Brake fluid help

[Bill in pa]

Hi all.
Bill in pa here.
Need to bleed my brakes.
I opened the brake master cylinde and this is what I got.
The cup with all the bubbles appears to me to be either water in the silicon brake fluid or D.O.T 3or 4 mixed in with the silicone.
The gray looking cup is where I added water and mixed it up.
Seams it separated which would mean its silicone brake fluid.

My question is. Can I completely bleed the system and start with fresh silicone fluid?
Can I just open the bleeders and let it gravity drain?

 

[doghead]

You can start by opening all the bleeders.

You will need to push new fluid through to get the system clean.

The system will not drain completely just by gravity.

A pressure bleeder is the best way to do it.

 

[porkysplace]

This is a inexpensive power bleeder ;
[h=1]Deuce Power Bleeder R4x4 Style[/h]

 

[Bill in pa]

My cap is different than the one in the picture.
The cap on my 813 was like the one on the bleeder.
Mine is yellow plastic with a rubber cap hose clamped to it.
while im asking....
Under the master cylinder is the air pack.
There is also what looks like a air pac on the Passenger side.
Is that also for the brakes?

I was just out to the truck and was able to get all the bleeder nipples to break loose.

 

[URSATDX]

My A3 has 2 air packs.
Bleed both.

 

[porkysplace]

My cap is different than the one in the picture.
The cap on my 813 was like the one on the bleeder.
Mine is yellow plastic with a rubber cap hose clamped to it.
while im asking....
Under the master cylinder is the air pack.
There is also what looks like a air pac on the Passenger side.
Is that also for the brakes?

I was just out to the truck and was able to get all the bleeder nipples to break loose.

Is this a M35A3 or a late model 1987-89 Air Force M35A2 ?
They have split brake systems with 2 air pacs & master cylinders.

 

[Bill in pa]

Mine is a 1987/M35A2C
Hercules diesel Not a cat.
Im thinking mine is the end of the A2
and the beginnings of the A3.
More like a "mutt".
Nothing under my truck matches my brother in laws truck.

 

[porkysplace]

Mine is a 1987/M35A2C
Hercules diesel Not a cat.
Im thinking mine is the end of the A2
and the beginnings of the A3.
More like a "mutt".
Nothing under my truck matches my brother in laws truck.

Air Force truck split circuit brakes.
This is the TM for them;
Deuce dual brake system TM

Edit: On a side note if you haven't already , you should add your trucks information to this thread;
[h=1]Late Model USAF M35A2C Registry[/h]

 

[Bill in pa]

Mine is a 1987 USAF truck.
Could see a ghost of the USAF on the sides of the hood.
Got the brakes bleed today.
Took almost 18 oz. of DOT5 just to top it off before I started the bleed.
Now all purple DOT5
Bleed each wheel till ran purple.
Seams to be a good strong pedal now.
Now need to replace the air tank bleeders.
Tried removing and cleaning but still seeping air.

 

[exhogflyer]

Now need to replace the air tank bleeders.
Tried removing and cleaning but still seeping air.

If the people before you weren't diligent in bleeding air out of tanks the bleeders get plugged up with crud. Replace them with the new style with cables on them so you don't have to crawl under the truck.
https://www.bigmikesmotorpool.com/c...able-operated-air-tank-drain-valve-set-of-two
And while you're at it put one of these on:
https://www.bigmikesmotorpool.com/c...products/remote-master-cylinder-reservoir-kit

 

[Bill in pa]

Well ive bleed my brakes and the pedal gets real hard.
Holding it though for maybe 15/20 seconds it starts to fall and goes to the floor.
I have NO air bubbles and purple fluid from all wheels.
I bleed the air packs and then each wheel.
So now im thinking I may need to replace the master cylinder.
Ive never dealt with air packs so any help is greatly appreciated.
1987 M35A2C USAF truck Has two air packs.

 

[porkysplace]

Did you bleed the air pac first then start at the farthest wheel ?

 

[Bill in pa]

Yes I did
Driver side air pack. then the passenger rear drive
then the driver rear drive
then the passenger front drive
then the driver front drive
Was better.
Then did the passenger side air pack.
then the driver side steer
then the passenger steer
feels harder but eventually drops,
A quick pump and its hard again.

 

[77 AMG]

Second the thinking about the M/C going out. Classic symptoms of failure- goes soft gradually while being held, then, firms up after a quick stroke or two, followed by creeping down again.