blowing brake fluid from the vent line from the air pack

[appellandscaping]

well i replaced the master cylinder and rebuilt the brake booster/air pack and it is still blowing fluid from the vent line that goes under the hood

 

[tsstout]

So, what are the symptoms?? Because the master vent, the airpack vent and the fuel tank vent are piped forward in a common copper tube, joining the slobber tube up front... I'm just trying to make sure I understand the situation.. The vent on the master is just a pressure vent, the airpack vent is return for air side of the airpack, and I believe the fuel is a pressure vent for the fuel tank.... So unless there is a malfunction in the airpack or something got hooked to the vent lines junction, I don't see how dot 5 gets there.... The slobber tube spits oily stuff on it's own... Could that be the symptom??

We need more info to help further....

Terry

 

[Westech]

take off the vent line. most people take off the line due to that fact. The vent line can suck up fluid if you have it too full or when the fluid is sloshing around.
If its draining the fluid you have a vent line issue... way too much vacuum.

 

[tsstout]

humm.. interesting.. so it's the vent from the airpack causing the suction??

I have a remote on the firewall with it's pressure vent teed into the air filter can... it must not get as much suction going.... when I finish the fording stuff I hope plumbing from the compressor (right next to the tee) doesn't cause that to start happening...

I guess I missed that detail when it was stock... of course my slobber tube would surely overshadow any drips of dot 5...

 

[kwiksilver]

slobber tube was never mentioned. The 3/8 line on the firewall is the blowoff for the airpack. It was plumbed into the airfilter can.

 

[Wildchild467]

I rebuilt one air pack and the cup for the piston was installed backward. I fixed the problem, but you may want to check the threads on here about rebuilding the air packs. one part in the TM shows it installed wrong and i believe that will cause the cup on the brake booster master cylinder to leak causing fluid to go past the cup, down the plunger rod and into the air piston. Its not hard to pull the end off the matercylinder on the brake booster and check to make sure it is installed correctly.

 

[JDToumanian]

Because the master vent, the airpack vent and the fuel tank vent are piped forward in a common copper tube, joining the slobber tube up front

Are you sure your truck is this way? It should not be so..... I believe there was an MWO to separate the brake vents from the fuel tank vent for safety reasons.... Fuel vapors can degrade brake system components.

The MC and Airpack should vent into a copper tube that runs up the firewall and terminates above the air cleaner housing.

My deuce used to spit brake fluid out of this vent line and there would be a wet spot or small puddle on the air cleaner...... When I switched to a remote brake fluid reservoir, there is no longer a vent line from the MC. I plugged the tee at the frame and the MC "breathes" at the remote reservoir. This solved my fluid spitting problem, so in my case it was an overfilled MC, not an airpack problem...

Jon

 

[tsstout]

I just did the master and airpack... and had already did the remote master... Been piecing the fording kit also... So I think I followed the copper carefully... I am sitting at work... not under the truck.... and I am getting old... but I'm 98% I guess

I remember because I thought it sounded kinda daring putting a fuel fume line on the same line as a rubber gasket-ted pressure device (airpack), but the merge into the slobber tube made me think I must not be thinking right... I guessed the pressure release of the airpack exhaust kept things going forward...

Heck, mine had the hydralic brake switch on it too....

 

[appellandscaping]

maybe i rebuilt the air pack wrong i will try installing the other one i have and did one of you say the master cylinder could be too full

 

[farmboy11]

Piston cup mistake

I rebuilt one air pack and the cup for the piston was installed backward. I fixed the problem, but ...

I made the same mistake on the piston cup. Won't forget that anytime soon. I have a question on the the other cup in the same drawing labeled (incorrectly) as piston u cup, the one that is positioned in the #2 spot. The pic shows it as straight seal but my kit came with a cup. Is the kit wrong and if not which way does the cup face? Same as the other one? Please help. Brakes are kicking my ass and wallet.

 

[Wildchild467]

the open part of the cup faces the end that has the brake pressure switch (not air pressure type).

 

[farmboy11]

Thanks. I'm glad this is a hobby and not a need. The learning curve is huge.

 

[kennys@wi.rr.com]

I have been reading a few threads on replacing and rebuilding the air pack. I have another members deuce here that needs this done so I want to make sure it is done right and ready to go for him when he comes to get it. My question isn't about how to do it but how to prevent damage in the future. I was thinking about an air dryer to be placed before the air pack. I have a tractor trailer salvage yard not to far away and they have all different sized air dryers on eBay from time to time from $15 on up. I figure it doesn't need to be a large unit because a deuce doesn't use anywhere near as much air as a tractor trailer. It seems a lot of the damage is from corrosion inside the cylinder caused by moisture, this should help. Has anyone tried this or have any thoughts on this? It's something I would consider doing on my deuce to try it.

 

[Jake0147]

well i replaced the master cylinder and rebuilt the brake booster/air pack and it is still blowing fluid from the vent line that goes under the hood

The first thing I would be doing is removing the vent from the master and the booster. I wonder (because I don't know) how long it takes to "blow out" all the brake fluid settled in the bottom of that common vent... That would also give conclusive proof if it was exiting from the booster vent before you tear it down again to check.

 

[nk14zp]

I went up and helped Rangerdave take his air pack apart that he rebuilt a while ago. Saw no damaged seals but it blows BF out the vent. Does any one have any pics of the right way all the seals go?

 

[kennys@wi.rr.com]

I have rebuilt a few and I have yet to see one that the seals didn't "look ok". It takes so little for them to stop working it seems.

 

[jkcondrey]

Bringing up this old thread rather than making a new one. Im having similar issues. All new brake cylinders, axle hard lines, rubber hoses, rebuilt the master cylinder. Got master bled, got airpack bled, bled lines. Pedal is really squishy. I hooked up pressure bleeder and fluid sprays out of the vent line behind the air intake. My setup still has the small cap vent that goes down to the main copper t fitting. I also have a remote reservoir t'd into the top of the cap. Not sure whats going on, if the airpack is bad or if i should take it all back stock(no reservoir) and restart the bleeding process. I have the newer short air pack, m35a2.

 

[doghead]

Probably your airpack.

 

[frank8003]

Bringing up this old thread rather than making a new one. Im having similar issues. All new brake cylinders, axle hard lines, rubber hoses, rebuilt the master cylinder. Got master bled, got airpack bled, bled lines. Pedal is really squishy. I hooked up pressure bleeder and fluid sprays out of the vent line behind the air intake. My setup still has the small cap vent that goes down to the main copper t fitting. I also have a remote reservoir t'd into the top of the cap. Not sure whats going on, if the airpack is bad or if i should take it all back stock(no reservoir) and restart the bleeding process. I have the newer short air pack, m35a2.

One would see the MC leak out of strange places if one kinked over the vent so she could not breath.
On the other hand one must remove the brake MC vent to that other system. That is in the PS database.

Also if you put a remote MC reservoir then one should follow this learned advise, first thing on page two.

Also I already built a sight glass for the Dot 5 MC/wheel cylinders interface so I could watch those hydraulics work.

You can have that too.
View attachment master cylinder remote roscommon nn17.pdf

View attachment brake reservoir IMG_2208 02212014.MOV

Your just have to click on this stuff I can not assure it works for you from here
PM if not understand

 

[frank8003]

If one installs a brake bleeder one should heed the advise