Buick has a weird brake glitch

[JDgreen227]

Redid the brakes on my '04 Lesabre less than 4,000 miles ago, in the last month it has been acting really strange about every 50th time I apply the brakes...the pedal pulses back and it acts like the ABS is kicking in, even though the pavement is dry. No, this does not happen during a hard or emergency stop, because I don't do those. When I release the pedal and reapply the brakes, nothing happens, until about the 50th time when it acts up again. For what it is worth, car is only driven 1-2 times per week, and the pulse back never happens unless it has been driven for several miles. Any ideas?

Thanks.

 

[Egon]

I've been told that GM products have a terrible brake system. When I think about the 2003 Pontiac we had it's very true.

A split rotor may act as you have desribed.

 

[Fixemall]

Relube the caliper slides, because you don't drive it a lot, any slight hangup in the slide will trigger a false ABS condition. While it is apart you should unplug and clean the sensor connections with electrical contact cleaner as well.

 

[automech]

If this is happening at a slow speed, when coming to a stop, it is most likely an abs stop taking place. This is common on GM cars and is usually caused by a wheel speed sensor going bad. The way to check this is to scan all four wheel speed sensors while driving and see which one is dropping out when the problem occurs. What the abs controller sees is one wheel showing 0 mph when the other 3 show 3 or 4 mph and so it thinks that wheel is skidding and activates the abs system untill all wheels are the same. This is easy to see with the right scanner, preferrably one that allows graphing of the signals from the speed sensors.

 

[Egon]

when the sensores go bad isn't there an ABS light that comes on?

 

[JDgreen227]

Thanks Guys, I should have mentioned that the glitch happens at brake applications of 35-55 mph and the ABS light doesn't come on. I like the suggestion about lubing the caliper slides...appreciate the detailed input.

 

[Fixemall]

Thanks Guys, I should have mentioned that the glitch happens at brake applications of 35-55 mph and the ABS light doesn't come on. I like the suggestion about lubing the caliper slides...appreciate the detailed input.

If you have a polishing wheel (not grinding) on a bench grinder, don't be afraid to clean them with brake cleaner and polish them up before regreaseing them, the end goal here is to get them to slide easily. Don't forget a dab of locktite on the caliper bracket bolts too.(blue not red!)

 

[roygage]

when the sensores go bad isn't there an ABS light that comes on?

The light will come on in the case of a open or shorted circuit. In the case of false ABS application as described by Auto Mech the wheel speed sensor is dropping it's signal as it comes to a rolling stop and the computer in charge of things is unable to see anything other then one wheel locking up and so reacts by activating the abs, same as if you had stopped on some ice.

In the light truck line it was rust building up under sensor pulling the sensor away from the tone wheel. This resulted in the signal dropping out at slow speeds.

If the problem is not ABS related then something is loose and shifting around, loose caliper, loose pad material ect. Good visual inspection is in order. Good rule, "first place to look is the past place you have been".

 

[toppop52]

GM doesn't have terrible brakes, and it's most likely sensor related, as mentioned, either a bad one or rust causing false signal.

 

[JDgreen227]

The light will come on in the case of a open or shorted circuit. In the case of false ABS application as described by Auto Mech the wheel speed sensor is dropping it's signal as it comes to a rolling stop and the computer in charge of things is unable to see anything other then one wheel locking up and so reacts by activating the abs, same as if you had stopped on some ice.

In the light truck line it was rust building up under sensor pulling the sensor away from the tone wheel. This resulted in the signal dropping out at slow speeds.

If the problem is not ABS related then something is loose and shifting around, loose caliper, loose pad material ect. Good visual inspection is in order. Good rule, "first place to look is the past place you have been".

When I redid the brakes I used better than OEM quality pads and rotors and since the car was outside at the time I powerwashed the calipers well after removing the old pad and rotors. Also used a brass wire brush to remove and clean any debris the power washer and used brake cleaner on anything that didn't look clean enough. BTW the 4,000 miles between brake redo and the first time the problem surfaced took over and year and a half to put on the car. I should have mentioned that after the second time the problem occurred I pulled all four wheels to check for something loose with no success. Thanks guys...I don't think the problem is serious enough to warrant any worry but now if it become more frequent I will have ideas to check on...:thumbsup:

And roygage, my 2000 GMC Yukon XL had a factory recall for that rust buildup under the sensor...I did the cleaning myself, very minor rust. I didn't think that problem could also affect my car...thanks for the heads up !!!