Master Cylinder replaced, brakes won't bleed
 

I am at my wits' end here.

06 X5 4.4.

Put on a new master cylinder. Bench bled - no bubbles, just fluid cycling through the lines.

Installed with the hoses still on the bleeder and submerged in the reservoir. Pumped brake to be sure still primed. Nothing but fluid cycling from both ports back to the reservoir.

Disconnected bleeder nipples and attached brake lines. Pumped brake - no pressure building. Opened bleeder valve on the rear wheel - will not bleed. Opened valve on the front wheel - will not bleed.

Fluid in reservoir not dropping.

Help please. I cannot imagine what I'm missing here.

You have to use something like a Foxwell NT-510, etc. to activate the ABS block then start bleeding RR, RF, LR, LF and to be fair many people have had to run through this several times (4x for me) before the system is fully bled.

My 4.8iS nuked the vacuum pump and I lost brakes completely of course I Flintstoned the hell out of it to stop in time.

Sent from my SM-A730F using Tapatalk

A little brake system background.
On anything built after 1995, they all have ABS systems. Some are simple early systems that cycle brake pressure to the front and rear wheel pairs based on speed readings while TEVIS systems ver 3+ can modulate each wheel brake based on individual wheel speed differences. It also has the ability to block any pressure to an individual caliper that it thinks has a complete failure, like the inability to hold pressure.
Your Bmw has one of these latter system. In order to bleed the system completely you will need the knowledge, tools and the process to pressurize the system and sequence to bleed properly. This process is simple and has been posted like 2,000 times that any quick search will find.

To save your fingers here is the process once again

Brake bleeding procedure (DIY annal version)
1. Suck all old fluid from master cyl reservoir
2. Top off brake fluid DOT 3/4 (Do NOT use cheap store brands) (Preference: Valvoline Synthetic DOT 4)
3. Pressurize system to 15-20 PSI using tool of your choice (Example: https://www.ecstuning.com/b-motive-p...eder/motivepb/)
4. Plug in scanner/test unit and select brake bleed for ABS (Tool example: Foxwell 510/530)
5. Move to RR, open caliper bleed screw with hose to catch bottle
6. Flow until bubbles stop (make sure fluid in Reservoir stays more than 1/2 full
7. Turn on ABS cycle purge, flow until no bubbles, then pump pedal 5 X
8. Turn on ABS cycle purge once again Bubbles? Flow until clear
9. Tap/hit Caliper with rubber mallet
10. Flow until clear
Move to LR, RF, then LF repeating steps 5-10
I personally do a final go around after all are clear to be safe.
11. Road test making sure ABS gets activated on loose road surface No need for stomp and lock on Hwy.
12. Final re-bleed to confirm all is well

Pedal should be normal at this point. If not look for master Cyl, vacuum line check valve, or power booster failure. On X5 4.8is there is a vacuum pump on the Right front cam that leaks and will fail sooner or later. On this fail, pedal is perfect until engine start, then it drops off.

Can you short cut this process and come out OK? Y/N

If all you are doing is a bi-annual bleed out and you have no pedal pump up (NO AIR trapped in lines). Your brake fluid flush is really simple, skip steps 7, 8, 9, and 12.

Helpful?

Valvoline DOT 3 and 4 Brake Fluid (32 oz.)

Seems like the witch has a contract out on you! [emoji1787][emoji1787]

When you removed the brake line to switch out the master cylinder, how long did you have the line disconnected, and how much brake fluid flowed out of the lines? Most likely you have an air pocket in the line. Brakes are not a good system to mess with, I would say have the X towed to a tech that can perform a bleed service.

Sure seems like it sometimes. [emoji1787]

The electric 4 series battery died 4 blocks from home today leaving my son less than happy [emoji849]

Sent from my SM-A730F using Tapatalk

I don't like to admit there are certain things on our BMW's I don't tackle... But brake fluid is one of them. I always pay an indy or the dealer to do my brake flushes. Last time I had the e53 done it was $160. Well worth the time savings and no headache.

Is your truck driveable to get to an indy at slow speed or would it need a tow?

:thumbup:
:iagree:

Sissies....