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More brakes

To: <tigers@autox.team.net>
Subject: More brakes
From: Bob Palmer <rpalmer@ames.ucsd.edu>
Date: Mon, 29 May 2000 21:24:03 -0700
Listers,

As a result of a discourse on this topic between SL and me, it was noticed 
that a change in the bleeding procedure occurred between the WSM.143 and 
WSM.143.144 editions of the Rootes Manual. As long as the subject has been 
brought up, maybe I should give you the full nine yards.

The following is according to the Rootes Manual WSM.143/144 1st Re-issue.

Starting with the instructions for the recommended annual replacement of 
brake fluid on page 4 of Section K:

Renewing the brake fluid
The brake fluid in the hydraulic system must be renewed every twelve months.
1.  Pump the old fluid from the hydraulic system by slackening off the 
bleed screw furthest from the master cylinder 1/2 to 3/4 of a turn and when 
the fluid changes to air retighten the bleed screw. Proceed with the next 
furthest and finish at the bleed screw nearest the master cylinder in a 
similar manner. Discard all the old fluid.
2. Refill the master cylinder reservoir with the recommended brake fluid, 
se under 'Recommended Lubricants' Section P and bleed the hydraulic system 
of air, se under 'Bleeding the hydraulic system.'

The following procedure for bleeding the brake fluid is given on page 12 of 
Section K:

GENERAL
Great cleanliness is essential when dealing with any part of the hydraulic 
system and especially when the brake fluid is concerned. Dirty or aerated 
brake fluid must never be used in the hydraulic system.
Use only the recommended type of brake fluid for topping up the master 
cylinder reservoir

BLEEDING THE HYDRAULIC SYSTEM
Bleeding or expelling air from the hydraulic system is not a maintenance 
operation and will only be necessary when a portion of the hydraulic system 
has been disconnected or when the fluid level in the master cylinder 
reservoir has fallen so low that air has entered the system.

Always keep a careful check on the fluid level in the master cylinder 
reservoir during bleeding since it is most important that a high level of 
fluid is maintained. Should air enter the master cylinder from the 
reservoir, the complete operation must be repeated.
1. Destroy all vacuum in the servo unit by repeated operation of the brake 
pedal, otherwise difficulty will be experienced in completely expelling the 
air from the hydraulic system. Do NOT start the engine before bleeding the 
system has been completed.
2. Both brake shoe adjusters on the rear brakes are locked hard by rotating 
them clockwise, this reduces the fluid space in the wheel cylinder bodies.
3. Ensure that all hydraulic connections are secure and the master cylinder 
reservoir is filled with brake fluid, which must be kept at a high level 
during the complete operation.
4. Remove the rubber cap from the bleed screw of the left-hand front 
caliper, fit the bleed tube and immerse the free end of the bleed tube in a 
glass vessel containing a small quantity of brake fluid.
5. Slacken off the bleed screw ½ to ¾ of a turn and with the assistance of 
another person depress the brake pedal a succession of long and short rapid 
strokes, i.e. the pedal depressed through its full stroke followed by two 
or three short rapid strokes and then allowed to fly back to the stop with 
the foot removed , any floor covering that prevents the full pedal stroke 
must be removed. Actuate the brake pedal in this manner until the brake 
fluid entering the glass vessel is free from air bubbles and then 
re-tighten the bleed screw on the next downward stroke of the brake pedal 
to the tightening torque given in the " General Data Section."
6. Remove the bleed tube and glass vessel from the bleed screw and refit 
the rubber cap.
7. Repeat the previous three operations with the right hand caliper and 
finish with the wheel  cylinder of the left hand rear brake; the right hand 
wheel cylinder has no bleed screw.
8. Re-adjust the rear brakes, see under " Rear Brake Adjustment."
9. Top up the master cylinder reservoir to the correct level and refit the 
filler cap ensuring its seal is in good condition and its air vent is 
unobstructed, as the latter may cause pressure to build up and the brakes 
to bind

Bleed screws
The calipers and wheel cylinder have conical ended bleed screws which bed 
on to a seat formed in the bottom of the bleed screw tapping in the body of 
that particular component.

