Porsche Enthusiasts Club Forum

I'm completing the final checks on the car before I drive to Germany on Monday am for a few days.

Everything major has been done although I thought I'd bleed the brakes and clutch (fluid is a couple of years old) and change the coolant today...again a couple of years old.

However there is one thing driving me mad! I have a rattle from under the car. It sound like a loose heat shield and is worse when hitting sharp imperfections in the road - causing compression on the suspension....

I think that makes sense! From the drivers seat it seems to come from the middle of the car? Then sometimes it seems to come from the passenger side.....then sometimes it's the front. or the rear????

In the seven years I've owned the car, I've spent quite a few hours trying to locate the source of the rattle. Everything under the car seems secure so I'm now at a loss. It's not a small rattle...it does sound like a loose heat shield but I cannot find anything obvious.

Any ideas (not involving petrol/matches) would be gratefully accepted before I go mad.

thanks

Jon

Has your exhaust ever been repaired/welded? Maybe there's something loose inside the pipe?

Thanks Andy,

the rear box I changed for a Dansk SS Unit about three years ago ( actually changed it twice as the welds on the first unit failed in 6 months). If I bang the underside of the exhaust along its length with a rubber mallet I cannot hear anything loose...but the Center box looks original so maybe the baffles are loose?

just about to crawl underneath and have a good thumping/wiggling/ hammering session to see if I can find anything hanging off.

In some respect I find rattles and noises worse than breakdowns - they got on your nerves and take so long to find sometimes. Hope you trace it quickly

This one is driving me mad! I spent six hours on my back underneath the car today (it was up on axle stands I hasten to add) thumping everything with a rubber mallet, shaking the exhaust system, checking all fixtures and fixings. Did I find it, no Did I 'eck. Bugger!

So I consoled myself by fitting GE Ultra plus 90 hedlamp bulbs and changed the coolant.

I had a rattle after changing to a Dansk. It turned out to the the pipe as it passed the rear anti roll bar. I slackened the rear box mountings & used a large bar to move it away.

I checked that Jim, the pipe and box runs clear of everything. I'm beginning to think it may be suspension related. I've checked everything is located correctly and nothings loose. so I am thinking possibly strut/inserts? I replaced th inserts about 25k miles ago but I'm now wondering if the inserts are generating the noise

I had a terrible rattle that sounded like what you explain in terms of location and turned out to be the nose cone fixings.... just tap it with your hands and have a listen. Mine just needed tightening down properly...
May not be the cause, but worth a try

Thanks Phil,

I'll check in the morning....tomorrows a sort the heated rear screen day so I'll be playing wiyprh the car anyway

Also worth checking that your plenum cover isn't torn or loose... I had a maddening rattle that I misdiagnosed as everything from heat-shield to dashboard before stumbling on it. It was "flapping" against the bonnet at speed.

Have you checked ARB mounting brackets, these are known to crack/break

okay,

Thanks for all your input guys.

Nose cone, rear bumber and valance, ARB links front and rear, everything in the engine bay in fact
I've been around the car and checked all external and internal fixtures. I've checked suspension and steering and brakes. I've checked all heat shields. I've removed all of my clutter from the car including in the boot floor tool boxes. I've taken out the spare wheel and tool wrap and jack... full size spare wheel weighs a lot!

All made no difference....however, I have an early car with the alloy engine undertrade. When I bang this, it does make a similar sound to the rattle....just maybe?

I'm off to Germany in the a.m. so I'll investigate further when I get back. Still think it may be the struts ...or maybe upper mounts?

It's now a 1000 continental miles ....or is that 1600 continental km's since I posted this.

In this time the wheels have been off three times, once to fit new tyres and twice more to rebalance...and i still have a shimmy ....well not me the car....at 60 - 70mph. Is it just me who has trouble balancing the £*%€€# wheels on a square dash!

...anyway i digress, the wheels have been off front and back and all suspension and fittings have been checked and are ok. I thought maybe it was the alloy engine tray....but drove the car with it removed and the noise is still there.

Narrowing it down, it's a mechanical metallic rattle that seems to come from sharp suspension compression.....like when the wheels hit a ridge across the road ... or the compression of the suspension coming off a speed hump. It's not speed related, i.e. i do not hve to be going fast....and the noise seems to come more from the left of the car (well it sounds louder with the passenger window down.....oh and it's not a gentle noise, it is quite loud.

Any further ideas...and i'm getting close to accepting free petrol and matches

Jon

Long shot but the centre cap on one of the wheels, one of the Fuchs on my square dash used to rattle.

Over the years I have had a lot of rattles to diagnose, but one of the oddest was on one of my old 944 S2's.

It would only do it as I decellorated calmly from maybe 20mph to about 10mph, and sounded a little like some springs in the handbrake mechanisms in the rear hubs had come loose, I would only really notice it when I had the windows open and it did not sound like a classical torque tube bearing issue.

However, after investigating everything, and having an apprentice in the car changing the gears and rpms while the car was on a two post lift, while I searched with a stephoscope, I found the rattle, which sounded tinny and shallow, not quite a buzz, but like a bit if tinn rattling...

Turned out it was the torque tube bearings... Changed the torque tube over for a new old stock one we had, and no problems ever again.

Changed a few torque tubes since for ones we refurbish with new bearings, but never had another fail with a noise like this one did.

More often than not, tinny rattles or buzzes, turn out, 9 times of 10, to be caused by the heat shield under the exhaust manifold having a crack in it, causing just the metal joining the crack to rattle, or the bolt tabs in it break off causing a rattle.

Noises like this can transmit all over the car and give false information about where they are.