Clutch issues weird problem

Need some help - Clutch issues weird problem

Hi guys. I've got a really strange issue with my clutch right now. For the story, I've change my clutch about a year ago for an exedy hyper single and every thing was fine. Last September I was loosing some clutch fluid so I've decided to change my clutch master and slave cylinder but it turned out it was the clutch slave hose who was to blame so I've replaced the clutch line by the SOS Clutch Damper Delete & Hose Kit and I've bled the system twice and every thing was fine. I didn't used the nsx for a while. But 2 weeks ago I took the nsx for a long drive and I've notice, after an hour on the highway that the biting point on the clutch pedal became really High and then the clutch had start slipping to the point where I could get the car in to gears but the car wouldn't move. I left the car for a few hours and when I've started the car again every thing was fine. So last week I took the nsx to my local Honda dealer and they've bled the system again and adjusted the pedal free-play and told me that every thing was good again. But this week end It started again. The clutch is fine for half an hour then it start to slip again to the point where I loose the drive completely, leave the car for an hour or so and every thing's fine again. It look like if the clutch is always under pressure but it doesn't smell like burning clutch. What could it be? I've never track the car and never drove the car to aggressively. Do I need to change the clutch again? Thanks for your answers.

Seems like your problem is with the clutch master cylinder.

I suspect you could pump the clutch petal and induce the problem.

When you release the petal the master shroud allow fluid to go back into the reservoir. I suspect your master doesn't release the pressure.
This could be do to a bad adjustment or bad clutch master.

nsxnut said:

Seems like your problem is with the clutch master cylinder.

I suspect you could pump the clutch petal and induce the problem.

When you release the petal the master shroud allow fluid to go back into the reservoir. I suspect your master doesn't release the pressure.
This could be do to a bad adjustment or bad clutch master.

Click to expand...

Every thing's brand new and with OEM parts and my Honda dealer did the adjustment last week.
Could it be the clutch bearing?

u check behind the carpet next to the clutch pedal?

Either something is blocking the return port in the clutch master, or there is not enough slack in the master pushrod.

BATMANs said:

u check behind the carpet next to the clutch pedal?

Click to expand...

What should I look for?

i heard that the phantom leaks/pressure loss are often from that area inside the cabin by the pedal.

Not sure exactly where. U will need to search for more details.

Does the clutch pedal have ANY free play?

I suspect not, LMK.

Regards,
LarryB

No it hasn't got any free play but Honda had adjusted the free play last week and said that it was at it's maximum set up.

If we rule out air and clutch assembly in the transmission.
Than it really sounds like a master cylinder going bad.

Since it's adjusted all the way to max (which isn't a desirable situation) could you pump the clutch system (push the pedal) for a good few times see if you can reproduce the issue.
Then check free play once more.

Hi, laurent1475.

Although you may have multiple issues, you wrote that
1: your CL doesn’t slip under normal condition
2: you don’t get this issue when the car is cold or once the car has cooled down.
3: the issue comes back once the car gets warm/hot.
4: it feels as if the CL is always under pressure when this issue happened.
5: there is no free play (Kaz: I’m not sure whether you are referring to the CL pedal mechanical play or the CL master cyl piston play).

Based on these facts, as others suggested, this is the typical CL master cyl pushrod adjustment issue.
It’s the effect of CL fluid expansion under heat.

As you removed the CL Hyd line damper and installed the damper-less joint, it becomes even more important to adjust it properly.
I have seen exactly the same issue when the owner of RHD NSX models installed Type-R/NSX-R CL pedal with damper-less joint and went too far in adjusting the pushrod in order to lower the CL pedal height and minimise the CL master cyl piston play described later.


By the way, any fluid leakage or air in the system will result in the opposite effect.
For these cases, you won’t be able to create enough travel at the CL slave cyl piston resulting in not being able to disengage the CL fully and thus, you will struggle to select the gear.
This is not the case for yours.


Following diagram will assist you in understanding what is happening with your CL Hyd system.


When the CL pedal height and the CL master cyl pushrod were adjusted properly, there will be a small but important piston play ‘A’ (blue) created.
There is another play of about 1 - 3mm called as the mechanical rattle/play at the CL pedal but I’ll leave this as it’s not related here.

When you press on the CL pedal, the master cyl piston (green) slides towards the feed port.
Until it reaches this port, the fluid (pink) is simply pushed back to the reservoir and no pressure is generated.

