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Re: soft brakes

if all calipers have been bleed, and pedal travel is still basically to the floor, before any braking happens, its the MC.....but its only 4 years old and has only seen 2 seasons (maybe 1 year) of service, why such an early fail.....
could any thing else account for this soft bake pedal

Thanks John

The Bentleys e28 MX Manual ...

Does not list this as a requirement for the e28 and since the e24 and e23 systems are the essentially same, I don't consider it requirement.

That being said, "cycling" the ABS whilst flushing IS a requirement for some of the early "IX" 3-series models.

Lastly, on your new MC... besure to fully charge it with fluid before intalation. It makes the ultimate bleed operation much easier.

And Finally... I strongly recommend the Bentleys e28 manual as a basic reference manual when doing surgery on the e23...jsJohn Stein
85 745 @ 1.2 bar
85 M635CSi
84 633

Thanks John - one more question...

Sounds like I need to get me a new master cylinder.

I recently acquired the bavauto pressure bleeder. Do I need to actuate the ABS when flushing? I read a post that said this is necessary to shake loose system contaminates. If this is req's, can it be actuated via pind connecter under hood?

As always thanks.

Fife

I second this great comment!

one last thought... a flashing / blinking ....

brake light can be as simple as a low fluid level or a loose wire / bad connection at the brake fluid level sensor .... js John Stein
85 745 @ 1.2 bar
85 M635CSi
84 633

A little bit about our brakes....

Failed brake bomb will give you:
* a VERY hard pedal
* a pedal "rebound" upon brake application
* very difficult braking

A failed Master Cyl. or (air in the brake lines) will give you
* a VERY spongy brake pedal
* erratic directional control whilst braking (depending upon where the air is in the line)


So what causes a failed bomb.... as far as I know..it is only age (time in use) related

What causes a failed MC ? Quite simply failed seals.

So what causes seals to fail..... the painful truth... poor MX

Quite simply, a brake system that has the fluid changed each and every year (as called for in the MX Manuals) will virtually NEVER fail ....

Why?

Because fresh brake fluid, with no moisture content is incapable of corroding the Master Cyl walls. MC wall corrosion creates micro-fine knives that CUT the lips of the rubber seals.

So, when you use the "pump" method to bleed the brakes on a tired poorly maintained brake system you are virtually assured of killing your MC.

Lastly.. one more reason to fully flush the brake system EVERY IAW the mx manuals....

Guess what happens during the first really hard freeze when you have old brake fluid LOADED with moisture... you get little ICE CRYSTAL KNIVES in your brake fluid.

Those little ice crystal knives cut the lips of the MC seals and .... you guessed it... you have a MC (brake) failure...

(hint.... if your brake fluid is more than 1 year old.. go change it. If you are lucky, the fluid will actually dribble out when you open the caliper bleeder. However you may need to help it along with a vacuum or blow through type bleeder. Worst case .... if you HAVE to pump it out... DO NOT !!!!!! use a full pedal stroke... Keep your stroke to the "NORMAL" stroke range.)

Regards All

JS
John Stein
85 745 @ 1.2 bar
85 M635CSi
84 633

Bad Master Cylinder Symptoms... ?

As I was telling Richard in his thread
http://bimmer.roadfly.com/bmw/forums/e23/7013946-1.html
I messed up my Master Cylinder in the bleeding process. Well the symptoms where very soft brakes (almost nothing) when braking slowly like at stop sign, my foot would reach the floor and the car would still moving. But there was some braking power(at least more than the first case) when I had to brake hard.
All this gone when I got a new MC ( on eBay for about $60, I got lucky).
Anyways, I think one way to test the bomb(ppl correct me if wrong) is to pump the brakes with the engine shut, and count how many times it takes until it gets hard... I think around 15 times is normal, but look it up because I'm not sure. I hope this helps.

Re: soft brakes

Sounds like air in the line. I would bleed the break first.

Accumulator goes, you would notice it at sudden/emergency breaking condition. Lack of break boost would makes it feel like your break is not working at all for forst second or two.

which dash warning light is on?

there are many:
brake linings, parking brake, ABS, & brake (meaning pressure - this one is for the bomb).

soft pedal could be caused by air trapped in lines; solved by flushing all lines.http://members.roadfly.com/mywong23/new mex.jpg

Re: soft brakes

Soft brakes are the symptoms of brake Master Cylinder.
Get the kit from dealer or Autohaus Arizona.
Cheers
Kumar

Re: Brake bomb

Please check with "AUTOHAUS Arizona"
They are the best in the market in price & delivery.
Cheers
Kumar

soft brakes

I guess I jumped to the conclusion that the bomb is the culprit. My brakes are EXTREMELY soft. Air in the lines? Accumulator? Any suggestions?

TIA
Fife
'86 L7

Brake bomb

Where can I get a brake bomb for a good price? I bought one about 5 years ago and it was $65 (ATE - OEM). Now they are $135. Is this a reasonable price or can I get one cheaper.

TIA

Fife
'86 L7