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Brake bleeding
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Southernscouse



Joined: 30 May 2024
Posts: 26
Location: Havant Hampshire

PostPosted: Thu Jul 03, 2025 2:13 pm    Post subject: Brake bleeding Reply with quote

Yes with the help of wifey bled the system the old way still no pressure
On Austin site was told to try pumping up pedal when have pressure jam a stick between pedal and seat leave overnight this is were I am at now
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Penman



Joined: 23 Nov 2007
Posts: 4863
Location: Swindon, Wilts.

PostPosted: Thu Jul 03, 2025 2:58 pm    Post subject: Reply with quote

Is the fluid level in the reservoir holding up overnight?
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alastairq



Joined: 14 Oct 2016
Posts: 2121
Location: East Yorkshire

PostPosted: Thu Jul 03, 2025 6:42 pm    Post subject: Reply with quote

Are the rubber seals in the master cylinder the correct way around?
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Southernscouse



Joined: 30 May 2024
Posts: 26
Location: Havant Hampshire

PostPosted: Fri Jul 04, 2025 12:37 pm    Post subject: Brake bleeding Reply with quote

So after some advice on the Austin forum. I pumped the pedal until I got pressure then jammed it down with stick against the seat left it for over 48hrs and I now have pedal pressure but low down so I pumped the pedal higher and replaced the stick
I have no leaks but why this works and the three other methods I tried didn?t escapes me
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Southernscouse



Joined: 30 May 2024
Posts: 26
Location: Havant Hampshire

PostPosted: Sat Jul 05, 2025 5:58 pm    Post subject: Brake bleeding Reply with quote

When first removing the stick jamming the pedal I d have pressure but after a short time the pedal goes down to the floor can be quickly pumped up
I think this means I still have air in the system
What are peoples thoughts on the best method to get the system bled
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Southernscouse



Joined: 30 May 2024
Posts: 26
Location: Havant Hampshire

PostPosted: Sat Jul 05, 2025 5:59 pm    Post subject: Brake bleeding Reply with quote

When first removing the stick jamming the pedal I d have pressure but after a short time the pedal goes down to the floor can be quickly pumped up
I think this means I still have air in the system
What are peoples thoughts on the best method to get the system bled
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alastairq



Joined: 14 Oct 2016
Posts: 2121
Location: East Yorkshire

PostPosted: Sat Jul 05, 2025 7:03 pm    Post subject: Reply with quote

Still sounds like an issue with master cylinder seal[s] to me....Doesn't matter if brand new, NOS, or re-used ''originals'', failure is just another fact of life keeping old motors going these days.

{I am still amazed at the number of owners of oldies who slap on 'brand-spanking-new' components, then fail to accept that, just because it's 'brand new,' doesn't mean it isn't faulty... ]
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4240
Location: South Cheshire

PostPosted: Sun Jul 06, 2025 10:08 am    Post subject: Reply with quote

How did all this start? Is this a car that you obtained that never had brakes? Or were the brakes working and these problems have arisen following a routine fluid change or have the brakes developed a fault if so did it happen quickly or got worse over time?
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Southernscouse



Joined: 30 May 2024
Posts: 26
Location: Havant Hampshire

PostPosted: Sun Jul 06, 2025 1:12 pm    Post subject: Brake bleeding Reply with quote

UKdave. It all started when I changed one rear cylinder brakes were working but this one cylinder had a slight leak
After topping up with dot4 fluid and bleeding the rear brakes pedal lost pressure. Then tried vacuum. Air pressure Single operation with one valve bleeding all to no avail
Came to think it was the master cylinder. So replaced the seals went through all the methods again no pressure at pedal by this time I had pumped over a litre of dot4 fluid through all wheels
So still thinking it was the master cylinder i spent ?200 on a replacement went through all methods of bleeding again same result
I can pump up pressure and it will hold when pedal is jammed with a stick for over 48hrs
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alastairq



Joined: 14 Oct 2016
Posts: 2121
Location: East Yorkshire

PostPosted: Sun Jul 06, 2025 1:26 pm    Post subject: Reply with quote

Is there a flexi hose to the rear axle brake line?
If so, it's possible the interior has 'collapsed'...preventing proper movement of the brake fluid?
Or, there's a pin hole in the 'rubber?'
Or the couplings aren't seated properly? Not allowing much stuff out, but allowing air to creep in when the pressure is ''off?''
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4240
Location: South Cheshire

PostPosted: Mon Jul 07, 2025 6:59 am    Post subject: Re: Brake bleeding Reply with quote

