Brake Failure - Stiff Pedal & No Assist (Solved)

[Happy]

I am not familiar with the bleeder device that connects at the reservoir. The one I used, connected at the bleeder valve.

I am assuming one pressurizes, and the other vacuums. While bleeding, it was just a matter of topping off the reservoir.

Good luck figuring it out my man. 🤞

[crystalworks]

Originally Posted by 80stech

Nothing beats a second man with some experience and a feel for what they are doing to bleed brakes. Sometimes there are high spots for which a fast flow is needed to purge the air and your pressure bleeder is no replacement for a good man on the peddle.

I'd agree with that. I've never been good at brakes whether doing them solo or tandem. But I've never had someone helping who truly knew what they were doing. I, obviously, don't.

I had another go at it solo and got the brakes to where they feel a lot better. It's hard to explain but braking is consistently good, at least normal feeling, if I hold the pedal from coming all the way up. If I let the brake pedal up all the way the next time I press it I won't get good assist. But if I then let up on the pedal slightly and press again, good brakes.

I haven't tried it on the road yet, just back and forth in the garage. I think I'll take it up and down the street and see what happens. I think I am just very slowly getting all the air out of the system since the master and lines were open. Gone through about 2.5qts now so I think I'll go buy one more qt tomorrow and do another couple of rounds of bleeding to see if I get it to where it should be.

If no success tomorrow, I'll drive it to the indy to have it flushed/bled.

Originally Posted by Happy

I am not familiar with the bleeder device that connects at the reservoir. The one I used, connected at the bleeder valve.

I am assuming one pressurizes, and the other vacuums. While bleeding, it was just a matter of topping off the reservoir.

Good luck figuring it out my man. 🤞

Thanks brotha, I'll get it handled one way or the other. At least I know the booster was at fault for the original problem and my diagnosis was correct. That's a small mental victory even though struggling with brake bleeding is certainly putting a dent in my ego as a shade tree mechanic. I've done engine swaps in Bimmers and a trans on this X5 damnit!

[ard]

I once emptied the braking system on an E39 during a 150 mile drive with a ruptured brake line... (younger and dumber)


As a result, when I repaired the hose and refilled- the bleeding would just not work. Tried it for hours, adding fluid, helper pumping brakes.


Gave up, had a master tech at the dealership do it. (Apparently you need to actuate the ABS system to drive fluid/air in/out of that.) Edit- This was before I had BMW tools on my laptop


He said it took 3 tries to nail it.


FWIW

[crystalworks]

Originally Posted by ard

I once emptied the braking system on an E39 during a 150 mile drive with a ruptured brake line... (younger and dumber)


As a result, when I repaired the hose and refilled- the bleeding would just not work. Tried it for hours, adding fluid, helper pumping brakes.


Gave up, had a master tech at the dealership do it. (Apparently you need to actuate the ABS system to drive fluid/air in/out of that.) Edit- This was before I had BMW tools on my laptop


He said it took 3 tries to nail it.


FWIW

Thank you Ard for the contribution. Makes me feel 100% better about my situ. Was actually just going to post an update. I did empty a lot of the system before the ABS pump when swapping the booster, despite my best attempts at keeping fluid inside the master and capping the loose lines.

So the update. I took the X for a drive around the neighborhood just now. Brakes feel very good. Maybe 95% of "normal." No more lack of assist at all that I was experiencing last night. So letting it sit overnight after all the bleeding and then moving it back and forth actuating the brakes over and over must have gotten some air to exit at the master overnight. So I guess I'll throw another quart of fluid through it and that should "get 'er done." So relieved, was haunting my dreams last night, literally.

