Goodbye, Porsche death rattle
Friday, November 13, 2009 at 4:11PM I said goodbye to a little "friend" today, the kind that you would stab in the back at first opportunity. That friend was a persistent, relentless hammering rattle from the back of my Porsche 968.
Understand the insidious nature of this unwelcome guest. A full two years ago, I began to hear a faint little buzz from the back of the car. It wasn't there all the time, and I figured it was just a little ‘character’ for a then 14 year old car. Likely just a little something rubbing against something else, it would go away with a little time.
I'm an idiot.
Months went by. The rattle persisted. It began to get a little worse. Against my fortunes, it was happiest between 2,700 and 3,200 rpm…which of course is what equals 65-75 mph on the freeway in 6th gear. Isn’t that lovely. I was able to live with it for a while, minimizing it by grabbing a different gear and altering the car's speed. Nevertheless, the annoyance factor was rising on the charts.
Alas, the initial strategy of changing speeds and/or gears did not prove up to the task. The rattle then began to bang away when I was driving around town. It got louder. Oddly, it was never there when the car was cold, only when it warmed up. Now that’s easy evidence, perhaps the exhaust.
Unable to stomach it anymore, it was off to the local Porsche specialist; a very competent and long-established shop. They couldn’t reproduce it (naturally), but they agreed it had something to do with the aftermarket exhaust on the car. I couldn’t confirm or deny, so I left it at that.
The rattle continued to fray my nerves. Understand, this wasn’t some little pinging from the rear hatch area that just made me grumpy. It got freaking loud. It sounded like something painful was going on back there. The best way to describe it is if you took a solid steel rod and banged it against the fender of an old Chevy. It sounded mechanical, loud, and destructive. I began to conjure up horrible scenarios. Maybe it was a piece of the unit body that was slowly hammering a fuel line to dust. Maybe a suspension component had come loose and was annihilating the transaxle casing. I didn’t know, and that made me want to cry.
More months passed. I tried to ignore it. I began to drive the car less and less. This is no way to own a Porsche. Time for another try at the shop, because we really need to find this little bastard.
Now entirely reproducible, I had a mechanic ride along with me and listen. Yup, definitely the back of the car, very likely exhaust due to the fact it needs to warm up before it happens. We put it up on a lift and poked around. In addition to a nice new weep discovered at the oil pan gasket, my mechanic discovered that the aftermarket muffler had a loose baffle and needed replacement.
Thank goodness. It was an entirely available part, and not expensive to fix. I whisked the car off to the local hot-rod exhaust installation guru, and he confirmed the diagnosis. Bad baffle, he’d seen it before on this particular type of muffler. Replace it and you should be good.
I had him perform the work, I picked up the car and drove off in a triumph. Xanadu! My car no longer represents my head in a trash can being banged with wooden spoons. Awesome. I thoroughly enjoyed the ride home, the new muffler smoking happily as it burned off its assembly resins.
The next morning, I’m off to my buddy’s house for a quick errand. I drive through town, then get on the main highway between our two houses and…….bzzzzz bzzzzz rattle rattle rattle!
No, please no. It was back, just like before! Actually, that’s incorrect, there was a change. It was incredibly worse. Not only was the rattle-buzz still there, it was now accompanied by a nails-on-a-blackboard squeaking that could only be high-grade steel on high-grade steel. It was a symphony now; a virtual wall of sound that almost defies description. I thought to myself I simply cannot handle this.
I kept driving it, but something had changed. Not only did it rattle under acceleration and on the freeway as before, but it even did so with the clutch depressed and the car at idle. I made it rattle magnificently even at low speeds, and also with the car stopped and idling. I would have no problem at all administering well-placed blows with a 5 pound sledgehammer if that’s what it took to eliminate it. ANYTHING!
So I call up my Pop and tell him I need a diagnosis buddy. An engineer by mind and a physician by trade, I couldn’t pick a more reliable and analytical resource to help with this adventure. With the rattle more or less constant now, I took out the rear mat, carpet, jack and tools, and basically created a bare shell in the back of the car to hunt down the satanic mechanical mouse. Man if I thought the noise was loud before, it made my ears ring now. There’s a reason guys wear earplugs in racecars. Mere pebbles in the wheelwells sounded like bullets hitting an airplane fuselage, and the rattle itself resembled artillery. I got the car to my Pop’s house, and with my torso stuffed in the rear hatch area like a wooden wedge under a door, dad dialed up the precise rpm needed to localize the noise.
A quick look under the rear with the exhaust piping hot and I didn’t see anything......or did I? Isn’t that muffler hanger oddly close to the body sheet metal? Geez, it can’t have more than 1/8th of an inch of clearance. A couple quick taps on the sheet metal elicited a “sounds promising” from dad, maybe I’m on to something here?
A quick break for lunch followed, featuring good sandwiches from the local sub shop. Examining the car again, the aforementioned muffler hanger was now a full inch away from the sheet metal.
You’ve got to be kidding me. The rattle is never there when the car is cold, but once it heats up the exhaust apparently expands backwards over a full inch (!) to hit the body in not one, but two places. As soon as the engine was turned off, the exhaust would begin to contract and appear as if nothing was amiss. I headed into my dad’s shop for a selection of pliers, bent a small bit of the sheet metal out of the way, and drove all the way home in what to me was a brand new, rattle-free car.
There’s a moral to this story folks, always trust your instincts. No-one knows your car better than you, and if you spend enough time troubleshooting a problem you’ll likely get to the bottom of it. I hunted down the little bugger myself and made the fix for exactly zero dollars. My shop guys might take a little razzing from me next time I’m there, as I’ve earned a little trash talk. We all own these cars because they are magnificent machines. Don’t be afraid to channel your inner enthusiast to make things right when they seem wrong.
Reader Comments (4)
I love your articles and I love the 968. I own a 6spd 94 coupe myself. Just wanted to say thank you for the entertaining read. I'll be checking back.
-David
Thanks David, owning the 968 has been a fun experience! I wrote a road test on it, you can find that here.
let's join our hands together to stop this kind of wrong doings. It may risk lives in the future if we just let them continue. egstcu egstcu - Giubbotti Belstaff Online.
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