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HELP... rear brake issues

dodgedieselnewbie
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dodgedieselnewbie

dodgedieselnewbie

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I'm starting get really upset... my rear brakes are still giving me issues. History... Back in January I had the rear cylinders swapped out to the Chevy 1 ton and the rear proportioning valve bypass. Also had new shoes installed. All seemed well up until about a month ago. My work is seasonal so things picked up a month ago.. so more driving and braking began. It seems the warmer the brakes (fluid?) get.. the worse they get. Recently had the rear drums turned, new spring kit and adjusters installed. The shudder is back and progressively getting worse each day.. and again the more use they see throughout the day.. the worse the shudder. They also become extremely touchy (grabby) and the antilock is kicking in kind of easily. 

 

I have not read any negative feedback on the larger cylinder upgrade or the proportioning valve bypass... So.. kind of stumped here. 

 

I brought it to my mechanic and he test drove... when he came back he was shocked at how grabby, shuddery <--- for lack of a better word and how easily the antilock kicked in. 

 

He suggested to go back to the stock sized cylinders to see if that helps. 

 

Could the front proportioning valve be the problem? How do you tell.. or test?  

 

What else can it be?

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CSM

CSM

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I've never heard of the self adjusting valve before.  I would want some sort of valve there, unless you want to lock up your rear brakes.  Locked up rear brakes tend to make vehicles swap ends.

 

Personally, I think there is some corrosion in the system that is causing the problem.  Could be the perportioning valve you pulled, could be in themaster cylinder. In short, it doesn't seem like a simple fix. 

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dodgedieselnewbie

dodgedieselnewbie

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I dunno.. I will repost here what I posted at CF..

 

My questions are these...

I have searched and found that everyone is happy with either/or the proportioning valve bypass and... the larger cylinders. Why is mine a problem?

Why is it only happening after extended driving... after things heat up? First thing in the morning and my local stop to stop it's not a problem.. 

It drove beautifully for a couple of days and then came back... why???

 

Here's a quote from from an old post over there from Mike

 

"As for the rear lines I say replace all the lines and you can ditch the rear proportioner and just direct plumb the the rear brakes. Later in time Dodge discontinued that whole system, like on my truck is direct plumbed in 2002."

 

 

Edited by dodgedieselnewbie
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dodgedieselnewbie

dodgedieselnewbie

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 This morning took truck out for 10-15 minute drive.. applying brakes a dozen times.. no problems. So it's something to do with when it gets heated up and seems to build too much pressure... ? 

 

Help.. suggestions welcomed. Replace master cylinder? Front proportioning valve? What else? 

 

Could a brake controller cause an issue if wires are crossed up? One was put in a few weeks ago.. I guessing no but I'm trying to think of anything.

Edited by dodgedieselnewbie
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TFaoro

TFaoro

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When it warms up the fluid runs easier and allows less foot pressure to make the same amount of brake pressure... just a guess.

 

I'd stick the proportioning valve back in for the rear. I know Mike says there aren't any on the newer models, but those have disc brakes. Apples to Oranges IMO

10 hours ago, CSM said:

I've never heard of the self adjusting valve before.  I would want some sort of valve there, unless you want to lock up your rear brakes.  Locked up rear brakes tend to make vehicles swap ends.

 

Personally, I think there is some corrosion in the system that is causing the problem.  Could be the perportioning valve you pulled, could be in themaster cylinder. In short, it doesn't seem like a simple fix. 

I thought the original was a fixed valve...

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Me78569

Me78569

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I'd put the valve back in also.  you are getting full pressure to the rear brakes all the time now vs only when loaded heavy.

 

I would guess your brake bias is all out of wack.

Edited by Me78569
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dodgedieselnewbie

dodgedieselnewbie

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I'm not disagreeing with the recommendation of putting the prop valve back in... but doesnt there seem to be something else going wrong if lots of others have done the same mods without issue? The are plenty of 99s with rear drums  (one locally) without issues. Just doesnt make sense... hopefully I still have what was removed

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Me78569

Me78569

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It sounds to me like your ABS is fighting the whole time.  I am honestly not sure how the RWD ABS works, only one sensor and somehow it knows when the rear end is locked up?

 

Question I would have for other guys in your area running without issues is, is there some tire / grip difference that is causing your issue?   IE: do they have better grip for one reason or another.

 

 

beyond that I would look at why your ABS is trying to engage.  Does the issue go away when you unplug the ABS? ( can you even do that on a 2nd gen to test? haha)

Edited by Me78569
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CSM

CSM

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2 hours ago, dodgedieselnewbie said:

What do you mean?

 

I would have to dig through the manual and part lookup tool in the articles and downloads, but I wonder if there is a normal perportioning valve as well as the secondary valve? 

 

You brake issues still aren't fixed even with removing the valve?

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Buzzinhalfdozen

Buzzinhalfdozen

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I find it a little odd people have had success removing the rear proportiong valve.

The "load adjusting rod" on mine that goes from axle to valve has been gone for years so I just tapped the adjusting arm on the valve up or down to find a sweet spot for towing/daily driving. I know that if I give it to much rear brake pressure the rear tires will lock up at highway speeds with a loaded trailer...

 

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Haggar

Haggar

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The rear "level sensing unit" or Height sensing unit is not THE proportioning valve.  (there is also some proportioning from the master cylinder itself, based on bores and strokes there....  most of us don't mess there but there can be some tuning available if needed.)

 

The proportioning valve (now called combination valve) should still be located near the master cylinder.  It should have both the front braking circuit running into it (and out) and the rear circuit running in (and out).  It has a check valve in it, that should the loss of continuity of one circuit, ALL braking will only go the the circuit with integrity.  This prevents un-needed loss of fluid, and signals the brake light on the dash that there is a problem.  (this will cause a constant on lighting of the brake light.  not flashing like parking brake on does.)

 

This proportioning valve is sized such that the larger diameter but low stroke of front discs can be combined with the small diameter but larger stroke of rear drums to work together.  

 

The "level sensing unit", is a rear axle system.   It "sees" the relationship (in elevation) of the frame to the axle.  It allows more pressure to the rear brakes based on the assumed load in the bed.   

 

It sounds like you need to re-adjust that rod.  You have too much rear braking force, for the weight you are carrying.  (or the valve you have is damaged.)  

 

Take a peek at this site.  The information is really good.  Read about the height sensing proportioning valves. http://stoptech.com/technical-support/technical-white-papers/proportioning-valves

 

Hope that helps!  You just may need to do a simple adjustment.  It sounds like your Height sensor is thinking you are carrying more weight.

 

Hag

 

 

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