2003 checy avalanche...need brake line routing from master cylinder to comination valve to abs pump ports

Something is wrong with your statement
it is a 99 caravan 3.3 no abs , then you are on about abs light pump etc
the abs pump only works when the master cylinder is under pressure and that pressure is suddenly reduced by the sensor reading a locked wheel and a valve is opened to release line pressure to that wheel As soon as that wheel starts to turn, the valve closes
while the wheel is stopped and that valve is open , the abs pump kicks in to maintain line pressure otherwise the brake pedal would go to the floor
master cylinders work through a. abs unit and not because of it so if the master cylinder becomes faulty, the abs pump will not operate until a wheel stops turning as there is no line pressure to stop a wheel turning
the abs light may not be on because there is nothing to operate the system to put it on

make sure ABS SNSORS ARE SET PROPERLY AGAINST TONE WHEEL, air gap is zero .for your brake light you need to reset brake pressure valve below master cylinder where all lines meet before going to abs modual ,an advanced scanner will determin what wheels are causing problem . good luck on it .
Woody

Best case scenario bad vacuum pressure to the brake booster. Worst case bad abs control module or valve body/motor the abs system works by add and removing hydraulic pressure through valves and electric motor. Try using block off plugs at the master cylinder( remove lines plug outlets at master cylinder) check if brake pedal position and pressure is good(if there is no change problem is master cylinder or brake booster/ vacuum) if plugging at master cylinder solved issue repeat procedure at abs valve body after reinstalling lines from master cylinder if your problem returns your issue is in the abs valve body if plugging at the abs solves problem reconnect at the valve body bleed each line one by one testing between each line until you find the problem

The brake system bleeding procedure differs for ABS and non-ABS vehicles. The following procedure pertains only to non-ABS vehicles. For details on bleeding ABS equipped vehicles, refer to the ABS procedures later in this section.

WARNING Make sure the master cylinder contains clean DOT 3 brake fluid at all times during the procedure.

1. The master cylinder must be bled first if it is suspected of containing air. Bleed the master cylinder as follows:
   1. Position a container under the master cylinder to catch the brake fluid.
   2. Loosen the left front brake line (front upper port) at the master cylinder and allow the fluid to flow from the front port.
   3. Connect the line and tighten to 24 ft. lbs. (32 Nm).
   4. Have an assistant depress the brake pedal slowly one time and hold it down, while you loosen the front line to expel air from the master cylinder. Tighten the line, then release the brake pedal. Repeat until all air is removed from the master cylinder.
   5. Tighten the brake line to 24 ft. lbs. (32 Nm) when finished.
   6. Repeat these steps for the right front brake line (rear upper port) at the master cylinder.
      

WARNING Do not allow brake fluid to spill on or come in contact with the vehicle' finish, as it will remove the paint. In case of a spill, immediately flush the area with water.

1. If a single line or fitting was the only hydraulic line disconnected, then only the caliper(s) or wheel cylinder(s) affected by that line must be bled. If the master cylinder required bleeding, then all calipers and wheel cylinders must be bled in the proper sequence:
   1. Right rear
   2. Left front
   3. Left rear
   4. Right front
2. Bleed the individual calipers or wheel cylinders as follows:
   1. Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end.
   2. Submerge the other end in a transparent container of brake fluid.
   3. Loosen the bleed screw, then have an assistant apply the brake pedal slowly and hold it down. Close the bleed screw, then release the brake pedal. Repeat the sequence until all air is expelled from the caliper or cylinder.
   4. When finished, tighten the bleed screw to 97 inch lbs. (11 Nm) for the front, or 66 inch lbs. (7.5 Nm) for the rear.
3. Check the pedal for a hard feeling with the engine not running. If the pedal is soft, repeat the bleeding procedure until a firm pedal is obtained.

Fig. 1: Loosen the front brake line in order to bleed the master cylinder

Fig. 2: Connect a bleed hose from the bleed valve on the front caliper to a jar of brake fluid

Fig. 3: Always follow the lettered sequence when bleeding the hydraulic brake system

Hope this helps to solve it; remember to rate this answer.

Your description does sound like M/C issue, but the amout of fluid is not much, that comes out...

It is brakes, so forget it and just replace the M/C. Also, pick up enough fluid to bleed all brakes and GET A M/C BLEED KIT, which are little hoses that screw in where brake lines attach to M/C, and route into the brake fluid reservoirs...Bleed until no air, then carefully remove one at a time, and install the brake line.

