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Re: Rattling Noise

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Rattling Noise
Lew - 1 week ago
I have been experiencing a rattling noise when I turn off the engine.....I don't hear the rattling noise when turning off the engine with the clutch pressed in. Is the Dual Mass Flywheel bad?
If you don't hear the rattle with the clutch depressed, but you do with it engaged, then I'd say that the noise is coming from the transmission.
Happy Boxstering,
Pedro

Pedro Bonilla 1998 Boxster 986 - 280,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Re: Rattling Noise
Lew - 1 week ago
I am thinking maybe the Dual Mass Flywheel and not the transmission. It shifts perfectly...But what do I know! .
Just kidding
Quote
Lew
I have been experiencing a rattling noise when I turn off the engine.....I don't hear the rattling noise when turning off the engine with the clutch pressed in. Is the Dual Mass Flywheel bad?

Probably not the DMF. (But it can't be eliminated entirely. See below.) When bad they clunk when taking off and sometimes when shifting.

The fact the noise is not present when you turn off the engine with the clutch pedal depressed and the clutch disengaged suggests to me the noise is coming from the transmission. In this case the transmission is disconnected from the engine.

If the clutch pedal is not depressed, as the engine stops running the engine's rotation becomes more erratic and the normal transmission shaft spline and gear fits/clearances lets some transmission hardware rattle.

As an aside, the DMF also acts as a vibration dampener. That it appears it is not effective in this regard could be the early signs of a going bad DMF.

Never heard this noise with my Boxster but when the Turbo transmission was up to temperature with the engine just idling the transmission would rattle a bit. I knew it was the transmission because the noise stopped when I disengaged the clutch.

Might add that at some point: when I had new plugs and coils installed or at another time new O2 sensors installed; the Turbo transmission rattle was gone. My theory is the rattle was from the engine running a bit "rough" and needing a "tune up". Th engine never misfired even under hard acceleration but I do recall after new plugs and coils and then again after new O2 sensors the engine ran noticeably better.

In the case of your car you can check or have checked the engine and transmission mounts.

If it hasn't been done recently consider having the transmission/diff fluid changed. I had this done to both my cars and I just let the dealer do it and use the factory fluid.

Also, if it hasn't been done recently have the brake and clutch fluid flushed and bled. This should be done every 2 years. My experience is letting this fluid service go even after just 2.5 years the fluid can deteriorate to the point the clutch hydraulic system is affected.
Re: Rattling Noise
Lew - 1 week ago
Thanks for the reply. I am up for the changing the brake fluid next month. I did it myself 2 years ago....My PBS only has 33k miles on it. The Transmission fluid change is on the list. Again thanks for your input. As said earlier the car runs and shifts great and there is no noise at anytime when driving. Just when I stop and shut down the engine I hear the rattle. Not sure how serious this is, but I plan on keeping the clutch depressed when turning off the engine. I think changing the transmission fluid might help and it might even be a little low. Will check ASAP. I do all the wrenching on my cars, and have only one fault code on the Boxster now which is a code 34 the passenger side motion sensor. I never have had a CEL on the Boxster. .



Edited 1 time(s). Last edit at 06/13/2018 07:44PM by Lew. (view changes)
You have to do more than just change the brake fluid you need to after you have gone around the car in the proper sequence and flushed/bled every caliper then you need to flush/bleed the clutch slave cylinder.

Without being able to hear the noise -- and this is not a subtle or not so subtle hint to provide one -- it is impossible to make any judgement call about the severity or urgency of the noise, what may be at its root cause. My advice is you have this checked out by a qualified Porsche tech, get his opinion.

33K miles is not a lot of miles. There is AFAIK no requirement to change/replace the transmission fluid based on time. 'course, I'm a fan of early/more aggressive fluid change schedules and I'm OK with an early fluid change to see if it has any positive effect on the noise. For my 2002 Boxster the shop time to replace the 5-speed transmission fluid was just 0.3 hours. While the fluid is a bit pricey it is not like one is having to buy this all the time. The transmission fluid service for my Boxster was the least expensive service.

Assuming no leak or a prior improper fluid service that left the level low and these transmissions do not "use" oil/transmission fluid, so what makes you think the transmission fluid is low? Certainly if the fluid level is low there is less fluid to act as a dampener and to keep the the transmission internals from rattling around.

If the fluid is low this needs to be addressed and just as important the reason why it is low needs to be addressed.
Re: Rattling Noise
Lew - 1 week ago
Quote
MarcW
You have to do more than just change the brake fluid you need to after you have gone around the car in the proper sequence and flushed/bled every caliper then you need to flush/bleed the clutch slave cylinder.

I understand on what all you have to do when changing the brake fluid. Each caliper in the proper sequence was bled using my vacuum pump, and the slave cylinder for the clutch was also bled.

Without being able to hear the noise -- and this is not a subtle or not so subtle hint to provide one -- it is impossible to make any judgement call about the severity or urgency of the noise, what may be at its root cause. My advice is you have this checked out by a qualified Porsche tech, get his opinion.

I talked to a Porsche Tech and he sees where a spring or springs on the DMF jumps off and causing this type of rattle. He will be seeing the car today

33K miles is not a lot of miles. There is AFAIK no requirement to change/replace the transmission fluid based on time. 'course, I'm a fan of early/more aggressive fluid
change schedules and I'm OK with an early fluid change to see if it has any positive effect on the noise. For my 2002 Boxster the shop time to replace the 5-speed transmission fluid was just 0.3 hours. While the fluid is a bit pricey it is not like one is having to buy this all the time. The transmission fluid service for my Boxster was the least expensive service.

My 04 since new has had the oil changed along with a new filter every 5k miles. It also has been kept in a climate controlled atmosphere since new. I recently did the 30k maintenance. Plugs, all the Filters, drive belt. and fresh engine oil. However I have never changed the Transmission fluid. My brake pads and disc are like new and never been changed. I might add I never abuse my car, but enjoy it's willingness to do what I what it to do. It does get a lot of TLC. At 59k new, it looks new today.

Assuming no leak or a prior improper fluid service that left the level low and these transmissions do not "use" oil/transmission fluid, so what makes you think the transmission fluid is low? Certainly if the fluid level is low there is less fluid to act as a dampener and to keep the the transmission internals from rattling around.

I feel certain the fluid level is OK in the transmission. However I plan on changing it myself ASAP. My 6 speed gets new oil until it flows back from the opening. Your 5 speed is a little different.

If the fluid is low this needs to be addressed and just as important the reason why it is low needs to be addressed.

Thanks again for your input MarcW,

:Lew
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