Once the piston blocks the feed port, it will then build up the line pressure and pushes the slave cyl piston outwards resulting in the movement at the CL release fork and you will be able to disengage the CL.
When you lift your foot from the CL pedal, it’s the reverse of the above sequence.

As for any Hyd system, the fluid, master/slave cyl metal body, hard line, hose, etc will expand as well as contract/shrink under temperature change and the expansion/contraction rate is different depending on the material of the parts.

Therefore, the piston play ‘A’ is very important to allow the fluid to move freely in and out of the reservoir when the temperature changes to absorb/compensate for the changes in overall Hyd capacity when the entire Hyd system is in the process of warming up as well as cooling down.

On the other hand, if you have too much piston play 'A', you will end up not being able to push the slave cyl piston far enough even when the CL pedal was already at the floor. The fluid is simply returned to the reservoir before it can start create any line pressure.
From the driver CL feeling point of view, it is best to minimise this piston play 'A' but you need to be careful and not over do it considering the effect of temperature.


What’s happening with your CL Hyd system is described in the lower diagram.

As you can see in the diagram, your pushrod adjustment is too long or your CL pedal height is too low that there is no piston play ‘A’ in the Hyd system.
As you were saying that you have no problem when the car is cold or cooled down, it is very likely that the edge of the master cyl piston is sitting right at the feed port.

When the CL fluid warms up and expand, there is no escape route back to the reservoir with your current set up.
So, it can only move the salve cyl piston outwards until the expansion force balances itself against the resistance force from the CL basket spring resulting in disengaging the CL. This is why you loose drive when the car is hot.

If you are lucky and the master cyl piston is just sitting on top of the feed port, you could do a quick temporary fix by ‘kicking’ the CL pedal when you started experiencing the issue.

‘Kicking’ means, when you release the CL pedal by lifting your foot while keeping the CL pedal under your shoes, instead, while the pedal is at the floor, slide your shoes towards you or side way so that the pedal will ‘flip’ up on its own and let it create huge ‘bang’.

This sudden shock/impact will generate tiny extra amount of travel at the master cyl piston and it may just let the blocked fluid under pressure back to the reservoir and eliminates the pressure in the Hyd system.
Obviously, this method won’t work if your pushrod was adjusted too long and the piston was already gone passed away from the feed port.

The permanent fix is to adjust the pushrod length and the pedal height properly but I don’t know how the Honda dealer adjusted your CL Pedal (and/or the pushrod).

If you installed the damper-less joint and if your master cyl piston is blocking the feed port, it will make the things even worse as there is no ‘damper’ to absorb some of the expansion in the fluid.
For the clarification, there is nothing wrong with the damper-less joint and its purpose is nothing to do with the fluid expansion effect because it should be absorbed by the master cyl piston play ‘A’.


Hope you can fix your issue very soon.

Kaz

Thanks for your answer. I can I resolve this problem?

laurent1475 said:

Thanks for your answer. I can I resolve this problem?

Click to expand...

Adjust the push rod up so the piston has full travel then adjust pedal clearance.

I'd need to dig up a diagram to explain it visually. but let me try in words.

If you view your pedal assembly from the side there are two adjustment points.
one is the actual push rod in to the master this you'd adjust backwards to gain some more piston stroke. (so to speak)
The other adjustment is a locking nut under the clutch position sensor (the one pointing to the floor) this pushes against the pedal upper arm,

So you can release push rod then adjust the upper locking nut forward then, then adjust the push rod.
Your clutch pedal should have 12-13 cm total stroke.

Great explanation Kaz. I have seen this many times. The clutch was improperly bled from the get go, and as you drive it bleeds out the air, then the pedal is too tight. You need to ALWAYS have end play in the pedal. Spec is 1-7mm, but I see most of them around 15mm. Loosen up the clutch master rod, so you have play, enjoy

Regards,
LarryB

Larry, are you saying 15 is ok. I recently had an OEM replacement. I like the freeplay I have now. Maybe 10/15mm.

Larry Bastanza said:

Great explanation Kaz. I have seen this many times. The clutch was improperly bled from the get go, and as you drive it bleeds out the air, then the pedal is too tight. You need to ALWAYS have end play in the pedal. Spec is 1-7mm, but I see most of them around 15mm. Loosen up the clutch master rod, so you have play, enjoy

Regards,
LarryB

Click to expand...

davidf said:

Larry, are you saying 15 is ok. I recently had an OEM replacement. I like the freeplay I have now. Maybe 10/15mm.

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I have had no issues with the 15mm or so play. The key is you MUST have play, or it will slip, and wear prematurely.

Regards,
LarryB