I broke down this past weekend and replaced my right front wheel bearing/hub assy. Since the dealer wanted $300 for a new one, I went with a quality reman unit from Eire Volvo for $75.

Since I was pulling everything off anyway, I went ahead and did the pads, new rotors, and caliper pins. I cleaned off both ABS pickups (diamond shaped tips) thoroughly with an old toothbrush and brake cleaner (both were quite covered in what I assume is brake dust and metal particles from the old rotors). I used a big pair of channellock pliers and the old pads to create clearance in the caliper for new pads.

Now my braking performance is great, and my crappy wheel bearing noises are gone. But now every now and then, very randomly, when I am applying hard pressure to the brakes at a complete stop, I will hear a sound and feel feedback through the pedal identical to the "start-up ABS test" I feel evey time I get in the car.

Is this because of a different air gap with the new hub? Did I squeeze some dirty fluid back into the ABS unit? Or did cleaning the pickups make them more sensitive? Should I even worry about it? If so, what should I do? Is the air gap even adjustable?

Dear keefus,

Hope you're well. The hard application of brakes could be what triggers the ABS system. The noise you hear seems "normal" and so unrelated to your brake system upgrade. You may not have heard any noise before your upgrade, because caked-on dust made the sensors less sensitive. Your cleaning likely restored their sensitivity.

I'm puzzled by your statement, "...feedback through the pedal identical to the 'start-up ABS test' I feel every time I get in the car." In many years of driving 940s, I've never heard of - and so experienced - as "start-up ABS test".

The ABS light goes out so soon as the engine starts. The only other time I've seen the ABS Light come on, is when a failed alternator drive belt caused the battery to drain and the car to stall. That cause all the instrument cluster warning lights to come on.

Hope this helps.

Yours faithfully,

Spook

Hiya Spook,

We've all seen how every once in a while a crusty old thread gets bumped to the top of the list. Other forum software is configured to keep this from happening, but Jarrod's code allows it. IMO it's not a bad thing for this crowd especially when it's a question like this one that was never quite resolved, or at least didn't appear to be.

Since I doubt that keefus will be monitoring his post, I'll take a crack at your puzzlement. All my front-driver Volvos (850s and V70) would do an ABS diagnostic the first time the car reached 10mph after startup. This was exhibited as a vibration and audible buzz of the ABS pump. Perhaps this is what they were referring to. Or perhaps the ABS system of the 940 works differently and I should just keep my mouth shut...

Either way, have a nice day.

-Will

Dear Will,

Hope you're well. It sounds - pun intended - as if the ABS self-test is a feature present on front-wheel-drive cars, e.g., 850 and V70 models.

The only times I've ever heard the ABS system "kick-in" in my 940 was during slip-slide (winter conditions) or very heavy, near-emergency stops.

Hope this helps.

Yours faithfully,

Spook

If I remember correctly, there is something about oversensitive sensors in the 700/900 FAQ.

Usually, when I put new pads on, I bleed the system so I don't push old fluid back into the ABS modulator. Last time I didn't, though, since I had just changed out the fluid altogether nine months before.

I'd say, as long as the system works and doesn't light the warning light, then don't bother messing around, unless it really bothers you. Especially on my 91 240, the ABS system seems way oversensitive at low speeds on uneven or imperfect surfaces. I haven't bothered to chase down the problem since the overall system works pretty well other than that.

My rear axle pinion seal was leaking heavily,,,so I replaced it & the bushings on the axle,now about a week later the ABS light comes on,,,its been raining here & when get time I will jack up the rear & clean out the elec connection,,I suspect the axle grease got in there..

I haven't messed with the ABS brakes on my 940 enough to be of much help - I got it with new pads and rotors. Since the majority of folks in the RWD forum work on pre-ABS Volvos, perhaps you'd have better luck posting on the FWD board. But let us know when you figure this out...