Clutch chatter... cause and correction?

[jakeru]

Hey guys, I've owned my 2001 Boxster base for about a year now, and it's currently at about 110k miles. This is my first Porsche, and I've been getting a feel for what I like and dislike and what may not be working properly. (I did my own PPI). I've put on about 3k miles in the year since I've owned it using it as a daily driver.

The clutch has some chatter, but only in certain conditions. I think maybe heat related... when cold it chatters (can be pretty severe chatter), and when warmed up it can virtually completely go away so it feels like a perfectly normal clutch. Clutch has never had a problem with excessive slipping (which is to say, when the clutch pedal is released, it always "fully" grabs). Generally speaking, the chatter is only a problem when getting the car going from a stop. When shifting gears, it's not a problem.

By chatter, I mean the car pulsates or "bucks" a bit, when slipping the clutch. It seems if you feather the clutch enough and use light enough pressure, it won't chatter. It also seems using heavy pressure eliminates the chatter. So it seems there is a certain pressure range and temperature range where the clutch will chatter.

I replaced the front motor mount with a new 987-spec rubber insert, hoping it would fix the clutch chatter issue, but it did not seem to make any difference. (Old mount was cracked in places, but not completely separated.)

I've driven the car long enough that I don't think the issue will fix itself from "breaking in" (if the current clutch happened to be recently replaced by a previous owner).

I've got some service records from the previous owner going back to about 60k miles, but found no clutch work. (I suspect I may not have compete service records on the car, however.)

So my question is what is likely or possibly causing the chatter, and what do I need to do to fix it? If I pull the tranny from the engine to inspect, I'd like to have parts lined up that likely need replacement. Should I just have a new clutch disc+pressure plate ready to go, or should I instead (or additionally) have a new or good used dual mass flywheel ready to go?

Any other ideas or suggestions? Thanks!

[jakeru]

Almost forgot to add... recently a couple times when the weather dipped below freezing, I noticed a sound similar to a noisy or chirping alternator belt on cold start-up, which went away a few minutes later after engine had warmed up. This noise would immediately go away when clutch pedal was pressed in, and come back as soon as the clutch pedal was released (until engine got a bit of warmth in it, in which case the noise would go away until the next below-freezing cold start). This was kind of perplexing, as it seems the transmission seemed to be making the noise? Not sure if it was related to the clutch chatter, but just in case it is, I thought I'd throw that in.

(Also, since I'm mentioning the transmission, I'll also add that it's hard to shift into gears when cold, and I have some new Porsche transmission fluid I'm planning to change whatever stuff is in there now, to hopefully fix that. When it gets warmed up, the transmission shifts nicely.)

[Smallblock454]

Hi,

i would say symptoms of a worn dual mass fly wheel.

Also at 110 k miles the clutch system itself could be worn. If it's the first clutch i would recommend to replace it.

In general i would first pull transmission and than decide what as to be replaced. Also inspect IMSB and crankshaft bearing. But if it's the first clutch i would replace everything related incl. dual mass flywheel.

If you would have slip in the clutch the clutch system would have been totally gone, because it adjusts itself (because it's hydraulic). In general this systems work without slip until some part really breaks or is completely shot.

Regards
Markus

[jcslocum]

The chirp sound like the throw-out bearing is letting you know it's at the end of life. The grabby clutch is also an indication, if it's original, that it's time to go new. The flywheel has 2 parts cushioned by rubber that can wear out as the rubber gets beaten up in use. The clutch disc has no springs in it like most do, that is what the rubber in the flywheel is for on the Box. The flywheel has a measurement for wear and a used one is an option. There are some good prices on clutch kits out there, so shop around.

[epapp]

I had the exact same symptoms at 90k. Chatter only with certain release pressure, whereas heavy or light release wouldn't cause the problem. My clutch also appeared to not be slipping (if I dumped the clutch, I could feel a definite 'hook-up' when the clutch disk locked rotation with the flywheel, no rising revs when floored in 5th etc). Then, one morning I released the clutch and got especially bad chatter (was trying to focus on not merging into a truck when releasing the clutch). That chatter broke my clutch fork, causing the clutch to feel like it was releasing higher on the pedal (clutch fork wasn't engaging the pressure plate completely when pushed down/released). Eventually I couldn't get it in any gear when the engine was running.

The (semi) good news is:

Do the work now and avoid getting stranded.

When you pull the tranny, you will most definitely need a new clutch and pressure plate, so you can have those parts ready.

