Clutch Pedal Drops to the Floor-Master or Slave?

[RoNSX]

95 NSX, approx. 43K miles, had major service about 3K miles ago.

Car had been sitting for about 3-4 weeks. No problems when last driven.

Got in the car to start it up, push in the clutch and it snapped to the floor and stayed there. Pulled it out with my hand, pressed it again and again it snapped to the floor. In my search of the forum, I note that others have had the problem occur once, but then was not repeated.

Checked the clutch fluid and found it low, near the bottom of the reservoir. Checked under car and there was no visible leakage.

Contacted Acura service center, they thought possibly was leaking fluid. Suggested I check the clutch pedal arm, and that I might find brake/clutch fluid there. I did not find fluid on the clutch arm.

I topped off the fluid level and there has been no change in the problem. I expect a bleed will be necessary, but still expected to note some difference in pedal pressure. Put the pedal continues to drop to the floor, where it remains til I manually lift it.

Others have discussed replacing the master and/or slave cylinders to address variations of this problem.

Still others have mentioned replacing a seal on the slave cylinder to resolve related problems.

I'm hoping to avoid towing the car to the dealer for a repair.

Any suggestions for fixing this problem?

 

[missnsx]

Not sure if this helps or not but a few wks ago I had to get a new slave cylinder b/c mine was, as the Acura repairman told me "worn out from age" (1995 w/19K miles). My clutch petal however did not stay to the floor when I pushed it in. There was little resistance when I pushed down but it did pop back up. Like I said, not sure if that helps you at all but figured I'd share just in case. Good luck, hope it's an easy fix!

 

[hlweyl]

If the clutch fluid is low, you do have a leak. If it's not wet around or under your clutch pedal (look closely), then there's a high probability it is the slave cylinder.

When mine went bad, I didn't noticed any fluid leaking from the car and my garage floor stays dry.

 

[D'Ecosse]

I topped off the fluid level and there has been no change in the problem. I expect a bleed will be necessary, but still expected to note some difference in pedal pressure. Put the pedal continues to drop to the floor, where it remains til I manually lift it.
....
Still others have mentioned replacing a seal on the slave cylinder to resolve related problems.
...
I'm hoping to avoid towing the car to the dealer for a repair.

Fluid doesn't just evaporate so you definitely have a leak somewhere, one end or the other. Since it was so low, it is not unexpected that you did not change the situation any by just toppping it up - it will need to be re-bled which will probably enable the car to be drivable again to avoid towing to a shop for replacement.
If you can bleed it, you can probably change the slave cylinder, which is pretty straight forward (you're going to be down there anyway) - the master is not really any more complicated, just awkward to get at.

 

[peiserg]

this should be easy. Like suggested, check inside the driver's footwell. wet=master cylinder. check in the hood. wet=master cylinder. Now, i just recently got my nsx, so i don't know exactly where the slave is, or if it's even visibile without a rack, but follow the plumbing from the master, it should lead directly to the slave. check for wetness. If neither one shows signs of leakage, possibly the springs in your clutch might be the problem? the last part is a guess, since i've never done clutch work, altho i have replaced multiiple slaves and masters..
oh one last thing.. make sure there isn't a return spring on the clutch pedal that came undone.. don't know if there is one, since i've never had a problem with my clutch! all my experiences are with my landcruiser, which i've been through virtually top to bottom, but mechanics is mechanics!!

 

[D'Ecosse]

The pedal falling to the floor is definitely a hydraulics problem, so no worries on the actual clutch (as least not as far as this symptom goes)

You will need to raise the car in order to access the slave cylinder - just needs to be high enough to get undeneath it. Put it on Jack stands & remove rear driver's side wheel. It should be fairly easy to find, located on the front left side of the transmission, just above the shift linkage asssembly. You should be able access nipple to bleed it quite easily however, if you decide to replace it, you should remove the linkage assembly to gain easy access - this is pretty intuitive procedure & fairly simple.

It's pretty obvious where the master is - remove the drivers seat if you decide to change that out. It will give you much easier access to the pedal assembly inside the car & you'll be gald you took the extra 20 mins. Should be pretty obvious on removal - on re-assembly hook up the hydraulic lines before you tighten up the MC bolts. to allow a little movment on it - there's not much give on those lines, so can be a little awkward to get it all in properly.

http://www.nsxprime.com/FAQ/Reference/1991_svcman/1991servman.pdf
- put page 321 [enter] in the box at the bottom that say 1 of 1420 and it will take you right to the section you're looking for.

It was $170 for both parts from Niello with the NSXCA discount. Also, get a Speedbleeder nipple before you start & it'll make the bleeding process much easier!

Incidentally -

Still others have mentioned replacing a seal on the slave cylinder to resolve related problems.

