can someone explain the brake bomb
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Guest
Yes, you have a hydraulic system accumulator (AKA "brake bomb" ) since your car has an M30.
Most of the time, the hydraulic pump can put out sufficient flow at pressure to operate the steering and brakes. However, if it can't keep up with the demand on the brake side (i.e. during a rapid application or if the engine isn't running), the accumulator will provide extra fluid at pressure (that's why it has a diaphragm with pressurized gas inside it) to help operate it.
This is why if the accumulator is bad , the brakes are hard to apply rapidly.
This is also why you have to pump the brakes repeatedly to discharge the accumulator before checking the fluid level.
[Edit by Shawn D. on [TIME]1115144980[/TIME]]
Most of the time, the hydraulic pump can put out sufficient flow at pressure to operate the steering and brakes. However, if it can't keep up with the demand on the brake side (i.e. during a rapid application or if the engine isn't running), the accumulator will provide extra fluid at pressure (that's why it has a diaphragm with pressurized gas inside it) to help operate it.
This is why if the accumulator is bad , the brakes are hard to apply rapidly.
This is also why you have to pump the brakes repeatedly to discharge the accumulator before checking the fluid level.
[Edit by Shawn D. on [TIME]1115144980[/TIME]]
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smackmybutter535i
- Posts: 426
- Joined: Feb 12, 2006
No.Originally posted by smackmybutter535i
Could I have funny shifting due to the Bomb? I know It's bad and I need to replace it but does it effect the clutch?
[Edited 8/24/2008 to enable BBCode]
Last edited by RonW on Aug 24, 2007 6:03 PM, edited 1 time in total.
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Aaron from Aus
- Posts: 559
- Joined: Feb 12, 2006
- Location: Australia
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I done a write up on my site that i will be redoing with what it actually is.
But it gives you an idea here:
http://users.tpg.com.au/schrick/Bomb.htm
But it gives you an idea here:
http://users.tpg.com.au/schrick/Bomb.htm
[QUOTE="88 535is south florida"]my brake pedal hisses when i push it most of the time.. was just wondering what the 'brake bomb' is and maybe if i 'have it' (@) [/QUOTE]
Since the original post was in regards to a "hissing" in the pedal, I'll suggest the problem may not be in the bomb but in the master cylinder and I'd suggest the E32 part from Steve Haygood as a possible cure. My experience with "bomb" defect symptoms is a hard pedal and little or no brakes during a simulated panic stop, as if the power assist isn't workingwhich essentially is what's happenning if the bomb dies. With a m/c failure you often get a slow drop in the pedal under braking accompanied by a "feeling" in your foot of air/fluid passing the seals which could be construed as "hissing". Just something else to consider.
Since the original post was in regards to a "hissing" in the pedal, I'll suggest the problem may not be in the bomb but in the master cylinder and I'd suggest the E32 part from Steve Haygood as a possible cure. My experience with "bomb" defect symptoms is a hard pedal and little or no brakes during a simulated panic stop, as if the power assist isn't workingwhich essentially is what's happenning if the bomb dies. With a m/c failure you often get a slow drop in the pedal under braking accompanied by a "feeling" in your foot of air/fluid passing the seals which could be construed as "hissing". Just something else to consider.
[QUOTE="BMWCCA1"]I'll suggest the problem may not be in the bomb but in the master cylinder and I'd suggest the E32 part...[/QUOTE]
If he has stock brakes, I'd suggest he stick with the E28 part. I have the big brake upgrade on my 535i and still have the stock M/C and the pedal feel is good -- an E32 M/C is not always in order even then.
If he has stock brakes, I'd suggest he stick with the E28 part. I have the big brake upgrade on my 535i and still have the stock M/C and the pedal feel is good -- an E32 M/C is not always in order even then.
