• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Slave cylinder rebuild...

Share this page

ronzet

ronzet

Jedi Knight
Offline
I have run out of techniques to remove the piston from the rear brake slaves on my MGA...

I have soaked in liquid wrench, tapped the side with a ball-peen, used my compressor at 130 psi....

I should just buy a new one, but this is the only cylinder that won't budge... I have rebuilt ALL of the others successfully... I am not ready to give up the ghost on this one...

Any suggestions??? /ubbthreads/images/graemlins/rolleyes.gif

/ubbthreads/images/graemlins/cheers.gif
 
several things to try. Heat the cylinder up quite hot with a propane torch (make sure the feed hole is not blocked - don't ask how I know that this is important). You have nothing to loose by heating the cylinder and it may loosen the piston. Use a drift punch and pound the piston down in the cylinder to break the corrosion loose. Finally, make up an adapter for a grease gun to feed hole and pump grease into the cylinder with the grease gun. This will puild up a tremendous amount of hydraulic pressure on the back of the piston. It's best to do this after heating and pounding the piston back into the cylinder. Hindsight, but compressed air is not the best thing to use to get a piston out of a frozen cylinder. First the pressure is limited and second, if the piston does break loose with the compressed air, it becomes a destructive projectile in your work space, often bouncing off many things you don't want damaged, including your body. Hydraulic pressure drops to zero as soon as something gives, things don't become projectiles when using that.
Good luck,
 
David,

1 -- yes, pray tell the story...

2 - If you face the cylinder down on the workbench then you get a lovely 'thunk' when it does break loose...

3 -- Great ideas... Would have saved me quite a bit of work on the other ones if I had emplyed these techniques...

Consider them now in my portfolio of tricks... Thanks...
 
A note though... Rather than using a drift punch, a deep socket with the same OD as the ID of the cylinder will cause less damage to the face of the piston....

Thanks again
 
The grease injection method works really well. I used it to free the slave cyl piston on the '56 MGA. Many years ago I attempted to use compressed air to free a wheel cylinder piston. When the piston broke loose with 150 lbs of air behind it, it shot out of the cylinder and destroyed the fluorescent lamp fixture above the workbench. I was picking tiny bits of broken glass out of me, the workbench the car, for weeks afterwards. Grease is best. It pressurizes and lubricates at the same time.
 
Sooo, what fitting do I use for the grease gun approach??? OR from what do I create the fitting???
 
Ron - For the cylinders on a TD, I used a 5/26 BSF bolt, but I don't know what the threads are onthe cylinder for a MGA. If a standard SAE bolt doesn't fit, then it will probably be a BSF thread. You will need the proper bolt and then drill a 1/8" hole lengthwise through it. Drill and tap the hole at the head to fit a standard grease fitting. That's about all there is to it.

My experience with a TD cylinder that I heated with the feed hole blocked was about the same as Bruce's was with 150 psi air, except I missed the floresent fixture. I do have an ugly black mark on the overhead (right next to the fixture) as a reminder not to do stupid things again.
Cheers,
 
Gentlemen... A quick update....

Thanks for your suggestions... I heated up the slaves last night and was able to easily remove the pistons.. although I did use my compressor, wearing body armor of course, to push trhe pistons out...

Slaves are now rebuilt and I am on the to the next item on the list....

I used the same heating technique for the clutch slave.... to no avail... this one is just too far gone....

Thanks again.

/ubbthreads/images/graemlins/cheers.gif
 
Back
Top