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Discussion Starter #1 (Edited)
After almost 14 years of owning my M5, I like to think I am reasonably knowledgable about preventive maintenance and try to be compulsive in that regard as the car ages. This week I took my car for a drive as it had been sitting for a month. The brakes did not seem right, although I am up to date with a brake flush. I cut the drive short and back in my garage I saw smoke coming from the front passenger wheel.:eek: And I saw some fluid under the car.

So it turns out that one of the two brake hoses sprung a leak. I suppose it is not surprising as the car is now almost 17 years old. These were just not on my radar to replace. Replacement itself is simple and the hoses are only $40 each. I'd recommend replacing them on virtually all E39 M5s given the age of these cars and importance of brakes. I'm feeling quite lucky that I got home before the check brake fluid light came on or the brakes failed.

Number 3 and 4 in the realoem.com diagram below:

RealOEM.com - Online BMW Parts Catalog
 
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I'm feeling quite lucky that I got home before the check brake fluid light came on or the brakes failed.

Number 3 and 4 in the realoem.com diagram below:

RealOEM.com - Online BMW Parts Catalog
...Or your engine caught fire! Glad you caught it right away. I’ve read about that a few times here. You’re right, we should all be changing them at this point.
 

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While I agree with changing the hoses as time permits, I have owned 82 cars. Some were old, most were daily drivers, some were true beaters. Heck two were even free! Not one has ever had a leaking brake hose. I have changed hoses on several of them, especially if I did not secure the caliper and it dropped from its perch during a brake job and ended up being suspended by the brake hose.


I will probably change the hoses to performance DOT approved stainless steel lines during the next brake job on the M5 just because it will be a good time to do so.
 

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Funny you mention this, I literally just did this job on a customer's M5 at my shop the other day. It's always those two brake lines near the ABS module that go bad, likely due to all the engine bay heat. And I did that job on a 540i/6 a few months back as well.
 

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Discussion Starter #6
...Or your engine caught fire!
Ha, that already happened to me soon after I bought the car...actually what happened was that the dealer didn't put the oil cap on corrected after an oil change. But it did seem like the engine was on fire at first!
 

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I caught this on four cars over the past two years, including both of mine. Rubber hoses over one of the hotter places in the engine bay don't last forever.

16-18 years is a really good run though...
 

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It is time for me to rethink this!! Seems like enough evidence of issue that I will take this to heart. Thanks all.
 

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There must be a bug going around. This just happened to me too!

Except this occurred at the end of a roadtrip! I barely made it to my garage as the DSC and brake lights were freaking out.

Ordered both next day, installed, now just need someone to bleed the pump.... and probably all the lines.
 

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I bought a brake bleeder kit about 5 years ago and LOVE it. No more asking for help to do a full brake/clutch bleed. Back the car up on ramps, jack up the front end and put jack stands in place, attach the pressurized bleeder, and then bleed away! It is a bit slow to get a bunch of fluid in the catch bottle, so there is time to look at how nice the M5 is underneath.



Knowing what I know now, I would have bought one in 1973 when I got out of college!!!
 

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I'm about to do this soon and I was thinking about the best way to get the air out of the new hoses. I can't activate the ABS pump so I was thinking of replacing the lines, then going for a drive and activating the pump by slamming on the brakes a few times. That should move the air pocket from the hose downstream to the rest of the circuit, which will then come out once I bleed the brakes.


Thoughts?
 

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Happened to me too just last month, hose burst spraying fluid all over the exhaust manifold, makes sense they would fail considering where they are located.
 

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I'm about to do this soon and I was thinking about the best way to get the air out of the new hoses. I can't activate the ABS pump so I was thinking of replacing the lines, then going for a drive and activating the pump by slamming on the brakes a few times. That should move the air pocket from the hose downstream to the rest of the circuit, which will then come out once I bleed the brakes.


Thoughts?
That's a pretty common method but can't say it's a 100% guarantee it'll be fully bled.

You can put INPA or DIS on a laptop to bleed the brakes? I did mine with INPA but the last owner used to use DIS.
 

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That's a pretty common method but can't say it's a 100% guarantee it'll be fully bled.



You can put INPA or DIS on a laptop to bleed the brakes? I did mine with INPA but the last owner used to use DIS.
I'd prefer to activate the pump but I have the Bavarian Technic cable (enthusiast version) and last time I checked, it didn't have that capability. I'll see how the pedal feels and if it's really bad, I'll buy the INPA software.
 

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I'd prefer to activate the pump but I have the Bavarian Technic cable (enthusiast version) and last time I checked, it didn't have that capability. I'll see how the pedal feels and if it's really bad, I'll buy the INPA software.
you're in the state with probably the largest collective of m5 enthusiasts, someone in so cal might help you out with bleeding w/ inpa or dis.
 

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I'm about to do this soon and I was thinking about the best way to get the air out of the new hoses. I can't activate the ABS pump so I was thinking of replacing the lines, then going for a drive and activating the pump by slamming on the brakes a few times. That should move the air pocket from the hose downstream to the rest of the circuit, which will then come out once I bleed the brakes.


Thoughts?
Why would need to worry about the ABS pump activation if you do not introduce air upstream of the unit? You can mitigate the flowrate of fluid out a connection by filling the reservoir all the way to the top edge and tightly sealing it with plastic wrap stretched over the top and secured with a rubberband. Keep an eye on it to make sure that the reservoir doesn't leak down too far when you have a line open for replacement. Alternatively, you can use one of those tools to hold the brake pedal depressed just enough to block the inflow ports, and I suppose almost no fluid will run out.

Hence, just do one or some version of above, replace all the hoses, and flush the system well. (and then still get stuck with the mr bock issue, lol). :)
 

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Why would need to worry about the ABS pump activation if you do not introduce air upstream of the unit?
I can't find a drawing right now that shows the entire circuit, but it's my understanding that power bleeding the brakes doesn't impact lines 1 & 2, hence the air pockets in the new hoses which are downstream of those lines don't get bled out.

As long as the bleeder screws on the calipers are closed, replacing hoses 3 & 4 should have no impact on the fluid that starts at lines 5 & 6 and goes all the way to the rear calipers. Activating the pump forces the air downstream into the part of the circuit that will get bled out. At least that's my assumption without seeing the full circuit diagram.


 

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I can't find a drawing right now that shows the entire circuit, but it's my understanding that power bleeding the brakes doesn't impact lines 1 & 2, hence the air pockets in the new hoses which are downstream of those lines don't get bled out.

As long as the bleeder screws on the calipers are closed, replacing hoses 3 & 4 should have no impact on the fluid that starts at lines 5 & 6 and goes all the way to the rear calipers. Activating the pump forces the air downstream into the part of the circuit that will get bled out. At least that's my assumption without seeing the full circuit diagram.
Anything downstream of the furtherest upstream connection that is disconnected will have air bubbles that need to be pushed through it. As long as a connection is not undone (and air is not introduced) upstream of the ABS unit, you should be fine. Brake fluid flows right through #1 & 2 all the time, and bleeding will or course force fresh fluid through them. In other words, all fluid flowing from the master cylinder to the calipers will only be flowing through those lines.
 
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