[QUOTE="BMWCCA1"]I'll suggest the problem may not be in the bomb but in the master cylinder and I'd suggest the E32 part...[/QUOTE]
[QUOTE="Shawn D."]If he has stock brakes, I'd suggest he stick with the E28 part. I have the big brake upgrade on my 535i and still have the stock M/C and the pedal feel is good -- an E32 M/C is not always in order even then.[/QUOTE]
MY '88 535is has stock brakes, all OE parts with Mintex pads except for the E32 master cylinder I put on it last year. It made a vast improvement in pedal feelmuch firmer pedal, easier to modulate, too. On top of that it was about $100 less expensive than the "correct" cylinder. My '87 535is came to me with E28 M5 front calipers (new!!), E32 rotors, and stock rear brakes with the stock master cylinder. When I got it I threw-out the warped-but-newish E32 Ate PowerSlut rotors (sic) and replaced them with E32 Brembos and Metalmasters from Steve. The '88 feels better than the '87. I have the new M/C from Steve to go on the '87, just too many other more pressing issues right now. There's no way I'd ever go back to the stock M/C on the stock brakes even if they were the same price. Why would you not do it? Not itching for an argument, just want to know how it could possibly be a bad idea. Balance stays the same, just with less travel required. My experience tells me this is a good thing. Thanks Steve!
-Phil
[QUOTE="Shawn D."]If he has stock brakes, I'd suggest he stick with the E28 part. I have the big brake upgrade on my 535i and still have the stock M/C and the pedal feel is good -- an E32 M/C is not always in order even then.[/QUOTE]
MY '88 535is has stock brakes, all OE parts with Mintex pads except for the E32 master cylinder I put on it last year. It made a vast improvement in pedal feelmuch firmer pedal, easier to modulate, too. On top of that it was about $100 less expensive than the "correct" cylinder. My '87 535is came to me with E28 M5 front calipers (new!!), E32 rotors, and stock rear brakes with the stock master cylinder. When I got it I threw-out the warped-but-newish E32 Ate PowerSlut rotors (sic) and replaced them with E32 Brembos and Metalmasters from Steve. The '88 feels better than the '87. I have the new M/C from Steve to go on the '87, just too many other more pressing issues right now. There's no way I'd ever go back to the stock M/C on the stock brakes even if they were the same price. Why would you not do it? Not itching for an argument, just want to know how it could possibly be a bad idea. Balance stays the same, just with less travel required. My experience tells me this is a good thing. Thanks Steve!
-Phil
[QUOTE="kendogg"]Now, what does it mean when if I stomp the bakes in a panic stop, it feels like the car wants to turn around on me, like it sways around once I hit the brakes? Is that just some calipers braking better than otherson my car?[/QUOTE]
You might have a sticking caliper which on BMWs this old is just as likely to be caused by defective brake hoses as it is defective calipers. Check for even pad wear on the fronts or excessive dust on one wheel more than the other, or smoke, flames, excessive heat after heavy braking, etc. Remember that at least on the early E28s with ABS the ABS dragged by-design on the right-front caliperthe one without the pad wear sensorand it was common to run the pads nearly to the backing plate before the sensor in the left front brake would light the warning. Many shops assume this is a sign of a sticking r/f caliper but it is not. BMW later switched the ABS lines or asked the Techs to do so in a service bulletin so that the front brake with the sensor would get the increased wear from the ABS "drag" function. I've seen shops replace perfectly good M5 calipers due to this mis-diagnosis.
When was the last time you bled your brakes or changed your brake fluid? Could also be a problem in the double-pivot front axle if your bushings are really bad.
You might have a sticking caliper which on BMWs this old is just as likely to be caused by defective brake hoses as it is defective calipers. Check for even pad wear on the fronts or excessive dust on one wheel more than the other, or smoke, flames, excessive heat after heavy braking, etc. Remember that at least on the early E28s with ABS the ABS dragged by-design on the right-front caliperthe one without the pad wear sensorand it was common to run the pads nearly to the backing plate before the sensor in the left front brake would light the warning. Many shops assume this is a sign of a sticking r/f caliper but it is not. BMW later switched the ABS lines or asked the Techs to do so in a service bulletin so that the front brake with the sensor would get the increased wear from the ABS "drag" function. I've seen shops replace perfectly good M5 calipers due to this mis-diagnosis.
When was the last time you bled your brakes or changed your brake fluid? Could also be a problem in the double-pivot front axle if your bushings are really bad.
