Is This Problem BPMV or EBCM?
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,085
Likes: 27
From: San Diego CA
Is This Problem BPMV or EBCM?
After a couple of laps on the track my brake pedal drops quite low. This has been going on for 4 track weekends. Often it happens from one corner to the next. It seems to happen after ABS is engaged the first time, but I can't be sure that is always the case because I am not always looking at the display. But this was the case yesterday since I watched it closely to test that theory. The pedal got a bit soft when the ABS engaged, and it was quite low for the next corner.
When I bleed the brakes I get a lot of air from both rears (not just bubbles, but large gaps in the fluid as it goes through the hose to the catch bottle.) Almost nothing from the fronts (a few small bubbles at most.) Using a Motive pressure bleeder, it takes about 20 seconds for the air to come out, so it is coming from a distance. I know it is not: the master, the calipers, the rotors, leaky brake line connections, pad knockback, etc. All parts swapped and lines inspected several times.
Supposed to race next weekend, so getting desparate.
TIA...
When I bleed the brakes I get a lot of air from both rears (not just bubbles, but large gaps in the fluid as it goes through the hose to the catch bottle.) Almost nothing from the fronts (a few small bubbles at most.) Using a Motive pressure bleeder, it takes about 20 seconds for the air to come out, so it is coming from a distance. I know it is not: the master, the calipers, the rotors, leaky brake line connections, pad knockback, etc. All parts swapped and lines inspected several times.
Supposed to race next weekend, so getting desparate.
TIA...
Tech Contributor
Joined: Oct 1999
Posts: 41,030
Likes: 9,782
From: Charlotte, NC (formerly Endicott, NY)
If you are getting air into the brake lines it isn't the fault of the EBCM. There could be a leak in the BPMV but I would suspect air got in the BPMV due to the system fluid level getting too low during brake bleeding or when somebody did some work on the brake system. Why not find some place where you can test the ABS by applying the brakes hard enough to activate it and see if it gets soft again. If you continously get air in the system after repeated ABS stops there might be a leak in the BPMV. Sometimes leaks in the BPMV will show up in the interface between it and the EBTCM.
When air gets into the BPMV the manual says to use a Tech 2 to activate the valves while bleeding the brakes so air caught in the valve will pass through it. Since most people don't have a Tech 2 at home some of them bleed the brakes and then go out and activate the ABS to get the valve to bleed. Supposedly this works but I have never done it so cannot verify that it does work.
Bill
When air gets into the BPMV the manual says to use a Tech 2 to activate the valves while bleeding the brakes so air caught in the valve will pass through it. Since most people don't have a Tech 2 at home some of them bleed the brakes and then go out and activate the ABS to get the valve to bleed. Supposedly this works but I have never done it so cannot verify that it does work.
Bill
Last edited by Bill Dearborn; May 31, 2009 at 07:30 PM.
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,085
Likes: 27
From: San Diego CA
Brakes had been Tech 2 bled (complete fluid flush - using different color fluid even) after manual bleed got the usual air. They said no air came out. The brakes have been manually bled about 20 times now (more than half before the Tech 2 bleed done.) I have done 2 track days of testing over the last few weeks. Same thing every session (about 7 times on track since Tech 2.)
Today I pulled the EBCM off. No leaks from the BPMV into it. No signs of brake fluid on outside of BPMV.
Can't drive car on street to test. Been testing at tracks.
Today I pulled the EBCM off. No leaks from the BPMV into it. No signs of brake fluid on outside of BPMV.
Can't drive car on street to test. Been testing at tracks.
Last edited by Bimota Guy; May 31, 2009 at 09:56 PM.
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,085
Likes: 27
From: San Diego CA
