Bleeding XK-140 brakes

I have installed rebuilt master and wheel cylinders in a 1956 XK140 DHC. The system is now closed, full of fluid but I can not get a hard pedal after sequentially bleeding all 4 wheels multiple times. Is it necessary to pressure bleed this car’s brakes?
I have gone around 5 times now and get no air bubbles out of any of the bleed nipples. I did not bench bleed the master cylinder.
Thanks, Mike Moore
56 140 DHC

Did you do the bleeder with tube into a can of brake fluid?

Hi Mike:

I just changed the brake fluid on my 1953 XK120 on the weekend and one of the things I did after bleeding unsuccessfully initially was to adjust the pedal push rod to reduce the clearance prior to it engaging the piston in the master cylinder. I have the tandem master cylinder with the segmented fluid reservoir and one thing one has to watch is that you do not let the fluid level go down too low in one compartment (don’t ask me how I know!). After the push rod adjustment and a re-bleed (just using the rubber bleed tube and a jar) keeping both the reservoir compartments topped up I achieved a nice, firm pedal.

Chris.

Chris, this is good info. Can you please look at the photo of the master cylinder Rob Reilly posted and confirm that is the cylinder you have? The car is not at my home and is a few miles away so I can’t look, but is the adjustment you made a threaded clevis of some sort? Thanks! Mike Moore

Mostly the same. I have an old pickle jar with a hole in the lid, through which an piece of rigid brake line with an “L” at the bottom passes through and is stitched to the lid with some wire going through a pattern of holes. A bleeder hose attaches to the upper end of the piece of brake tubing. The pickle jar is wide and not as easy to tip over. I do not understand the physics of how I can have no air bubble out of any of the 4 bleeders, move the shoes out when pressing the pedal, but still no pedal.

Sounds like an air bubble trapped in the master: When faced with that, I used rapid and full, deep strokes bleeding, doing a pump up, stop, releaseb bleeder, hold down, close bleeder, then repeat.

It takes two people.

Chris has this type which is called tandem.


Here you can see the Bleeding Valve marked X and Y in the upper picture.

You should have one in your single system master in the output connection.
Here it is marked B and C.


If the rubber washer A and rubber cup C are in good condition, and the tiny hole X is clear, brake bleeding with the jar should be an easy one man job.

OK, that goes on my list to do next. Thanks Paul. I have a pressure bleeder which I will try secondly.

Thanks Rob for the info. These cylinders all sleeved and rebuilt by Apple Hydraulics, so I am sure the innards are fine. You may see elsewhere I asked about thread size and that that my RR banjo bolt was threaded crooked. The machine shop commented that the rebuilder “missed the thread start” when he chased the threads. I don’t think that was what happened. I was extraordinarily cautious today when I installed the wheel cylinder and the banjo bolt. I watched as best I could to make sure I didn’t get the rubber boot caught beneath the banjo when I tightened it up and I noticed the banjo was slightly twisted in such a way that the banjo sealing surfaces were not parallel with the seating surface on the wheel cylinder. It was probably impossible to start the bolt straight in that condition. I (all by myself, and with no assistance from anyone), more than likely started the bolt slightly cocked.I used my large Crescent wrench and was able (with some difficulty) to remove the twist and it is now sealed well.

With the system all closed what happens if you pump the pedal a few times fairly rapidly ? Do you get any sort of pressure at the pedal?

Would I be correct in assuming that these are drum brakes? Are they adjusted up correctly?

Yes, although they must be manually adjusted on the rear. I believe what is happening is the shoes are expanding as they should whenever we push the pedal and as they do, they tend to center themselves properly which provides more clearance which I have taken up. Front drums are auto adjust.

I haven’t tried that. In fact the owner has been manning the brake pedal,

Hi Mike:

Yes, as Rob has stated, I have the tandem cylinder he shows. The adjustment is on the rod that goes into the rubber boot at the firewall end of the cylinder with a clevis attaching same to the pedal , there is a large adjusting nut and a smaller locking nut. I found that by sliding the boot off the cylinder and putting my left hand index finger on the rod while activating the pedal with my right hand (helps to be a contortionist) you can feel the clearance. Turning the large nut clockwise (towards the cylinder) decreases clearance, anti-clockwise increases. Bear in mind this is on a 120, not sure what the set up is on a 140. When the owner pumps the pedal can you rotate any of the wheels with the pedal depressed?

Chris.

I have now spent a couple of days trying to bleed the brakes on this XK-140 with newly sleeved cylinders by Apple Hydraulics. I have followed all the suggestions offered to date and still am not satisfied with the brake pedal. Lloyd Nolan drove up from Carmel today and helped me pressure bleed the brakes, but there is still something wrong.
We pressure bled the system using 16 psi air. We started at the right rear and bled fluid into a jar with a liquid seal until there were no bubbles. We pumped the brake pedal while the system was pressurized but just got more fluid generally. I adjusted the rear brakes until they were slighly dragging. We then realize the front brakes spun too freely, and despite the self-adjusting feature apparently were not self-adjusting I manually clicked the adjuster one step at a time and reinstalled the drums, pushed down on the pedal, clicked up another step until the drum was slightly dragging, Still no joy. The shoes are operating on all 4 wheels, and we can lock the wheel tight enough to allow me to tighten the nuts which hold the drums on without the drum slipping. I would appreciate any suggestions. I also did as Wiggy suggested and had the brakes pumped rapidly to a high pedal and then open the bleeder screw. No joy there either,
Thanks, Mike Moore

Hello
I do not know anything about XK 140 brakes but I had a similar problem with the brakes on a Healey 100 with a four stud rear end. I pumped seven litres of fluid through the system trying to get a good pedal, all to no avail. In the end out of frustration I talked to an old Healey chap who said that on the rear slave cyclinders the bleed screw was below the rubber cup & air was trapped under the cup. To rectify the problem you took off the brake shoes removed the piston from the slave cyclinder & then gently pushed down on one side of the rubber cup so the the other side rose up & the trapped air could escape. You then gently re-positioned the cup in the cyclinder so as not to trap any air under the cup. Bingo good pedal.

As I said I know nothing about 140 brakes & I would have thought that if Jags had the same problem as Healeys then someone on this forum would be aware of this remedy.

Cheers Peter

Probably not much help, but just to say that when I bleed drum brakes (e.g. my old Series IIA Landie) I adjust all the shoes up tight to the drums before bleeding. There’s no need for them to move during the bleeding process. Adjusting them up tight should speed up the process significantly as you’re not wasting pedal movement in moving the shoes. I never trust ‘self-adjusters’ but turn the ratchet up by spanner. Another old Landie trick is to fill the reservoir, fit a bleed tube into the jar and then crack the bleed nipple a half turn. Go away and have a cup of tea, sit in the sun, whatever. When you return there should be a steady, slow drip from the bleed nipple.
Roger

Have you checked that your hole X in the master cylinder is clear? Apple Hydraulics may not be aware of this hole, or didn’t notice if it was full of crud. It is very tiny.

Rob, if it were blocked upon, would I be getting fluid through the cylinder and even braking action I do have (even though unsatisfactory)?

Thanks Roger, on the rears I can do that, but the fronts with the self adjusters, there is no obvious way to adjust the brakes with the drum installed. And with the dry system we started with, there is no way to move the expanders out without fluid in the system, but even then, the self-adjusters are not adjusting. I have to remove the drum and force the shoes out one “click” at a time, install drum, press brake pedal a few times, see if the brakes are dragging yet and if not, remove drum, and repeat one click at a time.