Brake Line Help

map325 · October 26, 2011

Another description: 2000 Tahoe is the same.

When looking at the brake pipe port face of the BPMV, the ports are assigned as follows:

• Upper Left—Left Front Output

• Upper Middle—Right Front Output

• Upper Right—Rear Output

• Lower Left—Master Cylinder Secondary/Front Input

• Lower Right—Master Cylinder Primary/Front Input

The lower right port is labeled in the diagram as REAR input...not front

The whole point of my post was to point out that the lower left port that says front input is really the rear master cylinder line and that the right lower port that says rear input is really the front line on the master. The mechanics lable those two ports as right master and left master, in that order.

Primary will be for the front brakes and is the front portion of the master cylinder. Secondary is is for the rear brakes and is at the rear of the master cylinder.

"• Lower Left—Master Cylinder Secondary/Front Input

• Lower Right—Master Cylinder Primary/Front Input"

Your info has both inputs as "front", also the words Primary and Secondary might also be confusing, you would normally think of Primary as being the front and Secondary a being the rear. I like the way that the mechanics at my dealer label the 2 lower ports, the left one is "right master" and the right one is "left master". Less confusing that way.........

from a long-time listener, first-time caller...

George and David - Thanks for reviving this discussion, just as I am in the middle of a complete brake line replacement on my '01 2500 (non-HD). I too was scratching my head after viewing the BPMV diagram, since I tried to keep good track of the line routing during disassembly. Unfortunately several lines disintegrated in the 4-cluster just under the driver's door. I'm almost finished the full SS upgrade following my second OEM steel line failure in 2 years.

Can you elaborate on the "small problem" that led you to discover the MC input lines were crossed? Just wondering what to keep an eye out for as I finish bleeding and start testing. Thanks for all the tips!!

map325 · October 26, 2011

A brake line let loose on my '99 last weekend, so I ordered the same SS kit from Classic Tube. It arrived on Thursday (they are fast!) and today I was outside looking at how I was going to get started. It doesn't look like the front passenger line is going to go in easy. In fact, it looks like I'm going to have to remove the radiator shroud and a bunch of hoses and cables to get it in, unless I cut it and add a splice. Any tips?

Patrick

Reading posts here gave me the guts to finally fix this brake line mess properly, so here's my $0.02.

Almost finished a complete Classic Tubing SS kit install on my '01 after a complete blow-out under the driver's door just before the 4-cluster crosses over the frame rail to the BPMV. The worst part is last year I paid a dealer $$$ to replace the rear steel line after a pinhole leak just before the "T" on the rear axle. I decided to also replace the dealer line with SS after seeing the shoddy routing and bending job they did - bypassing nearly every plastic frame clip and even including a splice above the fuel tank. Here is a brain dump of my lessons-learned:

The complete removal and installation of all 7 hard lines and 5 flex lines ran me about 18 hours, usually with someone helping push/pull/twist the lines. I removed the front left wheel well splash guard (use a flat blade to pry between the center button and outer ring to pop the fasteners), as well as the splash guard under the radiatior. Also unclip the big electrical conduits near the wheel well lines (most plastic ring clips can be popped open by rotating a flat blade at the joint). Take careful notes or pictures of all routing of lines and conduits and it will save you major time and rework later. Unhook all lines from the BPMV (again after carefully taking notes/pictures), and unhook the 3 blue plastic clips holding the 4-cluster along the frame rail. The clips have 1 line cradled on top, then pry open to release the remaining 3 lines. Unclip and pull each line toward toward the back of the truck. The front right wheel is tricky, but you can drop the end on the front right corner, then pull toward the front left wheel well, while pushing back through the pinch point between body and frame at the driver's door hinge. You can coax it out with some bending and straightening. On the new lines I had to flatten some of the 45 deg bends at that pinch point because they didn't line up quite right, possibly since my 2500 non-HD frame seems to be a little rare.