The bleed screws must never be over tightened since their threads may 
become stripped.     Use only short spanners of 4 to 5 in. (10 to 12-5 cm) 
in length to tighten bleed screws.

The torque loading is: 5 to 7.5 lb. ft.

The above instructions differ from the earlier WSM.143 instructions in the 
following regards:

1. Item 2. has been added in WSM.143/144 1st Re-issue
2. Item 3 of WSM.143 (corresponding to Item 4 of WSM.143.144) reads: 
"Remove the rubber dust cap fro the bleed screw of the left hand rear wheel 
cylinder, fit the bleed tube . . ."
3. Item 4 of WSM.143 (corresponding to Item 5 of WSM.143/144) reads: 
"Slacken the bleed screw three quarters of a turn and with the assistance 
of another person, depress the brake pedal a full stroke and allow the 
pedal to return as quickly as possible, any check in the return travel will 
prevent effective bleeding; actuate the brake pedal." The rest of Item four 
being essentially the same as Item 5 of WSM.143/144.
4. Item 6 of WSM.143 (corresponding to Item 7 of WSM.143/144) reads: 
"Repeat the previous three operations with the bleed screws of the front 
brake calipers, finishing at the right hand bleed screw which is nearest to 
the master cylinder."
5. Item 8 of WSM.143/144, which relates to Item 2 of the same instructions, 
has also been added.
6. Item 9 of WSM.143/144, has been amended to read "[to] the correct level"

All of you are free to speculate, as I have, as to why the procedure was 
changed. It appears that probably all of the changes are the result of 
adding step 2 regarding tightening the rear drums in order to minimize the 
fluid volume in the rear master cylinders. Perhaps the thought was that 
this would be a good time to readjust the rear brakes as well, so why not 
tighten them all the way while bleeding. The normal procedure for adjusting 
the rear brakes would be to fully tighten them, and then back off until 
they rotated freely anyway. One could further speculate that the order was 
changed to put the bleeding of the rear brakes last instead of first in 
order to better expedite the procedure. Remember, this Manual was written 
from the perspective of a flat-rate mechanic, not as a self-service manual 
for owners with lots of time and desirous of the best possible outcome. 
Note also, that these instructions (both versions) are somewhat 
contradictory with regard to the recommended annual fluid replacement; 
i.e., "Bleeding or expelling air from the hydraulic system is not a 
maintenance operation . . ." etc. Also, it would seem very difficult if not 
impossible to remove all the brake fluid from the system first following 
the procedure on page 4 of Section K. Even fully collapsing all of the 
master cylinder pistons would still leave some brake fluid in them, but 
this step is not even included in the instructions. For this reason, it 
would be my preference to dispense with the removal of fluid per the page 4 
instructions and just flush the system with copious amounts of fluid in the 
hopes of removing most of the old fluid through mixing.

Regardless of the order in which you choose to bleed the brakes; either 
starting at the rear and working towards the master cylinder or vice versa, 
if the important and consistent parts of the procedure given, especially 
steps 1, 5, and 9 of WSM.143/144 are adhered to they should produce a good 
result.

Bob

At 10:11 AM 5/27/00 -0700, Bob Palmer wrote:
>Chris,
>
>Steve Laifman just pointed out to me that the order I gave for bleeding the
>brakes is at variance with the Rootes Manual, which says to bleed the left
>front caliper first. This seems illogical to me, so I presume this order
>refers to right-hand drive cars. Also, since I have rear discs, I'd
>forgotten that there is no bleed valve on the right rear drum cylinder.
>
>BTW, did you ever resolve the loss-of-power-over-five-grand problem?
>
>TTFN,
>
>Bob


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