but I would definitely bring it in for a check, possible warranty replacement.

From my limited knowledge, drilled rotors tend to have small spider type cracks emanating from the drill holes, not the edge to edge as you described.

Google it.

Yeah definitely wouldn't be as worried if they were coming from the holes, but I believe the D/S front has one big one that is in between holes. I'll definitely get some decent pics up tonight and get it to the Ford dealer.

 

[Tank]

Yeah definitely wouldn't be as worried if they were coming from the holes, but I believe the D/S front has one big one that is in between holes. I'll definitely get some decent pics up tonight and get it to the Ford dealer.

Ugg, I edited my post. Forget about what I said about my limited knowledge....It’s very limited .

Track Mustangs Online has a good thread on this subject.

 

[jmn444]

IMO if cracks go to the edge they aren't safe. Pics would be good though!

 

[DCShelby]

Not cracks in the rotor itself, it’s the pad material that’s been deposited on the rotor that seem to have cracks or flakes. You can take the rotor off and clean them up with a polishing tool. The Autofanatic has a video of it.

 

[MikeMM]

Not cracks in the rotor itself, it’s the pad material that’s been deposited on the rotor that seem to have cracks or flakes. You can take the rotor off and clean them up with a polishing tool. The Autofanatic has a video of it.

They seem to be in the rotor itself. Running my fingernail over the cracks there is a clear void or whatever you want to call it on them I can feel. The video you referenced was to clean up deposits and scoring, which is not what I'm seeing on my rotors.

 

[Austinj427]

This sounds crazy..

I'll look at mine when I pull it out, I have about the same amount of miles but 3-4 track days on them.

They really shouldn't crack like the way you are saying.

 

[MikeMM]

Just as an update:

I put a call over to the Ford dealer we contract with, and the service manager there told me it is a warranty item covered under the bumper to bumper as long as it wasn't damage caused by an external source or blatant abuse. So, looks like I'm getting a new set of rotors. I'll still post up some pics tonight just for the sake of sharing with everyone here.

 

[1 old racer]

First of all I am old school and love crossed drilled rotors and have them on my mustang right now. However please know that all crossed drilled rotors that I have owned have developed cracks sometime in their life. If you have them on your car the most important thing you must know is that the cooldown of the rotors determine how long the life cycle will be. When you track a car with crossed drilled rotors the cool down lap is very important. It allows the rotor and caliper to cool togather thus reducing the hot spot under the caliper and pads. Most people take advantage of this and the braking system cools down evenly. My personal bad habit is when I drive down our local mountains and stop for gas or a meal. I stop the car with the braking system hot and the rotors cool unevenly. The area under the caliper stays hot while the rest of the rotor cools causing uneven stress. Please note that over the years I have learned how to treat these types of rotors and now they last as long as my cars do. My last set of cross drilled rotors were on my CTSV with lots of track runs and over 45k daily driving on them and when I sold the car the rotors were in great shape. Just something to remember.

 

[MikeMM]

First of all I am old school and love crossed drilled rotors and have them on my mustang right now. However please know that all crossed drilled rotors that I have owned have developed cracks sometime in their life. If you have them on your car the most important thing you must know is that the cooldown of the rotors determine how long the life cycle will be. When you track a car with crossed drilled rotors the cool down lap is very important. It allows the rotor and caliper to cool togather thus reducing the hot spot under the caliper and pads. Most people take advantage of this and the braking system cools down evenly. My personal bad habit is when I drive down our local mountains and stop for gas or a meal. I stop the car with the braking system hot and the rotors cool unevenly. The area under the caliper stays hot while the rest of the rotor cools causing uneven stress. Please note that over the years I have learned how to treat these types of rotors and now they last as long as my cars do. My last set of cross drilled rotors were on my CTSV with lots of track runs and over 75k daily driving on them and when I sold the car the rotors were in great shape. Just something to remember.

Definitely appreciate the solid advice on track days or hard driving with drilled rotors. My route home from where I take my car to play has a solid 5 miles of brake free driving where they can cool before they sit. I have yet to track my car, so the heat cycles my rotors have seen have been minimal at best. The cracking I'm seeing is consistent with pictures of cracking I've found on cars with 15-20 track days on them.

 

[1 old racer]

You got some bad rotors. If the warranty replaces them it's a win.

 

[nastang87xx]

Ford has a 12,000 mile/1 year consumables warranty for stuff like this. I'd ask the dealership if that's something they'd be willing to shoot through the warranty process.

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