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Discussion Starter #1
have bleed the system 3 times ,new pads ,rotors ,stainless steel lines and m5 calipers ,car stops but long pedal ,thanks for any suggestions
 

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have bleed the system 3 times ,new pads ,rotors ,stainless steel lines and m5 calipers ,car stops but long pedal ,thanks for any suggestions
did you bleed the master cylinder?
If the system has been opened up the lines can be harder to bleed.
I will do a pressure bleed then a pedal bleed and another pressure bleed, in all at least 1 quart of new brake fluid.
The pedal bleed clears the vertical lines as the pedal bleed moves more fluid and moved it faster than pressure bleeding.
You will know when there are know more bubbles at the bleed tubing. You will want to use a length of clear tygon tubing slipped onto the bleed screw.

You could also have a bad master cylinder.
 

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Discussion Starter #3
thanks ,some have said i might need a bigger master cylinder [7 series ] to go allong with the bigger calipers ?
 

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thanks ,some have said i might need a bigger master cylinder [7 series ] to go allong with the bigger calipers ?
Not at all, not necessary, you will find the M5, 535 & 735 all use the same 23mm Master Cylinder.
An E32,750 used a larger 25mm master cylinder however that was done for other than caliper piston capacity/size.

Also, you will find the M5 front rotor is bigger however all the E34/E32 front floating calipers to include the M5 use a 60mm piston!!
The rear M5 caliper has a piston that is 2mm larger than the 535 rear caliper but that would not require a larger master cylinder as the E34, M5 & 535 use the same master cylinder!!
 

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We had a similar problem on the E38 750iL last year and we bled the system 2 or 3 times, put a new master cylinder in and it was better but still didn't feel right.

It had done 32,000kms since new and I said to the boys I bet it still has the original brake pads , IT DID.

We changed to new pads all round and the pedal felt firm and normal.

Go figure out why but it worked.
 

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We had a similar problem on the E38 750iL last year and we bled the system 2 or 3 times and still didn't feel right.

It had done 36,000kms since new and I said to the boys I bet it still has the original brake pads , IT DID.

We changed to new pads all round and the pedal felt firm and normal.

Go figure out why but it worked.
Could be the caliper pistons were sticking/binding in the caliper bores when they were extend to the limits of the warn pads.
Just a guess.

However my #1 assumption is; there was air in the master cylinder or at the top of a vertical lined and by push the pistons into the caliper you reverse bleed the master cylinder/brake lines.

If the master cylinder gets air in it bleeding the master cylinder and lines can be difficult, as pushing the air bubbles down to the caliper is going against the laws of physics, that is, while the air is being pushed down the brake lines, through the ABS and down to the calipers, if the fluid flow isn't fast/high enough the air bubble will just keep rising in the vertical line sections as you bleed the calipers.

IMHO, Pressure bleeding with 28lbs of pressure will not provide the flow necessary to bleed air from the vertical lines. Increasing the pressure above 28lbs may blow the brake reservoir off the master cylinder.
I use pressure bleeding only if I am replacing the fluid and there has not been any air introduced.
If I suspect air in the lines or I've opened the system up I will do a pressure bleed to fill the lines and calipers and then a pedal bleeding to force all the air bubbles out of the brake lines and do a pressure bleed just incase the pedal bleed created some small bubbles in the calipers by agitating the fluid with the high fluid flow rate from the pedal bleeding.
 

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Must admit I've been very tempted to try and come up with a reverse bleed system especially when doing the clutch. Anyone ever seen one or have I just revealed a money spinner to the genius who can?
 

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For the clutch, I reverse bleed with a first-aid kit irrigation syringe and a short stretch of clear line. You have to be careful to have ALL of the air out of the line and the syringe, but since it's all clear, that's easy enough. Then push it all through and up to the reservoir. If you've got a buddy working with you, they can watch for bubbles and for fluid level up topside.

http://www.amazon.com/Dynarex-Piston-Irrigation-Syringe-60/dp/B001B5NE38
 
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