Most of us e39 M5 owner found out you can upgrade the brake BMC withe the version from the E65 for improved performance. All you have t do is cut or grind down some of the metal at the top nearest to the top hole for the bolt (for clearance of the fluid tank) and your good to go.
the cabin filter air box has holes in the bottom for water to escape if it gets filled. Amazing how often these are clogged with leaves, dirt, etc. This is the main culprit to water destroying the booster. Also, ensuring the box is installed correctly under the cowl should prevent water from entering the box.
Great video and very timely. Boring story time - a couple years ago, the brake pedal on my E39 540 started going right to the floor, turns out the vac line to the booster was toasted - didn't realize loss of vacuum would manifest in that way! Kinda scary, feels like you have no brakes. Last fall, I noticed the same pedal behaviour showed in the diag video - perfect description, the car stops ok, but the pedal seems soft, and just keeps going down slowly (not like the vac failure above where it just dropped). Wasn't sure if it was another vacuum problem, or the master cylinder was toast. I tell this boring story to suggest another step of diagnosis - make sure the vacuum line is in ok shape, all the way back to source. Thanks for the tip on checking out the booster - wouldn't have thought to check that out/suspect it as an issue!
Ok I just replaced my brake booster in my 1998 e39 528i. I disconnected the master cylinder break lines outside of the booster compartment towards the passenger side. Placed a tall skinny container with small funnel below the connectors. You'll need a 11 & 15 mm to break free (no pun intended). With the master cylinder cap off, open the lines and let them drain out completely. Now, go under the dash and take off retaining bolts to the booster. You will now need to take off the compartment divider to get the two brake lines up and out. I put four disposable latex gloves over each break line connector for leakage. Now gently pull the booster out with the master cylinder empty and attached. Once on the bench drain out the old fluid and remove from the brake booster. While on the bench, put some fluid in the master cylinder and depress plunger until fluid come out the connector without air. Best part is I didn't have to take the filter out of the master cylinder, have a pump, or try to get at the break line or mounting bolts in a tight space! TY BMW. It was all done outside of the car. Then put master cylinder onto the booster and gently slide back into the firewall and reconnect pedal and tighten bolts to booster. Next position the empty container and funnel back under the break line connectors and thread lines in only part way. Start to fill the master cylinder back up until you see the fluid coming out of the connectors and then tighten. Good luck!
I've experienced a brake booster that filled with b fluid as a result of the m/cyl leaking back into it. The customer was topping up the fluid on a regular basis but never told us at the shop. I found it on a road test when the engine suddenly pumped out white smoke from the exhaust, which was brake fluid being sucked into the engine via the inlet manifold. It was quite spectacular! 😳
I have always wondered why people "top-off" their brake fluid. The added fluid needs to be removed when installing new brake pads. Dramatically-low fluid indicates a problem that needs immediate attention. Most hydraulic system failures can be avoided with regular brake fluid changes. I have found that most people completely ignore the service interval on the brake fluid. Congratulations to anyone that actually does change their fluid every two years.
Wow, that's insane there was enough brake fluid in the booster to get sucked out through the vacuum supply hose. There is also no way the brake pedal felt good at all leaking that much brake fluid. Great catch, thank you for sharing!
When the brake pedal pin was going in you should have mentioned pulling out the stem to the brake light switch to recalibrate it so your cruise control will work for sure.
I'm doing this job now on my e39 wagon. I had the car sitting outside all winter and spring with the leaves and rain. Caused the drainage hole to become blocked and allowed to fill with water. Let's just say I had to pump water out of the booster enough to fill a plastic water bottle. Check those drains!
There is an E65 brake cylinder upgrade that is widely discussed on the M5board. It basically is the same size as the E39 one but with slightly bigger bore so you should theoretically have a harder brake pedal. On my list of upgrades.
@@davidparker9676 You may be right, I don't know about this. However, I am pretty sure that BMW didn't put much thought into this in this car. The reason I say this is that they use the same master cylinder on all variants of the e39, from 520 in europe to the M5, and everything in between. However, if you look at the diameter of the pistons in the calipers, they differ between cars with M5 having the largest. A larger diameter caliper piston with the same master cylinder will have a softer brake pedal than a smaller diameter caliper piston all else being equal. As such, it is well known that the pedal is firmer in 6 cylinder cars (525, 528 and 530 in the US) than in M5. I think that is why this upgrade is popular, although I agree not strictly necessary. Now if BMW would match the master cylinder to each caliper used, or at least put a different one from the factory on the M5 then I think there would be no need for any upgrades.
@@borisp9499 BMW has a huge parts bin to draw from, I doubt they were seeking to cut costs by a couple euros on the M5. I have lost of older BMWs and they did offer the bigger master cylinders on some cars while others shared the same master as the base model. I am sure the BWM engineers saw it fit for the task. The softer pedal if typically preferred by race drivers for better feel and control than a hard pedal. I set up some of my cars with bigger master cylinders and kinda regret it now. Yeah I do have a firmer pedal and shorter travel but it did come at the expense of feel and doesn't make the car stop any better.