[QUOTE="BMWCCA1"]Why would you not do it? Not itching for an argument, just want to know how it could possibly be a bad idea. Balance stays the same, just with less travel required. My experience tells me this is a good thing. [/QUOTE]
Why would I not do it? I don't want harder brakes, and less travel isn't necessarily a bonus.
For example, when I put the Super Bell front disc setup (using early '80s Monte Carlo calipers) on my '57 Chevy, I went with a Monza power booster & MC setup. I lived with that for a while, but the brake was too soft and had too much travel. I switched to an F-body M/C, which reduced the travel by more than half, and accordingly the effort more than doubled. Now it's too hard. There are numerous caliper and M/C combinations available nowadays, so I'll get around to redoing the system sometime.
This is an opinion thing (kind of like suspensions that are "too soft" or "too hard" ). Note that I said I wouldn't suggest a change to an E32 M/C -- I didn't say it was "bad."
[Edit by Shawn D. on [TIME]1115218491[/TIME]]
Why would I not do it? I don't want harder brakes, and less travel isn't necessarily a bonus.
For example, when I put the Super Bell front disc setup (using early '80s Monte Carlo calipers) on my '57 Chevy, I went with a Monza power booster & MC setup. I lived with that for a while, but the brake was too soft and had too much travel. I switched to an F-body M/C, which reduced the travel by more than half, and accordingly the effort more than doubled. Now it's too hard. There are numerous caliper and M/C combinations available nowadays, so I'll get around to redoing the system sometime.
This is an opinion thing (kind of like suspensions that are "too soft" or "too hard" ). Note that I said I wouldn't suggest a change to an E32 M/C -- I didn't say it was "bad."
[Edit by Shawn D. on [TIME]1115218491[/TIME]]
[QUOTE="Shawn D."]Note that I said I wouldn't suggest a change to an E32 M/C -- I didn't say it was "bad." [/QUOTE]
I understand. My experience just doesn't bear out the reasons against it. My wife is 5'2" at right around 100 lbs. and she thinks the brakes with the E32 m/c are great! Remember the effort doesn't change since the hydraulic system is handling the boost, just how quickly the pedal "bottoms" is really the only change. Similar to going to braided brake lines.
If the cost difference is still half to go with the E32, I'm just saying don't not do it because you're afraid it's going to make the pedal effort too high. If you need a master cylinder, consider the E32 for the savings if nothing else. If your stock one is performing fine I wouldn't bother just to upgrade either. But if you need one, I'm all about saving money!
I understand. My experience just doesn't bear out the reasons against it. My wife is 5'2" at right around 100 lbs. and she thinks the brakes with the E32 m/c are great! Remember the effort doesn't change since the hydraulic system is handling the boost, just how quickly the pedal "bottoms" is really the only change. Similar to going to braided brake lines.
If the cost difference is still half to go with the E32, I'm just saying don't not do it because you're afraid it's going to make the pedal effort too high. If you need a master cylinder, consider the E32 for the savings if nothing else. If your stock one is performing fine I wouldn't bother just to upgrade either. But if you need one, I'm all about saving money!
So the hissing sound means the master cylinder needs replacement?
Lately I have noticed that hissing sound coming which sounds like it's coming from the pedal when I floor the brake with engine on. With engine off I can pump the pedal and it will become hard...I read that this means the accumulator is good.
Also last night before I shut off the car, I would pump the brake and hear this buzzing noise (sounded like it came from under the hood) as the pedal returned.
Aside from this noise, the brakes work great so that's why I've never looked into it before.
Lately I have noticed that hissing sound coming which sounds like it's coming from the pedal when I floor the brake with engine on. With engine off I can pump the pedal and it will become hard...I read that this means the accumulator is good.
Also last night before I shut off the car, I would pump the brake and hear this buzzing noise (sounded like it came from under the hood) as the pedal returned.
Aside from this noise, the brakes work great so that's why I've never looked into it before.
[QUOTE="88 535is south florida"]so will anything happen if i just dont do anything.. and let my brake pedal hiss[/QUOTE] IF the hissing is caused by an internal leak in the MC then . It could fail totally and the pedal will go to the floor. ~0 Does the system leak brake fluid or ATF? . If I had a question regarding brakes , I would get it checked out.
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