Brake bleed

[Non MemberParticipant]

Hi,

This has probably been asked before but,….. I think it’s about time to change the brake fluid as I’ve had the car a couple of years, it’s been parked up for the winter plus I do know the service history. Is it as straightforward as you would like or are there any pitfalls or clever dodges I need to be aware of.

Also what would be the correct brake fluid to use?

[ChrisParticipant]

Hi Justin,

I’ve always found it pretty straightforward – usual risk of bleed nipples snapping or rounding off – splash some WD40 around a day or two before and use a good fitting wrench is advice I have wished I had followed.

I have never had a problem getting a decently firm pedal so I don’t think there’s a special knack required.

As for the fluid – DOT 4 is fine assuming you have not already got silicon (DOT 5) fluid in the system. Both fluids look the same when new.  They don’t feel the same on your fingers but that’s not a great way to distinguish them. The two don’t mix well so, if you don’t know what you’ve got in there, whichever one you choose, you should probably plan to flush the whole system through – which probably means doing it twice.

That’s just my view.

Chris

[BernieParticipant]

Justin – be aware early wheel cylinders had a “double” bleed nipple with a small (M6 with a 10mm a/f head, I think) blanking screw inside the larger diameter bleed screw.

If you still have the old type, to bleed them the small inner screw needs to be replaced with a bleed nipple to accept the bleed pipe and then the large screw, which is the actual bleed device is slackened and tightened as per modern one piece nipples.  As long as the big screw is tight you can remove and replace the smaller one without any risk of fluid loss – or air ingress.

If the wheel cylinders have been replaced there is a strong likelihood they will have standard, one piece nipple so no problem.

B………….

[Martin de LittleParticipant]

Remember and  bear in mind that DOT4 falling/splashing onto Cellulose paint  is a particularly bad thing. Basically DOT4 will permanently damage cellulose paint. Guess how I know this !! Do not be cavalier in sloshing the  DOT 4 about.

As Chris says above,   the trick is to be particularly gentle with the bleed nipple. A bleed nipple that has sheared off in the back of a cylinder can be a  challenging experience.  A  ring spanner is the best way to undo or do up the bleed nipple.  “Shifting spanners”  or adjustable spanners are not good.

For the bleeding process  the Traction is remarkably tolerant. Choose your wheel. Convention says you start at the wheel furthermost from the master cylinder and work towards the wheel nearest the master cylinder.  Back off the chosen  bleed nipple. Fit a CLEAR plastic tube from it to something like a jam jar.

Position a  human being (whatever they may currently identify as is irrelevant)  in the drivers seat. On the word of command they press the brake pedal down  steadily (not fast and not slow) and hold. Oil squirts into the jar. Lightly tighten the nipple. On the word of command they lift the brake pedal  and await your next instruction.  Release the nipple. Shout out “down”. Watch the stream of oil going down the pipe. Repeat until such time as the  stream of oil is clear of  air bubbles the job is done. It should require only a few strokes of the pedal to get a bubbles clear flow. Check nipple is tight. Check brake pedal is firm, top up the master cylinder  and move onto the next wheel. By the end of the process you will have flushed all the old oil through  and out of the system.

If the shoes are up close to the drums there should be very little movement of the brake pedal and a rock solid feel to the pedal as the brakes are applied.

MdeL

 

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