[Cloud9...68]

I was flushing my brake fluid using my Motive pressure bleeder, and a strange thing happened. The rear brakes went fine - the old fluid drained out at the usual steady pace, replaced by the clean new fluid. But when I moved to the front right brakes, not a drop came out when I loosened the bleed screws (I have quad piston (?) Brembo calipers from a 1988 944 Turbo S, which have an inner and an outer bleed screw on each caliper). On the left front, fluid did come out, but at an agonizingly slow, drop-by-drop rate.



I've successfully used the Motive bleeder on our 2004 and 2007 3-Series BMWs with no issues whatsoever. I know the brake bias valve, as well as the ABS hardware, is located inside the fender near the front right brake, but I don't see why this would have prevented fluid from coming out of this brake's bleed screw. Any ideas, or similar experiences? Thanks.

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[flash]

likely clogged screws



i assume you went ahead to the front left after first having a problem with the front right, since otherwise would be out of order (farthest from master to nearest to master)

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[Cloud9...68]

Yes, clogged screws would make sense, as there's no other logical explanation I can think of as to why the rears would flow so much better than the fronts. Neither the outer nor the inner screw on the front right caliper flowed, and the outer screw on the front left caliper flowed VERY slowly, and the inner screw on the FL caliper didn't flow at all. I'll take the screws out and clean them. And yes, I went in the order of right rear, left rear, right front, left front, outer screw first, then inner. Thanks.

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[flash]

i'm going to assume the pistons move, as you would have noticed it in braking if they didn't - that rules out the seals there



so, i would remove the bleed screws and clear them out, or just flat replace them

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[Cloud9...68]

Yes, I'm sure the pistons are moving, as the brakes work great. I just wanted to rule out something systematic associated with the ABS system, since I remember a mechanic telling me years ago that there's something about the ABS system that makes bleeding on this car tricky, though he didn't elaborate. Clogged screws makes perfect sense as the cause of my problem. Thanks, as always.

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[DaveN]

Ok, slightly off topic but everyday needs a dumb question.

I can see bleeding in a specific order would make sense but I can't figure out why. It's a hydraulic system so without any chance of compression how can bleeding one leg affect the others if the order was not as indicated?

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[flash]

by starting at the farthest point first, you minimize the possibility of air bubbles making their way back upstream to the master



you'd be fine if you could do all 8 at once, but since you can't..................

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[DaveN]

It's really not that hard <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

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[Cloud9...68]

Yes, it turned out that all of the front bleed screws were indeed clogged. I cleaned them all out using a sewing needle, and the fluid flowed nicely afterward, allowing me to finish the job. Thanks for the suggestion, Flash. I also replaced the clutch fluid. The Motive bleeder is really a great device.



The job was not without its drama, however. As I was finishing up the right front caliper, I heard the ominous sound of rapidly dripping brake fluid. The tube on the Motive bleeder between the bleeder body and the adapter that goes on the car's brake fluid reservoir had burst! I was using less than 15 psi pressure, well within the unit's capability. Fortunately, no fluid spilled in any places where it could do any harm (like on the paint), so it didn't turn out to be too big of a problem. I replaced the flimsy vinyl line with a high quality, brake fluid-resistant, braided German line. It isn't transparent, but there's no need for this line to be. I wonder if many others have had a similar experience with their Motive bleeder.



One time-saving tip I would recommend is to siphon out as much of the old fluid from the reservoir as you can before starting to use the Motive bleeder to push the old fluid through the system. It's just a lot quicker to do it this way than to wait for the Motive to push all the old fluid from the reservoir all the way through the system to the first caliper (the right rear).

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[flash]

i believe the spec is 11psi - that may have been the problem

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[Cloud9...68]

The instructions on the Motive bleeder say to not exceed 20 psi, and that the pressure you should use is dictated by the car manufacturer's setting. I've just finished bleeding the brakes on four of our cars (the three BMWs, and the 968), and kept it between 10 and 15 psi. But again, it's the tube on the Motive unit that burst, at a pressure value well below their stated maximum, and the bleeding operation on the 968 was the third time I had used the unit. I think I'll contact Motive and mention my problem to them. At any rate, I feel much more secure using the unit in the future with my new tube.

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[flash]

hmmm - was it at the clamp? was fluid left in the tube the last time you used it?

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[Cloud9...68]

No, it wasn't at the clamp. There wasn't a significant amount of fluid left in the tube from the last time I used it. It looks like it may have burst at a point where the tube was slightly kinked as a result of having to turn it to secure it to the reservoir. Just seems like it was a defective tube. I'm lucky the fluid didn't spray all over my car's paint.

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[nissanite]

Just a suggestion, brake fluid is water soluable. Take a garden hose & flush the area. Brake fluid will lift and wrinkle your paint.

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[Cloud9...68]

I know - but fortunately, none of it got on my paint. It was all confined to the back of my engine bay, any my windshield. I promptly wiped it off from any surface it hit.

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[flash]

never leave fluid in the tube or the bottle - besides attracting water and contaminating the system, it will harden the plastic, causing it to weaken



take great care not to kink that hose - that will weaken it too

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[Cloud9...68]

Yup - I fully drained the tank, and wiped it dry, after letting any fluid that may have been left in the hose drain out.



As far as kinking it, this will be much less of an issue with my new braided hose, as it's more flexible than the old one. I'm surprised the original one burst after only its third use.

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[flash]

it's cheap aquarium hose - it doesn't take much to mess it up - i have to buy new stuff every time i go to bleed mine, as i have a section i stick on the bleeder and run into a jar - that section is always hard when i go to use it again

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