1989 Dodge Truck proportion valves

Tiny
POMIKE
  • MEMBER
  • 1989 DODGE TRUCK
Brakes problem
1989 Dodge Truck V8 Four Wheel Drive 999999 miles

There are two boxes onthe front and rear brakes. One along the frame, another in the back. The local mechanic says they are bad, but can't find the parts anywhere. The VIN is 1B7HM16Y8KS069536. Are these parts available anywhere, or can they be replaced with something else? Thanks.
Mike
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Sunday, May 2nd, 2010 AT 4:33 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Hi pomike. Welcome to the forum. What is the symptom? Does your truck have rear anti-lock brakes? If so, you might be referring to the hydraulic control valve in the front. About the only problem they cause is shorting internally and blowing a fuse inside the controller.

If you don't have anti-lock brakes, that box is probably the combination valve. I've never seen one of those cause a problem unless someone tried to take it apart.

The only thing I can think of in the rear is a height-sensing proportioning valve. They also rarely cause a problem. It is possible to break off a line nut when replacing a rusted brake line.

Any of those parts can be found in salvage yards but they should come from a similar truck. They can have significant differences due to different weight distribution.

Caradiodoc
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Sunday, May 2nd, 2010 AT 6:34 PM
Tiny
POMIKE
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The truck is 1989, so I think we can count out anti lock, don't you? I figured, with the VIN a parts breakdown of the vehicle could be found, which would show the parts. The experienced mechanic who tried to work on it said the vales are both shot, and that one might possibly be made to work, but not the rear one. He just did not have time to search for them out here where we are talking now. Can we find a parts drawing to go with the VIN I gave you. I know it is the right VIN, because when I input it to the carfax cover page, without paying for carfax, it showed the exact description of the particular truck. Mike
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Sunday, May 2nd, 2010 AT 6:46 PM
Tiny
CARADIODOC
  • EXPERT
The vin only includes engine size, manufacturing plant, model year, and things like that. It doesn't tell which options are on the truck. Only Chrysler has a record of the options it had when it left the factory. Carfax might be using the Chrysler web site to get that information. Rear wheel anti-lock first showed up on '89 models so they wouldn't have been real common yet. You will have a yellow rectangular "RWAL" light on the dash that turns on for seven seconds every time you turn on the ignition switch if you have that option. If the hydraulic control unit is shorted, the system won't work. That will leave you with the base brakes which will perform normally.

"Shot" doesn't mean anything. What are the symptoms? Are they leaking? Is the brake pedal too low and mushy? Do the rear brakes lock up easily? Why does your mechanic want to replace them?

Can you see how many steel lines go into the front valve assembly? If it's a brass block, about 4" long and 3/4" wide with five lines, that is the combination valve. In 28 years of doing brakes, I only replaced one for seeping brake fluid. That was on a Cadillac. That's why it seems strange yours needs to be replaced.

I can't find any reference in the service manual about a height-sensing proportioning valve on the trucks. My '88 Grand Caravan has one so I know they were in use by '89. They are used on pickup trucks and minivans because there can be such a huge change in weight distribution depending on how it is loaded, so they can't design a "one-size-fits-all proportioning valve to build into the combination valve. Can you describe the box you're referring to? Color, shape, dimensions, location, number of steel lines, etc. Can you see it from underneath without removing the wheels? I can't think of any other brake part that would look like a box.

Thanks Mike.

Caradiodoc
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Sunday, May 2nd, 2010 AT 8:15 PM
Tiny
POMIKE
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Thank you very much for the information. This is my friends truck, so I will get with him when he gets home from work today and track down your questions. Once I know more, I will get back to you,
Mike
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Monday, May 3rd, 2010 AT 6:09 AM
Tiny
2CARPROS LINSEY
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Monday, May 17th, 2010 AT 12:48 PM

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