Mastercylinder Help 98 Disco ABS

[weekapa1]

My buddy has a 98 Discovery with some problems: I havent had time to get over and help him with the truck personally.. just verbally
He had the Drivers side front left caliper leaking fluid:
He bought a rebuilt caliper and installed:
after several minutes of pumping/holding/bleeding/tighten/pumping /holding/bleeding he finally got some fluid to come out of the caliper. Problem is.. he has absolutely no pressure on the pedal
I told him this was odd that the master cylinder might have crapped out same time as the caliper.
I told he to gravity bleed all four corners starting at passenger rear. He gravity bled each wheel one at a time and fluid did come out at each wheel for several minutes each. He kept the resevoir topped up also. He still has no pressure in the system. He ordered a rebuilt Mastercylinder and it should arrive Tues. -Wed.
What are the steps for replacement? does it sound like this is a master cylinder problem?
Could someone explain in detail how to replace the mastercylinder...anything special we have to do because it is ABS? How do you prime the mastercylinder? Is this going to be an easy job?

 

[joey]

Sounds to me like he has air in the brake system. I would try to bleed the entire system, starting again at the passenger rear again. But not a gravity bled, I would use either a power bleeder or a two person method.

If you still need the master cylinder info, here you go. They are not that hard to change, but again... sounds more like air than anything.


MASTER CYLINDER ABS
Service repair no - 70.30.08
- Lucas Girling - Type 25.4mm CV/CV
NOTE: This master cylinder is identified by
a 3rd plugged outlet port protruding down
from the master cylinder body.
Before starting repair refer to general brake service
practice. See General Brake Service Practice
Remove
1. Disconnect battery negative lead.
2. Place a suitable container under master cylinder
to catch brake fluid from cylinder when brake
pipes are disconnected.
3. Thoroughly clean immediate area around all
outlet ports. Remove each brake pipe, sealing
each pipe and outlet port with suitable plugs to
prevent ingress of foreign matter.
4. Disconnect electrical plug from low fluid switch
on reservoir cap.
5. Remove two nuts securing master cylinder to
servo unit remove also spring and plain washers.
6. Detach master cylinder from servo, remove
reservoir cap and drain brake fluid into a
container.
Refit
NOTE: Ensure O ring seal between master
cylinder and servo unit is fitted correctly.
7. Fit master cylinder to servo. Secure in position
with two nuts, plain and spring washers. Tighten
to 26 Nm.
8. Fit brake pipes to master cylinder. Tighten to
15Nm.
9. Top-up master cylinder with correct grade of
brake fluid. See LUBRICANTS, FLUIDS AND
CAPACITIES, Information, Recommended
Lubricants and Fluids
10. Bleed system. See Brake System Bleed
11. Fit cap, reconnect electrical lead to fluid level
switch. Reconnect battery negative lead.

 

[mark D]

brake problems

this takes two people.
if you are replacing the master cylinder and the ABS was previously installed prior to replacing the master cylinder you will not need the dealers expensive bleeder tool.

First run down to your local Harbor Freight and buy a vacuum tester/ break bleeding tool for about 20 bucks. It will capture most of the brake fluid and keep the mess off the driveway.
Next remove the 2 brake lines leading into the ABS booster. Fill the master cylinder with Dot 4 or better fluid and place one finger over one of the break lines while pumping the vacuum bleeder until the fluid starts flowing. remove the bleeding tool and install the break line. Repeat the same process with the second brake line, replace the second break line.

At this point the small amount of air that might get into the line is not of concern but if your friend holds the pedal down you will have less air in the line.

Next start at the LFT front wheel and loosen the bleeder fitting. attach the brake bleeding tool to the end of the bleeder nut so the container can capture the fluid being expelled.

NOW start the car in order to bleed the brakes old school the ABS only works with the engine running.

Have your buddy pump the brakes three times but don't push too hard, after three pumps hold brake pedal and release the fluid and air. keep foot on the brake pedal until you re tighten the nut. repeat a few times until you get a good flow of fluid and no air. After fluid burps out close the fitting pump the bleeder tool a couple of times and pull the hose off the fluid with be sucked into the capture canister (do it in reverse and you better have your mouth closed cause it tastes awful), and repeat on the other front wheel and then to the back. After the last wheel is bled, repeat starting at the front again until the fluid is clear and there is no more air burping out. It will take about 5 to 6 regular bottles of brake fluid to get the lines flushed. Fluid should be clear and air free. Your buddy should be getting the pedal results right away seeing as the vehicle is running and the vacuum is working.

remember the vehicle has to be running to bleed old school just chock on the exhaust as little as possible.

worked for me. good luck

 

[Disco Mike]

I agree with Joey, before wasting money on a new M/C, first do a proper full bleed which is not bleeding each wheel once but bleeding each wheel till you get perfectly clear fluid which usually takes nearly 2 quarts of DOT 4.
One problem your friend may have on that old of a vehicle is if you only replace one caliper on the front, the vehicle will usually tend to pull when braking. You can get away with just one on the rear but front calipers should be changed in pairs on high mileage vehicles.