Can’t bleed brakes

[jcwhy]

Newly purchased 1994 530i w/45K miles

Replacing all the fluids/etc. Got to the brakes and noticed the fluid is brown. Removed most from the reservoir and added clean Dot 4. Attached power bleeder and cracker bleeder screw at rear passenger. Nothing. Moved to front passenger. Only a trickle. Removed power bleeder and got the wife to pump the pedal 10-15 times and hold down. Not much of an improvement so it’s clogged somewhere. Brakes work fine while drive but I need to get this brown crappy fluid cleared of all the lines.

Help - suggestions?

Thanks all.



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[biasvoltage]

Gunk in the calipers blocking the bleeder hole. This happened on my '90 535i on the rear calipers. No fluid out of the rears at all when I tried to bleed them. I opened up the line leading to the caliper and got a face full of brake fluid. I tried to rebuild the calipers but they were really badly corroded inside and the pistons were garbage, so a set of rebuilts from rockauto solved the problem.

[jcwhy]

biasvoltage - thanks

I'm thinking it's further upstream because I'm having trouble bleeding all the brakes.

Thinking I need to flush the master cylinder and ABS.

Need help.

[MIKYZZ4]

It's brown with rust. Purchase 1-liter of fluid and resume bleeding procedure with the wife: 3-pumps & hold,
starting at RR-LR-FR-FL in a continuous pattern until you have emptied the liter and the fluid flows clean.
Be patient, as it seems the lines have never been flushed. As a precaution-check for leaks at caliper piston seals.

[q20v]

May be obvious but have you removed the bleeder screws to make sure they're clear? I've seen them completely clogged and wouldn't let anything through. Easy to clean with a small pick or drill bit. Reinstall and let the fluid flow! BTW, I've been religiously flushing brake fluid on my car since I bought it about 7 years ago, and recently had a caliper seize because of a piston boot that wasn't seated properly. Anyway, when I pulled the caliper apart to clean it, I was blown away by all the sediment and crap that was still in the caliper (sitting in the lower portion of the caliper). Wasn't doing much harm sitting there but I'll likely pull the rest of the calipers to clean them out manually.

Good luck!

Barry

[jcwhy]

All - thanks very much for the replies. I didn’t consider the most obvious being a clogged bleeder screw. After a few days of business travel, I’ll grab the wife and take another shot at it. Due to the color of the fluid, it’s probably a good idea to check the calipers regardless.

This forum is awesome BTW!!


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[q20v]

Just be sure to check back in and let us know what it was in the end!

My fluid was dark when I first started power flushing a while back, and I never was able to really clean the reservoir with it attached to the master. Every year the fluid in the reservoir would be really dirty again until I finally pulled the reservoir off the master cylinder and manually cleaned it out. It had a lot of gunk in the bottom which was making the new fluid dirty over time. Also, not sure if your car is manual or auto, but I flushed the clutch line about 5-6 years ago (about 20k KM) and recently did it again... black as night was the fluid. Same procedure as flushing the calipers if you have a power bleeder (i.e. Motive Bleeder), and the clutch slave cylinder is easy to access (at least it is on an M30 engine).

[jcwhy]

More good feedback - thanks. I should be back at it by next weekend and will reply with an update.

BTW - I also own a ‘90 535i manual with 205K miles. Love the car and it’s in great shape (only needs a paint job). Thanks for the comment about the clutch fluid- I’ll be getting to that next.


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[jcwhy]

Finally resolved the problem by first removing the brake hose from the RR caliper. Hooked up the power bleeder and confirm (dirty) fluid is flowing. Removed the bleeder to check if plugged but it was clear. Discovered the blockage was in the small hole where the bleeder screws in. After siphoning a bunch of dark sediment from the reservoir, I bleed all the lines until clear.

Thanks to those who replied.



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[MIKYZZ4]

Now that you and now other newbs know the results of deferred maintenance,
be sure to keep up this flush procedure every 2yrs, or at the very least every brake job you perform,
Using 1Liter as replacement amount, as that is average BMW brake system volume/capacity.

[q20v]

Thanks for posting the results, and glad to hear they were positive.