Air blowing out of master cylinder vent

[Bcurtman]

Hey all. I need a little help. Yep, I've searched. Yep, I read the manual. I need experience talking to me from someone who has had this issue. Please read all my info-it does not seem to match up well with any other posted problem, although I may have contributed to the problem!

1. I have air blowing out the vent tube from the master cylinder constantly. Not a lot, but still blowing out.

2. My brakes are EXCELLENT.

3. I have power bled everything, new DOT 5, and no leaks anywhere.

4. I removed the air control portion of the air pak. Exhaust valve was not stuck, all clean inside, and piston glands looked worn but OK. I did not take apart the air pak to see inside the big cylinder or the hydraulic end. As I said, brakes are great.

5. My gauge never goes above 35 psi or so.

6. If I disconnect the output line on the compressor I can hold my thumb over the port and basically block it off. Doesnt seem like enough air. I have a Midland brand OE governor on the firewall-havent disassembled it but did peck on it. Compressor never changes its tune.

7. Here is where I may have shot myself in the foot. I ran a 1/4 nylon line to the air pak from the tank replacing the original copper line which I damaged. To do this, I tapped the fitting ID in the valve 1/8-NPT and screwed a push connect (all DOT approved) in to the original fitting. Could it be that pressure alone is not enough? I dramatically reduced the volume of air available to shift that valve.

8. My brakes do not drag, lock up, or otherwise act abnormal. I may not have as much boost as I should, but I can slide it on gravel.

9. Ive soapy watered it to the point that it is VERY clean underneath!! No leaks!

Do I need to rebuild the air pack?
Is my compressor bad?
Is my governor bad? If so can I get a new Midland?
Is that small line messing with the valve and venting off what the compressor makes?

Any and all help is appreciated. Please see the pic on "The Deuce" where I posted this as well.

 

[doghead]

Why two identical threads?

Do you have two trucks doing this?

 

[Bcurtman]

I thought I may not get an answer on the "unmodified" thread due to the way I've chopped her up....

 

[doghead]

Well, we call this cross-posting. It's against the rules.

Most people read the forums from the main page(latest posts).

You should have asked a moderator to either delete or move your thread, not start a duplicate.

You will not get any more replies or better help, in either of the deuce forums.

I'll go delete your other thread.

 

[gimpyrobb]

If you have air escaping from your master cyl vent, I would start by rebuilding the air-pack. That shouldn't happen.

 

[rrrr]

If your pressure is not going above 35 you have issues. Either your gage is wrong, your governor is bad or your compressor is not functioning correctly.

What I would do is try to pressurize your air system with a shop air compressor to see if you can get a higher pressure. Use the emergency glad hand in the rear of the truck. Add a little air tool oil inside the glad hand to help put a little lube in it. If you can get full pressure on your gauge then your governor or air compressor might be at issue. If not I would suspect your gauge. Get the air issue taken care of first.

If you can get full pressure then I would suspect your governor. I don't think they are expensive and your local napa might have one in stock. If that doesn't solve the problem then I would suspect your compressor. Make sure the air filter for it is clean and the belt is tight.

Once you get the air issues taken care of then work on the brakes. Gimpyrobb mentioned air escaping from you master cylinder vent this could also cause the lack of air pressure build up.

The advantage of using a shop compressor is you can shut it off and listen for leaks, test your brakes, etc.


Good luck and let us know the outcome.

 

[jerseyjeep2003]

I had the same issue, I rebuilt the airpack and slave cylinder and master cylinder....and it still leaked. I then checked the vent line that comes up next to the air filter and found the plug fitting on the end to be plugged up. That would cause the vented air from the pack to back feed into the master cylinder. Remove the plug and clean it or replace with a brass filter plug. Don't know for sure if that is all that you have going on since your pressure is low, but it worked for me.

 

[gimpyrobb]

If your pressure is not going above 35 you have issues. Either your gage is wrong, your governor is bad or your compressor is not functioning correctly.

What I would do is try to pressurize your air system with a shop air compressor to see if you can get a higher pressure. Use the emergency glad hand in the rear of the truck.

There should be a check valve in the system, this should not work.

 

[Bcurtman]

Here's the pic. Is that impacting the volume enough to cause an issue?

 

[Bcurtman]

I dont have any gladhands left in the back. I think I will however, take your advice and adapt my compressor to the air line coming out of the compressor to see what that gives me.

I keep thinking governor...Doesnt the air compressor pump air until it is told not to, or does it only pump when told to....

