Inconsistent clutch engagement. Help!

[Hapa88]

Hey all,
This just recently started happening. I first noticed it at a track day in AZ at the end of the day. Basically what's happening is the clutch engagement is becoming very inconsistent. Normally it engages and grabs at the midpoint of the pedal travel and always has. Now every shift is completely different. Sometimes it's normal, the next shift the clutch will grab at the very very bottom of the pedal travel. Rev match and downshift and sometimes it feels like the clutch isn't even disengaging, so I end up grinding the gear. Stop the car and take off and it's back to normal. Next stop, again the clutch catches at closer to the top of the travel. This is all in a span of less than 2 minutes!

Someone on FB thought it could be the pressure plate going out. Could it be a clutch master cylinder pushrod adjustment issue? It does appear to happen about 10 minutes into a drive (so the car is warm). Seems roughly normal for the first 10 minutes of driving.

Wanted to see if you any other ideas?

Things to note:
-1995 year with about 71,000 miles, original clutch. Owned car since 20,000 miles.
-I drive pretty moderate or conservatively. Every car I've owned has been stick shift and every clutch I've had got over 120k miles before replacement was necessary.
-Clutch master & slave cylinders were replaced about 3 years ago. They both look good and show no signs of leaking.
-Comptech Supercharged about 5,000 miles ago, but I have not driven it hard since (except for that one track day).
-New Transmission fluid replaced within the last 2,000 miles thinking it would help the situation. It didn't do anything.
-Clutch appears to be holding fine. There's no signs of slippage when going WOT or putting it in a high gearing and flooring it.
-Probably unrelated, but to note: quick shifts from 1st to 2nd usually result in a grind. This was the case since I bought the car. Most think its a syncro issue. Remedied by waiting a split second between shifts and there's no issue

Thoughts? [MENTION=3729]Larry Bastanza[/MENTION] [MENTION=25737]Kaz-kzukNA1[/MENTION]

 

[Mac Attack]

You said you replaced the clutch master and slave about three years ago, but were they Honda OEM parts or not?

 

[solidol]

Start with flushing your clutch line fluid.

 

[Hapa88]

You said you replaced the clutch master and slave about three years ago, but were they Honda OEM parts or not?

I was under the impression they were Honda OEM, though the person that installed them has been proven to be less than honest following my good experience. He was a local Acura mechanic doing side jobs. The parts were brought over to my house in OEM bags, but I didn't bother to check them out closely, I just assumed.

 

[Kaz-kzukNA1]

When people uses the wording 'bottom' or 'top' of the pedal travel, I don't know exactly what that mean because sometimes, they are used in completely opposite meanings.

I prefer something like 'close to the floor' or 'the pedal rest point'.


From what you wrote, sounds more like mechanical failure than CL hydraulic related.
With OEM CL, it is not that common but I saw many owners experiencing the torsion spring popping out from the disc, especially with those tracking their NSX or using nearly WOT quick shifting regularly.
May be your torsion spring has just started dislocating itself???
Obviously, I'm presuming that your CL is the OEM twin disc type as your NSX seemed to be the 95 model.


Your release bearing could be jammed somewhere on the release guide but then you should feel sudden change in CL pedal feeling/friction that you didn't mention so very unlikely.


For the free play, please enable the closed caption and watch this video;

If you don't have enough pushrod free play (please note that this is not the pedal mechanical rattle that is part of the free play), then you will feel as if the CL pedal is always under pressure without any free play at all once the CL Hyd system gets warm enough and if it gets worse, your CL will start slipping.

If you have air in the system or too much pushrod free play, you won't be able to fully disengage the CL but that would happen even when the system is cold and also you will notice it through the CL pedal feeling.

I believe your NSX is LHD so won't be able to use the Type-R CL pedal.
I’m presuming that you are using the standard damper joint and not the damper-less one.


Kaz

 

[Hapa88]

When people uses the wording 'bottom' or 'top' of the pedal travel, I don't know exactly what that mean because sometimes, they are used in completely opposite meanings.

I prefer something like 'close to the floor' or 'the pedal rest point'.


