whtnuklz

iTrader: (8)

I had my front calipers powder coated and rebuilt. Now everything is all back together and the fronts aren't holding very well and the pedal goes to the floor. Since the system drained out while the calipers were off I bled the entire system. I bled the master and then used a tech2 to auto bleed the ABS. Everything went fine it seemed but I can still turn the front rotors by hand when the pedal is pressed. The backs are holding and will not turn. The pedal feels good but will go all the way to the floor.

I bled the brakes again but the fronts are not building pressure. When opening the front bleeders after pumping the pedal the fluid just runs out with no pressure, on the rears it has good pressure. The thing that has thrown me off is doing the ABS bleed there was good flow from each caliper and everything seemed good. What could be causing this? Is there a proportioning valve in the system that could be stuck and cutting fluid to the front? I'm a little lost now

whtnuklz

iTrader: (8)

what would cause weak fluid flow to the front calipers??? I pulled the master cylinder off and checked it out it seems to be working as it should. I really have no idea what the problem is does anyone have an idea?

joshp14

iTrader: (5)

Still got air in there or the master cyl is bypassing. I would let it gravity bleed for a little while, then manually bleed with an assistant. After you do that, then perform the auto bleed with tech 2.

IIRC, prop valve is internal to the BPMV, but I cant remember for sure.

whtnuklz

iTrader: (8)

This thing is a real PITA. I guess I'll try bleeding it again tomorrow after work and see if it gets better.

1 FMF

iTrader: (1)

"gravity bleed" won't help with anything, as fluid drains out because of gravity the air bubble in the lines just rises and stay in there. If you got air in the lines it helps to have a pressure bleeder attached to the master to force fluid through the system, to push the air through the lines and out the caliper bleeder. Or if the scan tool commanding the abs module to purge flows enough fluid then you may be able to use that. I would push a 1/2 quart through left front and 1/2 qt through right front.
You need to get a good fluid flow to push air down the lines,
doing the method of pump pedal-stop-open & close bleeder-repeat doesn't move fluid fast enough if you got air way up in the lines, it only really works for pushing fluid into the caliper and pushing air out of just the caliper.
Other than that, look for leaks or you have a bad master.

yes, the proportioning is all done in the brake pressure modulator valve.

joshp14

iTrader: (5)

Gravity bleeding is an ok method to START with if you dont have access to a pressure bleeder...which most people dont. Thats also assuming you didnt loose a lot of fluid completly draing the M/C.

The pump method works fine if you do it properly, it just takes a little extra time. Obviously everyone would love to have a pressure bleeder, but a decent one isnt cheap.

1 FMF

iTrader: (1)

other problem with "gravity bleeding", no offense not directed at you josh, is you have to leave the cap off the master cylinder and the caliper bleeders open if you don't have the lines disconnected. And you are leaving it off and open for a significant amount of time... brake fluid absorbs moisture, and the longer you have the system open the more moisture and water is getting into the brake fluid and contaminating the system. It's no different than leaving a bottle of brake fluid with the cap off. So I highly recommend against the gravity bleed idea, i think you're better off just pumping the brake pedal with the bleeders open or lines off to move the fluid down the lines. Then perform the normal bleed procedure to get the little last bit of air out of the calipers, or use solo-bleeds, or a pressure/vacuum bleeder kit. The whole point is moving brake fluid at a significant enough speed to push and force the air down the lines and out the end. remember the master cylinder is the highest point of the system and the air bleed point is the lowest point of the system, fortunately cold brake fluid is viscous enough to push the air downward. This applies to any hydraulic system- brakes, clutch, power steering, log splitter, etc.

whtnuklz

iTrader: (8)

Well I have made some progress just bleeding them like normal; pumping the pedal and cracking the bleeders. I finally have a good pedal but its just taking for ever and I still have to bleed it more to get the all the air out