Thank you for pointing this out. We have heard of this particular upgrade. In this case the own of the car wanted to keep it as is but for anyone looking for a firmer pedal feel the E65 master cylinder . It's part number 34336785926 for anyone who is looking to do this.
Maybe this is supposed to be obvious, but did it fix the issue?! I am having the same exact problem from the diag video on my E92 and I am eager to know if the master cylinder returned the brake pedal feel to full potential.
Many of the flare fittings are a pain to get to. Having to remove the booster to get the master cylinder out for sure is an extra step that is a pain. The only major benefit in this case is the agility to at least see the inside of the booster unimpeded. Which in this case turned out to be beneficial since it was rotting internally.
I don't see where you bench bled the master cylinder before install. I've seen this strongly recommended (essentially required) for other makes. Did using the power bleeder eliminate the need for this ?
Lets see if I can get some help here. Car sat for over a year in very humid climate. The Caribbean to be exact. Had soft pedal did a brake fluid replacement. Pedal eventually got much better prob put 5k miles on the car one day both front brakes just locked up and stayed locked. I thought a caliper was bad so had both calipers rebuilt with all new pistons seals etc.. changed both brake lines to braided. Swapped rotors for new ones. Purchased swaben power bleeder did that full flush. Had my abs module fixed no more trifecta lights. After all this front brakes are still locked up! As soon as I press my brakes they lock immediately. Car has been sitting for over a year. After this vid I am going to change both master and booster. Maybe it is this? Anyone with any knowledge please reply.. thank you in advance.
So when you open the brake system to such a large extent, I would have expected that the ABS module would need to be activated to bleed completely. Do you ever find that necessary?
Most of us e39 M5 owner found out you can upgrade the brake BMC withe the version from the E65 for improved performance. All you have t do is cut or grind down some of the metal at the top nearest to the top hole for the bolt (for clearance of the fluid tank) and your good to go.
the cabin filter air box has holes in the bottom for water to escape if it gets filled. Amazing how often these are clogged with leaves, dirt, etc. This is the main culprit to water destroying the booster. Also, ensuring the box is installed correctly under the cowl should prevent water from entering the box.
Great video and very timely. Boring story time - a couple years ago, the brake pedal on my E39 540 started going right to the floor, turns out the vac line to the booster was toasted - didn't realize loss of vacuum would manifest in that way! Kinda scary, feels like you have no brakes.
Last fall, I noticed the same pedal behaviour showed in the diag video - perfect description, the car stops ok, but the pedal seems soft, and just keeps going down slowly (not like the vac failure above where it just dropped). Wasn't sure if it was another vacuum problem, or the master cylinder was toast. I tell this boring story to suggest another step of diagnosis - make sure the vacuum line is in ok shape, all the way back to source.
Thanks for the tip on checking out the booster - wouldn't have thought to check that out/suspect it as an issue!
Thanks for the heads up. Really appreciate it
Ok I just replaced my brake booster in my 1998 e39 528i. I disconnected the master cylinder break lines outside of the booster compartment towards the passenger side. Placed a tall skinny container with small funnel below the connectors. You'll need a 11 & 15 mm to break free (no pun intended). With the master cylinder cap off, open the lines and let them drain out completely. Now, go under the dash and take off retaining bolts to the booster. You will now need to take off the compartment divider to get the two brake lines up and out. I put four disposable latex gloves over each break line connector for leakage. Now gently pull the booster out with the master cylinder empty and attached. Once on the bench drain out the old fluid and remove from the brake booster. While on the bench, put some fluid in the master cylinder and depress plunger until fluid come out the connector without air. Best part is I didn't have to take the filter out of the master cylinder, have a pump, or try to get at the break line or mounting bolts in a tight space! TY BMW. It was all done outside of the car. Then put master cylinder onto the booster and gently slide back into the firewall and reconnect pedal and tighten bolts to booster. Next position the empty container and funnel back under the break line connectors and thread lines in only part way. Start to fill the master cylinder back up until you see the fluid coming out of the connectors and then tighten. Good luck!
I've experienced a brake booster that filled with b fluid as a result of the m/cyl leaking back into it. The customer was topping up the fluid on a regular basis but never told us at the shop. I found it on a road test when the engine suddenly pumped out white smoke from the exhaust, which was brake fluid being sucked into the engine via the inlet manifold. It was quite spectacular! 😳
I have always wondered why people "top-off" their brake fluid. The added fluid needs to be removed when installing new brake pads. Dramatically-low fluid indicates a problem that needs immediate attention.
Most hydraulic system failures can be avoided with regular brake fluid changes. I have found that most people completely ignore the service interval on the brake fluid. Congratulations to anyone that actually does change their fluid every two years.
Wow, that's insane there was enough brake fluid in the booster to get sucked out through the vacuum supply hose. There is also no way the brake pedal felt good at all leaking that much brake fluid. Great catch, thank you for sharing!
Ive watched this video about 10 times preparing myself to do it asap
When the brake pedal pin was going in you should have mentioned pulling out the stem to the brake light switch to recalibrate it so your cruise control will work for sure.
