kotik

I got the car with 18k miles, the previous owner said he did the clutch fluid changes via ranger method, fluid was clear when i got the car. I had the car on the autobahns for a month and a half now, put 7k miles. I change clutch fluid every two weeks (it's it's pretty much always clear), but during certain instances the clutch pedal becomes very soft and doesn't want to come up. During normal driving, the clutch is great (love the feel of it), but during my hard runs on the autobahn it gets very very soft and sometimes stays halfway to the floor. So i'll do like two runs in 3, 4 and 5th gear (to about 160-180mph)(redline 3,4th), and after that it starts... It also became a bit soft on nurburgring during my second lap... The liquid i put in is Liquid molly, and i'm pretty sure it's DOT 4 (i'll verify in the evening).

What can it be? slave cylinder?

KING_PIN6

Clutch master cylinder problem

kotik

is it a known problem? what's the easiest way to replicate? The dealership here in Germany is not, let's say, very knowledgable with corvettes (although they claim they are).

Is it covered under power train warranty?

KING_PIN6

I have no idea if its covered under powertrain warranty. You better ask the dealership

tim414

No, it's not covered. Clutch is a normal wear/tear item. It 'would' be covered if your within 3/36.

EX1

the clutch itself is considered a normal wear and tear item but the hydraulics like the master and slave are not. Dealers warranty masters and slaves often around here.

kotik

^thats what i think, but want to be armed with somw info before i go do all this

9157

Check to see if your clutch sping broke...up under the dash...it's purpose is to prevent exactly what you discribe...under hot/stress..it keeps the pedal constant...without It....it is pure hydraulics..when the fluid get hot...pedal gets soft...

erikszr1

what kind of fluid did you use? liquid molly? what is that? anyway sounds like you need a clutch master cylinder. easy fix, if that's what you need. make sure your using the correct fluid first, if its not then you may need to replace slave cylinder also.

Dirty Howie

I track my car alot and sometimes when its hot and very hard laps the pedal will not return all the way. I have to pull it up with the corner of my foot. But then its fine by the next session. Been doing this for over a year.


DH

kotik

will check tonight. Under normal conditions, clutch feels great/as it should.

kotik

I just hope it's all covered under warranty/dealership knows how to check for it.

Liquid molly is most widely used oil in Germany. From what i gather, it's very good quality. For motors thye also produce 10-60 (not many make that type... castrol and royal purple?).

kotik

if only that. I drive the car hard on the autobahn (well, I want to drive it hard, but i can't because of 140million issues). After few hard shifts, the pedal goes limp, and it's getting worse. At the track it got soft after two laps (well, lap is 22km), which doesn't bother me much, but on the Autobahn, this pisses me off!

erikszr1

make sure its brake/clutch fluid and not something else.

AZCE

If it's not the fluid then it sounds like a hydraulic issue, probably a bad master.

PRE-Z06

From what you're describing it sounds like the diaphragm springs are getting weak with heat and that is why the pedal sinks, it's only going to get worse as the clutch heats up more with slippage after hard use. If you track the car I wouldn't want to becoming up on a corner trying to down shift and you can't get it in gear, the only way to permanently fix it is with a new clutch.

kotik

say it isn't so... I got the car with 18k miles, the previous owner seemed like a good guy, and swore to me he never tracked it (after purchase I confronted him about swapped headers). I saw him drive it, and he seemed to know how to handle the clutch. I for sure don't burn clutches, and did maaaybe 3 launches in 7k miles that i've had it...

tim414

Clutch hydraulics (factory) in these carts is hit/miss. Twice here in 14k miles (replaced under warranty-MC/slave).

99SoCalFRC

The clutch itself is fine. You need a tick master cylinder. The stock master is a total POS. this is a known issue all the way back to the C5. If you want a solid constant pedal you need the tick master. Nothing the dealership can do will fix it, they are just going to install another crappy stock master.

I've been try the soft shifts a thousand times in multiple GM cars, the fix is the tick master.

pkincy

Folks, maybe I am losing my mind, but I don't think it is a great idea to use motor oil in the clutch hydraulic system.

The Castrol 10-60 is a special BMW motor oil designed to reduce there oil starvation problems in the E46 M3 motor.

How about trying brake fluid.