Clutch pedal fell to floor, then fine?

Re: Clutch pedal fell to floor, then fine?????

In regard to regularity if this problem, I have replace the master/slave on the last 6 NSX's I have worked on, because they ALL had either a bad master or slave or both. Very simple, open the clutch reservoir, if it is low, which is should NEVER be, order the parts. As soon as I see a low reservoir, I look at the master cylinder boot behind the pedal to confirm. It has gotten to the point I don't even need to check that any more!!

Cars 1997 and older seem to have this problem more then less.

Also I always do both master and slave, I know some folks do not, but I do not want the car back in 3 months for the part I did not replace.

Just my experience. I now keep a set on the shelf, since it has become so common a failure.

HTH,
LarryB

Re: Clutch pedal fell to floor, then fine?????

Larry Bastanza said:

In regard to regularity if this problem, I have replace the master/slave on the last 6 NSX's I have worked on, because they ALL had either a bad master or slave or both. Very simple, open the clutch reservoir, if it is low, which is should NEVER be, order the parts. As soon as I see a low reservoir, I look at the master cylinder boot behind the pedal to confirm. It has gotten to the point I don't even need to check that any more!!

Cars 1997 and older seem to have this problem more then less.

Also I always do both master and slave, I know some folks do not, but I do not want the car back in 3 months for the part I did not replace.

Just my experience. I now keep a set on the shelf, since it has become so common a failure.

HTH,
LarryB

Click to expand...

Larry’s position of replacing both master and slave cylinders at the same time is actually based on strong technical principles developed by the aerospace industry. Simply put all hydraulic cylinders age with time and use. Bore and piston wear, seal wear/chemical property changes etc. When a new cylinder is replaced it has what we call a “crisp hydraulic pulse” or spike. As a cylinder ages this “crispness” is diminished. Changing only one cylinder puts an unaccustomed stress on the aged cylinder and causes a greater likelihood of near term failure. The same is true for brake systems. Calipers should always be rebuilt in pairs to assure a greater reliability.

Re: Clutch pedal fell to floor, then fine?????

Larry Bastanza said:

ICars 1997 and older seem to have this problem more then less.

Click to expand...

Interesting. Do you have any idea why?

Re: Clutch pedal fell to floor, then fine?????

age.

This is imperical data from my actual replacements.

HTH,
LarryB

Re: Clutch pedal fell to floor, then fine?????

D'Ecosse said:

....Incidentally, I was surprised by the number of clutch hydraulic issues I found with a search on Prime - seems like a pretty common problem....

Click to expand...

nsxtasy said:

....And a few reports on NSXprime doesn't make it common, when you consider how many NSX owners are here.

Click to expand...

Larry Bastanza said:

In regard to regularity if this problem, I have replace the master/slave on the last 6 NSX's I have worked on, because they ALL had either a bad master or slave or both. Very simple, open the clutch reservoir, if it is low, which is should NEVER be, order the parts. As soon as I see a low reservoir, I look at the master cylinder boot behind the pedal to confirm. It has gotten to the point I don't even need to check that any more!!

Cars 1997 and older seem to have this problem more then less.

Also I always do both master and slave, I know some folks do not, but I do not want the car back in 3 months for the part I did not replace.

Just my experience. I now keep a set on the shelf, since it has become so common a failure.

HTH,
LarryB

Click to expand...

Remember - you heard it here first gang! <!--StartFragment --> <!--StartFragment -->

I completely agree with Larry - may as well just do both for the work involved - parts are not super expensive and you may be just delaying the inevitable, whether it be 3 months or a year.

Re: Clutch pedal fell to floor, then fine?????

Same thing happen to my Type-R a few months ago. I was pulling off hard in first, slammed it into 2nd and the clutch went completely lemp.

For me, I had low clutch fluid, and I guess when I accelerated hard the fluid moved back enough to let air in. Thats my theory anyway...

Re: Clutch pedal fell to floor, then fine?????

After the recent Canyon Drive, I parked my 95 for a few days. When I drove it again, the clutch pedal dropped about 1/2 way then seemed to catch and release the clutch...gears of course were difficult to engage since the clutch wasn't fully released.

I checked the clutch reservoir and sure enough, it was empty. Clutch pedal on driver's compartment side of firewall was damp with some slight drops on the floor mat. Seems this leak was happening for sometime before it finally drained out. Luckily, this didn't create a problem during the Canyon Drive.

New master and slave cylinders on are order, hope to install this week. Thanks to those who've documented this problem in this thread!!

Mike

Re: Clutch pedal fell to floor, then fine?????

