jhall Posted October 25, 2007 Report Share Posted October 25, 2007 Hi all, It's been a whle.... My wife's 2002 Deville is giving a pulsation in the brake pedal sometimes. This occurs when braking lightly from about 60 MPH. I can feel the ABS module cycle for a short burst at the application of the pedal, then it stops. Any ideas on this? I am not getting any codes on the system other than the on-going PCM 0741 telling me the overdrive is not active (wrote about this a while back, just letting it go). She also complains about a vibration a 65 - 70 MPH. I can't reproduce the shake when I drive it - at least not yet. Need some ideas before I have to trade the car,or something else , in Any help appreciated. Link to comment Share on other sites More sharing options...
coolnesss Posted October 25, 2007 Report Share Posted October 25, 2007 Pulsing from warped rotors feels similar, but not the same, as a jittering type feeling, usually accompanied by some noise, from ABS. Which sensation do you have? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted October 25, 2007 Report Share Posted October 25, 2007 If the ABS is kicking in momentarily when braking lightly from about 60 mph, it's probably due to the wheels not having the same rolling radius. I would check the inflation of all four tires to make sure that they all have the same pressure. While you're at it, check the tire make and size, and amount of wear. I've heard of someone who had an oil change at a filling station, and their Pirellis magically became no-name junk tires. Since the ABS works on both front and rear tires, you can't just match the axles, you need to match all four. Once you've resolved the ABS issue, then you can probably fix the shimmy from 60-70 mph by having the tires rotated and balanced at a shop that has a road force balancer. Any good tire store should be able to do this. Start with whoever sold you the tires. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Ranger Posted October 25, 2007 Report Share Posted October 25, 2007 Does the pulsation continue after the ABS stops cycling? Link to comment Share on other sites More sharing options...
jhall Posted October 26, 2007 Author Report Share Posted October 26, 2007 Pulsing from warped rotors feels similar, but not the same, as a jittering type feeling, usually accompanied by some noise, from ABS. Which sensation do you have? It's not a brake pulsation in the sense of warped rotors. This only occurs one time at the application of the brake pedal and is a short thump - the same feel you get when the ABS activates. It does not occur all of the time and it does not last longer than a short burst. The braking is smooth otherwise. Jim - Thanks - I'll check the tires. We had new ones put on a two months ago. My wife also reminded me that a day after the tires were installed, she hit a curb and ruptured the sidewall on the right front. I did not see any other damage other than a $100+ tire . The car was driving OK up until about two weeks ago. Not sure if any damage could have occurred to cause the ABS issue, but I'm thinking the right front is down on pressure. I felt a slight pull to the right when I drove it today - most noticeable on acceleration and slightly creeps right on the road at highway speed. I replaced rotors about 4 months ago, but all was fine with the front-end brakes up to this point. Thanks to all for the replies. Link to comment Share on other sites More sharing options...
adallak Posted October 26, 2007 Report Share Posted October 26, 2007 I would disable ABS (fuse if any, connector on the module) and see what happens. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
jhall Posted November 18, 2007 Author Report Share Posted November 18, 2007 Hi Guys, A follow-up: I checked the ABS unit main connector and looked at all the tires, air pressures, etc. I also checked the ABS sensor connections at each wheel and the main electrical connector near the firewall (driver side) just in case. My wife drove it tonight and the ABS unit is still cycling in a short burst once in a while when she brakes. No codes are showing up. I am wondering if the ABS unit is going out, but it seems a code should be thrown. Any ideas appreciated before I take it to the dealer and get hosed Regards, Jeff Link to comment Share on other sites More sharing options...
JimD Posted November 18, 2007 Report Share Posted November 18, 2007 ....Any ideas appreciated before I take it to the dealer and get hosed Do not take the car to anyone before you see a consistent / repeatable DTC. Drive it and wait. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
jhall Posted November 18, 2007 Author Report Share Posted November 18, 2007 ....Any ideas appreciated before I take it to the dealer and get hosed Do not take the car to anyone before you see a consistent / repeatable DTC. Drive it and wait. Thanks Jim - I'll hold out as long as I can stand the compliants from my wife.... I took a closer look at the tires today and noticed the one they replaced (from the curb encounter) is a Symmetry XSE rather than an X version. I tried to look up specs at the Michelin web site but had a tough time determining if the rolling diameters are the same for an X versus XSE style. I note that a couple of the Symmetry tire versions vary by about 0.3 inches. Note sure if this is enough to trick the ABS if I've got the "wrong' one. Now going back to reconfirm the inflation pressures of the XSE tire versus the other X series. Jeff Link to comment Share on other sites More sharing options...
