Problems getting firm brake pedal with silicone fluid

Discuss mechanical problems here.
Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Sat Apr 18, 2020 9:20 pm

Hi,
I was hoping someone can advise me:
I am unable to get a consistently firm brake pedal with the silicone brake fluid I have installed in my renewed braking system, the set up is this:
New brake master cylinder, with rubber 'cap' removed to allow for new Ford vented disc kit at the front (so new calipers).
New wheel cylinders at the rear plus new shoes.
New cunifer brake lines and new flexi-hoses, running through cleaned out and refreshed brass junctions.
The reason I emphsize the 'new' is so you know that none of it has been contaminated with age or previous use with Dot 4 fluid.
I have bled the system through with the 'Gunson Eezibleed' kit using tyre pressure and have silicone fluid at each bleed nipple.
Possibly not enough pressure though??
It will give me a firm(ish), though well depressed, pedal the first time of asking, which locks the front brakes....
But not the rears...
And the second time of asking it doesn't lock the fronts.......
This is with the eezibleed kit removed, with it attached I do get a firmer pedal before I disconnect......
So the question is: what am I doing wrong / not doing??
As an aside the rear brakes are set up correctly and the system does not include a servo or remote reservoir.
Many thanks in advance for any help.
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......

oliver90owner
Minor Addict
Posts: 932
Joined: Thu May 12, 2016 6:33 am
MMOC Member: No

Re: Problems getting firm brake pedal with silicone fluid

Postby oliver90owner » Sat Apr 18, 2020 9:27 pm

Seems, to me that one end of the system is limiting the braking to the other end. A poor man’s “dual circuit” braking system that is not working.🙂. I very much doubt it has anything to do with the brake fluid.

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Sat Apr 18, 2020 9:37 pm

I've run this set up before on others with Dot 4 fluid, without issue.......
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......

les
Minor Maniac
Posts: 7609
Joined: Tue Feb 12, 2002 12:00 am
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby les » Sat Apr 18, 2020 9:44 pm

I use the same method as you, using the ezibleed system, which works ok with silicone, the pressure of the driver tyre is 10- 15 lbs pressure from memory. It might be worth pumping the pedal a couple if times before disconnecting. I’m assuming the reassembly of the master cylinder was correct, after removing the top hot seal, I’m sure it was.
I have heard of the rear cylinders sometimes being difficult to remove air from. Jacking up the rear might be helpful, although I have not had to resort to that before.


midget
Minor Fan
Posts: 372
Joined: Fri Jul 18, 2014 10:51 am
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby midget » Sun Apr 19, 2020 10:11 am

During my restoration of the Van, I too renewed all cylinders/pipes and fitted esm/Marina disc set up and changed to dot5 fluid. Using the easibleed method I had similar pedal. Tried again using "Manual" method and they are now perfect.
I have no idea why this was, because I have successfully used the easibleed kit in the past with no problem?
John

simmitc
Moderator
Moderator
Posts: 3761
Joined: Thu Apr 15, 2004 9:43 am
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby simmitc » Sun Apr 19, 2020 12:26 pm

I doubt that it is the fluid. Basically as above suggestions, try jacking rear and manual bleeding with two people.

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Sun Apr 19, 2020 5:13 pm

I doubt that it is the fluid. Basically as above suggestions, try jacking rear and manual bleeding with two people.
Tried this without success............
However I found a weep when the system is under tyre pressure, which I may have missed before, between the rear flexi-hose and the brass union. Upon inspection it appears to have chewed the thread, despite my being really careful not to over do tightening things.
However, once removed, I tried it in an old union I have and it was very tight, so I am now wondering if it is the right thread for the Morris unions??.......
To play safe I have ordered a replacement from ESM, if this fits without issue I shall have words with the other company who supplied the flexi-hose I was using, as it was listed for a Morris Minor.
Once it's back together I will have another try at bleeding the system, though if it still doesn't work I shall be sorely tempted to drain the system, blow it through and refill with some Dot 4 I have on the shelf.......
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Sun Apr 19, 2020 8:29 pm

After all that I went off for some garden therapy, suitably chilled I now need a beer! :D
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......

Nickol
Minor Addict
Posts: 528
Joined: Fri Apr 18, 2014 2:40 pm
MMOC Member: No

Re: Problems getting firm brake pedal with silicone fluid

Postby Nickol » Sun Apr 19, 2020 8:35 pm

Bremsen layout - Gewinde Verbindungen.jpg
Bremsen layout - Gewinde Verbindungen.jpg (684.14 KiB) Viewed 646 times
This sktech which was originally here in the Forum from Declan, I think shows where differing BSF -UNF threads are used in the Morris Minor braking system
Gott schütze mich vorm Sturm und Wind und Autos, die aus England sind.
download/file.php?id=4822[/sig]

les
Minor Maniac
Posts: 7609
Joined: Tue Feb 12, 2002 12:00 am
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby les » Sun Apr 19, 2020 10:48 pm

It would be disappointing to refill with dot 4, to find the same difficulty. It can’t be the fluid because many, me included, have successfully bled the Minor system with silicone. Perhaps the issue you have found will help..