Interesting. Good hint to check the clutch reservoir over time. When or at what miles is the replacement recommended?

Re: Clutch pedal fell to floor, then fine?????

I have 50k mi on a 95 NSX-T (bought it about 2yrs ago with 30k mi on it)...since this is a slow leak, I'd check the reservoir regularly (each oil change) as well as take a look at the pedal area (to check for dampness).

BTW, does anyone know what brake/clutch fluid does when sitting out in the open? I've noticed a chemical smell on the interior and suspect it's this stuff evaporating as it's dripping into the car.

Re: Clutch pedal fell to floor, then fine?????

UFO said:

BTW, does anyone know what brake/clutch fluid does when sitting out in the open? I've noticed a chemical smell on the interior and suspect it's this stuff evaporating as it's dripping into the car.

Click to expand...

I thought brake/clutch fluid was corrosive...

Re: Clutch pedal fell to floor, then fine?????

BTW, does anyone know what brake/clutch fluid does when sitting out in the open? I've noticed a chemical smell on the interior and suspect it's this stuff evaporating as it's dripping into the car.

Click to expand...

Yes. It is making a gooey mess of your carpet while destroying your floorpan.

Pull up the carpet and clean it all out.

Re: Clutch pedal fell to floor, then fine?????

Carpet pulled, fortunately, no gooey mess. It did accumulate some dampness under the rubber clutch pedal foot pad...wiped it out.

Just installed the clutch master cylinder tonite. I think I threw out my spine getting under the pedals with my entire upper body. Usually enjoy a little low pressure wrenching but this one was not fun....I recommend paying someone to do this one.

I'll try to do the slave tomorrow.

Re: Clutch pedal fell to floor, then fine?????

UFO said:

I'll try to do the slave tomorrow.

Click to expand...

I strongly recommend you put a Speed Bleeder on that slave cylinder because manually bleeding the clutch line and waiting for the fluid to reach the slave is about as pleasurable as chewing rusty thumbtacks. The correct size Speed Bleeder for the slave cylinder is SB8125L. While you're at it get 4 of them for your brakes, SB10125.

Re: Clutch pedal fell to floor, then fine?????

Hugh said:

I strongly recommend you put a Speed Bleeder on that slave cylinder because manually bleeding the clutch line and waiting for the fluid to reach the slave is about as pleasurable as chewing rusty thumbtacks. The correct size Speed Bleeder for the slave cylinder is SB8125L. While you're at it get 4 of them for your brakes, SB10125.

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Excellent suggestion <!--StartFragment --> <!--StartFragment -->
(I have them too)

You must be especially careful when bleeding the clutch because of the small volume of fluid in the reservoir - it may need several toppings up before the job is done to be be bubble-free and if you let it go to too low as you are bleeding, you need to start all over again. So be sure to check & top the level every 3 or 4 strokes to ensure it is not going too low.

Re: Clutch pedal fell to floor, then fine?????

So be sure to check & top the level every 3 or 4 strokes to ensure it is not going too low.

Click to expand...

Six strokes on a full reservoir.

And not a single pump more: ask me how I know!

Drew

Re: Clutch pedal fell to floor, then fine?????

Just a thought on the problem. After reading all of the posts on this problem I have a theory. If the clutch fluid has gotten real dirty there may be small particles that could get under the seal edge of the plunger in the master cylinder. There is enough pressure, when depressing the clutch pedal, that this small interruption in the seal edge would allow for complete decompression of the high pressure area behind the plunger seal. The fluid by-passes the seal and returns to the fluid reservoir. This is why the pedal goes to the floor, and stays. When the pedal is manually returned to the up position the seal is pulled back and the particle is flushed out from under the seal because of the low pressure area created behind the seal on the slave side. Remember that brake fluid does not expand or compress, that is how a hydraulic clutch works. Pressure at the master cylinder is transfered through non-compressable fluid to a slave cylinder producing movement of a plunger that disengages the clutch pressure plate. The spring tension on the clutch pressure plate then returns pressure through the slave cylinder back to the master cylinder when the driver relieves pressure on the clutch pedal. This is what returns the pedal to the up position.

The solution. Flush the clutch fluid when ever it looks discolored. Some of this discoloration is from the deterioration of the master cylinder seal. This dirty fluid will continue to wear the seal of the plunger on the master cylinder and cause it to eventually fail. After time those particles will migrate down the fluid tube to the slave cylinder and begin the wear process on the seal in it. The slave cylinder is where most of the heat is collected in our hydraulic clutch system. This heat works to deteroriate the slave cylinder seal over time also. I flush this fluid annually.

