Bleeding the Master Cyc

[nf6x]

When I look thru the access panel in the driver's floor at the brake master cylinder I also see a disconnected hard steel line with a threaded fitting just to the passenger's side of the MC that connects to NUTHING.

That sounds like the vent line which is usually connected to a right-angle fitting on top of the master cylinder cap.

 

[BugEyeBear]

That sounds like the vent line which is usually connected to a right-angle fitting on top of the master cylinder cap.

Thanks "nf6x"!

That's what I'd assumed.

Does this vent line route to anything else?
(I know, I'll have to just crawl under and see where it goes...)

Is it OK to leave it as is? OR should it be capped?

(It has probably been this way for MANY years, but I just worry about a line that is left open...) (If nothing else I'll probably push a vaccum cap over the end to prevent any additional crud from getting in there...)


BTW: Love the "buy a cheeseburger for a dog" quote! I gave my neighbor's new puppy a few french fries when we 1st met & ever since then he follows me everywhere with his tail waggin' & his lips smackin'! His owner can't figure out why he is so fond of me!!

-Bear-

 

[nf6x]

I'm not sure where else it goes. I haven't tried following it yet. I think that capping it off sounds like a good idea. One of these days, I think i'll do a remote fluid reservoir modification, and I'll cap off the vent line then since the cylinder would vent through the remote reservoir cap.

 

[Garandfan]

The vent line off the top of the master goes into a "T" fitting into an airline that goes into the brake booster itself. It's almost as though it may work as an automatic oiler to the brake booster. The brake booster should be oiled, most, (including me) use pneumatic tool oil. I have a breather cap on top of my master cylinder so no air can get trapped in the master.

 

[hellrayzor1]

A large air line comes off of the airpack for venting purposes and as it passes the master cylinder there is a T fitting. A smaller line goes from a 90 deg elbow on the MC cap to this T fitting. The large line should continue to the passenger side frame and then up the firewall. It ends just above and toward the drivers side of the air cleaner housing. This keeps water out of your master cylinder and airpack if you get into deep water. Thats what it is for. I rebuilt my whole brake system a week or so ago and did a lot of reading in the TMs and asked a lot of questions on here.

I hope this helped and that I just didnt repeat what others have said. My brake system pressure bleeder is my 14 year old son sitting in the drivers seat pushing the pedal for me lol. The bleeder on the airpack will take care of air from the MC too. Just attach a peice of tubbing on the bleeder and run it into a claen container as you bleed each point so you can save the fluid and reuse. Also keep a good eye on the level in the MC. Last thing you want is to let it go dry and introduce more air in the system, time to start over again

Mark

 

[dabtl]

If the plug on the rear of the air pack is frozen in place, not unusual, you can take the air line loose at the rear of the piston can and insert air tool oil there.

 

[Keith_J]

The vent line off the top of the master goes into a "T" fitting into an airline that goes into the brake booster itself. It's almost as though it may work as an automatic oiler to the brake booster. The brake booster should be oiled, most, (including me) use pneumatic tool oil. I have a breather cap on top of my master cylinder so no air can get trapped in the master.

Air "trapped" in the MC could cause brake drag but if you are talking about the breathers like what is on the axles, this is a check valve, preventing air from entering the master cylinder. This can cause brakes to become inoperative if a vacuum forms. Like if there is a small leak in the system.

Older trucks have this breather. Newer trucks have the air vent line connection which is safer.

 

[spicergear]

I love my Hydro-Max power assist braking. No air, no alarm, and as soon as the engine is off the starter I have full braking and always a nice firm pedal feel.

 

[Somemedic]

Made my MC cap work as a pressure bleeder cap with a few things from Homeless Depot/Lowes. Use the numbers on the packages for you fellas like me who need the extra help. Other than the 4 fittings some 3/8ths clear hose and a 2 gal sprayer is all that is used. Plus some brake fluid. Duh...

1 1/8th elbow screws into the cap
2 1.5" long 1/8th male to male goes into the elbow
3 1/4 to 1/8th reducer ties into the male end leaving a 1/4" female port for a...
4 1/4 nipple to 3/8 quick connect fitting. Most garden sprayers use 3/8 diameter hose.

I know it was done before but I could have used the wrappers from the fittings since the store I go to never seems to have all the parts posted, causing me to improvise. If thats your case just remember that the opening in your MC cap is 1/8th" NPT threads and your going to have to go up to 3/8 diameter hose. How ever you do it can be up to you.

Hope this helps some.

PS I had thought the brakes had been ok before... they will put you through the windshield
now