Problems getting firm brake pedal with silicone fluid

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jagnut66
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Re: Problems getting firm brake pedal with silicone fluid

Post by jagnut66 »

I trust that you put the copper washer in place between the hose and union?
Thanks for the reminder Phil, sometimes the basics are easy to overlook when you are trying to work through a bigger problem.
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
Sleeper
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Re: Problems getting firm brake pedal with silicone fluid

Post by Sleeper »

jagnut66 wrote: Fri Apr 24, 2020 2:10 pm
I trust that you put the copper washer in place between the hose and union?
Thanks for the reminder Phil, sometimes the basics are easy to overlook when you are trying to work through a bigger problem.
Best wishes,
Mike.
And checked with a magnet they are copper..

John ;-)
jagnut66
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Re: Problems getting firm brake pedal with silicone fluid

Post by jagnut66 »

And checked with a magnet they are copper..
Did that as soon as they arrived. :D https://www.ebay.co.uk/itm/1X-80pcs-Cop ... Swp2hek~zG
With everything else checked it now looks like I have a weep from my 'new' drivers side caliper.... :roll:
Just as I thought I was getting somewhere......
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
dp
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Re: Problems getting firm brake pedal with silicone fluid

Post by dp »

From whereabouts on the caliper? Could just need the hose union or bleed nipple need tightening. If it's leaking from the pistons send it back for a replacement. If you get a brake hose clamp you can remove the caliper without having to re-bleed the whole system. I'd be inclined to pull out the pistons to see if there is scoring in the piston bores or a worn seal as evidence it was not reconditioned properly.

I know it's more work you didn't think you'd have to do but you're getting closer all the time.

As an aside, I've had to cut out and weld in new metal where standard brake fluid had rotted the paint away unseen on my old Merc so I love silicon brake fluid just because it doesn't strip paint.
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BobHood
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Re: Problems getting firm brake pedal with silicone fluid

Post by BobHood »

Dot 5 used to be recommended for bikes as well, but then it was discovered that it doesn't absorb moisture like Dot 4 does. So you could get pockets of water in the system causing corrosion. After that it was back to Dot 4 and no more problems with rusty joints!

One thing I've found when bleeding brakes is that it's a good idea to push the pistons back into their bores (on all the wheel cylinders) as far as they'll go and clamp them there. This helps prevent a scenario where there is air in the fluid behind the piston that doesn't get pushed out of the bleed valve during bleeding, but remains behind the piston and keeps the sponginess even after the bleeding has taken place.

I normally use a G clamp on each piston to keep it back against the back wall of the cylinder, so any fluid remaining will be flushed out through the bleed valve.
Bob's Boring! (or so I've been told) :D but I do honing as well!
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les
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Re: Problems getting firm brake pedal with silicone fluid

Post by les »

I’ve never had to go to those lengths, thank goodness ! :o —- and must have been lucky to have avoided pockets of water.

oliver90owner
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Re: Problems getting firm brake pedal with silicone fluid

Post by oliver90owner »

les wrote: Sun May 10, 2020 2:22 pm I’ve never had to go to those lengths, thank goodness ! :o —- and must have been lucky to have avoided pockets of water.
Only a problem with motorbikes, I would guess? The master cylinders and reservoirs tend to be open to the elements a tad more than any car. Air is being drawn in and exhausted to and from the reservoir on every operation of the brakes.
les
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Re: Problems getting firm brake pedal with silicone fluid

Post by les »

I sometimes wonder where these ideas originate from, it’s certainly a new one on me, and the first time I’ve heard it put forward.

jagnut66
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Re: Problems getting firm brake pedal with silicone fluid

Post by jagnut66 »

Could just need the hose union
It was weeping from where the flexi-hose screwed into the body of the caliper, I had tightened it as far as it would go, any tighter and I would have just have started stripping the thread.
I could have tried re-tapping the thread into the caliper but then I might have just made it looser and risked metal filings in the brake system.
One replacement caliper (and a hose to be sure) later and that has cured it.
I bled it through again, left it overnight with the rear of the car higher than the front (as recommended in an earlier reply) and then bled it again the following day, so far (plus touching lots of wood :wink: ), I have a firm pedal and brakes that lock the wheels when pressure is applied.
Hopefully that's the end of it.
Hopefully........
After all that messing about, repeating the same job several times just to come up against another issue each time, my confidence has taken a little knock, which will only be reversed once they have been working without issue for a while.....
As an aside, after all that the only parts of the original brake system to be still in use are the rear connectors and their associated brass banjos, new bleed nipples and copper washers on them though.
Mind you I have ordered replacements from ESM, in case these original parts decide to throw a wobbly........ :roll:
For now though I'm just waiting for a locking tool to arrive, so that I can get on with the engine.
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
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