brake dragging 5ktq

[Grant Lenahan]

I dont have an answer, but I did some thinking about this.

Since it is common to several calipers, but is not consistent to any 
one, it cannot be the calipers themselves, nor any of the 
hoses/plumbing that is dedicated to a single wheel.

I also cant see how the master would cause it - since that should, via 
the proportioning valve, apply pressure to calipers evenly.

Did you claim that the two calipers that acted up were the LF and RR? 
If so, that implies a diagonal correlation - pointing to something in 
the dual-diagonal redundancy (audis do have this, dont they?)

I somehow wonder about an ABS module applying random pressure....

Grant

On Nov 20, 2006, at 10:17 PM, Doyt W. Echelberger wrote:

> Gotta check with the wisdom of the list. My 87 5ktq brakes are not 
> fully
> releasing, and at times are dragging significantly....but only on the
> driver side, and not in a predictable pattern.
>
> I don't drive the car every day, and with this brake drag problem I 
> drive
> it even less. Maybe I drive it one week and then not the next at all, 
> or
> let it sit two weeks at a time.
>
> Last week I drove the car 4 miles, going about 55mph for the first two
> miles.  I could feel a brake drag when I pulled out of the driveway.  
> On
> the highway for about two seconds the drag slowed the car down a 
> little bit
> and then seemed to let up, so I kept going.
>
> At the two mile mark I stopped and walked around the car, looking at 
> the
> rotors and feeling the wheels for heat.  The driver-rear rotor was 
> glowing
> a medium red and the wheel was hot...too hot to touch. I figured it was
> cooking the grease out of the hub and it scared me a little. Never saw 
> it
> glow red that way before. Pretty alarming.  The other wheels were 
> normal.
>
> I turned the car around and drove it back home at a _greatly_ reduced
> speed, maybe 25-30 mph, and parked it, thankful that the trip didn't
> require a flat bed. Then I went inside and let it cool off for a few 
> days
> while I thought about it.
>
> OK, so it cooled off. Wonder if it will do that again? Did the same 2 
> mile
> drive, and there was some brake drag, but when I stopped and did the 
> same
> walk-around, all the wheels felt normal except the driver-front, which 
> was
> warmer than my hand but not hot enough to make me pull my hand
> away....maybe 140 degrees F ? That rear rotor was normal.  Now the 
> front
> driver caliper was acting up.
>
> Big mystery. Gotta take the system apart and look at everything first.
> Drove to shop, let everything cool for a day, put car on a lift and 
> pulled
> all 4 wheels and checked calipers and tested the pins that usually 
> hang up,
> and checked both rear emergency brake cables and levers.  Up on the 
> lift
> everything working and loose like it should be.
>
> Put the wheels on and drove it on the streets again and the brakes 
> started
> dragging again, so I parked it and sat down to write the list.
>
> OK, what are the facts/history:  I've been running the car with the ABS
> electricals disconnected where they plug in at the ABS controller 
> under the
> back seat.  Did that because the sensors were getting confused by the
> corrosion on the cogs in the hubs, and cleaning the cogs didn't stop 
> the
> shudder during the last few yards of a rolling stop. Disconnecting the
> electricals of the ABS worked fine for about 5 years, and I really 
> didn't
> miss it very much.
>
> Replaced the MC a few years ago because it was very old and was 
> causing a
> creeping increase in pressure as the brake fluid heated up on a long
> drive.....but that involved both front calipers grabbing, and 
> replacing the
> MC corrected the condition.
>
> The pads and calipers and rotors and flexible lines are not the 
> originals
> and are all only a few years old, as are the hard brake lines. I even
> replaced all the rusty old brake lines at the rear, when I replaced 
> the gas
> tank last year. And the brake fluid is about a year old.
>
> If a channel of the MC were causing a problem, I'd expect some drag in 
> a
> front and a rear on opposite sides. I've had a bad MC and it acted 
> different.
>
> So, I suspect a problem somewhere in the old ABS unit under the hood in
> front of the driver.  It is rather mysterious, and I don't know much 
> about
> it, and it's electricals are disconnected. But it has the ability to 
> affect
> one wheel at a time because I think that is how it worked to perform 
> its magic.
>
> There you have it.  Any lister been there and done that and fixed
> anything?  I'd like to drive this old workhorse another winter.  I'm
> considering re-attaching the ABS electricals and letting it chatter a 
> few
> times, if it will still  do that.  Maybe chattering will change 
> something.
>
> That's about all I can think to do.
>
> Replies appreciated.
>
> Doyt Echelberger
> still alive and living in Ohio and trying to keep an amazing old car 
> going.
>
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