The rear line was the hardest because I didn't want to lower the fuel tank and the steel line I removed wasn't routed correctly anyway. Pay close attention to the over/under routing around conduits and frame crossmembers, especially just under the fuel tank fill line. You need a 2nd person to guide the line from behind the rear axle while you guide the front "J" bend around obstacles. With a little coaxing you can push the ~2" J end (nut/flare turned up and long line turned down) between the frame, fuel tank, and conduit at the front of the wheel well. Once through there it slides nicely. Be sure to feel along the entire frame rail to find all the plastic clips to secure the line.

The final connection to all 5 ports of the BPMV required some slight modification to the Classic kit bends. Most of their bends were dead-on, but a few I had to bend more or less by hand. Still a much better option than starting with straight stock tubing.

I also did the Stop-Flex kit which was great except the "banjo fittings" that connect the hose to caliper weren't quite right. They sent two straights and two 90 deg fittings, but none of my calipers can use the 90 deg. Classic agreed to send four 30 deg fittings, since even the straight fittings when tightened would jam the hose coupling nut against the caliper. The OEM offset design allowed more clearance for a wrench on the bleeder screw, but I think these will work.

Final observation - best way to install brake lines is on an assembly-line chassis without the truck body in the way!!

Quadrasteer · October 26, 2011

Another description: 2000 Tahoe is the same.

When looking at the brake pipe port face of the BPMV, the ports are assigned as follows:

• Upper Left—Left Front Output

• Upper Middle—Right Front Output

• Upper Right—Rear Output

• Lower Left—Master Cylinder Secondary/Front Input

• Lower Right—Master Cylinder Primary/Front Input

The lower right port is labeled in the diagram as REAR input...not front

The whole point of my post was to point out that the lower left port that says front input is really the rear master cylinder line and that the right lower port that says rear input is really the front line on the master. The mechanics lable those two ports as right master and left master, in that order.

Primary will be for the front brakes and is the front portion of the master cylinder. Secondary is is for the rear brakes and is at the rear of the master cylinder.

"• Lower Left—Master Cylinder Secondary/Front Input

• Lower Right—Master Cylinder Primary/Front Input"

Your info has both inputs as "front", also the words Primary and Secondary might also be confusing, you would normally think of Primary as being the front and Secondary a being the rear. I like the way that the mechanics at my dealer label the 2 lower ports, the left one is "right master" and the right one is "left master". Less confusing that way.........

from a long-time listener, first-time caller...

George and David - Thanks for reviving this discussion, just as I am in the middle of a complete brake line replacement on my '01 2500 (non-HD). I too was scratching my head after viewing the BPMV diagram, since I tried to keep good track of the line routing during disassembly. Unfortunately several lines disintegrated in the 4-cluster just under the driver's door. I'm almost finished the full SS upgrade following my second OEM steel line failure in 2 years.

Can you elaborate on the "small problem" that led you to discover the MC input lines were crossed? Just wondering what to keep an eye out for as I finish bleeding and start testing. Thanks for all the tips!!

The small problem was my impatience to get the job done that night, I ASSumed that the front master line was for the front brakes. So I mangled the fittings at the pump, even though they lined up perfectly the way they were, to fit and then had to un-mangle them to put them back the right way. Your post further on in the thread explains the process very well! It took a trip to the dealer to find out that they label them differently than the diagram so there is no confusion. Now I'm having a problem with the conversion of the old style, smaller front brakes to the '07 larger style. The brake pad clips are hitting the rotor, it's always something...........

hikerfisher73 · October 27, 2011

Thanks for the advise, Quadrasteer! I hope it's as easy for me as it was for you.

Patrick

RV6junkie · November 5, 2011

I'm posting this so others that have a brake line failure know that an entire line replacement isn't necessary if the rust is limited to just a few inches of brake line.

