I need help with a possible new clutch!

[SENNA_GOAT]

So in the last 7 to 10 days I noticed that there is considerable slippage when I put the car in gear specially first and second gear, but also in third etc. The mechanic said I need a new clutch. But the clutch that is currently on my NSX only has 10,000 km on it. He said he hoisted the car and was able to look at the condition of the current clutch, and said that there was a lot of “clutch material” that was in the assembly. He checked the clutch slave cylinder and said it was working fine.The current clutch was an OEM clutch that was installed approximately 10,000 km ago. I’ve grown up driving stick from the age of 16 so I know I’m not riding the clutch nor do I drive aggressively and it’s only 1000 km per season that I put on it in the last 10 years. So please tell me how is it possible that my OEM clutch with about 10,000 km according to the mechanic has failed??

 

[Honcho]

This is very hard to estimate because clutch life is so dependent on the driver's style and the usage of the car. Kaz has pointed out that owners who daily drive their NSXs in urban Japan often see the clutches fail at 20,000 to 30,000km! It's not because they are bad drivers, but the constant stop and go, traffic and hills. It's a huge number of clutch engagements. By contrast, there are many owners living in suburban areas and driving on highways mostly who go well beyond 100,000km. 10,000km is extreme though, but not impossible. Do you live in a dense city in a hilly area, and/or with a lot of traffic?

You can remove the flywheel cover to get a small look at the flywheel, but it won't let you look at the clutch. The only way to inspect the clutch is to remove it. My suspicion is that it was an improper installation and/or failure to adjust the clutch pedal free play. Both of these can cause premature wear due to the clutch not fully disengaging.

 

[SENNA_GOAT]

The NSX was only driven during the summer months between May to November and only about 1000 km per season during that time. I’ve been driving standard cars since I was 16 years old. I don’t ride the clutch, especially on a car such as this. I live in a small suburban city. Those 1000 kilometres per year would mostly be driving on rural roads with little to no traffic.

PS how does a mechanic peer in to see the condition of the flywheel as you mentioned?

 

[Old Guy]

As noted by Honcho, there is an cover plate on the bottom of the bell housing facing the engine side (#1 in photo).



Removal of that cover allows you to see the lower part of the engine side of the flywheel which is of no particular value in terms of the clutch inspection. As also noted by Honcho It does not allow you to see the flywheel surface or the friction disc surface unless you were able to sneak an endoscopic camera in past the edge of the ring gear for a rather limited view. Based upon your description, it seems like the mechanic removed the cover plate and observed "a lot of “clutch material” " and surmised that the clutch was worn.

Rather than check the slave cylinder, it would have been more appropriate for your mechanic to check the master cylinder and clutch pedal free play. You can do that yourself as described on page 12-4 of the 1991 service manual. If the free play is not within spec you can adjust it and see if that resolves the problem. However, if the clutch has been slipping for a while it may now be at the point where correcting the free play will not fix the problem if the clutch plates are glazed. At that point the clutch needs to be removed for inspection / replacement.

Given the limited information, it is impossible for anybody to be definitive about why the clutch may be slipping. My OEM 6 speed clutch has approximately 120,000 km on it and I do a lot of urban driving. If checking the clutch pedal free play does not resolve the problem then removal is the next step.

For future reference it would be useful if you specified the model year because there is a significant difference between the early and later clutches. However, those differences may not be important at this point.

 

[SENNA_GOAT]

Thank you for your detailed reply.

The technician checked the unit pictured below - had one mechanic sit in the driver, seat of the car while the car was hoisted, pumping the clutch pedal, while another tech was checking underneath for any leaks. He said this part was working fine.

The clutch only started slipping recently (as in the last week) and is has gotten worse. I was able to drive it initially short distances under a kilometre or two. Now it’s engaging the engine only about 10%. I’m guessing so I’m not driving it any longer.

The car is a 1995 NSX-T with 164,000 kilometres or about 100,000 miles.

The technician and I also took the car for a drive and the technician was convinced that it is the clutch that needs to be replaced. I have suggested to him, just replacing the friction disc instead of the entire clutch, but he said that that would be a risk if he took the entire clutch apart and found all the components of the clutch were damaged, and that a full clutch would not be on hand to complete the job

 

[NSXnZ]

Make sure you have some free play in your clutch pedal. I had a similar issue after my master cylinder was replaced by a shop where the clutch fluid bled itself further, and I lost my free play, making my clutch slip. Little adjustment for that according to the shop manual, and I have zero issues.

 

[Old Guy]

That is the slave cylinder. As an observation, I have never heard of a slave cylinder problem causing clutch slippage. Slave cylinder problems cause failure to release / dragging clutch problems. How confident are you in the skills of your mechanic? Check your clutch pedal free play. If it is within spec, then I think the next step is removal of the clutch.

