Djbrand1

Just picked up another 88 Turbo S. At low speeds there is what sounds like a metal on metal "knocking" coming from the left rear wheel well area. The noise is only there with suspension movement. I took a look under the car and everything appears normal, no obvious issues. Previous owner said the Porsche dealer guessed it was possibly a bad shock but could not pinpoint it. Any things to check for? Highway speeds the noise is less evident, around town driving is when you really hear it knocking.

rdanford

Check the brake pads...I had a noise too. After replacing shocks and rebuilding both CV's I finally needed to change my rear pads. After replaced the noise has been gone, loose clip left the pad shift.

944Spec_Bound

Sounds like you arleady checked for loose bolts, but I had the same thing once, only happened at slow speeds when hitting bumps or into my driveway. Found the rear swaybar was loose where it attaches to the trailing arm.

kombatrok

I second checking the parking brake pads. The hold down springs on mine broke causing s rattle that I could only really hear at low speeds.

Djbrand1

Would loose brake pads really sound like metal on metal tapping? I'll double check the swaybar mounts.

Kevsporsche944

or an exhaust braket. or check your rear cargo bins.

Matt O.

The clip is probably missing from the brake pad (as has been mentioned). What happens is the rotor will be at a point where the friction grabs the brake pad and drags it a few millimeters, then rotates to a point where the rotor isn't grabbing it, essentially releasing the pad. Then as the wheel turns it hits that wide point again, grabbing the pad, and releases. Causing the clicking noise at slow speeds (higher speeds it usually just stays put).

It's not a guarantee, but a good possibility that's your issue.

Photodan

Not sure if this will help but...Make sure you give the top strut mount bolt a good tighten up. I had quite a rattle coming from the top of the rear wheel well after the shop did some work that required removing the rear struts. The top strut bolt seemed tight but it wasn't quite tight enough, it takes quite a load. I also had the innards of the emergency brake disintegrate and that was more of a "tinkling" sound.

Djbrand1

I'm going to take a look at the strut bolt this weekend. For how loud the clunking/tapping is I would be suprised if it was a loose brake pad. I will look at that as well though. Thanks for the suggestions.

What's the easiest way to get at the top of the strut bolt in the rear?

KuHL 951

My 83 had a terrible road surface related knock. I checked everything on the car for 2 months. It turned out to be the lower shock mount bolt wasn't tight enough to compress the rubber bushing. The bolt was tight but not all the way down. One turn of the wrench and the noise was gone for good.

Photodan

You can just jack the car up, take off the wheel and reach up in there. I can't remember the bolt size. It's really very easy and only takes a minute, you won't have any problems.

Sounds like kuHL 951 had the exact same problem only on the bottom mount. It does indeed sound "terrible". Hopefully that's all it is and you'll be good to go.

Djbrand1

I'll keep my fingers crossed, and keep you guys posted. Thanks

Djbrand1

So turns out, the previous owner replaced the rear shocks with some black standard shocks. No idea why the factory koni's were replaced with under 35k miles. Anyway, the left rear shock once removed must have had an internal failure, you can literally ring it like a bell. The metal dust boot from the top part of the shock would tap against the bottom. No way to really tell without pulling the shock out. Replaced with new koni yellows and all is well. Thanks for the suggestions though!