There are no replacable seal kits for the NSX cylinders - years ago all cylinders typically had rebuildable seal kits for a few $$$ - nowadays the whole thing is a throwaway.

 

[RoNSX]

It looks like it the slave cylinder

After carefully inspecting the master cylinder and finding no apparent problems, I moved to inspecting the slave cylinder. Using this link and the excellent photos

http://www.nsxprime.com/forums/showthread.php?s=&threadid=20258

I checked the slave cylinder. There is clearly hydraulic fluid leaking from the slave cylinder. I have ordered a replacement from Niello Acura $84), expect to receive tomorrow. Plan to install tomorrow night. Will let you know how it goes.

(Note: Prior references to replacing seals referred to the O-ring between hydraulic hose and slave cylinder. This part is not included with slave and is a possible source of leakage)

 

[D'Ecosse]

I'd forgotten I'd even posted those or I would have referenced it myself. Glad they helped.

 

[RoNSX]

Did I Do Something Wrong?

Received new Slave cylinder. Installed as follows.

Unbolted old slave cylinder from frame, leaving hydraulic hose attached.

Bolted new slave cylinder to frame. Had to put some pressure on part to hold in place while I bolted it. Most resistence came from within the "pipe."

After slave was securely on frame I removed hydraulic hose from old slave and bolted on to new slave.

Bled system.

When I finally got some pedal pressure (probably cycled about 40 pumps of clutch pedal) it lasted from only a moment and then pedal dropped to floor again. When I inspected slave I found hydraulic fluid was leaking out of the side opposite the bleeder bolt (the portion that inserts into the pipe).

Did I receive a defective slave cylinder or was there something wrong with the process I used to install it? I had considered bleeding the system before attaching the slave cylinder to the frame. Would anyone recommend this procedure? Any suggestions?

 

[D'Ecosse]

Sounds like you lost the o-ring at the connection between hose & cylinder; or maybe tweeked it or something? Maybe that was even your problem to begin with!

#27 in the exploded diagram below - remove it if its still there & see if it looks OK

Tip- If you don't want to lose all the fluid, pinch off the hose by clamping on a pair of vise grips during removal/re-installation

edit: o-ring is 8.8 x 1.9; part # is 91352-SD4-000

Good luck.

 

[RoNSX]

Leak

The leak is clearly from the opposite end of the bleed bolt, on the hydraulic press side (accordian). No leakage from where the hydraulic hose connects to the slave cylinder.

 

[D'Ecosse]

Re: Leak

The leak is clearly from the opposite end of the bleed bolt, on the hydraulic press side (accordian).

Sorry - misunderstood your previous description - that sure sounded like the supply connection!
I suspect that perhaps you didn't get the rod engaged properly on the clutch-actuating lever and popped the piston all the way to the end (it was potentially bleeding correctly but that first time you tried pressure after you closed the valve, just pushed the rod all the way with nothing to restrict it).
I know that was the "fiddly" part of the job - its kind of awkward to engage that.
Here's my note from the previous thread:

I removed the entire rubber boot assembly surrounding the clutch lever at the same time, so it all came off in one piece. I also took the trouble to pump some fluid through the lines at this stage until it ran clear before going any further.
During re-assembly, it is easier to slip the boot over the piston rod, then line the rod up with the cup in the lever before securing the bolts for the slave; then re-install the rubber boot (like a grommet) after you are certain the piston rod is seated correctly. Don't install the fluid line until after this step as you will need to compress the rod against the internal spring in the cylinder as you line it up with the cup & the bolt-holes.

 

[RoNSX]

Removal of Rubber Boot Assembly

I thought about removing rubber boot, but wasn't sure how it was attached, and if I could reattach it once removed. How did you do this?

I agree that would make it easier to align the coupling.

Your diagnosis of an over extended piston sounds logical and consistent with what I experienced.

I have ordered a replacement unit. Mike at Niello also suggested that piston may have over extended.

Am I understanding correctly that an over extended piston can be repaired by simply reinserting it?

 

[D'Ecosse]

Re: Removal of Rubber Boot Assembly

I thought about removing rubber boot, but wasn't sure how it was attached, and if I could reattach it once removed. How did you do this?

Just pull it out - it's literally just like a grommet.

Am I understanding correctly that an over extended piston can be repaired by simply reinserting it?

Sure! As long as the seal didn't get damaged & that is doubtful.

 

[jsample]

call my shop and ill help you over the phone. bleeding it can be hard.
jerry 858 569 0693

 

[MJK]

Re: Did I Do Something Wrong?

Received new Slave cylinder. Installed as follows.

Unbolted old slave cylinder from frame, leaving hydraulic hose attached.

Bolted new slave cylinder to frame. Had to put some pressure on part to hold in place while I bolted it. Most resistence came from within the "pipe."

