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MG MGA - Air in Clutch line

Problem #2: Air in clutch line.....I think

Like most everyone else who has replaced the clutch slave on an MGA, getting the air out when bleeding it presents a problem....for most of us anyway! I read a thread that suggested slaving a tube between the right brake caliper and the clutch slave cylinder and, depressing the brake, back bleed the clutch. Did it! Worked great! Since I've had problem with the ignition, I haven't had need to use the clutch. Just to make sure at least the clutch was still behaving, I push down on the pedal with my hand clutch. It was as if I never bled it out to begin with. Now, no signs of fluid leaking anywhere! Still topped with fluid. How can it be that I have clutch and then not without use? Any thoughts. Thanks!


Robert Maupin

I found the most successful method was to remove the clevis pin at the slave and compress the piston. Then use a large plastic syringe to force fluid through the bleed nipple and back bleed that way.

I bled mine many times before I finally declared's a real bear.

I'd say that a bubble is still entrained in your system, or maybe some small bubbles have now become one big bubble in the slave cylinder.

Other thought is that your rubber in the M/C is shot. I had this happen also on the brake side - pedal to the floor, no bleeding possible. Turned out that the skirt on the piston rubber had cracked off - on a new part from Moss. Ordered a new one (again from Moss) and no problems since rebuilding it again.

Before messing around a lot, I would pop the M/C apart and check the rubber pieces.

I used DOT 5 (at the risk of starting a flame war) and I am glad I did given the amount of paint I would have surely removed by now!

AJ Mail

Robert, I bleed the clutch hydraulics by removing the clevis pin on the slave as Jim says, and then push the slave piston in slowly by hand two or three times, and that's it. No mess, no topping up, no fuss. Works on my car anyway!
P.S. I have never been able to bleed the clutch on the MGA the conventional way.
Lindsay Sampford

I bought a gunsun presure bleeder and it works very well, Vin
Vin Rafter

I used the gunson Easibleed like Vin - but it did take 3 or 4 goes to get it right. Nice photo of you in The MGCC Safety Fast mag Vin!!
Cam Cunningham

I also have used the Easy Bleed. The last 2 times I have done this on the MGA and MGB I have filled the slave cyl with hydraulic fluid on the bench, and plugged the port with one of those plastic plug/ caps that is in a new cylinder. As I am mounting it on the car I remove the cap and quickly attach the flex line. I think it hepls in that the slave is almost completely full of fluid, so you don't have to use the master or Easy Bleed to pump enough fluid to fill the slave. Using that method and the Easy Bleed it literally only takes about 1 minute or less to bleed the air out.
I have read so much about this, especially on the MGB board. Even in the old days when I used the "kid" method (get one of your kids to pump the pedal!) I never had a problem. I personally would never use the line from the brake caliper. I can't see the wisdom of pumping possibly contaminated fluid into your new or rebuilt slave cylinder, and it should never be necessary.
Just my opinion.


Thanks for the input guys!

Ralph: Since the fluid for both the brakes and clutch come from the same reservior, the issue of contamined fluid is well...not an issue. By using the brake line, it back-flushes the clutch and instead of trying to force the air down the line via the reservior, you're pushing the air the way it perfers to go...up the line.

Robert Maupin

At the time I was thinking of an MGB, which has a seperate Brake and Clutch MC. However even on an A the same fluid stays in the caliper, so unless you have very recently flushed clean fluid through, there will most likely be thr usual dark dirt(worn rubber seals?) and rust. Even if you have flushed it there could still be some. My thought if it won't bleed from the top down, there is most likely a problem, and the back bleed will be a temporary fix. I'm not sure about newer cars, but pretty well the entire automotive world bleeds from the MC downward. It's an imaginative idea, but I think it is masking another problem.


This thread was discussed between 06/07/2011 and 07/07/2011

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