LS7 Clutch (VXR8)

[MontyPythonX]

Does the LS7 clutch need a specific LS7 slave cylinder?
The reason I ask is i'm getting some odd symptoms on my clutch pedal (I can go into more detail if required). I have the LS7 clutch, flywheel and pressure plate, but i've still got a standard LS2 slave cylinder.
I've gone through several master cylinders but the symptoms always return after a while.

[stevieturbo]

Should be the same. And I'd be very concerned as to why anyone would go through multiple master cylinders ?

[MontyPythonX]

I see, thanks for the info.

The issues I have are kind of hard to explain properly so i'll try my best...
Sometimes the clutch pedal seems to have about an inch of dead space at the top where it has zero resistance. When you press the pedal there is a noticeable absence of resistance at first, then it feels normal for the rest of the stroke and the clutch disengages fine. When you release the pedal it's fine for most of the travel until you hit this bit of dead space, where the pedal either sticks where it is and you have to use your foot to pull it up, or it snaps back fully up but feels odd under your foot.
It might do this for 5 or 6 gear changes, especially after i've been doing low speed maneuvering, and then return to a normal feel for the full travel.

The garage i've been using always says that this is a symptom of the seals in the master cylinder failing and that a new one is the solution. I'm not doubting them, but I think the master cylinder seals may be a symptom rather than the cause.

Apologies for the essay...

[Boosted LS1]

Have you had any issues with bleeding it?

[stevieturbo]

MontyPythonX said:

I see, thanks for the info.

The issues I have are kind of hard to explain properly so i'll try my best...
Sometimes the clutch pedal seems to have about an inch of dead space at the top where it has zero resistance. When you press the pedal there is a noticeable absence of resistance at first, then it feels normal for the rest of the stroke and the clutch disengages fine. When you release the pedal it's fine for most of the travel until you hit this bit of dead space, where the pedal either sticks where it is and you have to use your foot to pull it up, or it snaps back fully up but feels odd under your foot.
It might do this for 5 or 6 gear changes, especially after i've been doing low speed maneuvering, and then return to a normal feel for the full travel.

The garage i've been using always says that this is a symptom of the seals in the master cylinder failing and that a new one is the solution. I'm not doubting them, but I think the master cylinder seals may be a symptom rather than the cause.

Apologies for the essay...

I would doubt them. A master cylinder should last the life of the car. Maybe worst case need replaced once.

Dead spot at the top sounds like air in the system, or if there is any sort of adjustment relating to pedal/master install...something there is amiss.

[leigh1050]

I was under the impression that the symptoms you talk of are caused by dirty brake fluid.

[SturdyHSV]

Definitely flush the clutch fluid through, clean it all up nicely and see what's what.

It's more of an issue with the ls2 clutch, but who knows, cheap and easy driveway job to do.

For some background:

https://youtu.be/gBbsy0LjUvE

[MontyPythonX]

Thanks for the advice.

I would have thought if there was a mechanical issue regarding the adjustment between the pedal and master cylinder it would happend every time, not just some of the time?

I've not had any issues with bleeding it. I used an eezibleeder last weekend on it and put about a pint of brand new Comma 5.1 fluid through it and it all looked ok. Was getting some small specks of black coming through the bleed nipple (I've got the remote bleed line) but nothing big.

[bigwheel]

Then the ultimate fix is a LS7 clutch kit! A biggy but it cures this problem.

[MontyPythonX]

It already has the LS7 clutch, pressure plate and flywheel, this is what is confusing me.

Since I have the rest of that bottle of clutch fluid sitting around I might as well use it and flush the system again and see if any bigger bits of gunk come out of the lines.
Failing that I think it's looking like taking it to a different garage that knows these cars well (MWP is probably the nearest), and get them to do a proper investigation with a fresh pair of eyes.
It's still driveable at the moment, I'm just worried that it might become undrivable at any random gear change.

[fred bloggs]

stevieturbo said:

I would doubt them. A master cylinder should last the life of the car. Maybe worst case need replaced once.

I would listen to the advise of the professional mechanic. 2 tiny conical seals moving up and down an ally cylinder several hundred times every time you drive, submerged in a corrosive fluid are actually quite likely to fail.
The fluid return holes in the cylinder can block easily, giving your symptoms.

[MontyPythonX]

Is this what the infamous drill mod rectifies? By enlarging the fluid return holes you stop them from blocking up?

[stevieturbo]

fred bloggs said:

I would listen to the advise of the professional mechanic. 2 tiny conical seals moving up and down an ally cylinder several hundred times every time you drive, submerged in a corrosive fluid are actually quite likely to fail.
The fluid return holes in the cylinder can block easily, giving your symptoms.

The same "professional" mechanic who's replaced it multiple times...and still a problem persists ??

No, that just highlights them to be an idiot. Even a fool knows you cannot keep throwing the same part at something...and expecting a different outcome. ( except perhaps Theresa May and her deals ) And you should consider that such parts are actually designed with all those movements in mind, and brake fluid IS the lubricant for those parts, and it is not corrosive to any of the parts involved.

In all the years I've been driving, I've never had a vehicle with a faulty clutch master cylinder, other than something that has maybe sat for 20+ years and not moved. And that includes my own van with over 700k on it....which would be more than a handful of movements.

The problem is...there are too many "professional" or other so called mechanics out there, but barely any competent ones.

[wozzza]

MontyPythonX said:

Is this what the infamous drill mod rectifies? By enlarging the fluid return holes you stop them from blocking up?

Drill mod shouldn't really be needed on Monaros / R8's. It was a thing on F bodies not so much on our cars.

I would personally bleed the absolute crap out of the system. Next time the box comes out check the clearance between pressure plate forks and the slave. Some cars need a shim depending on the slave fitted. Tick sell them and have the relevant info on their site. It's rare an LS7 needs it though to be honest.

[MontyPythonX]

Thanks for all the advice guys

I'll get the rest of the fluid used up and see what the state of play is.

I was suspecting i'd have to take the box off and get a competent garage to look at what they find, was just wondering if anyone had had any similar symptoms.