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        General >> Problems >> New brake master cylinder problems
        
(Message started by: Kristian on May 23^rd, 2012, 12:06am)

Title: New brake master cylinder problems
Post by Kristian on May 23^rd, 2012, 12:06am

Hi fellow Scorpio owners,

I have replaced my brake master cylinder with an OE replacement. I did not bench bleed the master cylinder. The brakes have been bled at alle wheels according to the brake manual on this site.

My problem is that the brake pedal still feels soft and spongy although actual braking is fine. There are no leaks and all brakes at each wheel were just recently tested and passed the biannually emission.

The brake pedal does not travel to the floor, but can travel quite some ways when additional pressure is added.

Do any of you have any experiences and solutions to this problem?

Thanks!

Kristian (Copenhagen, Denmark)

Title: Re: New brake master cylinder problems
Post by leewar on May 23^rd, 2012, 12:11am

Sounds like you still have air in the system. Try rebleeding it. Cheers Lee

Title: Re: New brake master cylinder problems
Post by PJDavis on May 23^rd, 2012, 8:08am

That sounds like a master-cylinder problem. Silly question perhaps, but are the seals in the right way around? Also how long has that OE master cylinder sat on a shelf, could the seals be slightly perished?

Title: Re: New brake master cylinder problems
Post by Snoopy on May 23^rd, 2012, 8:17am

See HERE (http://www.fordscorpio.co.uk/manual/brake/BrakeBleed.pdf) as you have to make sure the bleeding procedure is followed otherwise you will have problems.
The bleed receptor has to be higher than the bleed nipple at ALL times.

Title: Re: New brake master cylinder problems
Post by gozz on May 23^rd, 2012, 9:30am

Kristian.
Presumably the softness is experienced when the engine is running and the servo is working ? If the pedal is high and hard without the engine, and all vacuum exhausted from the servo,then I would consider this normal.
GOZZ.

Title: Re: New brake master cylinder problems
Post by Mike H on May 24^th, 2012, 2:41pm

on 05/23/12 at 08:17:33, Snoopy wrote:

This bit:

"Position bleed jar base at least 300 mm above bleed nipple to maintain fluid pressure and prevent air leaking past the threads."

I've had similar problem with motorcycle calipers, even to the extent that end of bleed tube & jar ideally needs to somewhere near same height as the reservoir for most reliable results.

Just a note, a seized rear handbrake adjuster can produce a similar kind of symptom, insofar the long pedal travel (?)

What was the reason for replacing the master cylinder?

Title: Re: New brake master cylinder problems
Post by Kristian on May 24^th, 2012, 8:17pm

Hi guys,

Thanks for all the response. The master cylinder was on back order from the supplier. I suspect that it is fairly new (or reconditioned) with little time spent on the shelf in the warehouse. I bled the brakes according to the manual holding the bleed jar 30 cm above the bleed nipple. The brake pedal stays hard with the engine running. The handbrake was recently inspected and adjusted.
I replaced the original master cylinder because the pedal would travel towards the floor all the way - the seals were worn out.
Anyway, I guess I will bleed the brakes again and follow the described procedure precisely. I will run a lot of fluid through the lines this time. I will keep you posted if it helps. Thanks
Kristian

Title: Re: New brake master cylinder problems
Post by Kristian on Jun 10^th, 2012, 8:41pm

**UPDATE**

I bled the brakes twice making sure I followed Ford's instructions. I could not see any air coming through doing this. However, the brake pedal did get better. It seems that when replacing the cylinder and/or fluid one has to run A LOT of fluid through the system to get a good result. I would say that is about 2 litres of fluid.

Title: Re: New brake master cylinder problems
Post by Snoopy on Jun 11^th, 2012, 7:42am

I would suggest that if you have a reasonably good pedal now run the car for a couple of weeks and THEN re bleed the brakes. Any small bubbles will collect together and will be easier to see.