Great explanations and camera work. This should come in useful for my 2000 M5. keep the videos coming!
Glad it was helpful!
I'm doing this job now on my e39 wagon. I had the car sitting outside all winter and spring with the leaves and rain. Caused the drainage hole to become blocked and allowed to fill with water. Let's just say I had to pump water out of the booster enough to fill a plastic water bottle. Check those drains!
excellent vid… thanks
Thank you, I believe I have the same problem on my Mercedes clk 320, it looks like the master cylinder has been replaced everything else looks fine.
Worth a check at this point!
There is an E65 brake cylinder upgrade that is widely discussed on the M5board. It basically is the same size as the E39 one but with slightly bigger bore so you should theoretically have a harder brake pedal. On my list of upgrades.
A harder pedal gives you less "feel" and less fine control of the brakes in performance driving.
@@davidparker9676 You may be right, I don't know about this. However, I am pretty sure that BMW didn't put much thought into this in this car. The reason I say this is that they use the same master cylinder on all variants of the e39, from 520 in europe to the M5, and everything in between. However, if you look at the diameter of the pistons in the calipers, they differ between cars with M5 having the largest. A larger diameter caliper piston with the same master cylinder will have a softer brake pedal than a smaller diameter caliper piston all else being equal. As such, it is well known that the pedal is firmer in 6 cylinder cars (525, 528 and 530 in the US) than in M5. I think that is why this upgrade is popular, although I agree not strictly necessary. Now if BMW would match the master cylinder to each caliper used, or at least put a different one from the factory on the M5 then I think there would be no need for any upgrades.
@@borisp9499 BMW has a huge parts bin to draw from, I doubt they were seeking to cut costs by a couple euros on the M5. I have lost of older BMWs and they did offer the bigger master cylinders on some cars while others shared the same master as the base model. I am sure the BWM engineers saw it fit for the task.
The softer pedal if typically preferred by race drivers for better feel and control than a hard pedal. I set up some of my cars with bigger master cylinders and kinda regret it now. Yeah I do have a firmer pedal and shorter travel but it did come at the expense of feel and doesn't make the car stop any better.
Thank you for pointing this out. We have heard of this particular upgrade. In this case the own of the car wanted to keep it as is but for anyone looking for a firmer pedal feel the E65 master cylinder . It's part number 34336785926 for anyone who is looking to do this.
Maybe this is supposed to be obvious, but did it fix the issue?! I am having the same exact problem from the diag video on my E92 and I am eager to know if the master cylinder returned the brake pedal feel to full potential.
no bench bleed of the master cyl?
When vehicle is off, the brake pedal has normal pressure, when vehicle is on, the pedal hits the floor ... should I assume the BMC is the issue?
Quite a pain in the butt job. But new booster make driving so much nicer
Many of the flare fittings are a pain to get to. Having to remove the booster to get the master cylinder out for sure is an extra step that is a pain. The only major benefit in this case is the agility to at least see the inside of the booster unimpeded. Which in this case turned out to be beneficial since it was rotting internally.
Awesome video my friend..my 1998 is being done right now , you video helped a bunch. Thank you very much. 👍👍👍🍺🍺🍺
😎
I don't see where you bench bled the master cylinder before install. I've seen this strongly recommended (essentially required) for other makes. Did using the power bleeder eliminate the need for this ?
Those "really absorbent shop towels" are called pig mat and they're actually intended for catching spills
No need to bleed the new brake master cylinder? Just a regular brake bleeding procedure, as shown? Thanks
I’m wondering the same I did my master cylinder one year ago on my 540i, and the new one failed me recently. Does it need to be bench bleed?
When vehicle is off, brake pedal has pressure, when vehicle is on, brake pedal hits the floor, should I assume the MasterCyliner is toast? Thanks
Lets see if I can get some help here. Car sat for over a year in very humid climate. The Caribbean to be exact. Had soft pedal did a brake fluid replacement. Pedal eventually got much better prob put 5k miles on the car one day both front brakes just locked up and stayed locked. I thought a caliper was bad so had both calipers rebuilt with all new pistons seals etc.. changed both brake lines to braided. Swapped rotors for new ones. Purchased swaben power bleeder did that full flush. Had my abs module fixed no more trifecta lights. After all this front brakes are still locked up! As soon as I press my brakes they lock immediately. Car has been sitting for over a year. After this vid I am going to change both master and booster. Maybe it is this? Anyone with any knowledge please reply.. thank you in advance.
So when you open the brake system to such a large extent, I would have expected that the ABS module would need to be activated to bleed completely. Do you ever find that necessary?
It's not necessary on this system. The ABS is able to be bled without activating it.
It depends on the car. Many newer cars will need the ABS pump bled. In the case of this E39 M5 it was not needed (surprisingly).
Hi I hv a Hard Pedal n my left caliper isn't working....Could it be my master n booster?
Amazing engine M How many cylinder
E39 M5's have a V8, S62 engine designation.
Did you lose weight?
Asking the important questions...
@@runner3033 obesity is not something to be taken lightly, it leads to other health issues like BP, heart attack and more.