heres another possible cause that is limited to the late model AW11. 88/89. like your 89 model rainystreets.
 
front brake calipers. it appears they changed the design from the early 87/88's in the early models they had a collar that went over the caliper slide that kept the caliper square to the brake rotor. In my 89 model the caliper does not seem to have this collar but instead uses the rubber boots so to speak to keep the caliper in place.
 
Someone else I know had an issue with this not long ago. and I have a front end knock in mine everytime I hit the brakes. so with the wheel off I can only find one thing that is moving, I can grab the caliper (not the torque plate) and wobble the caliper out and in on the brake pads/rotor. it makes the same clunk I can hear when braking.
 
All the bolts are tight, I have a set of 87 calipers here and they are indeed a different design on the slide pin.

OMG!

Had my shockie strut mounts replaced today...........it's like driving a new car..........so quiet I can now hear all the rattles in my cabin LOL

I recommend that if you can't track the rattle down in the obvious places, then just go and replace the shockie strut mounts..........awesome!

Cheers, M

I blew the money replacing the front strut tops and when we pulled them out realised it was just the loose nut! lol
lesson here is check the nut first folks :)

Very late to the party but anyway. It's also worth taking a look at the uni joint between the steering shaft and the rack. I have replaced everything in the front end of my mk1 and it still rattles. Moving the steering wheel side to side I could hear what sounded like a rack rattle. When I pulled the uni joint to pieces some of the needle bearings had collapsed. I re packed the bearings and it was better but i need a new joint. Genuine only as far as I know and they are pretty dear.
Pete

The front-end rattle.
I've just replaced my steering rack ends, tie-rod ends, steering rack bushings and fitted the entire twos-r-us bushing kit.
The steering is heaps more precise, and no more play in the steering......
....but the knock/rattle remains! - when going over bumps or veering left/right.
But now I'm 90% sure the sway-bar links are the cause (or at least contribute to it), because with the front jacked up, I can push the sway-bar up, and it moves and makes the knock sound! - there's definitely some play there.
 
So I've ordered new sway-bar drop links off ebay from the UK (seemed to be the cheapest easiest standard option).
 
Adam.
 
 

I have just been through the same thing. After replacing the uni joint (as mentioned in the previous post) in the steering column the rattle was still there. I got to the bottom of it last weekend when I adjusted the pre load on the steering rack. The correct way according to the workshop manual is to measure the resistance on the steering pinion with a 0-5Nm torque wrench, but who has one of those? I just tightened the 24mm hex bolt until I felt very slight resistance when moving the rack back and forth. I used an old 24 mm bolt as an adjustment tool. You will need to pull the rack out to do it though. Took about an hour or so to do and the rattle is gone. Careful you don't go too heavy on the pre load as your steering will not return to centre properly. I suspect all the money I spent replacing bushes, bearings and ball joints on the front end was unnecessary but at least I know it is all sorted now.

I've just replaced the sway bar end links, and the front-end rattle has completely GONE - that was definitely the cause of it for me. Turned out to be the easiest suspension part I've replaced too, didn't even have to take the wheels off, just jacked it up.
 
The other thing I think I'm noticing is a little more vibration through the car in general, but its only slightly, could just be my imagination, and without the extra rattle in the front I'm noticing other sounds more easily. Could also be because of all the urethane bushing now fitted.