Clutch Problem

[rkanaga]

Could I ask for some quick clutch advice please guys?

After washing my 1991 NA1 when trying top put it in gear to reverse back up into the garage the clutch pedal went totally light. I can't now get it to go into gear (i.e. the clutch won't disengage.)

The pedal is light and sticks at the bottom but you can free it and it springs back up, but the clutch clearly is not disengaging.

It had a new clutch only 15K miles ago.

Any ideas?

(my inexpert internet research suggests clutch slave cylinder. Does that sound likely? How easy is it to change if so?)

cheers

Robin

[Kaz-kzukNA1]

Sounds like you have introduced air into the CL hydraulic system.
The main cause is leakage at the CL master, slave or hose.

Open the bonnet and take a look at the tiny CL reservoir towards the centre of the car.
If it is close to empty, that’s your problem.
There are several places to be checked.

Inside the cabin, look above/behind the CL pedal. You will see the pushrod that is connected to the CL pedal. If you see fluid at the rubber cap where the pushrod enters, your master cyl is leaking. Very common on NSX and leaked brake fluid will be absorbed by the carpet inside the cabin so you better wash it very soon.

If you go to the engine bay and if you can remove the air box, you can take a look at the slave cyl from the top. If it is leaking, you will see wet area on top of the white shift cable cover.
It could be leaking from the hose as well.
It is the one attached to the slave cyl and it normally leaks near the crimped metal fitting section.

There were some reports of CL hyd pipe being damaged by scratching against the panel, leakage from the 6 way joint under the bonnet near the 3 connectors mounted on the blower motor fan housing, etc.

If one of the three parts (master/slave/hose) were faulty, please make sure to replace all three as a set.

If you want a temporarily fix, it is best if you can bleed the hydraulic line at the place where your NSX is parked at the moment.

If it is not possible, try topping up the reservoir with the brake fluid and operate the CL pedal with your hand like 200 times.
If you are lucky, you may start feeling some resistance at the pedal after about 100 times and then carry on until you can no longer operate it with your hand.
Once you have managed to push out the air enough, you should be able to disengage the CL for several times just to get your car back in to the garage before it can be properly serviced.

The key is to flip the CL pedal with your hand very fast when you lift it from the floor.
This is to apply sudden shock/vibration to the master cyl to let the air climb up to the reservoir.
Make sure to close the cap while doing this otherwise you are going to splash the fluid all over with the vibration.

Keep eye on the fluid level at the reservoir and never let it empty as you don’t want the air to be sucked back into the system again.

Kaz

[rkanaga]

Wow! thanks for the very quick reply Kaz

The reservoir is empty so definitely a leak somewhere.

I managed to ease it into gear with the engine off and then reverse back using the starter so at least it's back in the garage.

I will investigate tomorrow, but it sounds like it will need a new master and slave cylinder and hose by the sound of things.

If I can refill it enough and bleed it presumably I could get it back into a state where I could drive the 10 (country) miles to my nearest dealer?

Where is the best place to bleed it please?

Thank you so much for your help

cheers

Robin




Sounds like you have introduced air into the CL hydraulic system.
The main cause is leakage at the CL master, slave or hose.

Open the bonnet and take a look at the tiny CL reservoir towards the centre of the car.
If it is close to empty, that’s your problem.
There are several places to be checked.

Inside the cabin, look above/behind the CL pedal. You will see the pushrod that is connected to the CL pedal. If you see fluid at the rubber cap where the pushrod enters, your master cyl is leaking. Very common on NSX and leaked brake fluid will be absorbed by the carpet inside the cabin so you better wash it very soon.

If you go to the engine bay and if you can remove the air box, you can take a look at the slave cyl from the top. If it is leaking, you will see wet area on top of the white shift cable cover.
It could be leaking from the hose as well.
It is the one attached to the slave cyl and it normally leaks near the crimped metal fitting section.

There were some reports of CL hyd pipe being damaged by scratching against the panel, leakage from the 6 way joint under the bonnet near the 3 connectors mounted on the blower motor fan housing, etc.

If one of the three parts (master/slave/hose) were faulty, please make sure to replace all three as a set.

If you want a temporarily fix, it is best if you can bleed the hydraulic line at the place where your NSX is parked at the moment.

If it is not possible, try topping up the reservoir with the brake fluid and operate the CL pedal with your hand like 200 times.
If you are lucky, you may start feeling some resistance at the pedal after about 100 times and then carry on until you can no longer operate it with your hand.
Once you have managed to push out the air enough, you should be able to disengage the CL for several times just to get your car back in to the garage before it can be properly serviced.

The key is to flip the CL pedal with your hand very fast when you lift it from the floor.
This is to apply sudden shock/vibration to the master cyl to let the air climb up to the reservoir.
Make sure to close the cap while doing this otherwise you are going to splash the fluid all over with the vibration.

Keep eye on the fluid level at the reservoir and never let it empty as you don’t want the air to be sucked back into the system again.

Kaz

[rkanaga]

Update:

I checked the carpet in the drivers footwell and there is no damp, so i presume that the master cylinder is ok.

I was able to top up the reservoir and pump the pedal by hand until the pedal feel returned. Hooray! I can now change gear! It didn't actually take that long and the pedal feels pretty much normal now so I don't think much air got in hopefully

I can't see any leaks under the front hood, so I will take the airbox off next when I get a chance to check for leaks around the slave cylinder and hose and also of course to bleed the clutch properly.

Thanks a million kaz for your useful advice.

Robin.

[rkanaga]

So I bled the clutch today. Took the air box off (3 bolts) and undid the slave cylinder bleed screw. Attached a piece of hose from this and put the end into a bottle of hydraulic fluid. Pumped the pedal and intermittently filled up the master cylinder reservoir.

Now back to normal

I can't see any leaks anywhere so I'm going to just keep an eye on the level until the next service.


Thanks for the advice. It saved me a flat bed trip to my dealer!

Robin

[gumball]

Be careful, the fluid must have gone somewhere.

[Kaz-kzukNA1]

I agree with gumball.

In order to empty the CL reservoir, the fluid has to go somewhere.

If it was leaking from the slave cyl but couldn't see wet area on the shift cable cover, you must take off the dust boot attached to the opening of Gbox covering the slave cyl where the CL fork sticks out.

From your signature, you seemed to own 91 model.
If you are still using the original design dust boot (no longer available, being replaced by the same one used on later model),
there is no escape window so some of the leaked fluid will be held inside this dust boot as well as inside the rubber boot of the slave cyl plunger.

Just lift the dust boot (you can't remove it without disconnecting the slave cyl from gbox case) and check inside.
Also, check the edge of plunger boot where it sits on the salve cyl although it is not easy to do this while keeping the slave cyl in place.
They should be dry but the plunger boot will look like wet due to rubber grease used though there should be no brake fluid there.

If the leakage was very slow over several months, then you may not be able to see the leaked fluid as it could be washed away.
The leakage at the master cyl won't go outside and it will be contained inside the cabin.


Just keep eye on the fluid level because it will go down depending on the rate of the leakage.

Ideally, you should operate the CL pedal many times to see where it is leaking from.

Kaz

[rkanaga]

Thanks, all good advice. I'll be sure to inspect the slave cylinder as soon as possible

Cheers

Robin