Clean fluids are the life of a vehicle. Don't be afraid to use too much fluid. Do a good flush. Collect the fluid in a clear glass container. You want to be able to see if you are getting all of the crud out. If you drive your car in high humidity and / or in the rain frequently check for discoloration more frequently. As the fluid gets hot and cold it will contract moisture. Fluid used in the brake system has a greater temperature change because of the heat produced from the friction of the pads against the rotors and the close proximity of the calipers. Check it too.

I hope that I didn't bore all of you who know these things, and I hope those that didn't, learned something new.

Brad

Re: Clutch pedal fell to floor, then fine?????

Slave cylinder FINALLY installed with speedbleeder (cotter pins on the shift linkage were very difficult to access, remove), bled the system tonite, took it for a drive. Pedal is smooth, easy to engage, clutch is grabbing well, shifter isn't hanging up anymore...most satisfying:biggrin: :biggrin: :biggrin:

Thanks to everyone for the diagnostic and install tips!

Re: Clutch pedal fell to floor, then fine?????

First - thanks to all. I used this thread to successfully change both the master and slave cylinders.

First, I would like to reiterate the suggestion of using a line wrench on the clutch pipe bolts. I tried with a regular open-end wrench and was close to stripping them. Buy a 12 mm line wrench - $16 at Napa. Then take off your brake fluid reservoir. Its not hard, just suck out the brake fluid (with your turkey baster) and loosen the clamp. The plastic slips up and off the brake cylinder. After doing this you will have much more room to get the clutch pipe bolt off the fluid manifold.

I did not take off the clutch pipe at the master cylinder. It wasn't necessary. After I had the master out of the car, I then took off the clutch pipe to transfer it to the new master. Much easier.

I managed to get the master out without spilling a drop of fluid. Make sure you have the reservior sucked dry. Then stick in a paper towel and put the cap back on. If you leave the clutch pipe on the master cylinder, then the only time fluid can come out is when you take the clutch pipe off the manifold. And the amount that comes out is easy to catch with a few shop towels.

Also - when you put the new MC in, don't bolt anything in until you have the clutch pin back in place. If you have a lot of play its easier to get it aligned for the pin.

Regarding the slave - I just did everything per this thread and it worked great. The cotter pins are a b**ch. Buy 3 new cotter pins when you are at Napa buying the wrench (3/4" by 1/16 are about the right size).


Cheers

Re: Clutch pedal fell to floor, then fine?????

Can some one please tell me what size clear tubing fits the slave cylinder bleeder?

So if I understand this correct, I want to:

suck out the fluid from the reservoiur have a towel to make sure nothing is dripping from the metal tube coming off of the Master cylinder and a towel off of the line from the reservoiur to the Master cylinder.
Then take out the cotter pin
then undo the two bolts
pull out and replace part and redo my instructions backwards.

then clear tube onto the bleeder from the slave then have one person watching the res to keep topped up and have a second person to pump the clutch pedal. So is it like brakes one pump have the bleeder open then close so air does not get sucked back up and keep doing that until the new brake fluid is coming in and you pass any air bubbles?

thanks!

Re: Clutch pedal fell to floor, then fine?????

Larry Bastanza said:

age.

This is imperical data from my actual replacements.

HTH,
LarryB

Click to expand...

I see.

Thanks to everyone for a thread with a lot of really good info. I may take this on as a weekend project. Sounds like good preventive maintenance.

Another successful master and slave replacement completed. Thanks to all for you insight, instructions and pictures that made this doable. I also had moments with the cotter pins but got through it. If anyone has questions about my experience please email me.

Thank

Jim

[email protected]

I'm ordering the master & slave cylinder right now, since my slave went out on me while out for a drive on Sat. Besides those two parts is there any other part I need to order? I looked through this thread and didn't see anything else, I just want to be sure.

Brooklynzson said:

I'm ordering the master & slave cylinder right now, since my slave went out on me while out for a drive on Sat. Besides those two parts is there any other part I need to order? I looked through this thread and didn't see anything else, I just want to be sure.

Click to expand...

Fluid.
Speed Bleeder (SB8125L) if desired.
If you take the slave out from below the car, new cotter pins.

Tom239 said:

Fluid.
Speed Bleeder (SB8125L) if desired.
If you take the slave out from below the car, new cotter pins.

Click to expand...

Thanks for the quick response. Any recommended fluid? Or will any Dot 3 brake fluid suffice? I'm ordering the Speed Bleeder now, hopefully shipping doesn't take forever.

Seems like my slave went out again. Theres a slow leak near the tranny....