Spongey Brakes

[mahon257]

Anyone come across this problem before?

Been trying to fix a problem with rusty rear brake discs... so bought a new (Lucas) Master Brake Cylinder. After reading around this forum and others, it seems the best way to "prepare" the MBC for installation, is to pre-bleed it in a vice - before installing to vehicle.

It's the first time I've tried this....

After 2 hours of trying (in the vice) ... using brand new DOT 4 fluid - I gave up. See photo! I'd rigged up a closed loop system... and allowed up to 30 minutes between pumping sessions - to allow any trapped air to "Rise".

For the love of god... I could not get the rear brake circuit free of air bubbles... I've now sent it back for a replacement. The front circuit was perfect - nice clear, bubble free, fluid flowing around the loop...

Is there some trick I'm missing?

[mahon257]

Sent the (new) Lucas Master Brake Cylinder back to Paddocks for a replacement. 3 weeks later... a new one arrived... (this week).

With the new one, I followed the same process - i.e. bled it in a vice - with a continous loop setup on both front/rear outlets. This time, no bubbles on either circuit. Thank f**k for that.

So... that's 2 Lucas MBCs in a row I've bought that were defective - both on the rear circuit...

"Top tip": When installing an MBC, bleed it in a vice first so you can ensure it works properly. In my case I had no idea the rear brake circuit wasn't working properly - only evidence was rusty rear discs.

Hopefully this one will last a few years!

[Nigelw]

Good advice there, I think a lot of us take it for granted that because it is new it will be perfect.

I always used to bench test my new glow plugs before fitting, you would be surprised how many are dead before they are even fitted to the engine!!!