I will spare you the details and try to get to the point...I have been chasing down a front suspension knocking noise for 6 months...the noise occurs in vicinity of hubs, both front wheels, but more pronounced on right. I have now completed a complete rebuild of front end, including:

Upper control arms (UCA)
Lower control arm (LCA) bushings
tie rods
drag link
ball joints
guide rod mounts (at foot wells)
guide rod mounts (at LCA)
rebuilt brake calipers
new rotors
new wheel bearings & grease seals

The noise I hear is a definite pronounced bump, bump, bump that happens when I drive over "washboard surface" from 10 to about 35 mph (dirt roads, railroad tracks, road patch, etc.)...sounds kind of like a bad ball joint.

I always thought the noise was suspension related, and not brake related, so only recently did I drive over washboard surface with brakes applied and not applied, and the noise does not happen when brakes are applied. When brakes are applied, the suspension sounds as tight as a new ferrari (almost), and when brakes are not applied, bam, bam, bam, bam.

I applied brake pad sticky stuff to the backs of the pads the other night, and this had absolutely no effect. Can anyone suggest what the noise might be.


Here is everything under the sun that I can think of:

1. Brake pads knocking? (not likely since sticky stuff had no effect, but maybe the old brake pad springs I have are weak...I will try putting in new brake pad springs...the brake pad pins are fine and tight, so it cant be them)
2. Brake caliper pistons knocking inside of caliper housing ?(If they were that loose, wouldn't they leak? I did rebuilt them, pistons are held in place by rubber o-ring and rubber seal...maybe the rebuild kit I used had squishy o-rings...not likely)
3. Loose wheel bearings (bearings are new, adjusted just right, no play. In fact earlier this summer I tried overtightening the right wheel bearing and that had no impact on the noise...in fact I drove it too long like that and ruined the new bearing and had to replace it again!)
4. Rotors loose? (I checked...also, I have done this job several times, and no way these rotors are loose...there are 5 or 6 bolts that attach rotors to hubs.)
5. Maybe its this: When noise doesnt occur when braking, the weight of the car while braking is thrown forward compressing the guide rod mounts, preventing them from knocking. (there is no way the noise is due to guide rod mounts, these are new, and the noise is definitely at the wheel/hub..down low way in front, and not at the foot wells)
6. Cracked steering knuckles? (just not possible)
7. Funky brake pads (they seem just fine, nice snug fit into caliper. There is very little play between the ends of the brake pads and the calipers where the pads slide into the calipers)


Can anyone think of anything else...I did order new brake pad springs...these are called "anti knock springs" so maybe this is the obvious solution...I can't wait till they arrive (but I really doubt this is the solution...if the pads are knocking, the noise would have been affected by applying the sticky pad coating). But I will try bending the existing springs to apply more tension and see if that effects the noise.

Thanks in advance for any help.

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)