MCI 102c3 6v92ta Mechanical Won't Air Up

[luvrbus]

Most air tanks have the Bendix thread not NPT yours could be NPT you never know who has been there before you, all buses used the Bendix fittings (B/W ) on the air system from the factory some are the same size as NPT and some are not

[Jcparmley]

What is a Bendix thread and where can I get the fitting?

Most air tanks have the Bendix thread not NPT yours could be NPT you never know who has been there before you, all buses used the Bendix fittings (B/W ) on the air system from the factory some are the same size as NPT and some are not

[luvrbus]

What is a Bendix thread and where can I get the fitting?

Hose supply outlets sells the Bendix if you need it ,the Bendix fitting will have a long nut for a flare fitting to prevent breaking of the copper lines auto parts and hardware stores sells cheap made fitting that break in time air brake fitting will have the DOT stamp and you can see the difference,they cost more too   

[chessie4905]

Some store fittings don't thread on. Different. Btdt. Good, correct ones are stamped bw or dot. Thicker material. McMaster Carr also carries correct supplies and fast shipping, if not available locally.

[Jcparmley]

So do I look for a flare fitting or a compression? 

Hose supply outlets sells the Bendix if you need it ,the Bendix fitting will have a long nut for a flare fitting to prevent breaking of the copper lines auto parts and hardware stores sells cheap made fitting that break in time air brake fitting will have the DOT stamp and you can see the difference,they cost more too

[luvrbus]

So do I look for a flare fitting or a compression?

Dot compression fitting work they are different than the ACE hardware compression fittings 

[Jcparmley]

I need to find 3/4 Female DOT/Bendix Thread to 1/2 Female NPT Thread. 

I have the fitting for the copper air pipe.  It's 3/4 DOT/Bendix.  I also found the male fitting that it mates with to compress the sleeve.  I have included those pics in this post.

What I need now is a fitting to go from the 3/4 male DOT to the Male 1/2 NPT on the Nylon Hose that was made by the diesel shop. 

What is the thread "code" for Bendix thread?  Is it DOT or something else?

[luvrbus]

They may be a tough find,on the air system any transition was made in one fitting or on the hose end   

[Jim Blackwood]

Try a hydraulics shop. Good chance they might be able to help you out.

Many fittings use a standardized thread in an inch or metric size measured as an inch fraction (or mm count) and a thread pitch such as 3/4-16 which is a fine pitch thread that would be used in fittings. You can easily measure the diameter and pitch with calipers. A 16 pitch would be 4 threads in 1/4". If your fitting uses a standard fine thread finding a match should be no problem.

Jim

[Jcparmley]

So I fixed the leak at the air dryer. Now I am able to build enough air pressure for the brake release button to stay down. However, the breaks still won't release. I tried holding the brake pedal to the floor for 30 seconds to a minute. I tried putting it in reverse and forward. I tried pumping the brake. I can't get it to release. Any suggestions?

[Jim Blackwood]

Waiting for BW to correct me but it seems like you are not supposed to apply the parking brake when you have the regular brake pedal pushed down. Something about making it hard to release the parking brake? So if that might be your problem maybe it just takes some energetic bouncing on the brake pedal while simultaneously trying to release the parking brake? Hopefully? Just a thought.

Jim

[buswarrior]

What is "enough pressure"?

It is either filling up, and the air drier purges, or it isn't.

How long has it been parked since it last moved?

How old is the inversion valve?

Concurrent application of service and parking.... something is ringing my "mythology" bell, I need to refresh my memory...

happy coaching!
buswarrior

[luvrbus]

Takes at least 85psi to release the DD3 brake lol 120 psi is better,the DD3 chambers need to vent the air to release can you hear escaping air ? if so then the shoes are stuck on the drum 

[chessie4905]

Need a full pedal application of 120psi, especially after sitting a while. Once you have 120, push brake pedal fully to floor, THEN push or pull button to release brakes.. ( some buttons need pushed to release, some need pulled. Whichever)Until you can get the pressure to that , don't bother. Try running engine now AND external air supply.

[Jcparmley]

I do not have 120 psi.  What I meant is I have enough pressure that break release button stays down and doesn't pop back up.  I thought the parking brake only needed 85 psi.  It has been sitting for over a year in it's current spot.  I don't know how old the valve is.  I never changed it.  I will keep chasing down more air leaks until I can get 120 psi or the air dryer purges.  I was hoping to release the brakes and move it closer to my shop so I can track down more leaks.  Right now its a couple hundred yards from my shop.  I wouldn't be surprised if the brake's are rusted to the drums.  Any clever way to break them free?

What is "enough pressure"?

It is either filling up, and the air drier purges, or it isn't.

How long has it been parked since it last moved?

How old is the inversion valve?

Concurrent application of service and parking.... something is ringing my "mythology" bell, I need to refresh my memory...

happy coaching!
buswarrior