1998 FGY33 ABS Question

[KingKarl]

I have a 1998 Q45t with a worrisome symptom. After driving at any constant speed for about 10 minutes, I notice a low-level rumbling sound/vibration that seems to be coming from the passenger side begin. If I continue to drive at the same speed for a minute or two, the symptom goes away and the car runs smoothly. This problem started about a month ago.

If I apply the brakes during the time when the sound/vibration is perceived, I feel the pulsing through the brake pedal, similar to the feel of a warped rotor. The car slows without pulling to one side or the other. At all other times, the car brakes smoothly with no pedal pulse.

I went through the front and rear suspension 30K miles ago....new struts and rubber parts, all OEM. I've had new tires installed and the wheels have been balanced and alligned. I've bled the brakes replacing the brake fluid and checked the rotors for abnormal runout, all done per the FSM. Although it seems better, the problem persists.

Could the ABS be activating on one of the rear wheels because of a bad/dirty wheel sensor? Could I have a wheel bearing problem? I'm stumped. Any suggestions as to where I might look next will be greatly appreciated.

[Q451990]

Does the ABS light come on on the dash? I would run the self diagnostics on BR-59 (and look through the rest of that chapter) of your factory service manual, and see if you have any codes. It's available at www.nicoclub.com/FSM/ if you don't have it already.

Good luck!

Heath

[KingKarl]

Thanks Q451990. No ABS light during driving but it shows during crank up.

I've got a hard copy of the FSM and have worn out the BR section. I don't have a Consult so I have been trying to solve the issue the hard way by ruling things out. I do have a compatible code reader so I'll have to see what it says if I can figure out how to run the called for diagnostic procedures with it.

[KingKarl]

Okay, I guess I need to spring for a Consult. The OBD reader just does not do the job with live data but as far as it went, the car generated no codes. Of course, I could not run the diagnostics listed in the FSM either.

[maxnix]

So back to maintenance history, when did you last bleed the brakes and ABS unit?

[Q451990]

The test in the BR section involves grounding a certain pin on the connector and counting flashes... no Consult required.

Heath

[KingKarl]

Max, I bled the brakes/replaced the brake fluid last weekend but did not bleed the ABS unit. (I take it that is a separate process? I don't seem to be able to find reference to it in the FSM.) Heath. I see the test on BR 59, just as you advised in your first response

Okay, I see I really need to improve my reading comprehension.

Much thanks guys.

[KingKarl]

Okay, now I'm lost. Ran the diagnostic procedure and found no ABS heel sensor codes. Wheel bearing? What perplexes me is that the vibration comes in at about 5 minutes at a constant speed and goes away after 3 to 3 minutes. Do FGY33s have self-healing properties?

[paranoidjack]

I've seen bearings fail like that - once they really grind, and get warmer/louder, parts can "settle in" at constant speed and symptoms disappear, but it's just a matter of time.

Easy test of a bearing is jack the car up and spin the wheel. Listen, feel, subtlety here is key...

[KingKarl]

Thanks Jack. I did that and could hear nothing. Also checked all four rotors with the dial gauge and they ranged between 2 and 3 thousands of runout so that's okay. Clearance between the rear wheel speed sensors and their rotors was within the range of tolerances listed in the FSM. While I was there, I changed the differential gear oil and the fuel filter.

I got all that done, re-bled the brakes and treated the back of my head with some foul smelling Red Line gear oil at the same time. The problem is that I still have the "comes and goes" wheel/brake/suspension vibration and pulsing.

[KingKarl]

I may have stumbled into the solution to my problem. I must have failed to adjust the parking brake shoes on the passenger side rear wheel correctly when replaced the rotors.

As I drove, the parking brake shoes created lots of heat dragging on the drum part of the rotor. The vibration/pulsing started and grew worse as the drum and brake parts heated up. As the heat continued to grow, the drum expanded to the point where the symptoms resolved but the shoes still drug enough to produce the heat necessary to keep the drum partially expanded. Does this even sound possible?

Anyway, after my next to last test drive, the driver side rear was cool but the drum portion of the rotor on the passenger side was two or three degrees cooler than the surface of the sun. So, I backed the adjustment wheel off one full turn, re-mounted the wheel and happy motoring for an hour with no more pulsing or vibrating. Now if I could just figure out how to get the gear oil out of my hair.....