Rear drum assembly showing brake cylinder, hand brake lever and adjuster
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Quick Job Guide: Brake Bleeding

Required Tools

• Vehicle Jack & axle stands
• Suitable sized spanner
• Rubber tube to go over bleed nipple
• Brake Fluid
• Brake Cleaner
• A friend to assist

Bleeding the Brakes

This is just a fancy name for removing any air from the brake lines. In theory it is easy and nine time out of ten it is. Fill the master cylinder or reservoir with New fluid and lightly fit the cap.

The method is to start with the wheel that is furthest away from the master cylinder. ie: the rear left wheel. Unless you have a fancy aid kit for bleeding the brakes you are going to need a friend in the drivers seat to work the pedal. Loosen the bleed nipple on the rear left side brake. Fit the tubing over the end of the nipple and put the other end into a jar with some fluid in it, this acts as a simple none return valve. Use your spanner to make sure you can open and close the nipple.

With the nipple open call “DOWN” getting your friend to push the brake pedal.

When the pedal is fully down close the nipple and call “UP”. If you have one of the bleeding kits you do not need to keep opening and shutting the nipple as they should have a none return valve built in.

Repeat this process until you have no air coming down the tube. Close off the nipple and top up the reservoir. Repeat this for the rear right wheel, followed by the front left and then right wheels. You may have to repeat the sequence once or twice. The pedal should now be firm with only slight movement before resistance is felt.

Once you have completed the bleeding process and the pedal is firm, ask your friend to press on the pedal, whilst you check all the joints and nipples for any leaks. Use brake cleaner to clean the areas around the cylinder, or if you have disc brakes fitted to clean the caliper and disc.

NOTE: if your car is fitted with a servo system, once you have completed the bleeding process, you will need to start the engine and then press the pedal again, to ensure that it is still firm. The servo, running off the engine acts as a pump to give additional braking force to the brake cylinders/calipers.

 

Problems:

These are normally down to the bleed nipple being blocked, the master cylinder not being topped up, or you have removed the master cylinder and put it back together wrongly. The blocked nipple is easily cured. Unscrew it fully and use a piece of wire to clean out the small hole. Note that this comes in from the side on the pointed end. If it is very corroded you cant find the hole, do look carefully as it is there!

If you let the reservoir become empty then you must start the bleeding process again!

If you have put the master cylinder back together incorrectly, then you will have to take it out and do it again.

Hoses:

There are usually 3 or 4 flexible hoses on a classic car, typically one for each front wheel, then either one for a fixed back axle or two for a split/independent rear axle (Triumph Stag, Spitfire etc). These do deteriorate with age and it is recommended to replace them every eight or so years. they are relatively cheap and could save your life. It can make it easier if you buy new nuts and fittings as well, as you can then cut the old ones off with minimal damage to the body fixings.

 

Brake Fluid:

Modern Brake fluid is extremely hydroscopic, this means that it loves water. In fact it can pull water molecules through the flexible hoses. This then remains in the system causing corrosion. it also makes the brakes less effective. This is not instant by any means, but over a number of years, as such it is recommended to replace your brake fluid every 3 years or so. DOT 4 or 5 Brake fluid should be suitable for most classic cars, if you are unsure check with your cars owners club.

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