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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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 Posted: Wed Mar 22, 2023 12:01 pm Post subject: |
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That link works fine.
Cup seals are fairly common.... but if possible I would have replaced the wheel cylinders complete, although I appreciate the cost might be prohibitive. |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4105
Location: South Cheshire
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bjacko
Joined: 28 Oct 2013
Posts: 362
Location: Melbourne Australia
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| Posted: Thu Mar 23, 2023 6:21 am Post subject: Brakes |
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I would think that if the springs were weak the brakes would drag.
Some older vehicles have to have one end jacked up to bleed the brakes to move the air to the highest point and be bled off at the nearest bleeder.
_________________
1938 Morris 8 Ser II Coupe Utility (Pickup)
1985 Rover SD1 VDP |
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Thu Mar 23, 2023 10:33 am Post subject: Re: Brakes |
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| bjacko wrote: | .
Some older vehicles have to have one end jacked up to bleed the brakes to move the air to the highest point and be bled off at the nearest bleeder. |
It might help... but pumping clean fluid through should push all the air out.
The thing that can happen is if the pedal is not kept down while the nipple is tightened, then air can be drawn back in. To avoid problems with bleeding brakes I have always pumped the pedal using a simple rubber bleed tube - blocked at one end - with a small split in it submerged in a jar of clean brake fluid.
I have always had to manage on my own and never had a problem with this method in 50 years. Maybe I have just been lucky.
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AVRO
Joined: 10 Mar 2023
Posts: 12
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| Posted: Thu Mar 23, 2023 12:08 pm Post subject: Re: Brakes |
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| bjacko wrote: | I would think that if the springs were weak the brakes would drag.
Some older vehicles have to have one end jacked up to bleed the brakes to move the air to the highest point and be bled off at the nearest bleeder. |
Sorry, i don't mean the big return springs that retract the shoes, i mean the small springs inside the wheel cylinder that pushes the seal flat against the piston (i think it also pushes the piston against the shoe).
Funny you should mention jacking it up, when i first assembled the rear brakes, i noted it was odd that the cylinder was vertical, so the top cup seal would be higher than the bleeder. I will try that.....
| Ray White wrote: |
Cup seals are fairly common.... but if possible I would have replaced the wheel cylinders complete, although I appreciate the cost might be prohibitive. |
I did try to get nos wheel cylinders, sod's law, the front which are readily available seem to work if i pinch off the rears. The rears unfortunately don't seem to have been used on much else so are rare, i found one used cylinder for sale but it was £250 with no guarantee over the condition. The wheel cylinders are hard to inspect for pitting etc but they don't leak.
I just find all this really odd, as i say if the pedal didn't go down so far before activating/locking the brakes up i'd be happy with it, they don't pump up, it stops straight and all four wheel lock up at the same time. The manual says there should be 3/8" of pedal travel before the master cylinder starts to move, then the wheel should lock 1.1/2 into the travel (which is about 1/4 of the pedal travel).... at the moment the pedal goes down to about 1.1/2" off the floor (3/4 of the total travel).
So as it stands, i'm going to change the 3/16 Master - Distribution block hard pipe for a 1/4" one and then i will jack it up (get as much angle into it as possible) and then have another go at bleeding it up..... if that fails i think i will change all the internal seal springs. |
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Thu Mar 23, 2023 12:40 pm Post subject: |
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What if the Master Cylinder is worn oval ( or pitted?) at the beginning of it's stroke?
It may seal when operating just the fronts but when you add the rears it is just not sealing until it gets down towards the end of it's stroke.?
This is the trouble with old hydraulic parts. With my MG I just threw all the old stuff out and started again from scratch.
My 1930 Austin Seven Swallow has a completely mechanical system and I was able to make/repair everything quite easily.
(I am in agreement with Rick Jones that cables/rods etc are much more satisfying to work with.) |
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AVRO
Joined: 10 Mar 2023
Posts: 12
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| Posted: Thu Mar 23, 2023 1:36 pm Post subject: |
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| Ray White wrote: | What if the Master Cylinder is worn oval ( or pitted?) at the beginning of it's stroke?
It may seal when operating just the fronts but when you add the rears it is just not sealing until it gets down towards the end of it's stroke.?
This is the trouble with old hydraulic parts. With my MG I just threw all the old stuff out and started again from scratch.
My 1930 Austin Seven Swallow has a completely mechanical system and I was able to make/repair everything quite easily.
(I am in agreement with Rick Jones that cables/rods etc are much more satisfying to work with.) |
I am fairly confident the master cylinder is working, when i first refreshed the seals i had a good look at the bore with an endoscope and then had it pressure tested to be 100% sure. Since then i have effectively screwed a bleeder into the outlet on the master cylinder which resulted in next to no pedal movement (remembering i added 1/2" of free plan and the first 1/8" the recirculation holes were open, if it moved 3/4" that was all.).
The only thing i could fault on the master cylinder is the recirculation holes.... in every diagram and rebuild instructions i've come across they say it should have four or six 1/16 holes in the piston, but this only has two which means it has to be bench primed before fitting and even then i takes an age to bleed. I should have drilled two more but with parts being difficult/expensive to get hold of i was loathed to start drilling holes in things.
