(Update: continued from post #39)
I completed Friday night's work by installing the new bleeder screws in the calipers. The old ones were quite crusty, and the fronts were clearly not OEM. The rear's are easy to access with the wheels still installed, but I was not able to get a wrench on the fronts with wheels on. So, I put the front of the truck on jack stands and removed the wheels. Now, I was all set up to start bleeding on Saturday.
- Step 19: With everything hooked up, I filled the reservoir to the MAX line and put the ignition to ON. The pump came on, along with the alarm and dashboard lights (Brake, ABS. VSC/TRAC). I wasn't really sure what to expect, as there was clearly a LOT of air in the system. The pump would run for about seven seconds, click off, and then click on again. It did this over and over for a LONG time--probably two minutes. All the time the alarm is on. At this point, I am convinced something is wrong. The fluid was clearly being slowly pumped out of the reservoir, but very slowly. At about two minutes, the alarm finally turned off. After another 20 to 30 seconds, the pump shut off, as pressure had been achieved.
(I was a little concerned during this process, but in hindsight, I think the pump was just struggling to build pressure against so much air. Anyone else who has removed and serviced their MC, I would be interested to hear your experience with this.)
On Saturday morning, I enlisted the help of my 8 y/o daughter to push the pedal. Now, here is where I ran into a snag (as outlined in the real time posts above). Here's what I did: starting at the rear, I had my helper press the pedal five times, holding it down on the fifth. With a clear plastic tube attached to the bleeder screw, going into a sealed mason jar, I cracked the bleeder screw. The pump immediately kicked on, and a large amount of fluid flowed out easily. Lot's of old, dirty fluid, and air bubbles. It took repeating this process about four times per side to get the rears fully flushed and bled. I found so much fluid coming out that I had to top off the reservoir before every repeat. I think I went through 2 32 oz bottles doing the rears.
Then, I went to the fronts, using the same procedure. However, the front's proved VERY difficult. Where the rear bleeders produced a strong stream of fluid that completely filled the plastic tube, the fronts produced only a thin stream... and there was always a big air bubble right at the bleeder. So, I bled each side 9 or 10 times, using about another half-bottle of brake fluid. I didn't really see a change in what was coming out of the bleeders. Then, I noticed that the right rear bleeder had leaked...s***! So, I topped off the reservoir again and bled everything again. The fronts seemed liked they were bled, and the brake pedal felt very firm. Stupidly, I put the wheels back on, took it off the jack stands, and THEN did the pump run time test.
My first hint that something was wrong was when I pumped the accumulator down. The brake pedal was VERY hard for the first five or so pumps. Then, it had kind of a "two stage" feel--softer for the first half of travel, then firm. After 30 or so pumps, it would go straight to the floor. I put the key in and ran the pump--it ran for 1 minute, 17 seconds (77 sec) before shutting off.
On Paul's advice, I checked the MC plunger, every bleeder, and every flare nut for leaks. I found a little seepage at the left front brake line flare nut on the MC--otherwise, no leaks. So, I tightened that nut and cleaned everything with brake cleaner.
I was convinced, at this point, that there was a significant amount of air trapped in the pressure accumulator. So, I attempted to manually bleed this. I am not sure if this was necessary and, if I were doing this again, I would bleed the front brakes 100 times before attempting to the bleed the accumulator, but YMMV. This might help you if run into the same issue I did (it did help me), but I am not sure it is necessary.
- First, you have to disconnect the wire harness for the pump from under the ABS block with the whole MC installed... this is HUGE pain in the ass! You need a mirror and either an offset screwdriver or a phillips bit in a small ratchet handle (this is what ended up working for me. Carefully undo the screws, and be careful not to drop them! Disconnect the other plugs from the MC assembly.
- Hook you battery up to a battery tender (this is imperative, otherwise you will quickly deplete your battery). Connect some jumpers with alligator clips to the wire harness and to the battery terminals--red to red, and blue to black. Connect the alligator clips to the harness first, then connect the red to the + terminal on the battery, and then connect the blue to the - terminal on the battery. When you make this connection, the pump will start running.
- Let the pump run for about 45 seconds, and then crack the flare nut on the pressure accumulator where the twisty, red-clad hard high pressure line connects. You'll need layers of plastic bags, cardboard, and many paper towels or rags under this in the engine compartment to catch fluid. I got some hissing, sputtering air and then a steady flow of clean, fresh brake fluid. I the retightened the flare nut and shut the pump off by disconnecting it from the battery.
