I spoke too soon, brakes still FUBAR

Doc. Have you checked your steel lines for corrosion holes anywhere. It could be sucking more air in as the fluid goes by.

Have you checked your steel lines for corrosion holes anywhere. It could

I believe this would be very unlikely to happen because these lines can have hundreds of PSI pressure on them.

I have thought about this one for some time. In the days of front and rear drums master cylinders had a residual pressure valve at the Master Cylinder outlet. This was to keep the wheel cylinder under a slight pressure to keep them from sucking air. I don't know how it could happen but could the brake lines to the Mstr Cyl been switched. Most Mstr Cyl have different threads for front and back but not all. I wonder if the fronts being locked up without pedal pressure is due to the residual valve that is/was intended for the rear drums and the rear drums are sucking air because of the lack of residual pressure? If that is not the case it must be the combination valve

I'm not sure if your bleeding with the pedal or using a suction tool like a MityVac. I think bleeding by operating the pedal is probably better in this situation. And not with the bleeder open and the hose imersed but by opening the bleeder and shutting it as the pedal is operated. I know this takes two people though, but it can dislodge stubborn air. b

This is probably not related but it comes to mind. A guy at work told me of such a problem that he had and it came after he had replaced his master cylinder. Anyway after a pile of hair pulling and another master cylinder it turns out that there are some O-Rings that need to be changed that weren't and they are either inside or underneath (wish I'da paid more attention). Anyway, he took the master sylinder off again and replaced the O-Rings and all is OK now.

I asked the obvious. Why would the O-Rings leak air and not brake fluid and he didn't have an answer.

Probably not related. Just a thought.

-- Regards Gordie

Do I remember you saying that combo valve was leaking at the nipple a while back? maybe air is sucking in through there getting to the rears...?

Im just catching up to your problem so I dont know all the details, BUT. Hows the truck running, does it sound like it has a Vacuum leak (Power brake booster could be shot). Or you could have some rust under the bleeder valve preventing an air tight seal, Look for rust on the face of the bleeder valve. How do the wheel cylinders look inside the drum, are they leaking? Is the master cylinder the type with the plastic resevoir? If so hows it look. You have an air leak somewhere, bleeding it out with multiple gallons of brake fluid is not going to help untill you find the leak and seal it. Good luck and dont throw a wrench thru the windshield (it wont do you any good but it will make you feel better)

I have had a similiar experance with a car kept losing my rear brakes like you I tried everything and what it was in the end was a hair line crack in the flare at the wheel cylinder and it wouldnt leak any fluid but would suck air just a little. Brakes would be good for a day or 2 and I would have to bleed them again. I just started changing lines one at a time till it was good and it was the first line I replaced so I was lucky I couldnt see the crack till I bent the line with some visegrips then it was easy to see. Line was dry no sign of leak at all!

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I spoke too soon, brakes still FUBAR Group: alt.autos.4x4.chevy-trucks Date: Fri, Sep 26, 2003, 8:42pm (CDT+5) From: snipped-for-privacy@noway.com (Doc)

DAMMIT!

Ok, here we go. Took her out yesterday for a healthier test drive (previous drive was

, Re: I spoke too soon, brakes still FUBAR Sat, Sep 27, 2003, 6:38pm (CDT+1) From: snipped-for-privacy@hotmail.com (John) wrote in......

I have had a similiar experance with a car kept losing my rear brakes like you I tried everything and what it was in the end was a hair line crack in the flare at the wheel cylinder and it wouldnt leak any fluid but would suck air just a little. Brakes would be good for a day or 2 and I would have to bleed them again. I just started changing lines one at a time till it was good and it was the first line I replaced so I was lucky I couldnt see the crack till I bent the line with some visegrips then it was easy to see.

Line was dry no sign of leak at all! ...........

Seen it happen myself.....after tightening lines on cylinder swaps.

good input,

Scrib