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tableclocks · Aug 25, 2007, 12:54 PM

I tried reground front rotors and new rotors and I still have a paulsaing in my brakes... abs light works but it is not on... asumming rotors and pads are good... is it possiable that the abs is on all the time... that causes the paulsaing?can I turn the abs off but unplubing a fuze?. I did not change the back rotors... is it possiable for then to be bad and cause the same paulsaing?I don't think so but I need a more prfession opinion.thank you... richard

TxGreaseMonkey · Aug 25, 2007, 01:10 PM

The problem may be related to the installation of the new discs. They may not be exactly at a 90 degree angle to the axis of the spindle. This is referred to as lateral runout (LRO). There may be rust on the hub or another explanation. It's best to use a Pro-Cut machine to resurface discs, rather than a lathe which turns the discs to the axis on the lathe, to eliminate LRO. Be sure to lubricate the caliper pins with silicone grease or Squeak Relief, to ensure they "float" properly and don't bind. Also, be sure and bleed the complete brake system, using an ABS approved fluid. I like Valvoline SynPower or ATE TYP 200 brake fluids. I would recommend ACDelco OEM pads for your Impala. There's a huge variation in the quality of pads on the market. Good technique makes all the difference in the world, when it comes to servicing brakes. Be sure and check for any ABS codes being thrown.

CaptainRich · Aug 25, 2007, 04:27 PM

Lateral run-out is critical and is difficult to measure and just as difficult to compensate for.

Hard spots on the rotor surface can also cause problems and are even more difficult to detect. They can show as dark spotting areas and also as tiny cracks.

Both of these can and will cause brake pulsation. And the pulsation can be from the front or rear. Be careful you don't get stung.

tableclocks · Aug 25, 2007, 04:57 PM

Originally Posted by txgreasemonkey

The problem may be related to the installation of the new discs. They may not be exactly at a 90 degree angle to the axis of the spindle. This is referred to as lateral runout (LRO). There may be rust on the hub or another explanation. It's best to use a Pro-Cut machine to resurface discs, rather than a lathe which turns the discs to the axis on the lathe, to eliminate LRO. Be sure to lubricate the caliper pins with silicone grease or Squeak Relief, to ensure they "float" properly and don't bind. Also, be sure and bleed the complete brake system, using an ABS approved fluid. I like Valvoline SynPower or ATE TYP 200 brake fluids. I would recommend ACDelco OEM pads for your Impala. There's a huge variation in the quality of pads on the market. Good technique makes all the difference in the world, when it comes to servicing brakes. Be sure and check for any ABS codes being thrown.

HOW DO I TURN OFF THE ABS SYSTEN... TO SEE IF ITS WORKING OVERTIME

tableclocks · Aug 25, 2007, 04:58 PM

Originally Posted by CaptainRich

Lateral run-out is critical and is difficult to measure and just as difficult to compensate for.

Hard spots on the rotor surface can also cause problems and are even more difficult to detect. They can show as dark spotting areas and also as tiny cracks.

Both of these can and will cause brake pulsation. And the pulsation can be from the front or rear. Be careful you don't get stung.

... HOW DO I TURN OFF THE ABS SYSTEM TO SEE IF ITS WORKING OVERTIME?

CaptainRich · Aug 25, 2007, 05:59 PM

Generally speaking, the ABS system engaging feels very different, much more rapid... almost "panicy", than the rhythmic pulsation associated with rotors and/or drums being out-of-true, etc.

That is why I recommend anyone with an ABS equipped vehicle "test brake", as if in a real ABS stop, just to see how it will feel. This should be done only is a safe area, away from other vehicles, moving or not.

I'll never recommend turning off a safety system. The engineers that designed the system have far more functional knowledge than I ever will.

And, honestly, if the problem was ABS working overtime, say for example a faulty sensor, a code would be stored, and the lamp would illuminate.

If any wheel is not locking up while you're feeling the pulsation, I would be inclined to believe the problem is not ABS related. Consult your owners manual and/or fuse cover for the fuses for any particular associated system.

BTW: I mentioned earlier that the problem, as you've described, may be front or rear.

tableclocks · Aug 25, 2007, 06:05 PM

Originally Posted by CaptainRich

Generally speaking, the ABS system engaging feels very different, much more rapid... almost "panicy", than the rhythmic pulsation associated with rotors and/or drums being out-of-true, etc.

That is why I recommend anyone with an ABS equipped vehicle "test brake", as if in a real ABS stop, just to see how it will feel. This should be done only is a safe area, away from other vehicles, moving or not.

I'll never recommend turning off a safety system. The engineers that designed the system have far more functional knowledge than I ever will.

And, honestly, if the problem was ABS working overtime, say for example a faulty sensor, a code would be stored, and the lamp would illuminate.

If any wheel is not locking up while you're feeling the pulsation, I would be inclined to believe the problem is not ABS related. Consult your owners manual and/or fuse cover for the fuses for any particular associated system.

BTW: I mentioned earlier that the problem, as you've described, may be front or rear.

... ok tks.I ll put on new rear rotors this week or proubly on sat.. tks