Air blowback into remote brake fluid reservoir

[dangerfieldinc]

First I would like to thank all for the really helpful post and great info on this site.
I found one other post during one of my many searches that described this problem but it did not have a resolution posted. It was a year or so old looked like it had been abandoned. But could not find it again to post their. Have tried to cover all the info, questions,& solutions I have seen in all the other threads so please read on and point out anything I have missed or have not tried.

What I have done to the brakes / hubs on m truck
Honed & rebuilt all the wheel cylinders with kits from NAPA
Rebuilt air pack looked good little rust in air chamber but honed a little used New Star kit followed TM directions and used pics in wonderful thread by DucesWild11
Honed & Rebuilt master cylinder with New Star kit, made certain all seals in correct orientation no pitting some gunk but not bad
Added remote brake fluid reservoir to master cylinder crimped old vent line closed
Relined all brake shoes
Took apart bottom adjustment cam on brake shoes cleaned & lubed reassembled all wheels
All shoes adjusted for proper clearance with feeler gauge per TM
All new brake lines hard & flex
Repacked wheel bearings put new seals in all hubs. Yes used cork and RTV in key way.
Removed all axel vents replace with tube run up to fire wall.
Replaced dust boots on front knuckles

Now the reason for post
Originally before any brake work brakes worked good truck just pulled to the right on hard braking but truck was new to me fresh from Warner Robins so it needed a good going through. Air pack functioned good not hanging up or locking brakes on. Also did not notice brake fluid out of slobber tube on firewall or any fluid in small now abandoned vent line that was attached to Master Cylinder cap.
After rebuilding it all and reassembling, & bleeding with power bleeder but before replacing hard brake lines brakes functioned great. Braking much stronger than before butt during hard braking (hard enough to lock all tires up on asphalt) upon letting brake pedal up I got air blowing back up in my remote reservoir. Got solider B back under it to look around while I pressed peddle hard and he found hard line with hole in it. Line looked great on outside but bad on inside. I had done what I thought was good inspection before I reinstalled all my new rebuilt parts. So this is when I replaced all hard lines. While system is open again I pulled air pack back off and disassemble it again to double check all my seal orientations they all seem correct according to all the diagrams and pictures I have found in the TM’s and pictures. And yes I did see correction diagram about seals getting mixed up. I have them correct.
I get it all put back together one more time bleed system again, peddle is good hard about ½ inch free travel. Build air pressure back up in truck using shop air ( turned down to 90 psi) connection so I can hear air pack function without truck running press peddle few times good and hard then press harder start to get air coming back into remote reservoir . Take for test drive on the many miles of dirt road around house brakes work great but peddle gets softer and softer get more and more air blowing back up through remote reservoir.
So what do I need to try next other than new air pack? I have another rebuild kit for air pack I am considering using it on pack just in case had some bad seals in first one. Opinions please.

 

[doghead]

The TM shows the shaft seal backward. This is the seal between the air chamber and the fluid side. If it is in backward, you may be getting air pressurized air into the brake fluid from that.

There should be a few threads about this TM error.

 

[doghead]

Post 8 on this great thread, shows it.

http://www.steelsoldiers.com/showth...-with-Photos!&highlight=airpack+seal+backward

 

[dangerfieldinc]

Yea I saw that error I have it correct in my rebuild. The secont time i took the airpack apart i was hopping to find seal in backwards but did not.

 

[dangerfieldinc]

Well took the air pack off of the other Duce today to take it apart and have an exploded view of a working air pack so I could take mine off and go through it for the third time. To make sure I had it all assembled correct and sure enough it was all good to go all seals pointed in right direction nothing torn no foreign objects. I was so frustrated that I took off the master cylinder as well to start completely over with the two units figured the problem had to be somewhere between the two. Figured I would use the two other rebuild kits I had gotten for the other truck and just rebuild them both again but. Could not believe what I found I had used some Teflon tape to help seal the master cylinder cap because it leaked the first time I used the power bleeder and a piece of it had peeled off and gotten sucked in to the small exhaust hole in the bottom of the fluid chamber and was blocking it also had a piece in the small bypass holes in the aluminum cylinder that the push rod compresses. The only thing I can figure is that in the master cylinder when releasing the brake pressure it did not have any place to go and created a vacuum that caused it to suck air from the air pack. I know it does not sound plausible but that was the only thing I found wrong. So I got it cleaned all out made cretin not to get any more Teflon tape in reservoir. Reassembled it all bleed the brakes for the umpteenth time it all works like a charm now. Brakes are a wonderful thing. Again thanks to all the helpful threads and great info on this site. I remember reading about the problems that having that small hole clogged can cause.