Southernscouse wrote:
UKdave. It all started when I changed one rear cylinder brakes were working but this one cylinder had a slight leak
After topping up with dot4 fluid and bleeding the rear brakes pedal lost pressure. Then tried vacuum. Air pressure Single operation with one valve bleeding all to no avail
Came to think it was the master cylinder. So replaced the seals went through all the methods again no pressure at pedal by this time I had pumped over a litre of dot4 fluid through all wheels
So still thinking it was the master cylinder i spent £200 on a replacement went through all methods of bleeding again same result
I can pump up pressure and it will hold when pedal is jammed with a stick for over 48hrs


If the master cylinder was fine before you changed the wheel cylinder, there is no reason to suspect it, it would be an amazing coincidence if it suddenly failed at the same time that a wheel cylinder was replaced.

I am convinced you have air in the system; when you pump the brakes up you are compressing the air, hence the brakes are on, and if it holds for 48 hours this suggests all the seals are good, although I will add that some times a poor seal will seal under hard pressure because the seals swell more than at low pressure.

When a single wheel cylinder is changed, it normally only requires minimal bleeding, a couple of pedal strokes to purge the air out of the cylinder normally does it, so I'd focus around the replaced cylinder even swapping the original cylinder back and see if the brakes can now be bled , its the only place where air could be in the system when the original repair was undertaken (appreciate you have since swapped the M/C so air could have been introduced then).
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V8 Nutter



Joined: 27 Aug 2012
Posts: 602

PostPosted: Mon Jul 07, 2025 8:57 am    Post subject: Reply with quote

If you have drum brakes all round try adjusting them until they lock the wheel, then bleed as normal. finally readjust the brakes, that sometimes works, but as others have said, I would suspect the master cylinder.
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Rusty



Joined: 10 Feb 2009
Posts: 278
Location: Bunbury, Western Australia

PostPosted: Tue Jul 08, 2025 1:33 am    Post subject: Reply with quote

Wow ! You are certainly being put through an ordeal, I don't think I have heard of so many "correct" things being done all to no avail !
Would there be any chance that the push rod that operates the cylinder could be the wrong length? Maybe if the pushrod was "too long" it may hold the piston back far enough that the compensating port is not uncovered, that could cause issues with recharging the cylinder, but with a pressure bleeder attached, the fluid would still be pushed through the system.
I gotta admit, after all you have done, I think most of us are "grasping at straws" for some suggestions as to what could be happening.
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petelang



Joined: 21 May 2009
Posts: 475
Location: Nottingham

PostPosted: Thu Jul 10, 2025 10:09 am    Post subject: Reply with quote

I have bled innumerable brake systems over the years and never had a problem, until about 3 years ago when I discovered a pool of fluid under the middle of my Daimler 15. The master cylinder was situated there and the seals had gone. So it was sent off to recondition, being that replacement was unobtainable, and I also did wheel cylinders.
On return, I initially was working alone so rigged up a pressure bleed using a tyre valve and endless hours of bleeding, filling, bleeding, filling, but could get no solid pedal. So switched to vacuum, using a squinty spray bottle pump. That used about a further 2 litres of fluid and achieved nothing. Still no pedal, air still coming out.
I enlisted a friend to pump pedal and switched to conventional methods. Adjusted brakes up to lock drums, did nearest first then working around the car. We were two days at this and eventually, no more air coming, but still a very low pedal.
The only was pedal height could be restored was to pump it like a madman, then hold it down, but once released, it went back to low again. We were totally confounded.
Nevertheless, persevering, using pedal up, pedal down, we persisted, and eventually, with just cracking the bleed open by the tiniest amount when pedal depressed, it gradually came better until I exhausted a full 5 litre can of brake fluid, and TBH my mates leg was dropping off. So we called it a day.
It worked fine ever since!
I have absolutely no idea why, nor do I wish to repeat it again.
Only solace I can offer is try minimal opening of the bleed, not letting all the pressure go, and keep trying.
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Daimler Fifteen 1934 (now sold)
Armstrong Siddeley 15 Long 1933
Daimler V8 250 1969
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alastairq



Joined: 14 Oct 2016
Posts: 2121
Location: East Yorkshire

PostPosted: Thu Jul 10, 2025 10:31 am    Post subject: Reply with quote

Sometimes....the actual position of the bleed screw also affects the ability to expel any air.
Particularly concerning certain clutch slave cylinders....where the bleeder gets positioned , not exactly at the 'highest ' point.
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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