Bad Master Cylinder?

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Nov 12, 2005 | 09:06 PM

#16

DaveMac2Vans

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From: North Alabama

Update for those interested:

This one is like everything else at this address. . .never simple and always a major event. FYI, this is my 94 XLT extended 3.0. This started out as what I thought was a bad master cylinder. Decided I'd better send it to the shop because of time constraints and other crises. (Wife home and doing well, thanks!) Had pads, rotors, rear shoes, drums done. Still had the same issue, pedal seemed to keep sinking even after a full stop, and at the end of the pedal, the ABS and brake lights came on in the dash. Turning engine off and restarting would always clear the lights, and I could stop the van, but it just wasn't right. Shop guy scratching head at this point, finally called his contact at the factory. Seems to be in either that multi-piped item after the master cylinder or the pulse pump thing on the anti-locks. I am more and more glad I didn't jump into this one. Maybe it will be done on Monday. Will post the final outcome when available.

Thanks!

Dave

Nov 12, 2005 | 10:14 PM

#17

73f100shortbed

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Joined: Oct 2005

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From: NJ

It does sound like your master cylinder is going bad. One way to check to be sure is to clamp off the rubber lines to the calipers and the rubber lines to the rear wheel cylinders. You can do this with vise grips, but do not clamp TOO hard or you risk crushing the lines. If your pedal drops with all rubber lines clamped off master cylinder is definitely bad. If it is hard and does not dropthen you need to look elsewhere, broken line ,etc.

Nov 13, 2005 | 11:35 AM

#18

DaveMac2Vans

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From: North Alabama

Have checked every inch of line, every connection, every caliper and wheel cyilinder, and all are dry. Replaced master cylinder to no avail. Pretty sure it is in either that multi-piped item after the master cylinder or the pulse pump thing on the anti-locks. They're the only two items left.

Nov 13, 2005 | 11:47 AM

#19

xuzme720

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From: Houston,TX

the multi piped thing is the RABS module...no? believe ken had a solution for that one with a proportioning valve installed in-line. forget the thread it was in though.

Nov 13, 2005 | 05:40 PM

#20

ha38349

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could be the RABS valve

Here is a pretty good article on the subject:
http://www.babcox.com/editorial/bf/bf60133.htm

One failure mode is that the RABS valve does not reset completly after ABS kicking in. I recall an article that warned folks not to try and test their rear ABS on older vehicles because it could lead to this type of valve failure.