Sleeper
Minor Addict
Posts: 625
Joined: Tue Nov 08, 2016 3:18 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby Sleeper » Mon Apr 20, 2020 6:46 am

DOT whatever , brake fluid ( hydraulic fluid ) doesn't compress , if there's air in the system , it needs getting rid of..

John ;-)

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Tue Apr 21, 2020 2:51 pm

Just waiting for replacement parts from ESM, so I can eliminate the air in the system issue, before I try bleeding the brakes again.
So I thought I'd reassemble my engine in the meantime, only to discover I've misplaced my head nuts...... :roll: :lol:
Not my day, is it........ :wink:
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......

oliver90owner
Minor Addict
Posts: 932
Joined: Thu May 12, 2016 6:33 am
MMOC Member: No

Re: Problems getting firm brake pedal with silicone fluid

Postby oliver90owner » Tue Apr 21, 2020 4:34 pm

Are they on the studs?

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Wed Apr 22, 2020 9:43 am

Are they on the studs?
:lol: If only!
Never mind, replacements ordered, along with some other bits. They'll turn up when I'm not looking for them, put somewhere where I wouldn't loose them no doubt! :roll: :wink:
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......

Murrayminor
Minor Fan
Posts: 416
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby Murrayminor » Wed Apr 22, 2020 11:00 am

I spent ages bleeding the brakes on my minor having fitted a new braking system all round, inc pipes, flexi shoes etc.

I appreciate you have discs fitted, but I found lots of air trapped in the system and had to bleed the system many times before all the air was expelled.

I than wedged the brake pedal down overnight with the rear of the car as high as I could get it, and that did the trick, the rear cylinders are designed with a suitable pocket where the air gathers.

Once I managed to expel the air all was well, oh and that was with Silicone brake fluid.

hope you get sorted.
Proud owner of my first Morris Minor

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Thu Apr 23, 2020 3:39 pm

I spent ages bleeding the brakes on my minor having fitted a new braking system all round, inc pipes, flexi shoes etc.

I appreciate you have discs fitted, but I found lots of air trapped in the system and had to bleed the system many times before all the air was expelled.

I than wedged the brake pedal down overnight with the rear of the car as high as I could get it, and that did the trick, the rear cylinders are designed with a suitable pocket where the air gathers.

Once I managed to expel the air all was well, oh and that was with Silicone brake fluid.
Duely noted.
Did you bleed them again in the morning, having left the wedged pedal overnight?

As an aside, I have now received a replacement rear hose and brass union from ESM and guess what??
They fit together a treat, perhaps I should have ordered the hoses from a main supplier in the first place......
Below is a picture of the original (wrong) replacement hose I ordered (top), with the correct ESM one and replacement union below.
You can see the threaded part is too long for the union, yet it was sold as a Morris Minor item....
The threads look the same, yet the one from ESM screws straight in by hand. The other was tight from the outset.
Which, I know, with hindsight should have been a giveaway from the start.
Now though, it's back to the bleeding.......

Many thanks to all and best wishes,
Mike.
Wrong Goodrich brake hose sent.JPG
Wrong Goodrich brake hose sent.JPG (1.22 MiB) Viewed 432 times
1954 Series 2 on axle stands needing more welding......

philthehill
Minor Maniac
Posts: 7739
Joined: Thu Jul 19, 2012 12:05 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby philthehill » Thu Apr 23, 2020 4:15 pm

I trust that you put the copper washer in place between the hose and union?


alanworland
Minor Legend
Posts: 1328
Joined: Tue Jan 30, 2007 10:09 pm
MMOC Member: No

Re: Problems getting firm brake pedal with silicone fluid

Postby alanworland » Thu Apr 23, 2020 11:08 pm

Those threads look different?
I seem to recall when working on my brake fittings they were of a different thread to later installations, BSF/UNF type of problem.

Alan
Image

Murrayminor
Minor Fan
Posts: 416
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby Murrayminor » Fri Apr 24, 2020 7:56 am

jagnut66 wrote:
Thu Apr 23, 2020 3:39 pm
Did you bleed them again in the morning, having left the wedged pedal overnight?

Yes I bled them the day after and they worked a treat with a solid pedal.
Proud owner of my first Morris Minor

Online
jagnut66
Minor Legend
Posts: 2556
Joined: Fri Apr 11, 2008 7:28 pm
MMOC Member: Yes

Re: Problems getting firm brake pedal with silicone fluid

Postby jagnut66 » Fri Apr 24, 2020 9:30 am

Thanks, I know it may have seemed like an obvious question, however I am new to silicone fluid, so thought I would ask.
Best wishes,
Mike.
1954 Series 2 on axle stands needing more welding......


Who is online

Users browsing this forum: Google [Bot], Napoleon Boot and 8 guests