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914World.com _ 914World Garage _ bleeding brakes after caliper conversion

Posted by: Neal Apr 24 2004, 07:07 PM

I just installed 320i calipers and I have bled all 4 corners but I still have almost no pedal pressure. I have ss brake lines and the calipers were rebuilt. Can somone give my an idea on what to do. I looked at Proportioning valve with a search but I don't know if you can bleed them also ?

Neal

Posted by: mike_the_man Apr 24 2004, 07:15 PM

get rid of the proportioning valve. Replace it with a T. What about the master cylinder? Did you replace it? Is it good? Get rid of the prop valve and keep bleeding. Good luck!

Posted by: Neal Apr 24 2004, 07:41 PM

Brakes were good this morning before the conversion. 19mm M/S which is new rear calipers are new. I asked if you could bleed the propotioning valve or where there could be more air trapped. As I said I have bleed all 4 wheels and I did not see any more air there.

Posted by: Dave_Darling Apr 24 2004, 08:24 PM

Keep bleeding, you've still got air trapped. You can bleed the prop valve the same way as the calipers, except that you crack open the outlet fittings (the inlet is the one on the bottom, the outlets are the other ones) one at a time instead of a bleeder valve. Have a rag wrapped around the fitting, as brake fluid is kinda nasty stuff. Clean up with water after you're done, because the water will neutralize the brake fluid and may save your paint.

Make sure that the bleeders are at the top of the calipers, not the bottom. If you bleed from the bottom fittings, you'll never get the air out because air rises. (Don't ask how I know...)

Bleed all around the car; air has a seemingly-magical ability to teleport from one end of the brake system to the other.

--DD

Posted by: Neal Apr 24 2004, 09:04 PM

Dave, when you say outlets are you speaking of the prop valve ?. The rear calipers on my car have two bleeders 1 top one bottom, I did bleed from the bottom. The 320i calipers only have one bleeder and it's on the bottom. Should I bleed the prop valve 1'st or the calipers. Thanks for taking the time to reply I need to fix this as I have no brakes at this time. When I bled I did not see any air in the clear tube I used how will I know when I am air free, is it by pedal pressure ?

Neal

Posted by: J P Stein Apr 24 2004, 09:13 PM

Air rises in fluid.
You're never gonna get it out bleeding from the bottom of the caliper. I know nuthin about BMW calipers
but it sounds like you have the fronts on the wrong sides of the car......bleeder screws on the bottom?

Posted by: Neal Apr 24 2004, 09:39 PM

JP, they only fit one way as far as I could tell

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Posted by: Slowpoke Apr 24 2004, 09:46 PM

Sorry, they are on the wrong sides. Bleeders must be on the top.
Peter

Posted by: Neal Apr 24 2004, 10:25 PM

Well isn't that the shits, well it's a learning procees. I get to do it agin tomrrow

Neal

Posted by: Dave_Darling Apr 24 2004, 11:26 PM

When I said "outlets", I did mean on the prop valve.

And you must always bleed from the top of the caliper. You have now experienced why you don't bleed from the bottom--you cannot get the trapped air out. Swap the fronts, bleed the rears from the top bleeders, and bleed the fronts.

The pedal should be nice and firm when you're done.

--DD

Posted by: Neal Apr 25 2004, 12:12 AM

Dave, you are the man !, I just swapped the calipers, bleeder now on top, which is something I will never forget. Bending the tubing for a second time to fit the inlet on the calipers is not fun !. I will follow your instructions tomorrow.
I had emailed the person I bought the calipers from and he replied and said I had them swapped. At least he is supportive of my ignorance.

Neal