I keep getting air in brake lines of 2005 town and country. Changed master cylinder and left front caliper, no loss of brake fluid

Don't drive it it happen to me ps fluied can ruin everything the best way to do a flush do it on wheel a time remov e the 10 mm bolt then hold your finger on the bleeder hole have someone slowly pump the brake paddle at she same time some one near the resort or needs to keep adding fluied once all the fluied drain out you can tell because it'll look clean do every tire side all 4 wheels good luck

I would change the rubber flex hose that goes from the body to the suspension.

one of the pistons in the brake master cylinder is poss stuck at the bottom of its stroke or the return spring has broken, dont take any chances with brakes change that master cylinder

Hello Patricia,

Have you checked the master brake cylinder reservoir for brake fluid loss?

I don't suspect the master cylinder as you have replaced it... but am more suspect of a leaking brake line or fitting which should have
been discovered when you had the system bled.

The only time I ever had a rear brake problem with a 2500 series Chevrolet was due to seized rear brake caliper guide pins...as your calipers are also new that is not your problem.

If your brake pedal feels spongy and travels to the floor board you have air in the system, a brake fluid leak or a failure in the power steering system, such as a broken hose, broken power steering pump drive belt, or failed pump, would result in a loss of pressure to both the hydro-boost and steering.

Find more information here:

. Hydro Boost Power Assist Systems Operation Diagnosis and Repair

Sounds like you may have a hydraulic leak somewhere. Check the rear wheel cylinders and front brake hoses going to the calipers.

Could be a couple of problems, bad master cylinder (not bench bled properly or bad seal out of the box, I have had a few like that), proportioning valve seal, brake line not tight/sealed properly sucking air into system,bad caliper. First of all, are you losing brake fluid along with your pedal? Need to know that first. If you are, try to find where you losing it from, you will find your problem. There can be absolutly NO leaks in a brake/hydraulic system. If not, check that all lines are tightly seated and nuts are quite tight using a line wrench to get proper torque. If so, you can replace the master cylinder again (take old one back to store for new one under warranty) and be sure to thoroughly bench bleed. When bench bleeding, take your time, do not push plunger in too quickly, use a SLOW steady push until ALL bubbles, no matter how small have been eliminated. Tapping on the bottom of the cylinder while bleeding will help remove trapped air. Even a very small amount of air will take forever to bleed out at the calipers. If cylinder/all calipers/lines appear to be right, I would suspect the proportioning valve is faulty. To find it, follow brake lines from master cylinder to where they go into the valve. Replace. Hope that helps.

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.

DId you bleed the system after you changed the caliper? If the Master cylinder lost it's fluid while you were changing the caliper, then there is air in the system and you need to bleed the entire system. start with the REAR RIGHT, then the REAR LEFT and then the FRONT RIGHT and last the FRONT LEFT. make sure the master cylinder NEVER runs low on fluid and DO NOT re-use any fluid that you get out of the calipers.

The master cylinder supplies the pressure to the brake fluid that travels between the maste brake cylinder resevoir and the brake caliper pistons (through the brake lines. If the master cylinder fails there will be insufficient compression of the brake fluid to make the calipers operate as designed. Leaks in the brake lines and/or cylinders is a possibility, and unrelated to functionality of the master cylinder. Also, pistons located in the brake calipers can form a corrosion ring on their inside walls if there is breakdown in the brake fluid or moisture that gets into the lines. Operating the vehicle when there is insufficient brake fluid in the master cylinder resevoir can also lead to air getting into the brake lines, causing bad working brakes. Air compresses more than brake fluid, and the master cylinder isn't designed to compress air in the brake lines. Sounds like a bad case of "lack of maintenance", as opposed to bad advice from the mechanics. That said, there's no excuse for bad installation. But, it's tough to improperly install a brake line since they are nothing more than hollow metal tubes. There should be no rubber connectors installed in the brake lines. When bleeding the brake lines one must remove all of the trapped air before you will see any fluid appear. If the valves in the master cylinder are not properly operating the master cylinder will not allow the brake fluid to get into the brake lines.

Hope this helps.

loosen the front brake line that goes to the master cylinder fill master cylinder up with fluid and bleed it first by attaching a flexible line from master cylinder front brake side submerge that line into jar of brakefluid keeping air from entering line get someone to pump brake pedal while ur holding line in a jar keep refilling the brake resivoir so no air gets in, once the master is bled front brake side then reattach the origional brake line then remove bleed screw from caliper and let fluid gravity flow down to calliper then bleed the normal way. more than likely your master cylinder has air trapped in the front portion good luck