Hi folks.

About 3 weeks ago, I swapped out all 4 calipers, rotors, and flex lines (replaced 7 year old stainless/braided lines) on my 97 D1. For the fronts, I upgraded to D90 calipers and pads + vented rotors. I have bled the system 3 times, the first pass getting a substantial amount of air out to the point where I no longer see bubbles at any corner. I used a combination of a power bleeder and my patient wife's foot with the pedal method. I also bled with the key on the second position to engage the ABS pump and with the key off. I used three 32oz bottles of DOT4 fluid during this process and used a glass jar with some fluid in it to bleed into.

After all this effort, the behavior I see is as follows.

With the key off, the pedal is firm.

With the key on second position, the ABS pump kicks in (pedal thump like it always has), and the pedal remains firm.

When the engine is started, the pedal becomes spongy, but a couple of light pumps gets a fairly firm (though not how I would like it) pedal, and the truck stops nicely. If I keep my foot on the pedal, it will NOT go to the floor.

The behavior above is consistent now, and before I did this job, the pedal was always very firm with the original calipers. I have changed the rotors and pads, and added stainless flex lines several years ago, and did not have this problem then.

I have read (on the Internet, so taking it with a grain of salt) that upgrading to the D90 calipers can stress the master cylinder, though this seems like clearly air that is trapped in the system. I suppose the brake booster or master cylinder could have magically developed an issue after this upgrade, but that seems unlikely to me.

The D2 seems to require the ABS modulator to be engaged/cycled as part of the bleed process, but I see no reference to that in the RAVE for the D1. In fact, all it says is do what I have already done, regardless of whether the truck has ABS or not. I also have an Autel scanner, but it will not communicate with the 97 ABS system (1998 and later is supported).

Has anyone here done this upgrade and/or replaced all 4 calipers and run into a similarly stubborn air pocket?

Does the Hawkeye or the new iLand scanner app/dongle from AB communicate with the D1 (1997 or earlier) ABS system?

Any other tips and tricks I should try before breaking down and allowing a local shop to touch my truck?

As always, thanks in advance for any help you can offer!

 

You've got air in the lines somewhere, or a pocket stuck in a caliper. I fought the same thing in my truck when I did my D90 brake upgrade.

When your wife is helping you do your bleeds, is she pumping up pressure(3-4 pumps) then holding the pedal as you release the bleeder? This method did NOT work for me at all.

I used vacuum bleeders at the shop for weeks and could not get the air out. How I got it in the end was with a passive bleed. One person in the car and with the bleeder already cracked, have them slowly press the pedal to the floor, and when they get there, hold it and you close the bleeder. Raise pedal up and rinse and repeat. You do not want to build any pressure in the lines, just gently depress the pedal while the bleeder is already cracked open. The key is not to raise the pedal with the bleeder open as it will draw air in. Do a couple rounds around the vehicle like that and you should be golden

I bled it for weeks using pressure and vacuum and couldn't get the air out of my calipers. The passive method got it all out in minutes

 

It is helpful to start with the wheel furthest from the MC and work your way around. Pass Rear, Driver Rear, Passenger Front, Driver Front.

 

I have replaced all my brake lines and front calipers so my system was vacant for a few weeks.
Yes the tried and true bleed method took forever (at least 4 to 5 bleeds at each wheel and then around again) - I like what Llamasayswhat said about a passive bleed - gonna try that next time.
but all in all I ended up doing 2 bleed sessions at about 45 min each.
I did not engage or activate the ABS nor had the key in the ignition.

mechanical bleeds have never been successful for me - though I think it was cheap tools not the process that was my issue.

there is also some interwebs discussion about bleeding that refers to bleeding the 13mm at the ABS after the wheels have been bled. IIRC you depress the brake pedal 5 times very slowly - hold, crack the 13mm loose (with a rag to catch fluid) to bleed the air out of the top of the system.

 

Thanks. I will try the passive bleed this weekend and follow up.

 

Yeah. I followed this pattern. It just seems like there is an elusive pocket of air that is either in the lines, or in the ABS system. The master cylinder seems OK given (I think) the firm pedal when the key is off. I also did the recommended master cylinder bleed (with key off, pump slowly 5 times, release pedal and wait 10 seconds, rinse, repeat).

 

I don't see any bleed nipples at the ABS system. Perhaps you are referring to individually opening each of the lines that enter the ABS module?

 

I do see that there is only one 13mm nut on the ABS module (upper right in the photo below).

 

If you are taking about this nut, that's just the modulator mounting nut with the bushing under it.

 

I am referring to this guy.