jhall Posted November 18, 2007 Author Report Share Posted November 18, 2007 Thanks Jim - I'll hold out as long as I can stand the compliants from my wife.... I took a closer look at the tires today and noticed the one they replaced (from the curb encounter) is a Symmetry XSE rather than an X version. I tried to look up specs at the Michelin web site but had a tough time determining if the rolling diameters are the same for an X versus XSE style. I note that a couple of the Symmetry tire versions vary by about 0.3 inches. Note sure if this is enough to trick the ABS if I've got the wrong one. Now going back to reconfirm the inflation pressures of the XSE tire versus the other X series. OK more info - drove the He** out of it this evening. Rechecked tire pressures. All are OK. There appears to be something more sinister at work. Above 45 mph with a firm brake application, there is a quick two or three bumps that occur and it feels eactly like the ABS unit and it feels as though the brakes are grabbing at a spot on the rotor - but just until the weight of the car shifts forward onto the front end. There is no push back or pulsing on the brake pedal as you would feel with a warped rotor, but you can feel the bump through the pedal and in the body. The car will steer straight during braking and I can hear the tires squeeling just a bit under the load. Now I'm wondering if my wife's encounter with the curb may have damaged the wheel bearing, suspension, or something else. I didn't see any visible damage at the time the wheel was replaced, but something is up. Jeff Link to comment Share on other sites More sharing options...
Regis Posted November 18, 2007 Report Share Posted November 18, 2007 I'm thinking that the lube in the caliper slides and bushings on at least one side is drying up and causing erratic behavior. Just something to consider. "Burns" rubber " I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. " Link to comment Share on other sites More sharing options...
jhall Posted November 19, 2007 Author Report Share Posted November 19, 2007 OK, Here's an update...... Checked everything over again and then measured the lateral run-out on the disks. Didn't see anything beyond about 0.003 worse-case. Considered turning the rotors since they are only about 6 months old, but did not want to guess any further (or keep pulling the car apart). Dropped some $$ and bought new rotors and ceramic pads (previous pads were semi-metallic). I previously have used the multi-stop method stated in the Helms manual to seat pads and did this when I replaced the rotors and pads last time. I noted the inside disk surface on the driver side appeared glazed. Both calipers were properly lubed and still moved cleanly since the last repair. I'm going with the tried and true method of "just drive it and try to avoid hard stops for a while". Hope the wife can do this. I'll keep you posted. So far, the trial run was OK and the braking is smooth with a nicer grip than the metallic pads (probably because of the new surfaces). Once the pads seat, I'll try some harder stops to see if this solved the problem. Hope it won't be a moderately expensive lesson! Happy Thanksgiving! Jeff Link to comment Share on other sites More sharing options...
jhall Posted December 14, 2007 Author Report Share Posted December 14, 2007 Hi All, Wanted to follow up on this post. The ABS buzzing came back - though not quite as bad. A roaring noise developed, but couldn't pin-point it. I finally took the car to the dealer this week - no time to repair it in the garage and it was a really irritating wife....I mean......problem. The right front wheel bearing seal was damaged and the bearing failed. The bearing slop apparently caused a reading error with the wheel speed sensor - but it was only part of the issue. The replacement tire (from my wife's curb encounter) that was reinstalled by the tire dealer was a Michelin Symmetry "XSE", the other tires were Symmetry "X". They look identical in design. XSE has silicone in the tread material. The tires are about 1 month old. When the dealer road tested the car after replacing the bearing, the ABS would buzz only on right turns. They measured the tire rotations and found a 2 mph difference between the front tires while moving forward and a 3 - 4 mph difference on corners (this part would be expected depending on how tight the turn might be). When the XSE tire was moved to the rear, the ABS problem went away completely. I questioned the dealer thoroughly on their measurements and they stood firm. I called Michelin and they stated the XES is slightly different in diameter, but neither they nor I could account for ABS interaction. The diameters of the tires are very close - 777 rotations per mile versus 780 rotations per mile. I asked about differences in the loaded, rolling profiles of the tires, but they stated that the variations between the tires under loaded conditions would be the same as the unloaded diameters. Car is back at the tire dealer to get another "X" style back on the car. I'm not convinced the tire was adding to the problem, but the results speak for themselves. I had a flat on my 2000 DeVille last week. It has Symmetry "X" tires also (bad month for tires) and the ABS never acted up with the smaller spare on the right front as I drove it home. Maybe her car is as sensitive as she is......... Link to comment Share on other sites More sharing options...
adallak Posted December 15, 2007 Report Share Posted December 15, 2007 Do you know how fast the car should move to have 2MPH difference in tires which differ by 0.25%? I mean (780-777)/780=0.2564%. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
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