You will almost certainly need a new flywheel, but the price online is the same as if you go to a Porsche dealer (1k), so just verify the dealer has them in stock before beginning work.

I would also buy a new slave cylinder and clutch fork if I were you. The chatter probably weakened your fork already and it would be a huge PITA to take the tranny off again just for a fork (its <$50, also a revised 987 design). The slave is $90 and so very easy to change if the tranny is out.

[jakeru]

Originally Posted by epapp

... Then, one morning I released the clutch and got especially bad chatter (was trying to focus on not merging into a truck when releasing the clutch). That chatter broke my clutch fork, causing the clutch to feel like it was releasing higher on the pedal (clutch fork wasn't engaging the pressure plate completely when pushed down/released). Eventually I couldn't get it in any gear when the engine was running. ...

Wow, thanks for sharing this experience and cautionary tale of your clutch release fork breaking!

I will make sure to at least give mine a good inspection (if not just outright preventively replace, as you suggest, it sounds like a relatively inexpensive part).

In the meantime, I'll try to go easy on the clutch to keep the chatter down. (As driving conditions allow, at least!)

Originally Posted by jcslocum

The chirp sound like the throw-out bearing is letting you know it's at the end of life.

Sounds plausible to me. I found a service bulletin on similar symptom (on a different application) caused by throw out bearing "skipping" on the pressure plate fingers. (Apparently normally, they're supposed to be in constant contact):
http://bulletins.schaeffler-aftermarket.us/displayTB.phtml?number=LB158

Seems like it might be what's happening in my case also of the 986 mechanism.

Originally Posted by jcslocum

The grabby clutch is also an indication, if it's original, that it's time to go new. The flywheel has 2 parts cushioned by rubber that can wear out as the rubber gets beaten up in use. The clutch disc has no springs in it like most do, that is what the rubber in the flywheel is for on the Box. The flywheel has a measurement for wear and a used one is an option. There are some good prices on clutch kits out there, so shop around.

I'm surprised the dual-mass flywheel has rubber in it! Was aware of the large curved coil springs, and the ball bearing in the middle (separating the two "masses"). I can perhaps see rubber being used to dampen the oscillations, somehow? Any additional details on rubber in DMF 986 applications would be good to know.

Here's the cutaway view visualization I have of a dual-mass flywheel (is it correct for 986 application?)
http://webcat.schaeffler-aftermarket.com/pim/upload/schaefflerDocs/datasheet/base/415_417_se_verb_en.pdf
(The normal "spring center" clutch discs that I'm familiar with on other applications do not use rubber.)

As for replacement clutch parts, I'm leaning toward the LuK kit. (Also LuK seems to have the most reasonably priced new dual mass flywheel, if I decide to replace that with new.)

Originally Posted by Smallblock454

... i would say symptoms of a worn dual mass fly wheel.

Also at 110 k miles the clutch system itself could be worn. If it's the first clutch i would recommend to replace it.

In general i would first pull transmission and than decide what as to be replaced. Also inspect IMSB and crankshaft bearing. But if it's the first clutch i would replace everything related incl. dual mass flywheel.

If you would have slip in the clutch the clutch system would have been totally gone, because it adjusts itself (because it's hydraulic). In general this systems work without slip until some part really breaks or is completely shot. ...

Thanks for the great tips!

I suppose I will weigh my cost of having the vehicle out of commission for a bit longer waiting for parts, versus having replacement parts lined up in advance (which may be overkill).

[And yes, I understand having the transmission out will be a natural time to inspect or otherwise preventively service the intermediate shaft bearing and rear main seal.]

[amagalla]

Originally Posted by epapp

You will almost certainly need a new flywheel, but the price online is the same as if you go to a Porsche dealer (1k), so just verify the dealer has them in stock before beginning work.

The Dual Mass flywheel should not cost you $1000. I got mine (a LUK brand that is actually a SACHS OEM stamped with the same SACHS name and part number) for about $350 with the pilot bearing installed. Rock auto is the best price I found. For that price, I figured that I might as well change it too, while I'm in there.

Tony

[epapp]

I too found much cheaper alternative clutch/flywheel parts than what I was quoted. Mechanic said he wouldn't mind putting them in but he could not warranty something he did not vouch for/know very well(said he only sticks to genuine sachs). I agreed with his reason. If I was running a shop, I would not like to risk putting my warranty on a part from a vendor I didn't know well.

