Break Line leaking at break modulator proportioning valve - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-10-2007, 12:12 PM   #1
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Default Break Line leaking at break modulator proportioning valve

I have my break lines leaking at the break modulator proportioning valve. Rusted thru I have to replace both of them going to the rear cylinders. I am running into all kins of problems. Couldn't open the bleed screws, had to replace the cylinders...Front calipers changed the bleed screws opened after lots of work...Now I need a tool that makes the bouble break line, anybody knows where to get something like that? Bubble shape I think. The break modulator proportioning valve costed me about $70 each at he stealership. Now I need fittings and a tool to make break line ends. Anybody knows what these break modulator proportioning valves do? I this is the right name for them, they are located on the break lines about the middle of the car going to the rear break cylinders....Are they necessary? The fittings going into them are different at each end. Do they have a sens, they go on the line or any is as good. They look like a small marker and I am not sure they go left to right or right to left? I blow into them and seems the same. I think is a new discussion topic.
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Old 03-10-2007, 12:37 PM   #2
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From your description, those are the proportioning valves for the rear brakes, and they are needed. In this article from "How Stuff Works" it tells you more about them. The picture there shows it as part of the master cylinder which is more how it is with newer cars. Same principle however.

http://auto.howstuffworks.com/master-brake2.htm

If you don't want to replace the entire line from fitting to fitting, you'll need a double flare or bubble flaring tool. They are available at hardware stores, or Harbor Freight. You may be able to get one from places like Advance Auto Parts with their "loan a tool" program.

Yes, there has been previous discussions on these.
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Old 03-10-2007, 02:29 PM   #3
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I gave it a search, but I couldn't find another discussion to answer my dilema... Does it matter the direction for installing these? They are installed on the break lines themselves. They do not have any arrows on them. Just the port holes are of a different size. If they are proportional valves I assume the directions should matter. I will rent the toll from one of our local stores, but I wasn't sure which one is better or bubble or double is the one I should get.
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Old 03-14-2007, 01:58 PM   #4
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I have installed the two proportional valves and it doesn't seem to have a sens, or I was lucky. The breaks work fine. I had some minor issues to make the line ends with the flare tool. It does not leak, and I found out that is cheaper to buy premade short brake lines and cut them and reuse the ends than to buy the end fittings separately.
Just an update.
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