Brake Issues HELP!

[nickm]

Clever People,
I have been chasing the source of air in the brake lines of my 88' petrol. I think I have narrowed it down to the back half, but not really sure. I get a pedal after a couple of pumps but it goes away straight away. If I clamp any of the flexible hoses I get a pedal.
If I gravity bleed the rear cylinders, no bubbles but no pedal. If I pump the pedal, there are no bubbles during the pumping, but as soon as I stop bubbles appear. This doesn't happen at the front. There doesn't appear to be air in the master cylinder and I cant find a fluid leak anywhere.
I am slowly going crazy..
Help me please!
[bigsad][bigsad][bigsad]

[Homestar]

Can be a pain. I found just gravity bleeding litres of fluid through each bleed nipple does the trick - just keep transferring what comes out back in by swapping between 2 containers. If you think the master cylinder is ok, and it is air in the system (not old flex lines are they?) then it should be doable.

[nickm]

The flex lines are new.

[pop058]

Pressure bleed the buggars or they will drive you crazy [tonguewink]

[series2aman]

i reversed bled my brakes and works perfectly[bigwhistle]

[Chops]

I had a lot of trouble with mine when we did them, seemed to have an enormous amount of air trapped somewhere in the rear section. It wasn’t until we pressured the system via a pushbike pump that we got virtually all the air out. But they are still not right, they sort of bind up as in they get a very hard pedal,, still seem to work ok, but in city traffic it goes hard, and when left for a while goes back to a normal pedal. So I’m guessing there’s still air in there. In my case though, new pads and drums and one last new flex line should fix it.
Ive never done “reverse bleeding”, so I’m not sure exactly how it’s done, can’t tell you if it’s easy to do or not, but with the pressure bleed, get a lid, put a valve in it, and away you go.
A word of warning though, use compressed air, not a bike pump [bigwhistle] I think 🤔 rangiemans arms still hurting [bighmmm]

[pop058]

I have one similar to this. Makes it a one man job as well.

133942

[JDNSW]

A couple of suggestions -

1. You can reverse bleed using a syringe of the type sold to fill gearboxes - but don't use one that has been used for oil, and make sure it is scrupulously clean (use metho).

2. You can bleed from any junction by loosening the coupling. Suggest bleeding the rigid lines first by clamping off all hoses and ensure there is no air anywhere, checking at the top of each hose. Then, bleed each section one at a time, with the others clamped off.

3. Slacken all adjusters right off - this minimises the volume in the wheel cylinders, thus minimising the space for air.

4. If brake adjusters are slipping, this can mimic air in the system, as can incorrectly assembled springs on the brake shoes, or shoes that don't match the curve of the drums, or shoes not sitting straight sideways.

5. Non - standard systems can have mismatched master and wheel cylinder diameters, making them very sensitive to slight problems.


What wheelbase, and is it a single circuit or dual circuit and is it boosted or not?

[Peter Shaw]

Our 1965 series 11a 88” with the CV type master cylinder single circuit had the same issue. Never had brake problems when we bled the brakes at the old house, because it was on a slight hill (front end uphill) when we bled them. When we moved to a new house with level garage we could never get the air out and never get as firm a pedal. Slow pedal strokes work the best and just cracking open the bleed screw instead of letting it stream out fast seems to have the best results don’t let the pedal fly up. Make sure you use Castrol brake fluid (or other UK supplied) many other cheap fluids will attack the master cylinder and wheel cylinder rubber seals, they end up softening and deteriorating and leaking from every wheel....

[Red90]

If pumping fixes it, it is not air. It means the shoes are not adjusted properly.

[nickm]

It is an 88' with the CB style cylinder and no servo with a shared reservoir. It is air but it is only visible at the rear brakes and only after pumping the pedal and then gravity bleeding. No air by gravity alone. While pumping no air is visible.

[County4.4]

I remember helping a mate out once with his IIa. He lived on a steep block so we parked the car on the steepest part facing uphill, blocked the rear wheels and then jacked the front up even more. I reckon we had it close to 45 degrees. We bled the brakes in this position a couple of times and it worked a treat.
Mechanic at the roadworthy place could not believe how good they were for an old landy.

[nickm]

Did you reverse bleed or standard?

[County4.4]

Just standard from memory. I remember reading somwhere in a workshop manual to do it this way i think. You could lock all four wheels up when you jammed the brakes on. Pity he rolled the old girl and wrote it off 6 months later.