Need help bleeding clutch please

[Citka]

I recently pulled the motor to do a new SOS clutch, timing belt service and general clean-up of an otherwise dirty engine and engine bay (on my 1991).

While I was in there, I replaced the clutch slave line with the braided steel unit, also from SOS. I’m having a bear of a time bleeding the clutch hydraulic system. I’ve run about a quart of DOT 3 through it (capacity is probably about ½ cup), but the pedal is still going straight to the floor with absolutely no resistance, and I have to raise it back up with my toe to return it to the “up” position. No signs of leaks anywhere and the fluid coming out of the bleed screw is clear and free from any air bubbles.

My slave is installed against the throw-out fork as it should be. No lines other than the slave line was disturbed.

What am I doing wrong?

 

[shawn110975]

you need to make sure the cap/lid is on after you fill it its a sealed system needs to build up the initial pressure.

make sure the slave is only finger tight

pump it about 30 times with your hands I normally do it very fast while someone is watching the bleed valve squirt when every pump of your hand there should be no bubbles it should look like blobs of pure fluid coming out when you see the blobs of pure finger tight the bleed valve.

check the front fill it again, put cap back on, then pump the clutch by hand it should then start to get hard to push yipppeee.

then go back to the bleed valve and turn in for a split second just to let the last of the bubbles out and you done.

hope this helps just did one 2 days again at a customers house

 

[Citka]

Thank you very much. I didn't have the cap on the reservoir (just setting on it the top, not screwed down). I'll give that a go tonight.

When you do the "pump it about 30 times by hand," are you having someone open the bleed valve when pushing the pedal down, and closing it when the pedal comes up as you normally would when bleeding brakes?

I also have a back bleeding tool, would you suggest back bleeding it?

 

[scammy]

It also can help to have the rear of the car higher than the front

 

[warrenw]

The clutch is self bleeding. I have done this a couple of times my self. Fill the reservoir. Open the bleed screw on the slave with a small hose to a catch bottle. Wait for the fluid to flow. You can help with some pedal pumps. Use your hand so you can return the pedal back up in between pumps. Keep an eye on the reservoir fluid level.
Once you have the bulk of the air out of the system, you will know it, because the fluid will just run out of the open bleed screw on the slave, you will probably have trouble keeping up filling the reservoir as it will flow out the slave at a rapid rate, even without pedal action. This is due to a syphoning action, and the fluid will be drawn out naturally. Once you think you have the bulk of the air out, close the bleed screw, and operate the clutch about 200 times, any left over air bubbles will naturally flow up to the reservoir as the clutch will self bleed.

 

[Citka]

Thanks to all for the advice. I'm going to give to another shot this evening. Silly that with all the work I did, something as simple as this is keeping it from going back on the road.

 

[Larry Bastanza]

There is no need to have the cap on, what you need to be sure of is that the reservoir is always full, check every five pumps. What are you using to bleed it?

 

[buckeyensx]

I am having a similar problem as the OP. My buddy (fellow NSX owner) and I tried to bleed the clutch today as a purely maintenance measure and now my clutch pedal is on the floor and I have to lift it by hand. When I pump the clutch pedal by hand with the bleed valve open, I am not getting any fluid. At first, I was getting fluid and air bubbles but now nothing seems to be coming out of the bleed valve. I used a vacuum bleeder and at first and we were able to pull new clean fluid through the system. I am stuck and would appreciate any help.

 

[tucsonsx]

Just do what warrenw says in the post above - the clutch hydraulics are indeed self-bleeding - PITA

 

[Larry Bastanza]

The alternative here is to go to the autoparts store and buy a "One Man" bleeder valve. The is a one way check valve with a hose you attach to the bleeder valve. Open the bleeder valve, and pump the clutch pedal by hand. Check at least every 5 pumps that the reservoir is full. The key here is when you raise the clutch pedal you must stop air from being sucked back in through the bleeder valve on the slave. The check valve will only let fluid out, and no air in.

https://www.youtube.com/watch?v=oUdLxUtukjU

This is a pic of one system. BTW, I DO NOT EVER pump the BRAKE as in the video showing the bleeder, that can ruin your brake master, however the clutch master will not fail using this method.

HTH,
LarryB

 

[Kaz-kzukNA1]

If you let the air into the master cyl by leaving the reservoir empty while the hyd system opened, you have created air pocket in the line.
Once this is done, you are just pushing the air back and forth inside the hyd line with your CL pedal stroke and you will never get the fresh fluid at the bleeder until you can prime the master cyl.

First, close the bleeder and fill up the reservoir.

Operate the CL pedal with your hand and if you can feel some resistance before hitting the floor, you didn’t let too much air in the system so skip the next steps and just carry on with the standard bleeding method as others mentioned.

If no resistance even with the bleeder closed, you have too much air in the system so carry on with the followings.
Pinch the feed hose from the reservoir to the master cyl many times with your finger. You can also shake/vibrate the feed hose to let the bubbles back to the reservoir.
It will also help by tapping on the master cyl body with soft mallet gently many times.
During this process, you should see small bubbles coming up through the hose back to the reservoir.

Once no more bubbles are coming up to the reservoir, top it up and close the lid/cap. This is very important before going to the next step.

Now get inside the cabin and lift up and down the CL pedal with your hand many times.
Every time when you are going to lift the CL pedal, try to flip it up in fast action.
This will create big vibration behind the master cyl in order to prime it further.
Closing the cap before this process is very important because the vibration is so big that it will splash the fluid everywhere without the cap.
(By the way, there is no need to close the cap for bleeding purpose. It's not a closed system. In fact, there is a tiny hole behind the cap to let the air in and out of the reservoir to compensate for the expansion/contraction of the parts/fluid as well as the release fork movement change.)
Repeat this many times until you start feeling some resistance at the CL pedal when pressing down to the floor.

From here, you can start the standard bleeding process by opening the bleeder.

The key is to prime the master cyl before opening the bleeder.

I just use pressure bleeding if in a hurry.


Kaz

 

[buckeyensx]

Thanks for the advice. I appreciate it! Going to get back after it in the next couple of days.