EDIT: I'm sure his shops profit margin on the parts played a role in his reasoning, but the fundamental reasoning was still there..

[jcslocum]

Clutches and flywheels on sale. This came to my email today:

EBS RACING End of Year Sale!
Orignal SACHS Porsche Clutch Kits
Orignal LUK Porsche Flywheel

SACHS Clutch Kits Application List Price EBS Special
914 116 911 00 SACHS. 914 $663.56 $250.00
931 116 911 00 SACHS 924T $602.00 $350.00
950 116 023 03 SACHS 911 87-89 Pressure Plate $572.00 $250.00
950 116 911 00 SACHS 911 87-89/'89 C4 $1,289.00 $475.00
964 116 911 01 SACHS 911 90-98, Optional Increased Clamping
$1,263.00 $495.00
968 116 911 00 SACHS 968 $1,019.00 $450.00
986 116 911 01 SACHS Boxster '97-'08 w/5 speed $686.00 $325.00
986 116 911 02 SACHS Boxster S -04 $424.00 $325.00
996 116 911 GT2/3 SACHS 996/997 GT2/3 $1,568.00 $650.00
996 116 911 TT-05 SACHS 996TT 6spd $1,405.00 $575.00
996 116 911 TT-05 SACHS 997TT 2007-09 $1,695.00 $575.00
9G1 116 913 03 SACHS 997 3.8S $771.00 $495.00

Other Sale Items
Application List Price EBS Special
950 116 023 03 SACHS
911 87-89/964 89 C4, pressure plate. $572.36 $295.00
928 116 013 23 SACHS 928 1987-, clutch disc. $310.98. $150.00
986 114 012 04 Box/Cayman 2000-08, dual mass flywheel $1,006.00 $450.00

This special is only available to our Team EBS Racing members and cannot be ordered through our web site. For more information or to place orders please contact jon@ebsracing.com, troy@ebsracing.com, don@ebsracing.com or call 1 800 462 3774. Quantities are limited!

[jakeru]

UPDATE: my chatter problem has magically disappeared!

Recently, my employer relocated offices, and my commute pattern changed substantially as well. For the last couple months, I've had a monthly parking pass so been driving to/from work everyday. As a result, I'm doing quite a bit more clutching in stop/go traffic, including up some fairly steep hills in downtown Seattle, and even up steep ramps to get up out the deep (multi-level, skyscraper) parking garage. The silver lining with the new commute situation, aside from spending more "quality time" in the Boxster, is my clutch chatter seems to have completely fixed itself! I guess it really did just need some more aggressive usage, or breaking/wearing in, or something?

Now the clutch system still isn't perfect, as my wife still complains the clutch pedal being heavier than she'd prefer; every once in a while after an extremely cold start without the clutch pedal being pressed in, the throw out bearing will make some awful noises; and practically all the time, the clutch system makes some groaning noise/vibrations when the pedal is moves (which seem to be originating back/underneath at the transmission). So, I imagine eventually I'll still do some work back in the clutch area (and have pretty much all new replacement parts already lined up). But at least the chattering is no more - it's totally smooth engagement, all the time!

I'm thinking it must be pretty rare when simply doing nothing or just driving the car fixes the main problem.

I hope this report helps others who may experience similar "clutch chatter" type symptoms in their Boxsters.

[Gelbster]

The " magic" did not work perfectly based on Post #10.
I would start collecting the parts for a complete clutch job -considering your miles.
A good used DMF - Ahsai on Rennlist 996 may have one with a new pilot bearing that you obviously need. I have one also.The problem is shipping 35 pounds of flywheel!
Then there is the 'while you are in there" list. Could be quite a project .
https://losangeles.craigslist.org/sgv/pts/5931088887.html

[Smallblock454]

Originally Posted by jakeru

UPDATE: my chatter problem has magically
Now the clutch system still isn't perfect, as my wife still complains the clutch pedal being heavier than she'd prefer; every once in a while after an extremely cold start without the clutch pedal being pressed in, the throw out bearing will make some awful noises; and practically all the time, the clutch system makes some groaning noise/vibrations when the pedal is moves (which seem to be originating back/underneath at the transmission). So, I imagine eventually I'll still do some work back in the clutch area (and have pretty much all new replacement parts already lined up). But at least the chattering is no more - it's totally smooth engagement, all the time!

I suspect the damage is now worse than before. A clutch system doesn't heal itself.

You'll see when you disassemble. I wouldn't wait too long.

Regards, Markus