Front end rattle

Can any off you give me a lead on what this might be. Driving the car from cold all absolutely normal but when fully warmed and perhaps half an hour into a trip I get a front end rattle when going over bumps, eg "sleeping policemen". It's not suspension as all this has been checked with new lower control arms and bushes fitted etc. Also I've noticed the coolant expansion tank is fractionally below minimum. No sign of any leaks or tell tale drips on the garage floor, but could this be connected through a radiator issue perhaps? I didn't check the coolant level after the last service so it could have been at this level then. Water temp gauge is normal and no warning lights have come on at all. If the coolant issue is unrelated, I can get that fixed but it's the niggling front end rattle over bumps when fully warmed up that I'm struggling with. Any thoughts would be really welcome. Thanks Chris

Had this same problem for several years, silence until car has done quite a few miles, especially when pushed around bends. Leave car stationary for an hour or so and silence again for a while. Causes sequentially 'identified' as drop links, top mounts, coffin arms, a/roll bar bushes, track rods, struts et al (ad inf!). All replaced and within car's first 45k miles. At no time was any issue found at mot. On each occasion after 'repair' completed and on next trip greater than about 50 miles the issue would return. Have spent considerable sum having suspension/steering items changed and am convinced is related to neither. Have kind of got used to it now - car has done 70k miles - and I suppose I 'tune' the noise out. Best of luck.

I had what seems like a similar problem, not quite the same scenario but near enough. I got rid of the noise by spraying grease on the front top shock mounts, I believe they dry out over time. Just pop the bonnet, pull off the plastic covers and give it a spray with some chain lube or similar. Might do the trick, if not it's not cost anything.

Thanks guys. It's nice to know I'm not alone with this problem but its such a niggle when up to recently it's been so quiet. Even so it hasn't affected the cars performance at all. It's just I don't like not knowing what it is. I'll certainly give the spray grease a go on the top mounts and see what happens. Regards Chris

Look forward to your results as I have noticed same creaking symptom after driving for a while in my C4. Tried WD40 in and around top mounts, but they all look pretty sealed up to me when accessing from above? Have been told by Max from Porsche Service Centre in Kings's Lynn that is very slight movement in the middle bush where the fork trailing arm connects to coffin arm. Does the problem occur when it has been raining?

Creaking (a bit like old bed springs) is usually the ball joint in the coffin arm (wishbone), and usually worse when the car is hot. I give up with diagnosing rattles, as there are so many possibilities. Wishbones, forked arm, drop links, ARB mounts, top mounts, etc. Basically, anything holding the suspension together can be the cause of a rattle! As for the coolant issue, the expansion tanks are prone to pinholing/cracking, and the early tank caps tend to blow off at too low a pressure. If it is the cap, you will probably see a little coolant in the lip around the top of the tank. From there it drains down a rubber tube to the underside. If it only happens at higher engine speeds (on the move) then you might not see drips on the ground. Check the part number on the cap - if it is 00 or 01 it is worth replacing anyway. The latest cap is revision 04, and they are £13.18 +VAT.

Thanks for the further responses guys. The rattle occurs in both the wet and dry. It's more of a tinny tinkling type of rattle rather than something like "creaking bedsprings" but it definitely only occurs when the car is fully warmed up and been running for about 45 mins+. and only over certain bumps like sleeping policemen of speed slowing lines in the road. Its not there on normal road conditions, even on B roads. Richard, thanks for your comments on the coolant expansion tank and top, I'll check it out. The tank has got an 03 number on it so I suspect it and the top are the originals (now 10 yrs old). When hot the coolant level is at the minimum mark in the tank and when cool drops to about half an inch below minimum. Could I ask you what the normal lifespan of the radiators and associated pipes might be and how prone the rads are to damage from external crud etc? Is there any additional maintenance that might help and what's your view on fitting mesh grilles to the front intakes? Thanks and regards Chris

The problem with the rads is that all sorts of debris (stones, mud, leaves, fag ends, twigs, dead birds, etc) collect in the front openings and build up around the base of the rads, which rots them out in time. They are supposed to be vacuumed out regularly, but even this doesn't stop it building up in between the water rads and aircon condensors, which are sandwiched together. It is usual that the aircon rads go first, as they are on the front. You really need to remove the front PU, and separate the rads to clean them properly. Min did a good DIY in the Technical Articles section. It is rare for the actual pipework to cause a problem, but the hoses do occasionally leak with age. As for life, it is a "how long is a piece of string?" question. Probably 4-5 years if neglected, depending on use. Grilles make a huge difference, and well worth doing. Lots of info here if you do a search, and there is a DIY in the TA section. I fitted them to both my 996s, and also have them on the Cayman.

Thanks Richard, that's really helpful. I'll dig out the tech articles and set about a thorough cleaning and fitting the grilles. Regards Chris

Had a thorough investigation today of my front end knock which occurs only when the car has travelled quite a few miles, with the car on a ramp and lots of bouncing followed by the knocking being repeatable. The cause was traced to the near side steering rack ballpoint nut being slightly loose which allowed the track rod to move slightly under suspension movement. Removing under tray and rack gaiter enabled access to the steering rack and the nut; a suitably large spanner was applied to tighten it. Have now driven approx 50 miles and the creaking/knocking has disappeared, so lets hope this a permanent fix and shows it might be worth looking beyond the usual suspects of coffin arms? The car has 20 000 miles on the clock.

That's an interesting development Stuart, I'll have to check that out. Mine is more of a tinny type rattle but it only occurs after about 30 miles or so and when the car is fully warmed up. Interestingly at the weekend, whilst going over some speed reducing lines approaching a roundabout, it was rattling away but then stopped when I touched the brakes. I'd not noticed that before, so I tested it again over some further bumps and sure enough it stopped when I touched the brakes to slow down. Anybody have any thoughts on that one? Sadly, it now sounds as if one of the exhaust mufflers is starting to blow. If it needs replacing, I shall do them both but wish to retain the original type equipment. Where is the best place to get replacements, likely costs and has anybody done this as a DIY? What are the problems I'm likely to face? I can't complain, the exhaust is the original and now nearly 10 yrs old. Thanks in anticipation

Further to the above post, and tightening the inner tie rod nut not being a permanent solution, I have replaced the inner tie rod on the nearside and all trace of the knock has disappeared [ ]