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clutch bleed

Last post 11-25-2009, 10:38 AM by Kiwimark. 25 replies.
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  •  09-16-2009, 6:03 AM 21071

    clutch bleed

    My old master cylnder on my 1979 MGB went dry due to a leak.  (Everything worked fine until I ran out of fluid last week.)  I replaced the master and slave cylinders and bled the lines with the help of an assistant.  The clutch pedal has tension on it, however, the clutch now catches about two inches off the floor.  In reading posts on the forum, someone said to "hold in the slave rod" while bleeding.  What are they talking about? You mean like physically push it in or mechanically with the clutch pedal to the floor?   Do I still have air in the lines? 

      Any help would be appreciated as I have bled and re-bled the lines 3 times already. I'm trying but not anywhere close to being a mechanic. --dan

  •  09-16-2009, 10:24 AM 21075 in reply to 21071

    Re: clutch bleed

    Cannot comment on whether or not you have air in the lines (as I am not a mechanic, either) but I did want to pass along a link to the MossTV clip that answers the first part of your post: http://www.youtube.com/watch?v=uj1dMdYgRK4&feature=player_embedded

    HTH

    -Mike

  •  09-16-2009, 2:44 PM 21082 in reply to 21075

    Re: clutch bleed

    Video makes sense.  I'll have to try it.  Especially since I found out that the slave cylinder ships with the bleed screw in the wrong hole.  I took the whole thing apart again, switched the screw and re-assembled.  My assistant was gone all day, so I'll have to wait to bleed.  (I feel like I'm bleeding with the project!)
  •  09-17-2009, 3:11 PM 21084 in reply to 21082

    Re: clutch bleed

    Bled the lines today.  Even pushed in the slave rod after I got the air out of the lines.  All I got was fluid.  Clutch still catches about 2 inches from the floor.  I don't understand it.  Like I said earlier, everything felt normal the last time I drove it last week until the fluid went dry.  What has changed? 
  •  09-19-2009, 3:53 AM 21094 in reply to 21071

    Re: clutch bleed

    For some reason this all sounds very familiar to me. It has been a while since I worked on this, but I have had this apart more than once. I think it would help if you gave a few more details. Oh, and it does not sound like air in the line to me. (unless the catch you describe is actually the point where the slave moves and you actually are just squeezing air until then, but you should easily tell if that is the case.)

    When you say 'it catches', is this a sort of 'catch' that you can push through, or does it completely stop?

    Is the clutch actually disengaging? (does it work?)

    did you feel this catch during the bleed process? or can you be sure it is not a linkage issue with the pedal (mechanical not involving the hydrolics).

    As far as someone saying to hold in the slave piston rod, I am thinking they mean to actually have someone push back on it while the bleed screw is open, to get any air pocket out of the cylinder. I dont know if you can do this while it is attached to the clutch. If you do disconnect it from the linkage, dont step on the pedal without the screw open or you will probably blow the piston out of the bore.

     

  •  09-19-2009, 6:40 AM 21096 in reply to 21094

    Re: clutch bleed

    Perhaps "catch" was a bad word choice.  I mean 'grab'.  The clutch grabs close to the floor.  I've only backup a couple of feet and went forward a couple of feet so far as I didn't want to get stuck out on the street with no clutch.  Maybe I should actually take it for a drive to see how it reacts. 

    As far as the "feel", I get resistance on the pedal about 2/3's of the way down.  The first 1/3 just the resistance of the spring.

  •  09-19-2009, 10:40 AM 21099 in reply to 21096

    Re: clutch bleed

    Took a drive aroung the block.  Seemed to shift smooth through all the gears.  I may be halucinating but the pedal even felt half way normal.  Maybe the magic air fairy sucked out the bubbles during the night.  I'll see how things go in the coming week and cross my fingers that it may be fixed.  Thanks to those who responded to my problem.
  •  09-20-2009, 4:03 AM 21105 in reply to 21071

    Re: clutch bleed

    My car (71mgb) also seems to engage/disengage kinda close to the 'floor' or end of travel. This becomes most noticeable when I drive a different manual shift car for a while, then get back into the B. I never really know if it is right or wrong, but after I drive it a few miles I get used to it. I also get the feeling that I have to keep the master filled almost to the brim. That may just be psycological on my part. I do not use the car often. I can remember a lot of times, I get in and feel like the clutch pedal is going to low, and i go check the fluid level. It is usually prety high and I still try to squeeze an extra half ounce into it. I had also changed the master and slave a few years ago (maybe like 10 years now). I switched over to silicone fluid at the time because of the paint damage from the prior leak.