The mechanic has a valid point. If the clutch friction material is damaged by heating then the flywheel surfaces may require attention which may or may not be repairable. They are also not interested in getting the clutch out and finding that they don't have the required parts to complete the repair which ends up with your car stuck in their shop taking up hoist space (once the transmission is out the car is pretty much stuck there) that could be earning money doing repairs on other cars. It may also be an academic discussion because in North America Acura no longer sells the individual friction disks. It is a complete new clutch assembly or nothing. Amayama in Japan might still continue to list the friction disks as being available individually. The complete OEM dual disk clutch assembly for the NSX is rather expensive. Science of Speed offers their 275 clutch at a price about 60% lower than the MSRP for the OEM dual plate clutch

ScienceofSpeed Sport 275 Clutch & Flywheel (includes bearings) - NSX, 1991-05

ScienceofSpeed Sport 275 Clutch & Flywheel (includes bearings) - NSX, 1991-05 The ScienceofSpeed Sport 275 Clutch & Flywheel Kit is the ultimate clutch and flywheel package for the factory powered or moderately modified street and track driven NSX. T

www.scienceofspeed.com

The Science of Speed kit is complete with everything including flywheel.

 

[SENNA_GOAT]

Make sure you have some free play in your clutch pedal. I had a similar issue after my master cylinder was replaced by a shop where the clutch fluid bled itself further, and I lost my free play, making my clutch slip. Little adjustment for that according to the shop manual, and I have zero issues.

There is still free play the best I can see.The problem arises when the clutch should engage it hesitates and only engages at maybe 20% of what it should be. I WAS hoping it was the clutch slave cylinder but the mechanic tested it and said it was working fine.

 

[TANTO]

Old guy doesn't need reinforcement, but no matter what the availability, on any car you should never ever simply replace the disc/disc's. In the old days we could have a machine shop "reface" the flywheel and pressure plate and use just a new disc, but in our case it would require four surfaces to be refaced and those old "clutch shops" with the expertise are simply gone. In case you didn't already know (which you likely do), growing up in the US V-8's drag crowd you could do a "clutch dump" with 350 ft lbs or so of torgue 50-60 times before you damaged your clutch. With the nsx/ porches/ferrari's you likely get about a half dozen "clutch dumps" before you have seriously degraded or "glazed" the surfaces to where it will slip. Can't understand why all these outstanding engineering groups would design clutches FAR inferior to a stock 56 Chevy? Back in the "day" when modern engineering software was not in use (except in aviation) instead of engineering a system, systems were often WAY overdesigned ( perhaps maybe 400%) as cost/weight/efficiency was not an issue. From what i understand Honda works at around a 20% safety factor. That is really tight thus these "drag" starts are simply not on the table without a yearly rebuild. Not insinuating ones habits, but i have seen a lot of folks in various high end sports cars that think they can certainly do a burn out now and then, right? Not so IMO, not even on most aftermarket offerings. Same goes for "powershifting". While personally my street race or burn out days are well in the past, I do kind of resent that i can't ever "abuse" my NSX clutch a bit (my old drag race friends think i'm now a wuss). I'm sure drift folks may have contrary opinions, just my individual experience. PS -clutch fluid needs replaced now and then. I remember my first fluid change at around 10k it looked like coffee.

 

[SENNA_GOAT]

Old guy doesn't need reinforcement, but no matter what the availability, on any car you should never ever simply replace the disc/disc's. In the old days we could have a machine shop "reface" the flywheel and pressure plate and use just a new disc, but in our case it would require four surfaces to be refaced and those old "clutch shops" with the expertise are simply gone. In case you didn't already know (which you likely do), growing up in the US V-8's drag crowd you could do a "clutch dump" with 350 ft lbs or so of torgue 50-60 times before you damaged your clutch. With the nsx/ porches/ferrari's you likely get about a half dozen "clutch dumps" before you have seriously degraded or "glazed" the surfaces to where it will slip. Can't understand why all these outstanding engineering groups would design clutches FAR inferior to a stock 56 Chevy? Back in the "day" when modern engineering software was not in use (except in aviation) instead of engineering a system, systems were often WAY overdesigned ( perhaps maybe 400%) as cost/weight/efficiency was not an issue. From what i understand Honda works at around a 20% safety factor. That is really tight thus these "drag" starts are simply not on the table without a yearly rebuild. Not insinuating ones habits, but i have seen a lot of folks in various high end sports cars that think they can certainly do a burn out now and then, right? Not so IMO, not even on most aftermarket offerings. Same goes for "powershifting". While personally my street race or burn out days are well in the past, I do kind of resent that i can't ever "abuse" my NSX clutch a bit (my old drag race friends think i'm now a wuss). I'm sure drift folks may have contrary opinions, just my individual experience. PS -clutch fluid needs replaced now and then. I remember my first fluid change at around 10k it looked like coffee.

The clutch fluid in my NSX is a golden light colour. Nothing dark about it.