Clutch slipping, but no smell

[r71]

Clutchmaster FX400, first time, it was great for ~200 miles. then it starts slipping. Id be in 4th in boost, it lets go around 6k. It starts slipping to a point where the car won't even move in 1st gear. The shop pulled the clutch thinking the disc is glazed, but it looks fine. They took it down to Clutch Specialities here in Atlanta. The guys didn't like the pads used by Clutchmaster. They upgrade the pads.

Get the car back and it runs great. No slipping. After 2 fill ups and change, same problem. 4th gear, in boost, breaks loose around 6k. Barely make it back but it's bad enough where it just spins in first gear.

No clutch burning smell. Could it still be the clutch? They did resurface the flywheel the first time. Could they have took too much material off?

Car is tuned to 400hp.

 

[charlee]

How about the pressure plate? It sounds like those fingers aren't doing their job.

 

[r71]

according to the shop, it looked ok. no sign of damage. In a sense, all they did was pull it, inspect it, and reinstall. Worked for a bit, then started slipping again.

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Update:
The car sat overnight. I came just took it out for a spin, it gripped like a mofo. I was on it hard 2,3,4 full boost 7 psi. No slippage at all. WTF? Any gurus out there before I start taking this thing apart?

 

[wazari]

This is my first post. I bought a brand new '92 NSX and kept it for 4 years and sold it in '97. Now in the market again for another one so I started lurking on this forum. I worked as a Honda tech, Acura shop foreman and service director for over 20 years before semi-retiring and doing something totally different.

Anyway I have seen the following things causing the symptoms you mentioned. One is a leaking input shaft seal. At high RPM's some transmission fluid gets on the disc causing slippage. Also could be "floating" of the diaphragm. The disc starts floating when the motor is at maximum torque which it sounds like you have a forced induction motor so when the boost comes on at max torque and HP the pressure plate is just isn't strong enough to apply enough force against the disc and flywheel at that RPM range especially in higher gears where there is more torque being applied at the flywheel. Lastly, I have also seen discs installed backwards causing this problem. Good luck,

 

[r71]

Thanks wazari, I don't thing anything was leaking. They took it out for inspection the first time around and made sure everything was correct. Floating, maybe. Only thing is after it slips, you can't even move the car. It slips everywhere. Not just in high RPM. Then the strength of the clutch. It's rated for way above 400hp. Putting the plate in backwards, well, who the hell know about that one. I found out they installed spring perch upside down.

My thing is, how does it explain the clutch functioning properly after over night. I'm going to take it for another spin after the traffic dies down. But if it went bad, shouldn't it keep staying bad? Also, shouldn't I be smelling some clutch burn?

 

[silver2002]

If there is no play in clutch pedal [3/4"], pressure can build/remain in system and force will be exerted on throw out when foot is off clutch. You'll hear the "throw out" spinning when it should be disengaged [unless you engine/exhaust is too loud]. Pressure may leak out back to resevoir overnight, allowing it to work in the morning.

 

[r71]

silver, I just checked, no play! Almost too tight. I'm going to loosen then report back. Makes sense and it's free.

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I'm assuming this free play is adjusted after removing the helper spring. The spring keeps the pedal pegged to the switch "A". But you were correct silver2002, there was no play even after removing the spring. I backed off th switch to give it about 5 - 7mm of play. Let's see if the problem returns.

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So what be the trick to get the damn helper spring back in? I'm leaving it out for now. Any drawback to that? I've taken it out of my 911 but that helper spring was to engage the NSX is to return the pedal.

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Just got back from beating the cap out of it. full boost in every gear. zero slippage. maybe that was the problem. now it catches mid to 3/4. perfect spot. easier to drive too.

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Thanks silver2002!

 

[silver2002]

all I remember was turning the lock nut not messing with the helper spring-- Hope this solves it!

 

[wazari]

The assist spring is for keeping proper pedal play (1-7 mm) which is part of the total free play and as you mentioned to keep pressure against switch A. The spring is normally not removed when adjusting free play. Using a 90 degree needle nosed pliers will help getting the spring back in.

 

[NSXcitement]

Just got back from beating the cap out of it. full boost in every gear. zero slippage. maybe that was the problem. now it catches mid to 3/4. perfect spot. easier to drive too.

Glad that fixed it. I wonder how it could slip so much without any tell-tale odor..

 

[r71]

Got the spring back in. Got on it pretty hard. No slipping yet. I'm hoping this is it. I can finally enjoy it. Knock on wood.

 

[Vuur1007]

If there is no play in clutch pedal [3/4"], pressure can build/remain in system and force will be exerted on throw out when foot is off clutch. You'll hear the "throw out" spinning when it should be disengaged [unless you engine/exhaust is too loud]. Pressure may leak out back to resevoir overnight, allowing it to work in the morning.

Did have these problems also since I renewed several parts. Remarks from r1 and Silver2002 and the caution-note on the Adjustment page made me open up the master cylinder again and check clearance between piston and pushrod. On the pushrod disk (don't know the proper name) the "cup" was pointing towards the cylinder, leaving no clearance between pushrod and piston at all.
I'm pretty sure it was like this before I renewed parts but after turning this disk the pushrod head is now resting inside the "cup" with space between pushrod and piston. The clutch engages at about 2/3, feels normal and no slippage for already 200km. Hope this solved it.