2008 DTS Brake problems

[CadillaC2]

I have seen the postings on this top[ic and wanted to say that I am having the same trouble. Front Brakes pulsating and shimmying. There were several thoughts as to the reasons for this but I did not see an exact fix for this. I do have something to add that I did not see written about as to the cause. I believe the cause is in the whole ABS system. Those of you having this problem take a look at your rear disc brakes and see if they are rusty. Yes rusty! This would indicate that the rear brakes are not engaging at all which in turn is severely overworking the front brakes. Thus the big problems in the front and the need to have the pads and rotors changed constantly. Does anyone know of the solution to this? Is there a different ABS unit that is not faulty(if that is the reason at all)? I have to take my car back to the dealer today, and all they are going to do is fix the result and not address the problem.

[KHE]

The back brakes not activating could be a seized piston in the caliper but would not believe it had to do with the ABS unit.

[Cadillac Jim]

There is an equalization valve for the rear brakes that drops pressure to balance traction but that shouldn't be a problem unless the brake fluid has turned to mud - which does happen if moisture gets into the system and it is ignored for years.

The most likely cause of uneven front-rear braking is stuck calipers, as KHE says. The important thing to watch in a brake job is rebuilt calipers, not just changed pads, particularly if you are having noticeable problems like the rear brakes not engaging.

The ABS system matches the wheels on the diagonals: front left with right rear, and front right with left rear. It's hard to imagine the ABS not engaging the rear brakes.

If you are having problems with pulsation, the most common cause of light but persistent pulsation, usually that you can feel in the brake pedal, is warped disks. That happens when they are not torqued in sequence or to all the same torque. If a filling station or some other outfit mounts a wheel, you should have it checked or remounted at a tire outlet or other outfit that does lots of tire mounting and uses torque-calibrated impact wrenches (no, they are not the same as just any impact wrench). If the warp has taken a set and remounting the wheel doesn't fix it, you will have to resurface the disks.

Another cause is grease or other material consistently wetting a disk, particularly on the front. That type of pulsation can be severe, up to a bang-bang brake grabbing. It is fixed by resurfacing the rotors, and possibly replacing the pads. You should check for leaks and such if that happens.

[winterset]

Hopefully you have done a brake fluid flush out of each bleeder valve at each wheel, stir the master cylinder, suck it out with a turkey baster, refill with fresh fluid, then bleed fl,fr,rl,rr in that order. You may have some moisture in the system, or the seals may need some feesh fluid to rejuvinate and lubricate the system. Get some good brake grease, and grease every pin on each wheel., and clean the piston on each caliper with brake cleaner,

[CadillaC2]

Thank you fellas for the responses. I did not take the car back yesterday because I was waiting for a little ammo or at least guidance for the salesperson who sold me the car. That is what worries me. I just bought the car 1 week ago. Immediately, the next morning I heard a bit of noise in the front and the pulsating started. This car was not cheap and was from a Caddy dealer so I know they had to know about the problem. Why didn't they fix it before putting their name on it and up for sale? I'm afraid that they will just slap some new rotors from China on and be done with it. I just cannot believe they would sell the car like this. Thank you guys very much.

[winterset]

All rotors are from China, i think there are only like 2 or 3 manufactures in the world (what i heard) more to the point, it should have gone thru a check. Tell them to fix the brakes, new fluid, etc. or you want your money back.

[JohnnyG]

I have a 2008 DTS and have had the problem solved for free. There is a recall on the OEM front pads. The recall stops at 2007 according to the wording, but if you explain to the dealership exactly what is going on, they will replace your front pads. All of this is assuming that you have the original pads still on your car. Even so, if they were ever replaced, the wrong ( I assume too hard) pad material may have been used. Mine would pulse under prolonged braking events, such as going down a mountain.

The rear discs becoming rusty is a whole other issue. The rear pads in this case are never touching the rotor. The most obvious cause for this would be a stuck piston in the offending caliper, but if the issue is equal on both rear discs then the problem must be at a point common to the rear braking circuit. An improperly bled ABS pump or the distribution valves come to mind. If the car sat on the lot for a long time, then it may be normal rust which may work itself off after some driving. It is not uncommon, especially near a road salt or seaside environment, for rotors to rust.

[Pontiacivan]

Rear disc breaks are usually adjusted by pumping the emergency/parking brake. They will self adjust to a certain point but the lever on the back of the caliper will ratchet out the piston when the pads wear past a certain point. It is relatively unlikey that a system with so much time and testing like ABS is causing the rear brakes to stop working unless they are stuck to begin with or there are problems with the wheel sensors ( possible poor quality aftermarket bearing replacement.) Also, if you never engage the emergency/parking brake, don't start today, it will like lock up the caliper. Have a mechanic or yourself ( if capable ) ensure that the lever will move and return by manually rotating it. You will likely need channel locks or vise grips to overcome the return spring pressure. If it doesn't spring back, you need a caliper.