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Old 12-01-2008, 10:13 PM   #1
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Problem with acceleration

I'm having a new issue now when accelerating. I'll put it in 5th gear at 35 MPH to cruise, but accelerating to 45 MPH the rev's will go as high as 5000 RPM as if I was in a lower gear, but then go back down to its proper less than 2000 RPM.

I'm thinking this is my clutch on its last legs slipping, but I have no idea to be honest. Any idea what this might be?

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Old 12-01-2008, 10:23 PM   #2
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Yup. Clutch it is.
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Old 12-01-2008, 10:33 PM   #3
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Yup. Clutch it is.
So I have to change the clutch, any other things that needs repairs while I'm at it? Should I change the flywheel or leave it as it is?
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Old 12-01-2008, 11:52 PM   #4
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I believe your mechanic will take care of the things associated with changing a clutch such as a new throw out bearing, most likely resurfacing the fly wheel, new pressure plate if needed, etc. But you shouldn't need a new fly wheel. The clutches usually come in a kit with everything you need and the parts should not be more than 400 bucks. If your pressure plate is fine you only need to change the clutch and throw out bearing which lowers cost by a nice amount

http://www.pelicanparts.com/catalog/shopcart/996M/POR_996M_Tclutc_pg1.htm
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Last edited by fragdude; 12-01-2008 at 11:56 PM.
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Old 12-02-2008, 06:00 AM   #5
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Personally, if I was going that far into the engine I'd change the flywheel, Bentley says to scuff it with scotch bright if it's glazed; I don't like that idea at all.
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Old 12-02-2008, 09:10 AM   #6
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Yup, sounds like a slipping clutch. How many miles do you have on the current clutch? The link to Pelican Parts is good. You can get the pressure plate, clutch, and throw out bearing as a kit for about $400. You can simply check the flywheel to see if it's within the serviceable limit, which it probably is. There's no issue really with keeping it as long as it's clean. If not and there's enough material left, get it resurfaced. The replacement for my S at Pelican is $670. It can't hurt to change it, but if it's good, then why throw the money away?

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Old 12-02-2008, 09:27 AM   #7
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I thought we have dual-mass flywheel which is not servicable? That's not if the OP changed to an aftermarket flywheel previously.
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Old 12-02-2008, 01:41 PM   #8
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Quote:
Originally Posted by Kirk
Yup, sounds like a slipping clutch. How many miles do you have on the current clutch? The link to Pelican Parts is good. You can get the pressure plate, clutch, and throw out bearing as a kit for about $400. You can simply check the flywheel to see if it's within the serviceable limit, which it probably is. There's no issue really with keeping it as long as it's clean. If not and there's enough material left, get it resurfaced. The replacement for my S at Pelican is $670. It can't hurt to change it, but if it's good, then why throw the money away?

Kirk
IMO because if it takes a dump before the next clutch is worn out, or chatters upon reassembly, you have to spend all that money again to get back at it, way cheaper to eat the 600 clams up front. Once a dealer did the belts on my 944, when I got it back it was leaking like the Exxon valdeez. They had ruined the seal doing the repair, when I asked why they didn't replace it they said, you didn't ask us to. Well yeah true enough but at that time I didn't know the propensity of the seal to be damaged and they did but never suggested replacement. They replaced the seal and charged me for the complete job, no responsibility taken for their F^&kup, now their out of business, sweet karma sweet karma..
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Old 12-02-2008, 02:05 PM   #9
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I suppose the RMS should be checked and have the updated one installed since the tranny is out. You don't want to re-spend the cash later when the RMS starts to leak.
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Old 12-02-2008, 02:18 PM   #10
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Quote:
Originally Posted by ekam
I thought we have dual-mass flywheel which is not servicable? That's not if the OP changed to an aftermarket flywheel previously.
Generally that's true. The traditional lathe/cutter tends to 'skip' on the flywheel surface leaving it 'choppy' and ruining the cutter. Some shops have done it, but most will not and Porsche does not recommend it. But, the flywheel should be cleaned up assuming it's not warped or hot-spotted.

Just like a brake pad and rotor, the clutch deposits a layer of the friction material on the flywheel surface and it's this friction material-to-friction material contact which makes the best bond. ScotchBrite or even 80 grit sandpaper will clean the old material off the flywheel surface so the new clutch can lay down a new layer as it 'beds-in'.
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Old 12-02-2008, 02:20 PM   #11
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"I suppose the RMS should be checked and have the updated one installed since the tranny is out. You don't want to re-spend the cash later when the RMS starts to leak."

I thought that as well when I had my clutch done, but the indi Porsche mechanic I was using said that my RMS seal was completely dry and if it was not leaking not to mess with it. So I did not replace it. I have often wondered if that was the proper strategy. I guess I have put another 30K on the car since the clutch and flywheel were replaced and no leaks so far....

