Brake bleeding

[southernscouse]

What is people’s opinion on bleeding the brakes on my Devon van
Vacuum type kit or air pressure kit First tried the assistant pedal pumping method buy master cylinder which was ok now seems not to get pressure cheers Tom

[MikeN]

Ive bled the brakes on my truck about 6 months ago using a Gunson brake bleeding kit that works off the spare tyre. However I had to fabricate a better adaptor to fit the master cylinder. I bought a reconditiined master cylinder off ebay about 3 years ago. It’s been fine so far. Also, my vehicle was running with silicone brake fluid when I bought it 5 years ago. It still is.

[southernscouse]

I have now tried the vacuum type still no pressure at pedal
Purchased a pressure type have firm pedal when connected to air but fails when released
I have put over a litre of fluid through no the system
I can get pedal pressure if I operate the pedal quickly and it will hold if I keep pressing but fails when released

[southernscouse]

I have received some information about problems with the slow return valve I think this is called the recuperation seal so will buy a kit and replace

[southernscouse]

In Austin manual it says when fitting the seals the end cap has to unscrewed
Is this necessary if after removing the circlip and operating rod the whole assembly can be removed from this end
The screwed on end cap is very tight and I was hoping not to disturb

[number5]

The A40 braking system is the same as the A70 Hampshire, and A90 A90 Atlantic convertible, and it is essential to ensure that the brake shoe mechanical adjustments been undertaken to ensure that the shoe travel is not excessive.

This also applies to the pedal movement, for if this is not fully out when released, it may not be allowing fluid to flow through the non pressurized compartment into the pressurizing side. For the special washer and the internal seal, such can only be replaced with the removal of the screwed cap.

If the piston assembly is not fully returning to the released position when the pedal is fully out, a few mm from the end of the piston, there are two holes on opposite sides of the piston, and with the piston fully released, these holes automatically align with the rear edge of the internal seal to allow flow to pass through the special washer into a small recess in the back of the inter diameter of the seal, aligning with the two holes, that allow fluid into the compression chamber of the master cylinder. If not aligning, it may not be letting sufficient fluid into to be able to compress.

Presuming all the adjustments are correct,and before resorting to the removal of the master cylinder, one thing you might try is what a Healey 100 owner once said to me—-if quick pumping gets pressure, have a suitable piece of timber at hand, and with pressure built up, wedge the pedal down with the timber against the seat frame, and leave it stand overnight. Whilst if sounds odd, he said that he learnt this from other Healey owners, who said that it worked, and it did for him.

Hope this helps in some small way, Cheers

[southernscouse]

Cheers No5 I did what you suggested but left it for 3days it worked I have pressure but pedal is low so pumped it up higher and replaced the stick will leave it a while
I have no leaks
But why this seems to work escapes me when all three methods I tried didn’t

[southernscouse]

When first removing the stick jamming the pedal I do have pressure but after leaving it a short time pedal goes down to floor but can be quickly pumped up so I think this suggests air still in system so what’s peoples thoughts on the best method

[number5]

Why the keeping of the pedal depressed can work I don’t know-told to me by a Healey 100-4 owner when I was having some problems years ago, and it did give results. It may be that the MC has to be removed to thoroughly clean it and install a new seal kit. With the front brakes, have you checked the adjustment clearances, and also if the wheel cylinders in each are returning to their normal closed positions. I do know that the two small holes at the end of the piston must be aligned correctly at the rear face of the inner seal, to enable returning fluid to enter the small recess on the centre of the seal,allowing it to pass through the washer into the cylinders non pressurized section, otherwise it does create a problem.
Cheers-Peter

[Author]

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