Soft Brake Syndrome

[karmajampa]

Hi All,
Kel here again from Aotearoa New Zealand with a '93 827 Sterling, NZ assembled.
My mechanics who do my vehicle inspection certificate indicate a concern regarding the brake functioning, not that the brake does not act properly but that the pedal does not start to take effect until 2/3 depressed, whereas they would prefer it to engage at 1/3 depression.
I have in the past had the master cylinder refurbished twice, not for the same part of the device, and a brake fluid hose replaced that appeard to be letting in air.
However this concern about the brakes being 'soft' remains, and several people who drive my car for me, as I am myself blind, comment that the brakes are not what they are used to.
Does anyone have any comment that I can pass on to my mechanics the next time I am due for a warranty test that they can check. I have already spent reasonable dollars on this and would like to see a more convincing result.

TIA
Kel.

[BlueRover]

When any brake work is done, the system needs bleeding in a particular order for the abs system to operate correctly. The fact that there is a cycling pump in the control unit means that if the system is bled incorrectly there may still be air in the pipes. I don't know in which order it's supposed to be done but if you search the forum the information is there. I would suggest a full bleed of the system with fresh fluid.

Found the order (for all models) :-
1. Front Left
2. Right Rear
3. Right Front
4. Left Rear

[dollysprint]

Hi Kel
Forgive my ignorance, would I be right in thinking that New Zealand drive on the left like us Brits, so right hand drive? Therefore this car would effectively be a UK spec vehicle? And I assume it has ABS braking?
From what you describe in all other respects do the brakes work as they should? and is the pedal "soft" or just long? And did this problem start before or after the master cylinder rebuild?
I would check the brake pedal clevis pin first to see if there is any wear there, its where the master cylinder plunger meets the brake pedal, this hole can elongate through wear and give an impression of a long pedal travel.
Secondly I would check that none of the rubber hoses are "bulging" under braking due to age fatique, although I would assume you vehicle inspection certificate, like our MOT would check for this.
Thirdly the ABS pumps can give problems especially if air was drawn in during the master cylinder rebuild, try a vacuum brake bleed through the whole system with the pump energised, i e engine running, if nothing else this will ensure any dirty old fluid is removed.
Lastly, and I dont know if this applies to your car, but has it got the correct fluid in it? Again a vacuum bleed with a decent dot 4 fluid would ensure it has, a few years back when silicone fluid was all the rage you just could not get a good pedal on some brake systems.

Dave

[Richard Moss]

Dave, both Australia and (more civlised) New Zealand have right hand drive cars and drive on the correct side of the road.

[karmajampa]

Thanks for the info Guys, I will pass this on,
Yep, we are right-hand drivers, reasonably civilized with some tendency towards impatience.
Dave, the long reach of the pedal was there before either refurbishing of the master cylinder but the bleed sequence and oil type will be of interest. I don't do a lot of distance so think the oil is fairly fresh.

Kel.

[rovering]

As a point of interest......my Mk2 has much 'softer' brakes than my Mk1.
Both cars have had fluid replacement, pads etc.
The other Mk2 I had as spares was the same as well.

Has anyone else noticed this between the Mk1 and Mk2?

Graeme

[mercedade]

Graeme,

Yes, mine is the same. The Vitesse has Goodridge braided hoses all round, fresh fluid, the lot and is still nowhere near as sharp as the Mk1 I had.