• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

New clutch master - the expected bleeding nightmare has arrived

Share this page

RickB

RickB

Yoda
Offline
All right you geniuses and gurus out there, I know bleeding the clutch can be a nightmare and due to my old master acting up I went ahead and ordered and replaced my master cylinder.

I've just spent the past couple hours trying to bleed it.

I have clear tubing going from the slave back up to the master so the bubbles and fluid recirculate.

I have pumped and pumped and no longer have any air bubbles.

Yet when I tighten the bleeder I have no pedal at all.

I have repeated this several times now with the same result.

Oh and it's raining and 45 degrees F and I was soaked so I gave up until the weather breaks.

Hints, clues, stories? Anything?

I did bench bleed the master before starting this process.

Have heard some have success disconnecting the master and getting it higher than any bend in the tubing and bleeding by hand, I will try that if it might work.
 
There may be air in the slave. Did you bleed it with the slave cylinder clamped "in"?
 
yes, I didn't do anything to the slave except open the bleeder
 
Try pulling some suction on the slave itself. I had a great deal of problems getting Bugsy's slave to get fluid. I solved it by pulling vacumn of the slave itself and pumping and all of the bubbles went away. Been good for last 10 years. When I removed the CLutch Master and Brake Master several weeks ago to replace the Brake Master, replace fluid in both, Clutch was simple. a few pumps and old fluid pumped out and new clean fluid was bled out. Sometimes it's easy and sometimes a PITA.
 
I guess I'd do a search here. I had a LOT of suggestions when I went through this last fall... with about 5 major ways to do this (including installing a permanent bleed tube to above the master). I just patiently kept at it (though I did acquire a syringe as a method to shoot fluid backward from the slave). There is a method where you pump the fluid from the reservoir (fashioning a rubber tire and a air compressor). Anyway, a search will turn up all these methods (possibly in the thread I started).
 
Ok, BillM sent me a message that I have to extend the slave pushrod all the way in before I start bleeding.
I've got a "special" setup.
 
I called Bill M. this morning after trying and failing some more.
According to Bill I needed to get a bike tire pump and a long piece of tubing.
Then hang the end of the tubing up as far as possible and pump until the fluid was up to the top.
Then using the tire pump force the fluid back through the slave and up into the master reservoir.
If I did it right I'd see bubbles in the reservoir.
So I did this several times, saw bubbles, then after there were no more bubbles I got Peter out to help me with the good old:
"Down" he pushes the pedal down and holds it while I open the bleeder to let out bubbles and then close the bleeder
"Up" He lets the pedal up
"Down" he pushes the pedal down and holds it while I open the bleeder to let out bubbles and then close the bleeder
"Up" He lets the pedal up
"Down"
And repeat until... It worked!!

Now my clutch feels and acts better than ever before!
 
woo hoo! get out there and drive!
 
Rick,

This doesn't make sense. "have to extend the slave pushrod all the way in" Sounds like pushing in slave pushrod opens up room for fluid to fill in behind pushrod or something like that. Feeding fluid backwards in effect backflushed with fluid from the bottom up allowing air to get out of the line. Then going to conventional Push pedal, open valve, close valve, release pedal allowed you to get it finallly working.
 
Yes, the rod was already all the way into the slave anyway due to the pressure of the springs.
It's the second advice that worked for me.
Seeing a huge bunch of bubbles in the reservoir the first time I did this convinced me, then there were less and less bubbles each time until there were none.
The slave still had a bit of air so that needed a little conventional bleeding at the end.
The way this new master feels shows me just how far gone my old one was!
 
Rick, I'm curious, Are you using a BMC or Datsun slave?

Kurt.
 
It's a Datsun B210 slave.
Bill's idea.
I'm not sure of his reasoning for using this one, but in general I trust Bill's reasoning.
 
I wouldn't trust that guy! :smile:
It is the slave to the B210 5-speed only. Works pretty well.
BillM
 
It works great! Think I should adjust it though as right now it's releasing a bit too close to the top for my liking.
I'll turn the rod out a little ways and see if I like the feel better.
 
Adjusted this evening, feels just right now!
 
I see I'm a bit late to this thread, but perhaps this tip will help someone. I had the same trouble some months back filling a dry clutch system. Friends told me it was because the 1/4" diameter of the clutch line (as opposed to 3/16" for the brakes) makes it much easier for the bubbles to rise from the slave cylinder back into the lines in between pedal strokes. They loaned me a small bottle with a magnet and about 3' of clear plastic line ending in a rubber cone that is supposed to be jammed into the hole where the bleeder was removed. I was told to mount the bottle higher than the master cylinder and assured the device would have the clutch system air-free in 6 pumps.

Well it wasn't quite THAT easy, but the concept certainly worked. I didn't remove the bleeder & use the cone, instead I just put some hardware-store tubing on the bleeder nipple and opened it a couple of flats. You'll want to open the bleeder just enough that fluid can easily escape under light pressure, but you don't want it so loose that it is easy to suck air around the bleeder on the pedal upstroke. You want the master cylinder to suck more fluid around its cup seal more easily than the bleeder can suck in air.

I sat in the car and pumped the pedal, and the best part was I could actually SEE the air bubbles come out of the slave cylinder, up the tube and into the bottle, and since the tubing was clear I could also see that the fluid wasn't reversing back into the slave cylinder on the upstroke. It was 10 or 12 strokes to make sure the bubbles were gone, then tighten the bleeder, job done.

I thought this was so cool that I immediately used the little bottle on all 4 wheel cylinders just to make sure there was no air there either - there wasn't any, but it's nice to be sure.

I don't know who made this little bottle system but all you really need is a few feet of clear tubing from a hardware store and a clear bottle you can mount somewhere high & visible. Run the tubing from the bleeder to the bottom of the bottle, crack open the bleeder and pump the pedal. If it's taking any appreciable force, crack the bleeder a tiny bit more. Remember the best part is you can see the fluid flow.

Glad to hear you got the system bled, we all manage to get it working eventually.
Andy
 
Back
Top