Brake Line Overhaul, questions on sizing/procedure - pics enclosed

[JFerguson]

Hi everyone. Working on my car:

1991 Oldsmobile 98 Regency Elite, V6, 3.8L
Teves MK IV ABS system without TCS (Traction Control System)

I've been having some poor performance with my brakes lately (fading/mushy brakes) and I am doing some work to rectify this.

I think part of the problem are these Fenco remanufactured master cylinder units I've been getting from AutoZone. They've been giving me these units with 6-1/2" bores that are supposed to be compatible with my car, despite the fact that the vehicle originally came with one with an 8" bore. I dunno, I think they're crap anyway -- I should've got a Cardone.

Besides that, the brake lines in the forward/engine section of the car are in pretty bad shape and I am replacing them. Here's a pic:



These are four lines that enter the ABS Hydraulic Unit (auto parts store naming convention?)... from there they go to the four wheels. I have another reference that refers to this device as the Pressure Modulator Valve (PMV). Here's a pic (shot from above), oriented as it was installed in the vehicle:



Here's another pic, from the side. You cannot see them, but there are two ports on the left (underneath the resevoir), for connection to the master cylinder:



This vehicles uses 3/16" brake line with bubble flaring and two differently sized fittings. Here's a pic:



The two brakes lines from the Master Cylinder to the hydraulic unit were in pretty bad shape at the hydraulic unit end (in fact, both lines broke when removing the connections there). The four brakes from the hydraulic unit to the individual circuits are in pretty bad shape from the hydraulic unit to the engine firewall -- beyond that, they look pretty good.

Some questions:

In the fourth picture above, I have been able to find preflared brake line with the smaller fittings at AutoZone (European line). Neither AutoZone or Advance Auto Parts knows what to make of the line with the larger fitting. I was wondering if anyone has any information on these lines?

I'm going to replace the Master Cylinder to hydraulic unit brake lines with preflared 40" lines (assuming I can find the one with the larger fitting) -- should fit pretty good with a little bending. I'm going to get 60" lines for the four brake lines coming out of the hydraulic unit and splice them into the individual circuits (probably not necessary for the front left circuit, though). When splicing, is this the correct procedure?

Cut and double-flare (with fitting) the individual circuits.
Connect to pre-flared break line with union.

Is there a union that accepts bubble flaring on one end and double-flaring on the other? I'm thinking I'll probably have to cut one end off the pre-flared lines and double-flare them as well. The guy at AutoZone said I can get the unions at Ace Hardware?

Thanks for any help...

[JFerguson]

Well, not much activity going on here. I've been digging in on this for the past couple days -- visited a couple auto stores. Struck out at one NAPA, but picked up a few things of interest at a Lee Auto Parts (Chicago) and another NAPA store.

Take a look at these pics:





The top upper left fitting is a brass double-flare union I picked up at Lee Auto Parts. That's standard stuff: cut two lines, double-flare them with fittings and connect them up. Probably makes a good connection, but there seems to be some debate regarding the use of brass in braking systems?

The top two upper right fittings are what's needed to adapt the large GM bubble-flared fitting. It adapts to a female double-flared fitting and will accept standard double-flared lines/fittings. No one seems to understand the purpose of these GM fittings, and no one has pre-flared bubble line with these fittings either. Even a reputable local GM parts/dealership was of no help with this.

The bottom two fittings are interesting. According to NAPA, these are DOT-approved compression unions for use in brake lines. The general consensus out there is that compression unions are a big no-no in braking systems. They convinced me though, and I bought a few. The top one is one I opened up; you can see that they do differ in design from the typical compression union found in water supply systems (household plumbing). On the left, I took out the compression ring and hand tightened the nut down; I imagine this is closer to how it will appear with an actual line in and the ring/nut tightened down. The bottom one shows what they look like as purchased from the store and hand tightened with compression ring inside.

Also, when I stopped by an AutoZone on the way home and asked them about brake compression fittings, they showed me a brass one like that found in household plumbing.

Just an FYI...