During our October snow storm my left rear brake line sprung a leak about 2 inches from where it attaches to the rubber line, right at the high point. Luckily I was in my driveway when the pedal went to the floor. I was prepared to replace the entire line but noticed that the rust only traveled about 10 inches. The remainder of the line was perfect. I decided that a line repair was more palatable then bending an entire line.

I cut the brake line about 3 inches behind the fuel tank (allowing me ample room to work yet removing as much line as I could from the rusted section) which resulted in needing a 20 inch repair section. I removed the rusted section and used used that as a template to bend a new steel line. With the line looking more or less like the removed section I installed the fittings and flared both ends. I added a fitting and flared the original line as well, allowing about a 1/4 inch gap between the new and old sections. A brake Union was installed between the sections. Using a union results in a safe permanent repair, unlike some other approaches (like a compression fitting).

The entire job cost me $14; $2 for fittings, $2 for steel line, $2 for the union and $8 for a large bottle of Dot 3/4.

When I bleed the left rear brake the fluid was so green that I thought that my truck had bronchitis. It took quite some time to get clear fluid to run out of the bleeder. So I will be doing a complete fluid refresh soon.

Anyway, I hope this little write-up helps someone else that is looking a big project. To do a simple repair took about an hour and I didn't have to drop the fuel tank or any other cringe-worthy job.

One last thing (since I don't post here often); my 2004 now has 115k. I like most everything about this truck EXCEPT its brake system. The brake feel is wooden and stops are long. Changing pad material has had no effect. The other item that wears often on my Silverado are the front wheel bearing assemblies. I've replaced both left and right and the right side is starting to groan again so it looks like I'll be replacing another. Both times I've used a mid-priced Dorman assembly, but this time I'll try something different.

Quadrasteer · November 7, 2011

I'm posting this so others that have a brake line failure know that an entire line replacement isn't necessary if the rust is limited to just a few inches of brake line.

During our October snow storm my left rear brake line sprung a leak about 2 inches from where it attaches to the rubber line, right at the high point. Luckily I was in my driveway when the pedal went to the floor. I was prepared to replace the entire line but noticed that the rust only traveled about 10 inches. The remainder of the line was perfect. I decided that a line repair was more palatable then bending an entire line.

I cut the brake line about 3 inches behind the fuel tank (allowing me ample room to work yet removing as much line as I could from the rusted section) which resulted in needing a 20 inch repair section. I removed the rusted section and used used that as a template to bend a new steel line. With the line looking more or less like the removed section I installed the fittings and flared both ends. I added a fitting and flared the original line as well, allowing about a 1/4 inch gap between the new and old sections. A brake Union was installed between the sections. Using a union results in a safe permanent repair, unlike some other approaches (like a compression fitting).

When I took the lines out they were badly rusted in places that you could not see if they were still installed in the truck. I laid them all out on my trailer (because you NEVER throw anything out untill after the job is done) and after a few days I bent them up to fit in my garbage can. When I bent them they folded up way too easy in certain areas of the tubing, so I looked at where the bends were and saw that it was not always in the areas of the most rust. I guess that some of the rust flakes off and looks like it's less rusted than it really is. Even the lines from the master, that look like new from above, were very rusted above the chassis in the area in front of the pump. I have changed full sets on other vehicles too and this was the case with most of them. When you change them all you don't have to worry about when the other rusted lines are going to cause a problem, especiall if you plan on keeping the vehicle. Not easy but I think it's the right thing to do in more ways than one, just IMO. Why the manufacturer does not use a better quality line that would last the life of the vehicle is another story all together.

bobocall · November 11, 2011

I have been working on replacing my brake lines on my 02 GMC Sierra, just completed the rear lines up to the control unit under the cab. Now I have to replace the front lines but was having trouble following the four lines that run forward to the master cylinder and the front wheels. Could not find any info in my Chilton Manual on port identification. I was lost until I checked in with GM Trucks.com, great info and the diagram is just what I was looking for. Should be able to keep things straight as far as brake line ident goes, now the fun begins.