From what you wrote, sounds more like mechanical failure than CL hydraulic related.
With OEM CL, it is not that common but I saw many owners experiencing the torsion spring popping out from the disc, especially with those tracking their NSX or using nearly WOT quick shifting regularly.
May be your torsion spring has just started dislocating itself???
Obviously, I'm presuming that your CL is the OEM twin disc type as your NSX seemed to be the 95 model.


Your release bearing could be jammed somewhere on the release guide but then you should feel sudden change in CL pedal feeling/friction that you didn't mention so very unlikely.


For the free play, please enable the closed caption and watch this video;

If you don't have enough pushrod free play (please note that this is not the pedal mechanical rattle that is part of the free play), then you will feel as if the CL pedal is always under pressure without any free play at all once the CL Hyd system gets warm enough and if it gets worse, your CL will start slipping.

If you have air in the system or too much pushrod free play, you won't be able to fully disengage the CL but that would happen even when the system is cold and also you will notice it through the CL pedal feeling.

I believe your NSX is LHD so won't be able to use the Type-R CL pedal.
I’m presuming that you are using the standard damper joint and not the damper-less one.


Kaz

Thank you Kaz. For reference when I say "bottom of pedal travel", I mean the pedal is pushed in and close to the floor. When I say top of travel, I mean close to fully released. My car is also left hand drive (USA car) with the OEM Twin Disc clutch (to the best of my knowledge) and the standard OEM damper joint.

Based on what you described, my symptoms do not sound like the clutch master cylinder pushrod adjustment issue since when the clutch pedal is fully released, it doesn't appear to have any clutch slip at all. It seems to hold fine.

In terms there being air in the system, in some shifts you do feel as if the clutch doesn't disengage sometimes and you can feel it through the pedal. But on the very next shift it will be fine and back to normal.

I'm leaning toward it being a mechanical issue as well, which I believe requires me to remove the transmission. I was hoping there could be something I could fix or try without having to go that expensive route.

 

[Kaz-kzukNA1]

So, based on your OP, the CL bite point changes dramatically and unpredictable.

Sometimes, it's fine but next time it's close to the floor and on other occasion, it could be only near at the rest/top point.

CL Hyd sys is fairly simple design and since you replaced the CL master/slave cyl not that long time ago, very unlikely to be the cause.
OEM rubber CL hose can leak from the crimped section but never seen it expanding like ancient brake hose on classic cars.
If we ignore the expansion/contraction rate of the parts under temperature change, the biggest variable factor is the metal diaphragm damper joint but that won't cause your huge inconsistent bite point phenomenon.

The only other thing that I can think of outside of the gbox is the plunger of the salve cyl is not seating properly at the saddle/pocket of the release fork.
I saw this happening after someone installed the slave cyl from the top by removing the air box and not checking the seating of the plunger from the bottom after the installation.
Having said this, if this was the case, you would have noticed the strange pedal feeling immediately after replacing the slave cyl so very unlikely to be the case.

Before opening the gbox, you may want watching the movement of the release fork and the slave cyl while the car is on the lift.

You can also remove the slave cyl without disturbing the hyd line.
Just make sure not to touch the CL pedal while the slave cyl is removed as it will shoot the plunger in the air.

You can pop the release fork out of its spring loaded mount and look inside of CL case through the small opening but very limited space so may not find anything there.

At least, you can say you have checked everything you can before removing the gbox.......


Kaz

 

[nis350]

I hope it wasn't Robert... If so, you'd better check to ensure that they were actually replaced.

I was under the impression they were Honda OEM, though the person that installed them has been proven to be less than honest following my good experience. He was a local Acura mechanic doing side jobs. The parts were brought over to my house in OEM bags, but I didn't bother to check them out closely, I just assumed.

 

[Hapa88]

I hope it wasn't Robert... If so, you'd better check to ensure that they were actually replaced.

It was but from all evidence shown, it looks to have been replaced. Another Honda/Acura mechanic in Tucson checked them both out and they look good with no leaks. They've been working fine for the last 3 years.