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Old 12-02-2008, 02:22 PM   #12
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Quote:
Originally Posted by Sputter
I suppose the RMS should be checked and have the updated one installed since the tranny is out. You don't want to re-spend the cash later when the RMS starts to leak.
Two schools of thought here; One - replace it while everything is disassembled hoping to save some $.

Second - if the seal is not leaking, leave it alone.

Not all RMS leak prematurely, maybe 20-30%. It's a specialized 'skill' to properly install this seal. If not done properly, the 2nd seal may begin to leak soon after requiring additional expense, not saving it.
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Old 12-02-2008, 03:30 PM   #13
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Agreed.


Quote:
Originally Posted by Lil bastard
Two schools of thought here; One - replace it while everything is disassembled hoping to save some $.

Second - if the seal is not leaking, leave it alone.

Not all RMS leak prematurely, maybe 20-30%. It's a specialized 'skill' to properly install this seal. If not done properly, the 2nd seal may begin to leak soon after requiring additional expense, not saving it.
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Old 12-02-2008, 05:15 PM   #14
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It all depends how far you are on the clutch's last legs. If you have worn through the friction material, you will be scraping the rivets that hold the friction material to the clutch disc across the flywheel, and if this is the case, your flywheel is toast.

With all this apart, I would swap the flywheel out, and in doing so going to a lightweight unit. I suppose if you're lucky and the original flywheel looks great, then just clean it up and take your chances, but I'm not sure I'd want to take the risk.

As to the RMS, I'm inclined to think it's better to replace it while you're looking at it- just make sure whoever installs the new seal does it correctly.
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Old 12-02-2008, 06:00 PM   #15
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Originally Posted by bmwm750
It all depends how far you are on the clutch's last legs. If you have worn through the friction material, you will be scraping the rivets that hold the friction material to the clutch disc across the flywheel, and if this is the case, your flywheel is toast.

With all this apart, I would swap the flywheel out, and in doing so going to a lightweight unit. I suppose if you're lucky and the original flywheel looks great, then just clean it up and take your chances, but I'm not sure I'd want to take the risk.

As to the RMS, I'm inclined to think it's better to replace it while you're looking at it- just make sure whoever installs the new seal does it correctly.

BMW, does the lightweight flywheel you have make more noise as all articles seem to suggest? If so is it acceptable? Can you tell us all how it changed the feel of your car?

Thanks
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Old 12-02-2008, 06:38 PM   #16
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I know you can change the RMS with the engine in the car, but can you also change the IMS to go to the new Raby unit? I'm just wondering if this isn't something else that should be upgraded while doing the clutch IF it can be done with the engine in the car. Anyone know the cost of the Raby/Flat 6 Innovations IMS?

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Old 12-02-2008, 07:20 PM   #17
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If you're doing the work yourself and you're not that experienced at evaluating what needs changing, have someone experienced evaluate your parts. Is this the first clutch in your '98? If you're past 100K, and you've been driving with a slipping clutch for a while, I wouldn't be surprised if your flywheel shows bluing and needs replacement.
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Old 12-02-2008, 07:29 PM   #18
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Thank you everyone, all of the posts have been very helpful!

Here's some more information about the issue: I am NOT working on it myself, way too much work to be doing, especially when I'm nearing finals week at school. So I'm getting an independent shop that does work on all European luxury brands (BMW, Merc, Porsche, etc.). I have no idea if this mechanic is experienced with Boxster RMS leaks, perhaps I can get another shop that does work on only Porsches and Ferrari's to look at it? (they charge a whole lot more, a flat rate of 90 bucks an hour for labor I hear).

I've had this car for 5 months now, and the previous owner said this was the original clutch, which means it now has around 92k miles on it. I haven't done a 90k service yet, so I guess this is a good opportunity to get that done as well. The big problem I'm having is that we need that Porsche as a daily driver, otherwise 2 people will be missing school/work. So we need to work that out, maybe a rental car is needed.

EDIT: oops, almost forgot, there IS a slight seepage from the RMS, just wanted to point that out.
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Old 12-02-2008, 09:27 PM   #19
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The light flywheel totally transformed the car. It gets rid of the typical German sluggish rev response and makes the motor MUCH more rev happy. Heel-toe downshifts are a breeze after the change. I swapped the flywheel on my last M3 too, and it, too, made a world of difference.

As to the noise, if you swap out the factory dual mass flywheel for a lightweight (which will be single mass), you should use a sprung centered clutch disc to allow for some damping in the system. This will eliminate most of the chatter.

If you are getting seepage, then you're likely going to need the RMS seal. If you're on the original clutch/ flywheel, I would almost certainly replace it after that many miles. Call it cheap insurance and a job done right. If you're not doing the job yourself, you're not going to want to pay the shop to pull the transaxle again after swapping just the clutch. While in there you might also think about updating the IMS seal (not the IMS itself) and using the new encapsulated bolts.

As to updating the IMS, unfortunately this requires splitting the cases of the engine, so it's only something that can be done at rebuild time.

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