Low speed 'rattle' from front end

neilm · Jun 12, 2012

Once again I'm asking for assistance with a persistent niggle! Many thanks to the forum members for suggesting solutions to my previous issues with coolant loss (as suspected, a cracked tank) and random misfires (coil packs now replaced)!

Since I've had the car I've noticed a rattle from the front end when going over low speed bumps in the road. It disappears (or is inaudible) above about 25mph.

At first I suspected a suspension bush, but the front shock absorbers and mountings were replaced last year with no benefit to the rattle.

Essentially it is a 'knocking' noise that occurs when going over low speed bumps such as manhole covers, potholes, speed humps etc. It doesn't seem to be one side of the car or the other, but if driving down my drive at 5mph which is very potted with lots of left/right movement it is at it's most apparent.

My Indy has had a look at the suspension but can't find anything amiss, and I've tried removing anything from the spare wheel compartment that could be causing it (it sounded initially just like the jack handle hitting the spare wheel!) and temporarily removed all the plastic panels from under the luggage compartment.

It's one of those things that's driving me mad!

The car is a 2004 C4 manual with 85k on the clock.

steveoz32 · Jun 12, 2012

Knocks on the front not specifically to Porsche but to cars in general (that I have experienced) are normally ball joint / mounting on wishbone, roll bar bushes or drop links.

Drop links give a loose rattly knocking on the front, fairly rapid over uneven, rough roads. Ball joints on the bottom of the strut normally give more of a clonk in a similar fashion over more heavy bumps at low speed, but not so rapidly occurring as the drop link noise, roll bar bushes tend to knock again on uneven terrain or also a sharp acceleration from low speed / rolling you will get a clonk / knock.

All are fairly inexpensive (apart from the ball joint, as most people replace the whole arm, although you can get new ones pressed in if you do it yourself and save a few pounds). Roll bar bushes are about under £20.00 a pair from Porsche (well when I bought a pair a couple of years back), drop links are around the £50.00 mark each, but you can get non OE ones cheaper.

The odd thing is though, that if your Indi has given the suspension components a good going over he should have already ruled out the things above :S

If it were me I would have the car up and have a look at it, and check for any leaking, soft or squishy/flat joints on the drop links and wishbone (or coffin arm as they are also known, as technically they look nothing like a wishbone!). I'd also examine the bushes on the roll bar and if required detach the roll bar from each side and check for excessive play.

Cheers,