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How Brake Master Cylinder works

Posted by Ninh Huu Chan 
February 18, 2009 03:51PM
Dear friends,

I couldn’t open old page of BEN, but I see here many famous names, so I believe that you are the right people I have contacted. I studied in Slovakia with the name Jan Novy
My previous E30 was 325i - 12/1988, present is 320i – 10/1988 (by VIN its could be 325i). Compare with previous the present is weaker and fuel consumption is more better.
I have now problem with brake.
Firstly very bad brakes, I have changes seals of Brake Master Cylinder, now front wheels are OK, but rear brakes do not work. Brake fruit does not get to rear.
I see at the end of smaller piston of Brake Master Cylinder there is very small Valve, its seem one way valve, open when release brake pedal to normal position and close when brake.
My question is how this valve works and what happen on my car could cause by this valve.
Thanks a lot

Chan.
sdp
February 18, 2009 03:59PM
Maybe this can help you get started...

[auto.howstuffworks.com]
February 18, 2009 05:33PM
That was a great article explaining brake systems. I am no expert by any means but with a rebuilt MC you should be able to get juice to the rear calipers. There could be a big air bubble in the brake lines. What happens when you bleed the rear calipers? I would think that with the bleeder valve open you would get fluid to come out unless the line has a blockage in it. Brake lines can corrode over time, especially if the brake fluid is not changed regularly or if the car has sat for a while. Hope you get it figured out!
rkj
February 18, 2009 06:13PM
Quote
Ninh Huu Chan
Dear friends,

I couldn’t open old page of BEN, but I see here many famous names, so I believe that you are the right people I have contacted. I studied in Slovakia with the name Jan Novy
My previous E30 was 325i - 12/1988, present is 320i – 10/1988 (by VIN its could be 325i). Compare with previous the present is weaker and fuel consumption is more better.
I have now problem with brake.
Firstly very bad brakes, I have changes seals of Brake Master Cylinder, now front wheels are OK, but rear brakes do not work. Brake fruit does not get to rear.
I see at the end of smaller piston of Brake Master Cylinder there is very small Valve, its seem one way valve, open when release brake pedal to normal position and close when brake.
My question is how this valve works and what happen on my car could cause by this valve.
Thanks a lot

Chan.
rkj
February 18, 2009 06:50PM
Quote
Ninh Huu Chan
Dear friends,

I couldn’t open old page of BEN, but I see here many famous names, so I believe that you are the right people I have contacted. I studied in Slovakia with the name Jan Novy
My previous E30 was 325i - 12/1988, present is 320i – 10/1988 (by VIN its could be 325i). Compare with previous the present is weaker and fuel consumption is more better.
I have now problem with brake.
Firstly very bad brakes, I have changes seals of Brake Master Cylinder, now front wheels are OK, but rear brakes do not work. Brake fruit does not get to rear.
I see at the end of smaller piston of Brake Master Cylinder there is very small Valve, its seem one way valve, open when release brake pedal to normal position and close when brake.
My question is how this valve works and what happen on my car could cause by this valve.
Thanks a lot

Chan.

Hey Chan

You might have to spring for a new master, but do you have separate feeds for the incoming fluid, and is there a proportioning valve in the rear of the car (I think 5series are when Bmw started that though). You could try to bleed the master, the rear brake line at the master to see what you have coming out of it.

Rick
February 18, 2009 07:55PM
Thank Rick, I have separate feeds for the incoming fluid, I am not sure about proportioning valve, I need to check. It seem that fluid doesn't get into smaller cylinder area and doesn't get out from it to the rear pipe. The reason could be the valve of smaller piston. This E30 in in Vietnam longer than 15 years, nearly all origin parts. I would like to repair as I can before ordering new spare parts.
Thanks.
Chan.
rkj
February 19, 2009 01:07PM
Quote
Ninh Huu Chan
Thank Rick, I have separate feeds for the incoming fluid, I am not sure about proportioning valve, I need to check. It seem that fluid doesn't get into smaller cylinder area and doesn't get out from it to the rear pipe. The reason could be the valve of smaller piston. This E30 in in Vietnam longer than 15 years, nearly all origin parts. I would like to repair as I can before ordering new spare parts.
Thanks.
Chan.

I shy away from non working hydraulic cylinders only because of the risk factor, to me they're expendable.

Good luck Chan
February 20, 2009 01:18AM
I will order new Cylinder, 300 USD, receive in 3 days.
Thanks every body.
Chan
February 20, 2009 09:37AM
Quote
Ninh Huu Chan
I will order new Cylinder, 300 USD, receive in 3 days.
Thanks every body.
Chan

Go to stopshopanddrive.com and get new MC for $257. No need to pay $300 if you don't have too!
February 20, 2009 07:11PM
Thanks Dan, 300 US payment to commercial Company is not too much, if I import by myself with all kind of Taxes, I must pay more. Chan.
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