Yet Another ABS Modulator Bleeding Question
#11
01-08-2014, 03:08 PM
#12
01-08-2014, 04:22 PM
Rock Crawling
Join Date: Mar 2013
Location: Oregon, north of Salem
Posts: 452
Likes: 0
Received 25 Likes
on
16 Posts
Based on my review of the schematic in RAVE and in the WABCO literature, it appears that there is a portion within the modulator where the fluid is isolated from the braking system via solenoids and non-return valves where the fluid is pressurized and moved only by the return pump. The only way to get any air out of this portion of the system is to activate it, which is what bleeding with testbook, Hawkeye and Faultmate, etc. all do. This circuit is also activated when the HDC operates.
____________________________
I really have no idea what this brake system has gone through prior to my owning it. There are no lights on the dash at 108,000 miles so the modulator may have been dealt with before. The lines were changed over to SS extended ones before I bought it so it was bled then, and the fluid looked fairly new when I got the truck at 80,000 miles. I have also flushed the fluid using a vacuum bleeder and had it done with a pressure bleeder and yet the pedal still feels like crap so at this point I think I'm left with trying to bleed the modulator then the lines again.
____________________________
I really have no idea what this brake system has gone through prior to my owning it. There are no lights on the dash at 108,000 miles so the modulator may have been dealt with before. The lines were changed over to SS extended ones before I bought it so it was bled then, and the fluid looked fairly new when I got the truck at 80,000 miles. I have also flushed the fluid using a vacuum bleeder and had it done with a pressure bleeder and yet the pedal still feels like crap so at this point I think I'm left with trying to bleed the modulator then the lines again.
"Bingo," what you describe, is exactly how I understand it, and my electronic bleeding of the modulator with my Hawkeye, along with traditional mechanical bleeding at brake calipers worked beautifully for me! My brakes now have better feel than I ever had before.
No doubt that your modulator has been dealt with before; may need maintenance again. Falconworks land rover of Arizona says on their website, that the rubber seals in modulator shuttle valves last only about 60,000 miles, to possibly max, of 80,000 miles before you need to change said seals to new ones, which Falconworks sells (not available anywhere else). My experience has shown that Faconworks is spot on accurate on life expectancy of those seals, so for certain, someone, somehow, has dealt with seals in your modulator before, and they probably need attention again, since you have 108,000 or so. When these seals wear out, they cause brake fluid to leak down onto the shuttle valve switch plastic framework at the bottom of the modulator, which shorts out the switches to some degree, causing three amegos dash lights to come on. Maintain non leaking shuttle valve seals, and keep your shuttle valve switches dry of brake fluid, and all is well.
Last edited by earlyrover; 01-08-2014 at 04:25 PM.
Thread
Thread Starter
Forum
Replies
Last Post