Originally Posted by
RodFarva
I didn't bleed the calipers yet, after the install I hoped in and tested the pedal got the same BS jumped out slammed the door and gave the car the finger.
don't try to diagnose something as wrong until the entire job is complete.
replacing the BMC and not bleeding the entire system is paramount to rebuilding and engine and starting it before putting oil in it and then trying to figure out why it won't maintain idle.
Get the system thoroughly bled and then we'll go from there.
Originally Posted by
KendallH
Also boosters never go bad.
even more
you're kidding right?
a rubber seal, that is in an engine bay with a widely varying temperature range, that as different levels of vacuum applied to it never goes bad? Wow.
I wonder what I was doing wrong with the handful of boosters that I've replaced. I mean, they quiet obviously wouldn't hold any sort of vacuum, and just whined, and one of them wouldn't release the pressure as it built up until it eventually ruptured.
So yes, boosters do go bad.
perhaps no where near as often as other parts, and is typically not the issue, but they do in fact go bad.
Originally Posted by
RodFarva
I know I haven't finished the job because the calipers haven't been bled. But the issue I'm having difficulty understanding is how they work fine when there is no vacuum but when vacuum is supplied they malfunction. Something I forgot to mention earlier is if I rev the engine the pedal moves up and down with the engine speed I.E. revs up pedal rises a bit back to idle pedal goes down, higher rev up pedal goes even higher.
they aren't really working fine when there is no vacuum. You just think they are working because you don't have the same strength as you do when you get the vacuum assist from the booster. When you are using just your foot, no assist, then you can only apply so much force. The pedal will feel firm, and the calipers will engage, some. Which will make you think that it is work.
Then you apply the vacuum assist and it multiplies that force several times. This is what makes the pedal more soft to push on as compared to when there is no vacuum. Now what is happening is that you are compressing the pockets of air in the lines, which is letting the pedal go basically to the floor and not supplying much if any stopping power. Ironically enough, it is the same amount of stopping power that you thought was there when you pushed with just your foot.
now, since you say the pedal moves in relation to engine speed, that would indicate to me that either A) you need to adjust the rod that connects the pedal to the BMC. if it is a bit too short, the brakes will be partially engaged and when the booster fluctuates the amount of vacuum assist it can supply, the pedal will move. and/or B) it would also make me question if the booster was tweaking out and staying engaged itself. Holding too much vacuum.
Did the car sit for a long time?
One the few that I had to replace, the car has been sitting for 6 months to a year.
I got lucky and had a parts car to pull what I needed off of so I've never had to buy a brand new booster.
Also, something to consider, the BMC's you get from advance are re-manufactured units. meaning, they are metric pieces of metal that are torn apart and filled with SAE seals, so they can very well be bad when you get them.