Can someone tell me the right procedure to avoid the sticking drums.
These are according the documents self adjusting.
My brake cylinders/ hoses are new. Same for self adjuster bars. Shoes aren’t worn according to me.
But I didn’t succeed in free-running drums.
Have you checked that you have free play in the pedal when not depressed? I note that the system needs to depressurize and this only happens with freeplay.
Did you rebuild the front brakes or have you otherwise checked the functioning of the self-adjusting mechanism?
Apparently your brake shoes can’t move back after the brake pedal pressure has been released.
This system is well described in detail on this site, including the “pads”, the correct pressure from the nuts, the right direction of the teeth, simple corrosion, etc.
It’s worthwhile to have a look at what has been written by others on the subject. I learned a lot from other peoples efforts and experience.
Mine are working perfectly (although on a later XK 120 but are identical to yours). See pic.
I think we need a bit more info here: are the brake shoes “used” in the sense they have run on the car BEFORE the other parts were renewed? IF they are new or relined, I’ve seen a problem with the lining material being too thick to allow enough clearance between the shoe lining and the drum even with the wheel cylinders fully retracted.
Assuming that is NOT the issue, then I think Luis’ suggestion should be investigated fully because even if the friction pads were improperly adjusted, that would only cause a “long pedal” as opposed to a brake drag situation…the adjuster bar is designed with a built-in clearance due to the oversized hole at it’s anchor end.
A common problem is the brake line to the wheel cylinder. They deteriorate and block the return of fluid.
Thanks all for the response. The XK140 FHC is new for me. I owned the car now for 2 weeks.
I ordered direct a workshop manual at SNG Barret. But still not avavilable …
The brake cylinders front & rear are new. Flexible hoses as well. Shoes aren’t renewed.
So I’m still have some questions about the brakes.
Are the self_adjuster_bars correctly placed? Because when I look at the picture of Bob the self_adjusters are placed opposite compared to my adjusters when I removed the drums. So I placed the new adjusters in the same position (see attached picture).
Or does it make any differences.
I need to slacken the #11 nut so far that I can’t place the #12 split pin anymore. Initially I turned the #11 nut so far that I can place the split pin. But this results in that the friction was so high that the brakepiston
wasn’t able to move the shoes.
After cleaning the drums and bleed the system again. The front brakes are more or less working. Although the free pedal play is high according to me. The rear brakes doesn’t work. Need to look at that. B.t.w. What is the right sequence for bleeding a single brake system? I did the bleeding starting with front left, front right, rear left, rear right. Is that correct?
The free pedal movement is still much according to me. Probably the rear brakes or still air in the system.
Just a note of interest, Harrie. Mine is a December ‘53 production XK120 and features the same front and rear brake arrangement as your car but with the tandem master cylinder. I’d done a complete brake system rebuild with everything new with the exception of the four original front wheel cylinders, which I kitted.
I had excessive free play in the pedal despite having set the m/c pushrod at the recommended 1/32” and multiple attempts at bleeding. The pedal was also soft and slowing the car required excessive force. I did a simulated panic stop and determined the car was pulling to the right.
It turned out to be two separate yet related issues. Pulling to the right was traced to a slightly leaking left front lower wheel cylinder. I replaced the defective wheel cylinder with a new one, after which I could get the brake drum back on only with considerable effort, even after having relieved the auto adjustment fully. Even then I couldn’t get the wheel to rotate.
I removed the brake drum and new wheel cylinder and calipered the fully compressed distance between the notch in the piston and the base and found it to be a full 0.100” wider than the original
The difference was in the steel pad in the cylinder bases, the thicker one in the new cylinder causing the shoes to bind.
Cured by filing the replacement down. Reassembled the left front and bled the system again.
That move improved matters but pedal freeplay and braking effort were still excessive. Had to be air still retained in the system. After a few additional bleeds I got the tiniest stream of air bubbles out of the right rear wheel cylinder and that cured the problem. Firm pedal and reasonable braking effort (for a four-drum system without a booster, that is).
If all your components are new, verify the wheel cylinders are not pushing the shoes outward toward the drums excessively while in the resting position. And keep on bleeding as often as it takes. The brake lines in these cars are 1/4” ID as opposed to 3/16” ID in later cars, so are more of a challenge to clear.
Most recommendations say to start the furthest from the M/C when bleeding…RR, LR, RF, LF.
Your adjusters look fine to me as long as the hole at the end with the horse shoe clip is about 30 thousandths bigger than the pin it rides on…that clearance is what maintains the shoe-to-drum clearance adjustment.
If the wheel cylinders could not overcome the friction pads grip, it is probably because there is still air in the system…
Exactly right. After getting that tiny bit of air out of the RR there was none to be seen at the other three corners.
On my 140 I open the longest line (usually to the passenger side rear brake) and let the fluid drip from the bleeders then go to the other rear brake cylinders. Then I pressure bleed the rears. The fronts are done the same way. Make sure to top up the master cylinder every so often so you don;t introduce air into the system.
I put all new flex lines on mine when I rebuilt the drive line and with 2 weeks had a line problem with the symptoms you are experiencing.on my right front wheel. New doesn;t always mean it works as it should.
Just an update of my “brake-issue”.
This week I decided to replace the linings of the brake-shoes (front and rear).
My local brake-shop cleaned the front brake-drums.
After rebuild all components the front brakes are working better.
Only the rear brakes doesn’t run free after a firm brake. I release the hand-brake to minimum. That helps a bit.
The free-pedal play is still much according to me. What is usually the free-pedal play?
I hopped in the driver’s seat and applied the brake as my wife measured at the firewall. I have a half inch of pedal freeplay and the brakes are fully applied at 3 inches.
Idd here i would say about 20mm 2/3" and fullt depressed at max 50mm 2"
Is your handbrake well adjusted? It has a big impact on the pedal feel through the rear drums
Seems the fully applied distance in your case is quite a bit shorter than mine … I will need to check the handbrake adjustment as you suggest.