    I only bother to mention it all because I would not mind if any other mgb owners can comment on their clutch pedal travel. Where I live, I have almost no other MG's to compare to. Does anyone else feel that the point where the clutch catches or engages/disengages is prety close to the end of pedal travel? ...or does anyone think that this is a sign of some problem?

  •  09-21-2009, 2:25 PM 21123 in reply to 21099

    Re: clutch bleed

    danoz,

    When you replaced the slave cylinder, did you loosen the hose, undo the bolts holding it to the bell housing, then unscrew the cylinder off the line?, and then reverse the process to remount the cylinder? If so, you may very well have ruined an old hose. This is a very common mistake, brought on by the fact that releasing the hose from the chassis is a painful process by comparison. The problem is that the hose often has to be twisted and distorted by the time the slave cylinder has been remounted. This twists up the inner tubing and eventually breaks or kinks it, hampering correct bleeding or operation.

    The correct method is to screw the hose firmly into the slave cylinder first, then mount it to one of the multiple positions allowed by the chassis mount such that there is no twist or stress placed on the hose. It's worth the extra ten minutes, believe me.


    Motorbill
    From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon
  •  09-25-2009, 8:14 AM 21172 in reply to 21123

    Re: clutch bleed

    Yeah, I couldn't get the slave hose off.  It didn't look bad so I left it on.  What is the procedure for getting that hose off.  There is no room for a wrench from underneath.  Do you remove from the top of the mounting?  Disconnect the metal tubing first?
  •  09-25-2009, 10:24 AM 21175 in reply to 21172

    Re: clutch bleed

    Yes,

    Disconnect the hard line from the fitting first. Then, I think you'll find that you can just sneak a wrench in there. It's not terribly difficult, though I wouldn't place it in the "rolling off a log" category. The bracket and keeper help quite a bit in holding the hose end. I'm sure you'll get it. Have fun.


    Motorbill
    From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon
  •  10-21-2009, 12:50 PM 21458 in reply to 21175

    Re: clutch bleed

    Back from all the family responsibilities in Florida.  Yippee!  First time grandpa.  Had some time so I figured I'd try the slave hose again.  After 3 hours I'm very frustrated.  Can't turn the bottom nut.  Can't turn the top nut.  Fitting seems to be welded to the top.  I'm afraid all I accomplished was to round out the edges on it.  Wrench seemed to fit, 7/16. 

     I do see a seepage on the hose.  I guess if fluid comes out, air must be getting in as well.  That is really a confined area.  What's next?

  •  10-21-2009, 4:27 PM 21465 in reply to 21458

    Re: clutch bleed

    Yes, these fittings can become stuck and difficult. The proper tool here is a flare nut wrench. It just barely fits over the hard line, and more fully "surrounds" the nut, engaging just about the whole thing. These also come as crowfoot type wrenches which will fit on the end of an extension and allow access where sometimes a full on flare nut wrench can't reach. Let's hope you have enough hex shape to engage one.

    In the worst case, you could always cut the line and get a new one. This is time consuming, but not expensive. Let me know how it's going. We'll get you through it. Take heart.


    Motorbill
    From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon
  •  10-22-2009, 8:25 AM 21469 in reply to 21465

    Re: clutch bleed

    A flare nut wrench eh!  I'll have to look into one of those.  Are you saying that I'd disconnect the top of the hard line at the master cylinder and slide the wrench down the pipe to the nut?  I'm wondering if the nut isn't really a 7/16ths.  I tried my 11mm wrench and it was a touch small.  I don't have a 12mm but would buy one if it were the proper size.  Since there is the limited access, at best I probably only rounded one side of the hex.  I guess I need to get to the tool store and see what the flare nut wrench is and the crowfoot.  Thanks for the tip.  I'm determined.
  •  10-22-2009, 8:46 AM 21470 in reply to 21469

    Re: clutch bleed

    No, the wrench is similar to a 6 point box end but with one flat cut out. That slips over the hose or pipe then down over the nut. It contacts 5 sides of the nut instead of just 2.

     


    Bayless
    Never express yourself more clearly than you can think
    '48 Prefect
    '67 Sprite (project)
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