Spongy brakes still, master cylinder gone?

[tuscan_al]

Have been bleeding my brakes but they are still spongy and takes a few pumps for the pedal to go hard now, guess the master cylinder for the brake has gone?? Think I should have used a pressure bleed rather than the pedal...

Is it a seperate master cylinder than from the clutch?? How trick? Lots on the cerb forum but little for the tuscan about it?

[dilbert]

tuscan_al said:

Have been bleeding my brakes but they are still spongy and takes a few pumps for the pedal to go hard now, guess the master cylinder for the brake has gone?? Think I should have used a pressure bleed rather than the pedal...

Is it a seperate master cylinder than from the clutch?? How trick? Lots on the cerb forum but little for the tuscan about it?

Don't have a tuscan, but my practical aspect is saying that the clue to your problem is in the reason you were bleeding the brakes.

If you're bleeding them because the brakes have been worked on, but were otherwise fine, then you've probably got an airlock. If you're bleeding them specifically to try to reduce sponginess that spontaneously appeared, then there is probably something else wrong.

Pressure bleeding, IME, is not as good as the two man method, if both know what they're doing. The two man mathod, can be much simpler and quicker, with less fuss. If either person is not quite up to speed with what they're doing, the two man method can be much worse.

An alternative to pressure bleeding is to use suction bleeding. Both require a compressed air source. The suction method really requires the use of a compressor, whereas you can get away with a tyre as an air source with pressure bleeding.

Pressure bleeding, can be a pain with a tyre, becuase the volume of air in the tyre is so small. The actual pressure in the tyre varies from say 30psi, right down to 1 or 2psi, and you don't get much chance to bleed over that range. In addition, it's quite difficult to get a seal on the reservoir, and you end up wasting air and making a mess.

If you have a 12V compressor, it's not too bad because you just pump the tyre back up again.

You don't have anywhere near as much hassle with suction bleeding, because the fluid is drawn out of the system at the caliper end. Consequently ther are no problems with seals on the reservioir. Suction bleeding generates a vacuum from a compressed air source, and uses much more air. A 12v compressor is insufficient for suction bleeding.

If you aren't short of a penny, and plan to do this lots, just get a small compressor for £70, and a suction bleeder. The compressed air is also good for removing pistons that get stuck in calipers, it's also great for cleaning down the lawn mower and allsorts of other things.

Edited by dilbert on Saturday 15th March 19:33

[tuscan_al]

they were good brakes a year ago! But the pedal has got softer i feel, even though you get used to the feel of a pedal over time. I bled them to try and sort the soft pedal, so it prob is the brake master cylinder..

[dilbert]

Ping!!

I added some extra stuff whilst you were posting.


Cooked brake fluid will also have a tendancy to make the brakes feel spongy. For a car like this, it's perhaps not a bad idea to replace the fluid yearly anyhow.

Edited by dilbert on Saturday 15th March 19:35

[dickkark]

there is an easy way for checking the master cylinder,
push the pedal down to the point at which it becomes firm and then hold the pressure on,if the pedal starts to drop away slowly then its the master cylinder at fault.

[tuscan_al]

dickkark said:

there is an easy way for checking the master cylinder,
push the pedal down to the point at which it becomes firm and then hold the pressure on,if the pedal starts to drop away slowly then its the master cylinder at fault.

thanks will pop out and try that now,dont need the ign on for the servo assistance do I??

There is a spoosh type noise too when pressing the pedal so thinking it is the master cylinder.

Is it a hard job to change? May claim on my AA breakdown cover if it is!