Pre 94 Discovery brake bleeding,

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Pre 94 Discovery brake bleeding,

Post  Gozling2 on Wed Feb 18, 2009 1:21 pm

Brake fluid changing & brake bleeding

Hi Guys thought this might be useful, Discovery 200TDI up to MY 1994 (non abs)

There are two separate braking systems on a discovery, the Primary and the secondary, looking at the master cylinder the primary brake system pipes are closest to the brake servo unit and the secondary are the two pipes closest to the end of the master cylinder.

As brake fluid should be replaced Bi-annually thought this might be useful for those feeling proficient enough to attempt this procedure themselves, this is just my way of doing the job but, by no means the only way

In order to ensure that all the air is removed and brake fluid replaced from the brake system, it will be necessary to bleed the brakes on all four wheels.

The order in which you perform the bleeding is not critical but is recommended that you start at the (NSR) passenger side rear (furthest brake calliper from the master cylinder) and then (OSR) drivers side rear, do these two wheels first then proceed to the (NSF) passenger side front then lastly the (OSF) drivers side front, this will minimize the amount of potential cross-contamination between the new and old brake fluid.

Parts required

New sealed bottle of brake fluid

Pressure Brake bleeder kit (follow manufactures recommended procedure).

If manually bleeding the brakes get an able assistant to press the brake pedal, a hose long enough to reach into a receptacle for bleeding the old brake fluid into, I use an old glass Iron Bru Bottle with a hole punctured in the screw top and a length of rubber hose inserted (if container is knocked over no brake fluid will get out) which is longer than the length of the bottle and coiled 2/3rds around the bottom of bottle, I then fill the bottle to just above the hose/pipe (when brakes are bled no air will be drawn back into the tube as it is immersed in brake fluid).

1. Jack up and secure the car with axle stands, remove the wheel(s) and locate the bleed screws on the brake calliper body, I always make sure that the bleed nipples are free before fully disabling the vehicle, remove the old brake fluid from the master cylinder reservoir (I use an old syringe) and re fill with new recommended brake fluid.

The bleed nipples will more than likely have a protective rubber cover over them they will need to be removed and then re-fitted after bleeding.

2. Place your spanner onto the bleed nipple

3. Place one end of the plastic/rubber hose over the nipple (end) of the bleed screw on the calliper, the other end should already be inserted in to the bottle.

4. Place the bottle for the waste fluid on the ground close to the calliper and make sure it is secure and that the tube is submerged in the brake fluid at the bottom of the bottle, once you have everything ready it is time to start bleeding the brakes, crack the nipple on the calliper about a turn and get your assistant to slowly pump the brake pedal, I check the master cylinder level about every 8-9 pumps of the pedal and top up with new fluid as necessary the reservoir must not be allowed to run dry of fluid as this will introduce air into the braking system.

5. Once you can see clean fluid coming from the end of the tube in the bottle, tell your assistant to press and hold down the brake pedal, your assistant should NOT release the brake pedal until told to do so, lock of the bleed nipple and ask your assistant to release the pedal.

6. Continue with steps 1 to 5 for the other rear calliper.

There is a slightly different procedure for bleeding the front callipers.

As there are two braking systems on a Discovery this can sometimes cause a problem when bleeding the front callipers. The Secondary braking system works on all four brake callipers and goes to the rear brakes via a PRV (pressure reduction valve) the Primary braking system works as a back up system and works only on the two front brake callipers (the 2 upper pistons on the front callipers), the callipers that usually causes a problem are the front, this is the sequence that I find works for me;

One side of the calliper has 2 nipples (inner side of calliper) the other side has only one nipple (side closest to the wheel studs), the first nipples to bleed on the front calliper are the 2 nipples on the inner side of the calliper (it is recommended that these 2 Nipples are bled simultaneously), the next to bleed is the single nipple on the rim side (outer) of the calliper, this should help to remove any residual air and old brake fluid from the braking system.

7. After bleeding each of the nipples on each of the callipers in turn, check that there is sufficient brake fluid in the brake reservoir of the brake master cylinder, have your assistant press the brake pedal whilst you visually check for any leaks from the nipples and braking system.

8. Reassemble any parts which were removed to aid bleeding and access.

9. Before you drive anywhere, make sure that you have tightened all nipples & refitted everything, bleed nipple covers, wheels, wheel nuts and re torque the wheel nuts.

10. Sit in the car and pump the brake pedal a couple of times this will give you a good indication as the the feel of the brakes, once you are confident that they feel better and that the car is safe to drive, take the car for a slow steady drive, no more than 10 - 15 miles per hour until you have confirmed that your brakes are working proficiently, check the brakes before you get up to any great speed, they should feel slightly firmer and possibly more responsive.

Hope this is of some help.

Goz Razz Razz Razz


Posts : 9
Join date : 2009-02-13
Age : 54
Location : Aberdeenshire

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