After slave was securely on frame I removed hydraulic hose from old slave and bolted on to new slave.

Bled system.

When I finally got some pedal pressure (probably cycled about 40 pumps of clutch pedal) it lasted from only a moment and then pedal dropped to floor again. When I inspected slave I found hydraulic fluid was leaking out of the side opposite the bleeder bolt (the portion that inserts into the pipe).

Did I receive a defective slave cylinder or was there something wrong with the process I used to install it? I had considered bleeding the system before attaching the slave cylinder to the frame. Would anyone recommend this procedure? Any suggestions?

I know it is too late for this to be of any value to the original poster, but this happened to me today as well.
If you don't get the tip opposite the bleeder value seated in the dimple on the clutch actuation arm (a metal rod inside the rubber boot attached to the translmission) then when you try to pressurize the system the piston pops out the end allowing brake fluid to fill that accordian shaped grommet and eventually go everywhere.

To fix it, I took off the shift linkage (grey plastic) covers for better access and removed the slave. I also used a ziplock + rubber band on the fluid hose to keep even more fluid from going everywhere.

From there, pull the slave apart per the Canadian (?) instruction in the service manual. Regrease and reinstall the pistion, then the boot. Put some more greas around the ring on the transmission rubber boot, and in the dimple on the clutch actuation arm. Slide the slave in again, and be careful to get the alignment right this time. You can feel by squeezing the rubber boots or by sticking your fingers through the slots on the bottom of the now outer boot (mounted to the transmission housing). The push rod be seated might in the dimple in the metal clutch actuation arm.

From there, just reassemble the linkage cover, rebleed the system and you should be good to go. Be sure you clean as you reassemble that way there is no doubt where any brake fluid that drips after reassembly came from.

 

[ATERPAK]

For those of you who have been having problems with clutch hoses which start to leak I've finally have a perfect solution for that. I've replaced all the pieces involved and gone with a AN quality stainless steel line and two fittings. The one at the hard steel line is an adapter for the stainless line and I've had a local machine shop make a custom fitting which goes into the slave cylinder just like the stock unit. This fitting has been tested and works like a charm.

The whole assembly should take care of any possible leakage problems you might get from an old hose. The nice thing about this setup, is that it should last the lifetime of the car and it definitely is the way to go if you have an aftermarket heavy duty clutch. I will have a picture of this installed on my car to show you what it looks like in the very near future.

Currently it cost $75 from the dealer for a stock hose. Our clutch hose will sell for $85 which includes shipping and handling and we will gaurantee it for a one full year. I expect to to be able to ship within the next week.

 

[juejaimon]

Does anyone know what the part # is for the reservoir hose item called out as #20 in the diagram?

I'm thinking of replacing this 12 year old hose since i'll be replacing the clutch master cylinder. Can anyone confirm if this hose get pressurized during a clutch movment?.. or is it a "one way" feed to the master cylinder only because the master cylinder does not allow fluid to return to the reservoir?

TIA

Sounds like you lost the o-ring at the connection between hose & cylinder; or maybe tweeked it or something? Maybe that was even your problem to begin with!

#27 in the exploded diagram below - remove it if its still there & see if it looks OK

Tip- If you don't want to lose all the fluid, pinch off the hose by clamping on a pair of vise grips during removal/re-installation

edit: o-ring is 8.8 x 1.9; part # is 91352-SD4-000

Good luck.

 

[D'Ecosse]

Does anyone know what the part # is for the reservoir hose item called out as #20 in the diagram?

46971-SL0-A01

In case you need any more ..........

 

[lowellhigh79]

I believe the round dampener (#24 in diagram) is leaking and needs replacement. Happened to me once. You can't simply put it back together by hand as one stroke and it all comes back out. It was hard to change out with the car on jacks. Good luck.

 

[juejaimon]

46971-SL0-A01

In case you need any more ..........

Ken- thanks for helping me out yet once again! I was one nsxsc and tried looking up the part but the description did not go past #18

anyhow... thanks again!... hopefully i'll get off work early today.. and have time to pick this part up.

 

[tucsonsx]

call my shop and ill help you over the phone. bleeding it can be hard.
jerry 858 569 0693

I use vacuum pump and found that bleeding can indeed be hard - I just barely open the bleeder and am really careful to keep the resevoir full. Pumping the pedal a few times after you start to get some pedal seems to help also. It can take awhile - Good Luck!

 

[ATERPAK]

Well for all who want to replace their clutch hose with some better and at the same price as stock, then check into my stainless steel wrapped teflon replacement hose for the clutch. Fits just like the stock except the hose will not expand and is made of the same material they use for the brakes. See my complete description with picutures in the vendor section. Price is $80 which includes priority shippping. The kit is complete and comes with instructions.