 

[Heavysteven]

Make sure your vent line to the draft tube is not blocked. Try adjusting the air regulator or replace it. I agree with other probably need to rebuild the airpack.

Yes the air compressor runs off the governor. Here is a video reviewing the multifuel engine.

[media]http://www.youtube.com/watch?v=k5UUpqagrf0[/media]

Here is a video of my airpack operating

[media]http://www.youtube.com/watch?v=-q74Hkk0m4g[/media]

 

[Speddmon]

6. If I disconnect the output line on the compressor I can hold my thumb over the port and basically block it off. Doesnt seem like enough air. I have a Midland brand OE governor on the firewall-havent disassembled it but did peck on it. Compressor never changes its tune.

When you say you are putting your thumb over the port, are you putting it on the compressor side?

If that is the case, only 3 things I can think of would cause an issue like you are having.

1, the governor is not working and or set properly
2, the unloader on the compressor is sticking
3, the compressor is bad.

Start in order, 1-3 and check, replace or rebuild as needed and your problem will probably go away

Edit; The above suggestions will do nothing for the airpack issue, but it should help you get more than 35 PSI from your compressor

 

[Bcurtman]

I installed a new governor last night with no change in results. I have worn out the TM's and search looking for an exploded view of the compressor. If someone could point me to one, I would really appreciate it. I have a single cylinder style. I'm going to pull the top off of it tonight to see if the unloader is stuck and will also service the intake filter. I did find another post after really digging, where the hydraulic side of the airpack may be stuck. That will be next, and I think I'll just rebuild it. Really want this toy on the road!

 

[rrrr]

PM sent with telephone number.

 

[Bcurtman]

I put air to the output line off of the compressor this evening. Had my son watch the gauge . Still built only 30-35 psi with my shop compressor hooked to it. I'm convinced now that the compressor is ok. I've been studying the airpak. It occurs to me that during the process of bobbing the deuce, I did have the rear ends completely out of the truck with open brake lines. At one point, I had my son start the truck, and out of habit he pushed both the clutch and the brake pedal while doing so. The open brake line began to spit / pour brake fluid and air. I hollered at him (gently) to let off the brake. Is it possible that with zero resistance on the brake fluid, the hydraulic piston in the airpak was able to travel to "new" territory and become stuck? Perhaps the air cylinder end? As I said earlier, I have had the air valve off and everything there was in decent shape. Would either or both of the above conditions allow air to pass through to the vent? Maybe the bushing between the 2 halves? The airpak is coming off this weekend. We took it for a run again tonight and the brakes are great, just not well or maybe at all boosted. Took it on rural gravel road only! Your thoughts / experience is appreciated.

 

[Bcurtman]

Can I pull the plug on the front end (hydraulic end) of the airpak and push the piston back with the bleeder valve open??? Anyone tried this?? I'm convinced this is it. Everything is forward so far that the air is just going right out the exhaust.

 

[Bcurtman]

Airpak wins. We pulled the little plug on the front of the airpak and stuck a longggg screwdriver in without touching anything. Wrong again. I'm ordering the airpak rebuild kit yet tonight. Almost has to be bad seals and bushings on the air end. I love troubleshooting, seriously. It was always a passion of mine to figure out what was ailing a machine in our plant.

 

[rrrr]

Great job. Hopefully we'll meet up at an event. I'm headed to Buchannon's mudfest this morning taking the 5 ton out for a little fun

 

[Bcurtman]

I completely rebuilt the airpak yesterday in about 4 hours. Yes, I made sure I got the pushrod seal and the piston seal in there correctly. Cleaned everything up with gas, blew it all off well with air, lubed it all with new DOT 5, and reassembled following the TM with my iPad. I used a very thin coating of Indian Head gasket shellac on all of the gasket surfaces. Should get it re-installed Tuesday evening. I'll be adding a remote reservoir at the same time, and have all of those components in hand. I can't wait to see if this fixes it so I can report back. Seems like a lot of folks have a similar issue.

 

[Bcurtman]

Got the rebuilt airpak installed last night. Topped off the master cylinder with DOT 5. Started the truck, and watched to see if I build air pressure. NOPE. No change. So I now have a rebuilt airpak and a new governor on there, and I'm still not building air. Air is blowing out of the vent fitting on the airpak, and I verified that is where I am losing all of it. I didn't bleed the brakes or build pressure on the hydraulic side--will that help? If you read my original post, you'll see that my brakes were great, and I suspect they will be this time too once I bleed the air out. Any suggestions on the air loss out the vent??