- Remove your rags, spray the hole area down with brake cleaner, and dry with clear paper towels. Then, pump the pressure accumulator down with the brake pedal--40 times. At this point, I noticed my brake pedal felt much better.
- Then, I re-jumpered the pump and let it run until the pressure relief valve started burping fluid back into the reservoir. The inlet is toward the front of the reservoir, making the air/fluid burp very easy to see. I got some bubbles for the first few seconds, and then just fluid. I disconnected the pump, reconnected the harness and all the ABS unit connectors, checked everything for leaks again, and then pumped the accumulator down. Then, I did the run-time test again. This time, the pump only ran for 56 to 58 seconds--not good, but better!
So, there was definately a lot of air in the accumulator, and this helped. However, I cannot say if it was necessary, and it was a little butt-puckering to actually do it. I'm therefore not going to RECOMMEND this as a procedure, but I want to outline what I did if you are also having trouble.
Finally, I followed Paul's bleeding procedure from above, which I will recap here. IMO, his is the only description that actually makes sense and is accurate. I used a helper for both the fronts and the backs.
- Step 20: Ignition key ON, helper in driver's seat, battery tender connected... connect your bleeder tube to the bleeder screw on the rear right caliper. Make sure reservoir is topped off, and have the helper depress the brake pedal and hold it down. Open the bleeder screw, and fluid will flow out (the pump will kick on). Let flow for about 10 to 15 seconds, checking for bubbles in the tube. Close the bleeder screw. Make sure your helper is still depressing the pedal, and repeat once more. If no air bubbles come out the second time, you are good to go. If bubbles are still coming out, keep repeating until no more bubbles appear. (Note: be careful not to run the reservoir below the MIN line. Mine pumped out about 4 oz of fluid every 10 seconds, so make sure you are keeping an eye on the reservoir and topping off as necessary.
- Step 21: Repeat on left rear caliper.
- Step 22: Top off the reservoir and move to the front.
- Keeping the ignition ON, have the helper pump the brake pedal 20 times, holding it down on the last pump. Connect the bleeder tube to the bleeder screw on the front right caliper. Open the bleeder screw. Fluid should flow out, and the pedal should drop to the floor. Leave the bleeder open for 3 to 4 seconds, at which point fluid flow should slow and stop. Close bleeder screw, and have helper release the pedal (AFTER screw is closed)!
- Have the helper pump the pedal 5 times, holding it down on the last pump. Repeat as above, making sure the pedal is not released until after the bleeder screw is closed.
- As the brakes are bled, the volume of fluid in the hose will increase until the bleeder hose is fully filled with fluid, like the rears. You will still get some bubbles.
- (Per Paul) When the bubbles stop, repeat this another 7 to 10 times! Every time you do it, have the helper report on the pedal feel. The pedal feel should improve with every repeat. (Note: Each repeat dispenses between 0.5 and 1 oz of fluid. So again, make sure you keep the reservoir topped off and between the MIN and MAX line.
- Step 23: Repeat on left front caliper.
For my fronts, it took me 10 times to bleed per caliper (no bubbles), and then I did 10 additional on each side. Then, I ran the pump run-time test again. It dropped from 57 seconds to 40 seconds! Success!
I cleaned everything up and checked for leaks. Finding none, a put everything back together--and changed spark plugs while I was at it!
What I still need to do is activate the ABS several times and then do a final bleed, but this will have to wait until this weekend. However, the pedal feel is normal (like it was before), with a consistent feel until 32 or 33 pumps with the key OFF. Also, the braking "strength" is noticeably improved. It was not bad before, but it is better now. The pump is also a lot quieter than it was before. Before, the sound was noticeable in the car when the pump ran. Now, I feel the vibration in the pedal, but I don't really hear it.
I've had no lights and no alarms either, even though the overnight temp was below freezing last night (this would typically trigger an alarm on start-up in the past.
So, for about 10 hours of labor (taking my time, and dicking around with the bleeding, not doing it right!) and less than $400, I seemed to have fixed the issue!
Hope this helps other who are facing the prospect of a $4000 MC assembly replacement. Cheers!
