8 replies to this topic

[Stiggytoo]

Hi everyone. 

 

I'm having a few issues with the brakes on my 83' Austin City E.

Just a bit of background info. It has drums all round. It came in a shocking state; with rear shoes fitted backwards in place of the front shoes etc. These have been replaced with new shoes. Slave cylinders were leaking, so have been replaced along with the main rear brake line as it was badly corroded. Just to add, the car never stopped well at all - it's not hard to see why... (Saying that the handbrake works fine ) What's more, the guy who sold me the car said that he had spent some money on the brakes, and that they were great. Judging by the mistakes made I don't really trust that it has been plumbed in correctly.  

 

Anyway, after fixing these problems I have encountered another problem.                       

I have attempted to bleed the brakes countless times, using a pressure bleeder and the good old fashioned manual method, however, I am always left with a pedal that goes straight to the floor. Pumping the pedal just a few times will improve the feel. But if I leave it for a few seconds the pedal will once again go straight to the floor. 

 

This leads me to believe that either the brakes are not adjusted correctly or there is air in the system. 

 

In the case of my first suggestion, pumping the pedal will gradually bring the shoes closer to the drums, leaving the pedal will allow the shoes to retract to their original position. But surely the system would suck in some fluid from the reservoir and take up some of the slack? Either way I have adjusted all of the brakes, so this shouldn't be the cause of my problem. 

 

If there was air in my system, that could also explain the problem, as pumping the pedal would compress the air and again, improve the pedal feel. The new slave cylinders have been installed correctly, with the bleed nipples facing up by the way. My next suggestion was that the master cylinder is playing up. Just to be sure we have bled it, and even tested it with a brake pressure tool. (Well - actually we attempted to test it, only to find that the 23 year old piece of kit was blocked so fluid couldn't exit the master cylinder.   Anyway, this proved that the master cylinder was at least creating some kind of pressure as the pedal was solid)

 

 

At one point my dad decided to clamp one of the front flexi brake pipes. This seemed to harden the pedal and fix the problem. We tried this on the other side with the same effect. Again, this could be due to air in both slaves or mis-adjustment?   

 

My dad seems to think that the PRV is playing up, or has been plumbed in wrong. 

 

 

Please reply with any useful information or suggestions you might have. I've got a lot to get done before L2B!

         

[blacktulip]

if the PRV was wrong them the pedal should still be soft when the hoses are clamped up. are you 100% sure they are adjusted properly? sound like the shoes are too far away from the drum faces. or indeed the master cylinder is playing up.

[Stiggytoo]

Thanks for the fast replies! 

 

We did try quickly bleeding the PRV, and then bleeding the rest of the system again. 

 

Erm another thing to add. The car did come with another master cylinder in a box, so it's possible that it has been replaced. Saying that it doesn't look new.

 

 

Do any of you happen to know which way round the pipes should be from the master cylinder to the PRV? And could it be the cause of some of my problems if it was installed incorrectly? 

[jaydee]

Is it the yellow tag master cylinder? Try bleeding the master cylinder also, then bleed again all the system, including the damn valve.

 

The order is illustrated on the hynes, just figure out what master cylinder you have and check on the hynes.

[lrostoke]

I always found drum brakes to be very sensitive to adjustment. especially the fronts

rears are easy turn the square adjuster until the wheel locks or there is quite a lot of resistance then back off a quarter turn.

fronts you pretty much have to adjust each adjuster so the wheel is close to locking..

one of them is a pig get at so I did that first...then the other I could get a proper square adjusting spanner on for easier control.

it was actually main reason I switched to 7.5 discs once adjusted they worked a treat but was just a pain

Edited by lrostoke, 04 May 2013 - 04:24 PM.

[Stiggytoo]

Is it the yellow tag master cylinder? Try bleeding the master cylinder also, then bleed again all the system, including the damn valve.

 

The order is illustrated on the hynes, just figure out what master cylinder you have and check on the hynes.

I have not got the yellow tag master cylinder, it's the earlier front/rear split type with the brake failure switch on the master cylinder body.  

[Stiggytoo]

I always found drum brakes to be very sensitive to adjustment. especially the fronts

rears are easy turn the square adjuster until the wheel locks or there is quite a lot of resistance then back off a quarter turn.

fronts you pretty much have to adjust each adjuster so the wheel is close to locking..

one of them is a pig get at so I did that first...then the other I could get a proper square adjusting spanner on for easier control.

it was actually main reason I switched to 7.5 discs once adjusted they worked a treat but was just a pain

Thanks, I'm sure my dad was just tired of being under the car, and gave up because the square spanner wouldn't fit We'll hopefully get it sorted today. 

[Stiggytoo]

Ok, so it seems that a pair of new front drums may have solved the problem. The massive lips caused by the narrower rear shoes being used on the front meant that the brakes could never really be adjusted fully. I'd imagine that as the brakes were pumped up, the shoes would swivel and come into contact with the rest of the drums. 

[tiger99]

There is another simple thing that it could have been. The shoes have to be adjusted up very close to the drums. Unfortunately the adjuster can be turned both ways, and if you turn it the wrong way, the shoe is pushed sideways so that only the end away fron the cylinder is making contact. It does lock the wheel, sort of, so all seems well, but the cylinder end of the shoe will still be a long way from the drum.

 

Guess how I know about that! Some annoyances you do not forget, even after 40years....

 

If I recall correctly, the adjusters should be turned in the direction of normal wheel rotation, until the brakes are tightly on, and then backed off slightly.

 

Of course a rear drum, or very old single leading shoe front, uses an expanding wedge adjuster at the shoe pivot, so it is not possible to get it wrong.