Clutch shudder at takeoff - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Lordblood · 07-27-2011, 02:08 PM

I've changed my rear brake pads recently, after which I went on a 3 day vacation while my Boxster sat in the garage. When I came back, I noticed that after cold starts, the car would shudder (sometimes violently) as I engaged the clutch. This would continue only at takeoff for about 5-10 minutes until the car warms up, after which the shudder goes away.

I'm wondering if this has to do with the clutch itself, the brake pads, or perhaps the fact that over my 3 day vacation the monsoon season started in Arizona and the dew point and humidity shot up dramatically. I heard that due to the humidity there can be small buildup of water around the clutch, making it uneven. Can this be a cause?

landrovered · 07-27-2011, 02:23 PM

Clutch judder is normally caused by grease or oil getting on the clutch disk, water can cause it as well but that happens when a car is immersed or wades a stream or deep puddle. I have never heard of humidity causing it.

The reason it goes away is because the grease, oil or water is burned off by the friction of the clutch engaging.

It would be very odd for it to have anything to do with your rear brake pads.

sparker · 07-27-2011, 06:05 PM

I too have this problem. Was wondering what the cause was... Will see if the problem still exists once we start to warm up a bit (if it is dew on the clutch).

Sam

The Radium King · 07-27-2011, 06:37 PM

or it's you ims failing, spewing oil onto your clutch ...

Burg Boxster · 07-28-2011, 04:57 AM

^

Anyhow, could be a number of things... more likely one of the following as opposed to overly-hyped IMS* issues:

- When was the last time clutch was bled? Should be done at a min every 2yrs w/ brakes but most dealers will skip unless you specifically request.

- Possible Master Cylinder issues?

- Possible bad motor mount?

- Possible clutch going bad. Any slippage in other gears?

- Possible bad clutch work? No offense meant but Porsche clutches have more travel and different pick up points than most other manual cars out there. To that point, from driving various Porsche models, the Boxster clutch is even different than other P-cars IMNSHO.

So, I'd start w/ something cheap like bleeding the brakes and clutch.

Good luck

* Yes, I agree some IMS issues exist and Porsche should stand behind within reason. However, from my experience and subscribing to numerous active forums, it's not nearly to the chicken little "sky is falling" extent some who profit from selling allegedly 'better' aftermkt replacements would lead you to believe.

jcb986 · 07-28-2011, 06:11 AM

In my experience with clutches and this goes back to my hot rod days. When revving the engine and letting out the clutch you get a point of slippage this then can cause hot spots on the pressure plate and the flywheel and usually will fade away after the engine "clutch assembly" warms up. Basically hot rodding and usually us guys like to get it on. Also, the other forum members have some good point of views. If it's an oil leak from the IMS or rear seal, you should have an oil leak so check under the engine. As I understand it, the clutch usually needs to be replaced once it has about 70K miles on it. City driving can wear on it faster.

Yeah, that is why I got one with a TIP.

Lordblood · 07-28-2011, 04:17 PM

If the IMS is starting to go, what would be the best route to take? I don't suspect it being the IMS because from what I know it's not THAT common compared to other problems. As I bought this car 6 months ago I have no idea when the brakes have been bled, and will start there. The car has 51k miles on it right now and the biting point on the clutch still is halfway up, there is no slip in any gears that I can feel (though I don't engage 6th gear...ever :P). I will have it checked out.

What is the average lifetime of a motor mount? I suspect this may be a problem as well. Are there other symptoms I should be aware of?

Paul · 07-28-2011, 04:43 PM

The IMS leaks onto the ground since it is behind the flywheel and very low on the motor.

san rensho · 07-28-2011, 04:45 PM

I have the same problem. Its just a bit of chatter when launching at low rpm, 1200 of less. If I go above 2k rpm, the launch is smooth as silk. I changed the motor mount and it really didn't make a difference. Read somewhere its the dual mass flywheel.

My buddy, who has a 996, drove it said he didn't feel a thing, but he flogged the hell out of it. I try to launch as smoothly as possible, the clutch has 117k miles out of it so I want to milk it as long as I can.

Lordblood · 07-28-2011, 09:30 PM

Quote:

Originally Posted by Paul

The IMS leaks onto the ground since it is behind the flywheel and very low on the motor.

If that's the case, the chance that it's an IMS leak is very low. I check underneath the car in the garage all the time every couple of days. So far it's been bone dry. I'm suspecting a small seepage or a worn out clutch/flywheel altogether.

jcb986 · 07-29-2011, 11:39 AM

The person before you setup how the clutch has worn because they were the drivers. What I would do, is find nice little stretch of private payment and re-seat the disk. Do you like your buddy did...rev up and get it on...no you will not have to burn rubber, but that might be fun to smokem' a little.

ppbon · 07-29-2011, 01:59 PM

... a RMS leak, not an IMS Bearing leak.
The Rear Main Seal seals the main engine shaft where the flywheel and clutch are mounted.
Check under your car and see if you have oil collecting in the center of the engine.
If you have a bad enough RMS to cause clutch shudder you need to repair it soon or you will also have to replace the flywheel since petroleum products damage the dual mass elastometer in the flywheel.
Happy Boxstering,
Pedro

Hello.AmeerM · 12-12-2022, 09:09 AM

11 years late on this post, but I'll leave what I've come up with for posterity. I had the same issue: Clutch engagement was not smooth and in-turn causing what felt like wheel hop when moving from a complete stop-- especially in rain or on painted lines. Brake fluid was not running low, so I wrote it off as neither a bad master or slave cylinder. Then, I bled the system and it got better for a short period of time.

Turns out there was a small leak at the feed and pressurized lines on the master. I replaced the master and slave then bled, result was a completely different clutch feel which has been sustained.

Tips for master/slave replacement:

1. A pressure bleeder is necessary to do a proper bleed. A vacuum will not work well on the nipple on the slave. Bleed it longer than you think as well.

2. There are two different connections for the slave/master pipes on the 986. Find out which type you have to avoid ordering the wrong part.

3. Replacing the master requires contortion unless you remove the seat, and even still its an upside-down job.

4. Replacing the slave is easier if you have no cats or remove the metal plate under the transmission. It will still require you to maintain ~50lb of force, with one hand, at an odd angle while you use the other to try and thread the bolt. It's a bad time. I found the easiest angle of attack to be from a creeper with my head under the engine and legs under the muffler. DO NOT connect the hydraulic line before the slave is bolted in.