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Author Topic: Brake drag, and hot MC??  (Read 1406 times)

Brian

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Brake drag, and hot MC??
« on: July 22, 2010, 01:48:24 PM »

I've been having a on going problem with the rear drums in the wagon. 
After a while of driving, when things get warm/hot, the rear drums
drag.  They get so hot you can't touch the rims!  I just had to change the brake shoes since they were all cracked.



I have a new booster and I'm running an aluminum master cyclinder, from
the mid 80's to the 90's mopar full size cars, trucks, vans.  I
installed a new proportioning valve last year, still the same problem.



I was in the middle of pulling the MC so I could back off the push rod a
 little further with the hopes that this would possibly help with the
brake drag, when I got to looking at how close the HP manifold runs to
the MC.



Could the master cylinder heating up cause my brake drag problem?  I
know hyd fluid expands when it gets warm/hot so I thinking that maybe
this is my problem?  The brake drag doesn't start until after 10-20
minutes of driving, if it was a booster/MC adjustment issue they should
drag right out of the garage.



Thoughts?

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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Steve

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Brake drag, and hot MC??
« Reply #1 on: July 22, 2010, 02:25:21 PM »

Brian. . .
 
When it gets like that, have you cracked a break line for the rears at the master?  Or is this a single master?
 
If it was the rod, the fronts would drag too.
 
Maybe the rear brakes are contaminated.  That crap and sludge that develops over the years.  It clogs the check in the master.
 
Open the system up and flush it with denatured alcohol.  If you can come up with a way of pressurizing the alcohol, that would be even better.
 
If you crack that line when the brakes are dragging, and a small gush of fluid comes out, then that's what the problem is.  You'll need to flush the master too.
 
Contaminated systems are not that uncommon is infrequently used vehicles.  Stewp up to DOT5 brake flude and it will never happen again.
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Brian

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Brake drag, and hot MC??
« Reply #2 on: July 22, 2010, 03:44:00 PM »

I've probably pushed over 2 gallons of fluid through this system over the last few years.  So I don't think that I have much for residue left.  When I bleed the system it always comes out nice and clean, almost no discoloration.




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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Brian

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Brake drag, and hot MC??
« Reply #3 on: July 22, 2010, 03:52:43 PM »

Just thought of this, might be a contributor to the problem.  

When the car is warm/hot, and you apply the brakes, the pedal does not return to the top of it's stroke right away.  You can depress the pedal and then release, and then tuck your foot under the pedal and pull it up the last little bit.  It will return to the top, but takes a few seconds to do so.

I've checked for vacuum leaks, as well as the check valve on the booster.  Everything is fine.



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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Steve

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Brake drag, and hot MC??
« Reply #4 on: July 22, 2010, 04:27:53 PM »

Uh Huh
 
Again. . .get the rear brakes sticking and release the nut on the master and see if you get a squirt.  All of that points to the same thing.  Been there!
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Brian

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Brake drag, and hot MC??
« Reply #5 on: July 22, 2010, 10:41:06 PM »

I decided, from some other advice, to put a new hardware kit on the beck brakes, since who knows when that was last done.  Definitely more spring pressure with the new kit, so maybe that might help a bit?




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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Steve

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Brake drag, and hot MC??
« Reply #6 on: July 23, 2010, 05:50:31 AM »

Knowing you, I had already assumed the springs were new.  There's that word again. . .Assumed. 
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Brian

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Brake drag, and hot MC??
« Reply #7 on: July 23, 2010, 08:36:18 AM »


Quote from: POLARACO
Knowing you, I had already assumed the springs were new.  There's that word again. . .Assumed. 

Yeah don't know why I hadn't done that yet...heck for $10 for the kit it's not worth using the old stuff.  Just never even occurred to me....

Think I'm going to replace the wheel cylinders as well, since I usually don't replace them unless they are leaking, and just ASSUME that if they ain't broke then you don't need to fix 'em.




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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Steve

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Brake drag, and hot MC??
« Reply #8 on: July 23, 2010, 10:08:25 AM »

What's Wrooonnnnngggg  with you!  I figured that would all be done.  I never thought about any of that stuff because I know how you work!  Check the parking brake cables too.  Especially the front and the RR wheel too.  That can cause it too
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Brian

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Brake drag, and hot MC??
« Reply #9 on: July 23, 2010, 12:27:08 PM »


Quote from: POLARACO
What's Wrooonnnnngggg  with you!  I figured that would all be done.  I never thought about any of that stuff because I know how you work!  Check the parking brake cables too.  Especially the front and the RR wheel too.  That can cause it too

Old habits I guess.....

I have the E-brake cable backed off so they can't be part of the problem.  Don't want to adjust them until this is all figured out.

What do you mean by..." Especially the front and the RR wheel too.  That can cause it too"???
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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Steve

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Brake drag, and hot MC??
« Reply #10 on: July 23, 2010, 04:23:40 PM »

Front and RR P brake cables.  The front goes to the E Brake pedal, the RR is the long one.  The tend to jam up unless they ar used allot
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Brian

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Brake drag, and hot MC??
« Reply #11 on: July 24, 2010, 03:40:10 PM »




               Ok here's something I did not expect....I pulled the flex line and
decided to bleed the main line before I installed the new flex line.
Now here's the weird thing, the line is not gravity feeding?  I can pump
 fluid through but once i stop that's it no brake fluid coming out of
the line.  I did back off the push rod another 1/4 turn could that have
something to do with it?  All the other brake systems I've done before
have bleed like a deep cut once you open the line.








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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Brian

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Brake drag, and hot MC??
« Reply #12 on: July 24, 2010, 04:02:14 PM »

Decided to pull the rear line from the master to the proportioning
valve...ran like a stuck pig.  So perhaps then my whole brake drag
problem could be because of a faulty "New" proportioning valve??  But
this problem persisted before I replaced the proportioning valve, could
it be that my old proportioning valve had the same problem, what are the
 odds of that?

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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

Steve

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Brake drag, and hot MC??
« Reply #13 on: July 24, 2010, 05:11:21 PM »

Could be a colapsed rear hose too
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Brian

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Brake drag, and hot MC??
« Reply #14 on: July 24, 2010, 06:05:32 PM »


Quote from: POLARACO
Could be a colapsed rear hose too

Flex line is removed, so straight off the hard line.



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Brian

02 Chrysler Concorde Lxi
84 Dodge Crewcab, Cummins/5speed
68 Chrysler Station Wagon 440/auto
48 Desoto 2dr Sedan flat 6/3spd manual

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