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'77 gmc 3/4 ton brake lines

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New User

Oct 5, 2007, 10:22 PM

Post #1 of 2 (1581 views)
post icon '77 gmc 3/4 ton brake lines Sign In

I am having difficulty disconnecting the front brake hoses from the steel brake lines on my '77 gmc truck. Is there a particular "trick" to doing this or a tool I need, or are these connections just really stuck from years of use?

Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 6, 2007, 4:24 AM

Post #2 of 2 (1577 views)
Re: '77 gmc 3/4 ton brake lines Sign In

1. Prepare to replace the steel line and flare nut. Depending on how rusted it will come out and not spin the line if the nut is heated (oxy-acet) to glowing with pin point tip - then fast work to get a tubing wrench while it's still glowing on nut just to get it started and watch that it isn't spinning the line. Go back and forth as long as it will and then stop and let cool. Now with PB penetrating oil it should come off with just an open end wrench.

It's old enough for anything so be prepared to make up a new line and route it exactly as possible as the original.
Remember - you only want to heat the nut - not the line. Rubber brake hose should NEVER be reused if exposed to that kind of heat.

If the line is going anyway cut the brake line and use a six point socket to remove the nut. Most of the time you can make a new line end using a flaring tool, new nuts and union,


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