Hi all,
2011
Boxster Base
with $107K miles. I just purchased it long-distance with a Lemon Squad inspection that didn't mention this issue.
The Problem:
On start-up and when pressing on accelerator, there is a loud metal scrapping noise from the bottom and back on the passenger side. I took it to a Porsche indy center and they identified it as something wrong with the passenger side muffler. Sadly, a $2,200 OEM replacement part so I am trying to see if a) that's the issue and b) an after-market part that is less expensive.
Curiously, they identified that when they turned on the sports exhaust system, the sound went away... They think it has to do with some valve issue.
The Question:
Anyone knowledgeable enough to either confirm their assessment? Any thoughts on why the sound goes off when the sports exhaust is turned on?
Thanks
Is it a scrape sound, or maybe vibrations between two metal pieces?
Regardless, I can think of a couple things. With sport activated there's different back pressure in the exhaust. Also, the harmonic vibration is different due to a difference in the tone.
You might be able to find a used sports exhaust for far less than a new one. There are also aftermarket options of various cost and quality. In addition to this site, there are various groups on Facebook that are good for buying used parts.
It sounds like metal dragging on the road. It isn’t a rattle or vibration sound.
I'd loosen all the mounts up to the joints near the axles. ..to the point of removing it....and also giving it a good shake to see if something is loose inside.
then carefully reinstall it and align it and make sure it is hung correctly.
The clearances to the gearbox are close and it could be rubbing at certain resonant frequencies.
If that doesn't do it go find a used one. people are always replacing with aftermarket.
Possibilities include: loose baffle inside the muffle, which when you’re stepping on the accelerator is moving, giving the metal on metal scraping sound; since it is a valved exhaust, maybe one of the flaps, or mount for the flap of the valve system is loose and causing the sound; exhaust system mounting brackets or attachment points may be loose, leading to the sound.
Thanks for the advice.
I have a local one-person indy shop that can take the time to give the muffler a full inspection including removal and reinstall to see if he can see anything wrong.
If it's shot, a used one seems to be the call.
I appreciate it.
The
Porsche
sport exhaust has a baffle on each side that opens and closes via a vacuum actuator. No vacuum is open (loud) and vacuum is closed (normal). When the car is off they're in the open (no vacuum) position, then as soon as you start the car engine vacuum gets applied and they rotate into the closed position. With
PSE
turned on they go to the open position and they may also open even with
PSE
off under some conditions. Anyway, both of mine make a bit of a scraping noise when they rotate, and I suspect that's what you're hearing.
You can test this by hitting the sport exhaust button with the car at idle. You'll probably hear a scrape noise every time you turn it on and off. Unless it's super loud I doubt it's an issue, mine's been doing that since I got the car ten years ago.
If you look under the rear corners you'll be able to easily see the valve on the exhaust tubes on each side. The vacuum actuator is on top of one of the exhaust tubes and you'll see the pivot for the flap on the bottom side. If your pivots have gotten rusty they may be making a little noise: you could try spraying the top and bottom of the baffle's pivot with a little penetrating oil, and if the noise gets better then that's your problem. I'm not sure what would work to lubricate that long-term as probably any oil will burn off...I'd probably try some sort of a dry graphite lube spray? That should penetrate the pivot and then the graphite will lubricate and not burn off.
Anyway if that's your issue then it's probably nothing major and not worth replacing the whole exhaust.
Those pivots are known to rust and seize too. I take some white lithium grease with me when the car gets its annual service and I get the service techs to inspect them and give them a spray. So far, so good.
WD-40 300g Specialist High Performance White Lithium Grease
I appreciate the comments. I found a 30 year
Porsche
mechanic who is willing to take a close look to diagnose. I am sharing your comments with him to see if it's an easy fix rather than replacing the entire muffler.
