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Clutch slip when aggressive usage.

Alex

Nordschleife
Joined
6 Mar 2014
Messages
22,425
Every since I've owned my car I've never been 100% happy with the clutch pedal action. When I had my second clutch fitted I disconnected the pushrod from the pedal to see how the pedal felt. The clutch pedal has a 'clutch assist' spring mechanism to make the clutch feel lighter. The spring works in rocker action and either plants the pedal either to the floor or to it's top position. The problem I found is when lifting the clutch slowly and the pedal is at the position where the spring is in its mid change over point, there is slight resistance off the spring that almost locks the pedal in this position (hope I'm making sense). If you sit in your car and press/release the pedal slowly a few times, you'll soon feel where this position is.

Problem is, if I really give it beans setting off from standstill or sometimes on gear changes plant the throttle, the pedal would lock in this position and clutch would slide. The clutch biting point is exactly at the change over point for the spring.

Yesterday I thought I'd remove it (mod that seems more popular in the states than here). Took if for a spin after removal and didn't like it at all, mainly because the pedal isn't then firmly held up in the top position when not in use, thus causing havoc with your cruise control. Also clutch felt a lot heavier.

In my opinion that spring was far too strong, so I decided to have a go at reducing it. Standard length is 100 mm (Think mine measured around 105mm - 110mm). So I gripped it in a vice, closed it up to 80mm, applied some heat to part of it with my Rothenberger and hey presto - spring is now 80mm long.

Assembled it back together and fitted back on the car. Clutch action feels much smoother now and I can't feel the croos0ver point where the spring changes direction. Give the car a bit of a blast on the way home and can't get the pedal to stick like it was doing. Don't know whether my spring was just too strong or whether they're supposed to be like this, but the pedal action feels miles smoother than before.

Alex is a happy man :)


Part in question:

wsAQJsL.jpg
 
Good result
Is the clutch assist spring an after market item or fitted as standard on UK manual cars? I can't check mine as my car's away on it's winter holidays :)
 
It's a standard item. Most cars have them on these days to make the clutch feel lighter.
 
Alex said:
It's a standard item. Most cars have them on these days to make the clutch feel lighter.

Nice job! I've read afew articles on stiff clutch padels (heavy) may well be a strong spring, maybe it would easy with age/mileage?!
 
I know exactly what you mean and have seen it in action .. im small and can get under the dash to watch it lol .

I would have just fitted a new booster spring to be fair and checked the pedal operation was free ... it would be interesting to see the difference from a new to your modified one .

Interesting modification though so i've taken note of it for future reference as it's not something i would have considered . :thumb:


Heavy clutch is often the clutch cover plate being the issue .. lost count the number of cars i see with a heavy clutch .
 
Interesting thread this.

I've noticed that when the weather is hot and dry (ie. when the tyres have good grip) if I give a full beans launch in 1st the clutch will tend to slip which is pretty embarrassing. I've fitted a new clutch and flywheel only a few k miles ago so all is tip top at that end, I wonder if the same thing is happening to me and the clutch isn't full disengaged?

I tend not to launch the car very often anyhow but worth thinking about. Will have a poke around under the dash (my least favourite job)
 
You need to remove both air circulation pipes above the pedals and also remove the clutch switch to gain access. Only takes a matter of minutes to do that. The grenade pin in the end of mine was inserted by me to hold the spring in its compressed state. This way it's easier to remove the assembly from the car.
 
my car had a slight squeak from this for a while, which eventually became stiffer in the mid range of pedal travel. Eventually the pedal would remain stuck part way when releasing the clutch after a gear change.

After looking at Rennlist threads, where it seemed to be a common mod to remove the spring, I decided to have a go. Removing the spring fixed the sticking, the pedal throw was much smoother, but noticeably heavier.
Having said that I think I could have lived with it if the car didn't see much use in stop/start traffic.

After a few months, I asked Precision Porsche to replace it with a new spring at it's next service, but the pedal soon started to stick again. At its next visit Johnny & Andy suspected it might need a new master &/or slave. Fortunately Ian (DeMort) had a poke around & diagnosed it the upper part of the mechanism needed to be re-greased, which cured it.

When I looked at replacing the assist spring, we came across several different part numbers. Porsche Service recommended one, but other sources suggested a different one for my car.
I don't have the details now, & I never found any spec's, but assumed the differences were likely to be spring rates to modify the level of assistance & pedal feel.
 
The clutch isn't the easiest thing to bleed either. This can also cause the pedal to stick like that.
 
Resurrecting this thread for tips on how to get the bolt out that connects the spring to the pedal please.

I've tried levering it out with a screwdriver but it feels well set.
 
Have you taken the circlip off the end?

Gold clip seen here on the end of it:

1711829054318.png
 

This was in a different thread the other day for a 997, in the video the creator (who is a member here) says that the bolt doesn't come out and actually it clips in to a C shaped bracket. May be different on a 996 but perhaps not.
 
Yep, circlip off. Pesky bolt is tight in there.
 
It should just push out. I always disconnect the clutch pushrod off the pedal before doing anything with the helper spring. Maybe try doing that and put the pedal in the 'floored' position as this may relieve pressure from the spring on the pin (not bolt) you're trying to push out.
 
Last edited:
Good idea thanks. Will give it a go next weekend.
 

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