*fixed* 1990 rear brake line confusion

[Ju1cE]

*fixed - previous hack spliced 1/4 to 3/16 in the run to the rear. Will be replaced w full run of 1/4.

Hey GMT400 Forum,

I’m new to the platform and new to the platform but am not new to wrenching.

I just bought a 1990 K1500 Sport that had been hacked on by previous owner and questionable mechanics. I’m running new brake lines through the whole truck (replacing some poorly replaced lines) but am confused about the rear line. It comes out of the proportioning valve as 1/4 but the attached to the rear hose as a 3/16. I’m imagining something else had been in line before but is now missing since the last guy under here was a hack (pic below)

Guidance is appreciated!!

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Yes that’s a plumbing tee, adapters and cap screw and yes it leaked haha

 

[Pinger]

Like you I'm replacing that brake line and had to ask here about fitting sizes. The consensus is that all GMT400s have a 1/4'' line from the front to the rear flexible hose (3/16'' across the axle).
The line is in three parts. Front section from ABS unit (in my case) to union at bottom of front bulkhead (firewall), second section from there to below rear seat doors (Suburban) and the final section from there to the flexible hose. All unions are 7/16'' 24 TPI with the exception of the nut at the very front (ABS unit) which is 1/2'' 20 TPI.

 

[89RCLB]

This is the factory setup for the rear on my 1989 GMC K1500. 1/4" hard line transitions to flex hose, then 3/16" hard line to the wheel cylinders. I bought the 3/16" hard lines from Inline Tube. The flex hose came from Rock Auto.

 

[mwilliams55555]

Hey GMT400 Forum,

I’m new to the platform and new to the platform but am not new to wrenching.

I just bought a 1990 K1500 Sport that had been hacked on by previous owner and questionable mechanics. I’m running new brake lines through the whole truck (replacing some poorly replaced lines) but am confused about the rear line. It comes out of the proportioning valve as 1/4 but the attached to the rear hose as a 3/16. I’m imagining something else had been in line before but is now missing since the last guy under here was a hack (pic below)

Guidance is appreciated!!

You must be registered for see images attach

Yes that’s a plumbing tee, adapters and cap screw and yes it leaked haha

Sometimes you have to do what you can do to get home or to keep moving forward LoL, yes 1/4 line from front to rear junction rubber to rear end, 3/16 to wheel cylinders, I'm replacing the lines on my 99 suburban, bought rolls of line, double flare tools are really cheap and easy to use. Plus gives you the satisfaction of doing it yourself and extra money for gas to enjoy your work lol

 

[Ju1cE]

Thanks everyone!

No idea how this previous hack got a 3/16 line to attach to the original rubber hose but I just checked my new one and yes indeed it will be correct for the 1/4 line and proper tube nut. Guess I should have checked that first but really appreciate all the quick answers and guidance!

This old rig will be out on the dirt soon!

Happy motoring!

 

[mwilliams55555]

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This is what I used, don't have to worry about it rusting

 

[evilunclegrimace]

Sometimes you have to do what you can do to get home or to keep moving forward LoL, yes 1/4 line from front to rear junction rubber to rear end, 3/16 to wheel cylinders, I'm replacing the lines on my 99 suburban, bought rolls of line, single flare tools are really cheap and easy to use. Plus gives you the satisfaction of doing it yourself and extra money for gas to enjoy your work lol

These lines are supposed to be double flared

 

[mwilliams55555]

Your right, I just know that the tool's are really reasonable to do the flares needed, not like the Bubble flare on most foreign stuff

 

[Ju1cE]

You must be registered for see images attach

This is what I used, don't have to worry about it rusting

I ran what I had left of NiCu and the ready in Ultrabend (pretty much all the same stuff) and borrowed my buddies Master Cool flaring set (gawd I love that tool)

 

[Road Trip]

When it comes to a decent double-flaring tool, the really cheap tools are
only good to test your patience. On the other hand, spending $$$ on a
pro shop setup is hard for me to justify on a 'price-per-use' basis.

Given this, if you are looking for a no-frills budget tool that has never
failed to work for me (especially with NiCopp) is the OTC 4503 Stinger.
(Amazon link here.) According to the sticker, made in Taiwan.

Doesn't feel cheap in the hand, gotten flawless results from it.

Don't delay -- get rid of the PO's hackery asap!

Safe travels --