BTW, my bleed procedure:

1. Hook up to ISTA-D with ICOM (complete identification required)
2. Fill pressure bleeder with brake fluid and attach to master cylinder
3. Pressurize bleeder bottle
4. Navigate in ISTA > Service functions ‐ Chassis/Suspension ‐ Traction control systems ‐ Bleeding routine
5. Add bleed routine to test plan and run it
6. Open bleeder at right rear of truck
7. Actuate the ABS pump using the bleed routine
8. Close bleeder and pump pedal 5-10 times
9. Tap on caliper with rubber mallet and open bleeder for a few seconds (stream is solid at this point) to try and free micro bubbles
10. Close bleeder, clean area
11. Repeat steps 6-10 for left rear, right front, and then left front

So, hopefully this is going to have a happy ending without any further monetary expense (beside another brake fluid bottle) or damage to my ego. I was starting to second guess my re-installation of the master on the booster as it doesn't seem to fit exactly flush on the bottom and pushes out a tiny bit when actuating the pedal. Thought I might have gotten the booster's push rod misaligned with the master cylinder piston when reinstalling, but if that happened I'd imagine it wouldn't brake as well as it now does. I was getting paranoid.

[80stech]

Good that things are looking up!
It's my understanding and experience with my 2004 3.0L that running the ABS pump only helps pass the little bit of air that might be caught in front it. I previously was under the impression that the pump actually bled the system but found out it when I changed a brake hose recently that it actually only spits out a few drops from the bleeder so proper bleeding for the rest is still critical. Having a second man on the brake peddle while you work the screw is still the best but one trick if you are by yourself is to pump the peddle 4 or five times but progressively less each time or sometimes it works better to pump short strokes working from the bottom up if that makes sense.
The clearance of the brake peddle rod to the booster socket (or master cylinder) is absolutely critical though. If there is not enough clearance the compensating port in the master cylinder will not be exposed properly causing all kinds of head scratching problems.

[Happy]

Originally Posted by crystalworks

So relieved, was haunting my dreams last night, literally.


pressure bleeder



I was getting paranoid.

Hahaha… I am glad you got it! Nightmare’s suck!

I figured it was pressurized. Any difference in your opinion, a pressure vs. vacuum bleeder?

Hopefully it didn’t have you peering out the window every 5 mins or so.. LoL..

[crystalworks]

Originally Posted by Happy

Hahaha… I am glad you got it! Nightmare’s suck!

I figured it was pressurized. Any difference in your opinion, a pressure vs. vacuum bleeder?

Hopefully it didn’t have you peering out the window every 5 mins or so.. LoL..

Yes, now having used both. I highly prefer the pressure bleeder to vacuum.

Originally Posted by 80stech

Good that things are looking up!
It's my understanding and experience with my 2004 3.0L that running the ABS pump only helps pass the little bit of air that might be caught in front it. I previously was under the impression that the pump actually bled the system but found out it when I changed a brake hose recently that it actually only spits out a few drops from the bleeder so proper bleeding for the rest is still critical. Having a second man on the brake peddle while you work the screw is still the best but one trick if you are by yourself is to pump the peddle 4 or five times but progressively less each time or sometimes it works better to pump short strokes working from the bottom up if that makes sense.
The clearance of the brake peddle rod to the booster socket (or master cylinder) is absolutely critical though. If there is not enough clearance the compensating port in the master cylinder will not be exposed properly causing all kinds of head scratching problems.

That's the only thing that has me concerned. Going to stick a camera in there to inspect the push rod to cylinder alignment and maybe blow some smoke into the booster to see if there is a leak around the master... or elsewhere.

Update: Still having nightmares about bleeding brakes. But after this 4th bleed and driving the car around, the hydraulics are 100% good now. Actually they might have been after the 3rd bleed. X5 brakes hard and quick while driving.

But, I am having a problem of the system loosing assist after the car is shut off. So after startup (not sure how long it takes to loose vacuum) I have no assist. This points to a vacuum leak in the booster, at the check valve (I tested this, could suck but not blow), or the vacuum pump (tested this to supply consistent 28in hg).

Going to do some poking/testing around it today. Going to be pissed if the brake booster is bad right out of the box...

[80stech]

It would be a good idea to replace the check valve and grommet.

[crystalworks]

Originally Posted by 80stech

It would be a good idea to replace the check valve and grommet.

I came to that same conclusion, new grommet came with the new booster... the check valve however is on galactic back order. Thanks BMW for building your check valves into your vacuum hoses.

Local dealership said zero in stock, zero in the US, and zero in Germany. I think I can order one from Latvia on Ebay.

[Happy]

Originally Posted by crystalworks

zero in the US, and zero in Germany. I think I can order one from Latvia on Ebay.

One reason Archer was shacked up for a while. Parts are getting harder to source.