brucelimerick · August 17, 2013

I was wondering about the plastic clip that was mentioned on page 1. One of the brake lines I'm replacing runs through the bottom group in the clip. I was wondering just how to open the clip without wrecking it and release the brake lines. As it now turns out I need to replace all the lines due to corrosion. This job started due to the back line bursting before the T splitting to each rear wheel. After reading about problems with lowering the fuel tank and how easy it was to take the box off that was what I did. I'm also going to replace the vent valve for the charcoal canister as well, another postponed job. Looking at the ABS control box and finding I couldn't get a wrench on the line I need to replace, looking at the terrible condition of the other lines I realize I have to detach several other lines from the ABS control. If they don't break immediately they will soon. So I have decided to replace the whole mess seeing I have half the truck disassembled anyway.

I must say I'm a little disappointed about my 2001 Sierra, massive corrosion underneath. Nothing like my 68 chev 1/2 ton or my Dad's 69. My 68 is now a trailer, frame like a rock and still in use. This one I wonder if my Reese hitch will hold. It is not like I'm an amateur, I did my first tune-up at 16 on my Dad's 69 40 years ago. I just don't like breaking things, looking for the secret spot to put my screw driver to release it. With all the crud on then and my old eyes it is hard to see the spot, lol.

Bruce

ziffel · September 18, 2014

I have a semi retired 99 Silverado (new sheet metal) that only plows snow in my parking lot. No longer even licensed or insured. We carry fuel to it in a can. Lots of very rusty brake lines. (265,000 miles) None blown yet, but the temp is still; in the 60's. The ABS brakes are not useful when plowing snow at 5 mph. I could get done much quicker if I bypassed the ABS unit and hooked the lines directly to the master cylinder. I think that would be the rear axle to the front port and the front brakes to the rear port on the master cylinder. Correct me if I'm wrong. Anybody ever done something like this and how did it work? Thanks.. Ziffel

Edited September 18, 2014 by ziffel

jhm · September 19, 2014

I have a semi retired 99 Silverado (new sheet metal) that only plows snow in my parking lot. No longer even licensed or insured. We carry fuel to it in a can. Lots of very rusty brake lines. (265,000 miles) None blown yet, but the temp is still; in the 60's. The ABS brakes are not useful when plowing snow at 5 mph. I could get done much quicker if I bypassed the ABS unit and hooked the lines directly to the master cylinder. I think that would be the rear axle to the front port and the front brakes to the rear port on the master cylinder. Correct me if I'm wrong. Anybody ever done something like this and how did it work? Thanks.. Ziffel

Pull the fuse?

ziffel · September 19, 2014

As I said in the post, I want to eliminate all the extra brake line and the labor to install. It is my intention to run a line from the master cylinder directly to the rear brakes and the same for the front. That should give me good brakes and certainly enough to plow snow on my half acre parking lot. The fuse isn't of any concern. Thanks

flthomas · September 9, 2019

Working on a 2003 Silverado 2500 standard cab long bed, the Dorman SS lines fit perfect, and the Raybestos hoses were perfect, and had all the brackets. I started by removing the brake hose from the right rear hardline and using a bleeder hose from it to a drain pan, and using compressed air, blew it out from the loose master cylinder line---in effect reverse bleed all four corners to get the fluid out of all the lines. The calipers were drained after removal. That removed the mess. A scanner will be necessary for bleeding the ABS module.

The long line to the rear brakes can be the hardest one to install, but if you remove the bed bolts on the drivers side and lift that one side of the bed about 1 1/2", that will make it an easy line to replace. For extended cabs, I have heard of lifting it also. The line can be routed on the outside of the frame, then lifted over the frame.

Sealing the stainless steel brake lines will be much easier if the flares are lapped, the same as home mechanics did to intake and exhaust valves decades ago to get a better seal on older engines.. Kool tools has a lapping kit for brake lines.

Edited September 9, 2019 by flthomas