Now, do not allow M/C fluid to drop, or start all over again....

So, now continue bleeding at each wheel. At the end of it all, you want to do a "lift your **** off the seat" application of the brakes, as hard as you can. If the system passes this test, it usually will be good.

I presume that you have inspected each brake and found no faults...leaks, or anything.

under the hood by the master brake cylinder

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/thomas_c50676e836a18949

You bleed it like you would a normal system but you must use the boost assist to do it, in order to do this start the truck pump the brakes three times and bleed that cylinder farthest away from the master cylinder do this twice or until you get clear fluid to run out. add fluid for every cylinder before moving on. Do this for each wheel and after doing all four wheels you should be ready to go. If it feels mushy you will have to bleed it a second time. But you must have the engine running to bleed the brakes unless you have a power bleeder. You may want to bleed the master cylinder first to do this add fluid to the cylinder then pump brakes three times crack the front line open and allow it to bleed air rout of the line do the same for the rear master cylinder once yo get solid fluid from the master cylinder you can dot the same for the ABS then do the wheel cylinders and wheel calipers. This needs to be done sometimes, be sure to never let the master cylinder run out of fluid and check it each time you bleed the wheel cylinders.

You have to replace the master cylinder because the fluid that leaks from it is getting into the brake booster and compromising the seals. So you can probably get away with the booster and cylinder. Unless the ABS unit is a part of the either of the affected parts, or isn't working properly, you can leave it alone. ---------------------
A fluid-distribution system includes a plurality of fluid-distribution nodes with three-way ports attached to bleed/flush lines and alternate ports attached to vacuum lines. A first pump is used to draw new brake fluid from a new fluid container, push it through the manifold and ports, and through the bleed/flush lines. Fluid flow through the ports is selectively controlled by a computing device. In this manner, a vehicle's brake system including individual brake lines and ABS systems, may be flushed in a prescribed sequence. The vacuum lines are connected to a second pump via alternate ports of the sequential control valve manifold and may be used evacuated air and contaminated brake fluid from the vehicle's bleeder valves or master cylinder. Additionally, the bleed/flush lines may be connected to the alternate ports during priming or purging of the system. This also facilitates storage of the bleed lines as it prevents brake fluid from spilling and prevents air from entering the system. thanks.

first thing to check is your fluid level. ensure you have enough fluid in your master cylinder. it sounds like you have air in the system. its not really hard to bleed. just get a friend to come over and one of you climb under the car with a bucket and a wrench and some rags. open the bleeder valve on the calipers and have your buddy press the pedal. once oil shoots out straight from the valve close it while its still squirting. if the oil has alot of air in it have your buddy keep pumping to until its not. also make sure you watch your master cylinder level as you are just squirting it all out. do that to all the brakes. as far as it being the master cylinder thats a way later thing. you check the fluid level/air in lines first. as far as the abs. is your abs light on? problem with abs is that it requires specialized work so your best bet is taking it to a shop. but if there isnt air in the lines and there is plenty of fluid then start looking at your brake adjustment. if that is good then possibly the master or slave cylinder

The most common bleeding procedure is to bleed the ABS brake furthest from the master cylinder first, then bleed the other brake that shares the same hydraulic circuit (which may be the other rear brake on a rear-wheel drive car, or the opposite front brake on a front-wheel drive car or minivan). After these have been bled, you then bleed the other brake circuit starting with the furthest brake from the master cylinder.
Air can be very difficult to remove from an ABS modulator assembly because of all the nooks and crannies inside the unit. The modulator may have eight to 10, or more, ABS/traction control solenoid valves, plus various check valves and dead-end ports. Some ABS modulators have special bleed screws to help you vent the trapped air when bleeding the system. Others do not and require the use of a scan tool to cycle the ABS solenoids while you bleed the system. 1. To bleed the isolation valves in the modulator, there are two bleeder screws. Start with the one toward the engine. Turn the ignition on and apply light pressure on the brake pedal. Open the bleeder screw and allow the fluid to flow until clear. Close the screw and do the same at the second bleeder screw. 2. Depressurize the accumulator by pumping the pedal 40 times with the key off. Wait about two minutes for the brake fluid to de-aerate, then refill the fluid reservoir with DOT 3 brake fluid. 3. Now you can bleed the boost section. This is done by applying moderate pressure on the brake pedal and turning the ignition on for three seconds, then off. Repeat this a total of 10 times. Make sure the pedal feels firm when you have finished, and give the car a road test to make sure the brakes are working properly.