Chris. |
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AVRO
Joined: 10 Mar 2023
Posts: 12
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| Posted: Thu Mar 23, 2023 2:00 pm Post subject: |
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I've ordered a couple of your seal springs to check a theory off the list 
They look a lot beefier than the ones currently in the cylinders, i noticed some of the other sizes say they don't require the crown washer, i assume these is the same??
sorry i didn't see your post until Thursday morning..... there is no rush.
Thanks. |
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bjacko
Joined: 28 Oct 2013
Posts: 362
Location: Melbourne Australia
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| Posted: Fri Mar 24, 2023 7:41 am Post subject: Avro |
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Is the truck at the Avro Museum Woodford? I was an Avro apprentice at Woodford.
_________________
1938 Morris 8 Ser II Coupe Utility (Pickup)
1985 Rover SD1 VDP |
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AVRO
Joined: 10 Mar 2023
Posts: 12
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| Posted: Fri Mar 24, 2023 11:51 am Post subject: Re: Avro |
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| bjacko wrote: | | Is the truck at the Avro Museum Woodford? I was an Avro apprentice at Woodford. |
It is indeed.... if you haven't been for a while i suspect you won't recognize Woodford aerodrome now with all the houses... which is a little sad to be quite honest with you.
The museum is using what was the CAE simulator building next door for storage etc and it's in there with the 707c, Shackleton, Tri plane, 748 nose section, some engines etc.
The Museum is in what was the fire station, it's not a very big building and they are in the final stages of planning to build quite a large hanger on the side for all the exhibits collected in CAE. |
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bjacko
Joined: 28 Oct 2013
Posts: 362
Location: Melbourne Australia
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| Posted: Sat Mar 25, 2023 6:24 am Post subject: Avro Museum |
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Unfortunately I am never likely to get to the museum as I live in Australia and don't see myself traveling to UK again at my age. That fire station was not even built when I worked at Woodford.
I have seen the airfield on Google Earth with all the houses and the museums tour on the website.
_________________
1938 Morris 8 Ser II Coupe Utility (Pickup)
1985 Rover SD1 VDP |
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AVRO
Joined: 10 Mar 2023
Posts: 12
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| Posted: Wed Apr 05, 2023 5:35 pm Post subject: |
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Bit of an update.......
So i had a few things to try
I bought a pair of Dave's more modern-style cylinder springs (Nicely made and the turnaround was quick too highly recommended).
I visited Classic Brakes again but this time i took pictures and the manual, they suggested because the cylinder was mounted vertically i would need to well prime them before fitting, also spend some time getting the shoes square to the drum as perfectly set up as possible via the shoe rests.
I took our big long-reach jack to get the back end as high up in the air as possible whilst bleeding.....
So Tuesday came around and i disassembled the rear brakes again, the first obvious thing was one of the shoe square adjusters was wound out?? (i hadn't noticed that) that meant one of the shoes was visibly out of square.
I then carefully took apart the cylinders and that's where i noticed the second issue, the top crown washers on each side was dry so i'm guessing both cylinders had big air bubbles in the top, and between the crown washer and the seal was dry on the bottom ones too (i assume the crown washer was sealing round the edge trapping air under it)
At this point, i was feeling confident..... so i removed the cylinder bodies from the backing plate, cleaned the parts thoroughly and reassembled the cylinders with Dave's new springs that eliminated the need for the crown washers, i primed the cylinders with fresh brake fluid thoroughly!! and refitted the cylinders to the back plates.
The next step was to spend 30 mins with all sorts of set squares and rules getting the shoes as square as possible before reassembling the drum/hubs.
Last i jacked it up as high as it would go and bled the brakes (i had to use the pressure bleeder as i was on my own).
The result?? well, the pedal goes down to about halfway now, getting more like it but was a bit deflated at the time to be quite honest.
I've done a bit more reading up and it seems you need to introduce as much turbulence into the cylinder as possible when bleeding vertical cylinders to dislodge the air from the highest point, seems the theory is a pressure bleeder doesn't swirl the fluid enough in the cylinder to aerate the fluid.... so the knock-on effect is the fluid goes in about halfway down the cylinder and out again below the level of the bubble.
I still haven't quite got my head around why they would mount a cap-style seal twin-piston cylinder vertically?? having the bleeder halfway up the cylinder meaning half the internal volume is higher than the bleeder seems odd?? and a pain to bleed...... what's even odder is if this is simply air in the system is why the pedal is rock hard and doesn't pump up??
So next week i am going to take a helper and old school to bleed the brakes and go a bit old testament on them.
I have also spoken to a guy that restores old Landrovers, he has had a similar issue in the past and suggested pinching off the fronts while bleeding the backs to get as much displacement of fluid as possible, he also said if the shoes are new they might not fit the drum very well causing a false adjustment (i was told to cover the shoe face in calk and reassemble/adjust and then check for high spots).
Getting there a bit though now..... Then i have the clutch!! O Joy. |
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