8 replies to this topic

[JamesC]

Hi all

I’ve been searching for a while now and unable to find the answer.

I have a single line brake setup with 7.5 discs up front and drums at the rear.

The discs and pads have plenty of material remaining. The rear drums have been completely replaced and new fluid throughout. The rears have been adjusted to suit and a little bit of driving to bed them in.

The system was bled three times with a Gunsons easy pressure bleed kit.

The problem I have is the pedal requires pumps to build pedal pressure. The pressure then fades if holding down the pedal.

Would this mean the seals in the master cylinder are failing?

This pressure issue was also around before the drums were replaced. I hoped the new parts and a fresh bleed would sort it out.

Thank you

[hunterg30]

Sounds like the master cylinder seals are leaking

[richmondclassicsnorthwales]

If you are running with the original tin master, I would second hunterg30 opinion

 

The rear brakes can take a good bit of bleeding

 

The symptoms you describe though, do point to the master not doing it's job as it should

[cal844]

Give all 4 corners a good bleed using the two man method, also try to hold pressure whilst opening the nipples, see if that helps.

Can you pump the pedal solid and then hold the pressure, or does the pedal drop if you do this?

[JamesC]

If you are running with the original tin master, I would second hunterg30 opinion

The rear brakes can take a good bit of bleeding

The symptoms you describe though, do point to the master not doing it's job as it should

Ok thanks. No, the master was replaced just over a year ago with one from MiniSpares. I believe it’s the 3rd one in my 6 years of ownership.

[JamesC]

Give all 4 corners a good bleed using the two man method, also try to hold pressure whilst opening the nipples, see if that helps.

Can you pump the pedal solid and then hold the pressure, or does the pedal drop if you do this?

Ok will try to bleed again. Pumping the pedal does build pressure. Only really needs 1-2 pumps to work. It then starts to lose pressure and feel weak under the foot.

[Shooter63]

Ok thanks. No, the master was replaced just over a year ago with one from MiniSpares. I believe it’s the 3rd one in my 6 years of ownership.[/quote]

Definitely check the master cylinder minispares had a duff batch ( how the hell you have a duff batch of master cylinders is beyond me on a safety critical part)

Shooter

[Chris1275gt]

Have a read of this:-

https://miniworld.co...safety-grounds/

[JamesC]

Thank you. Exactly, such an important part. I’ll take it off and have a look. Are there any upgrade options beside the KAD AP racing set?