Air System Issue - Brakes Locked Up

[LMTV89]

Hey all, my air system suddenly stopped building air, I was able to make it to a parking lot before the brakes locked. I hear the compressor running, there is some air coming out of the pipe under the air drier on the drivers side. so I think its some sort of routing or valve issue. What should I be checking / ordering to fix?

On a side note is there any way besides hooking up external air to get the rear brakes to release?

 

[canadacountry]

normally if it was one or few tires at fault I would had suggested caging the offending brakes and limp carefully with limited brake power from the remaining tires, but since the entire system isn't able to air up in the first place this won't apply. in that case yeah, short of pinching off the brake system downstream of the valves/compressor and inject an alternative air supply in you'll have to simply tow/flatbed your truck instead

this is just a bit of a green opinion from non-fmtv me, someone else might have something else to say

 

[Mullaney]

Hey all, my air system suddenly stopped building air, I was able to make it to a parking lot before the brakes locked. I hear the compressor running, there is some air coming out of the pipe under the air drier on the drivers side. so I think its some sort of routing or valve issue. What should I be checking / ordering to fix?

On a side note is there any way besides hooking up external air to get the rear brakes to release?

.
You might walk back to the box under the side of the truck where the air is leaking. Put the flat palm of your hand over the leak. It should close eventually and you could be back to normal. The thing needs to be serviced...

 

[TOBASH]

Torn hose. Loose fitting. Broken valve?

Soapy water and spray gun and isolate leak and post pictures.

 

[Ronmar]

well if you have air coming out around the dryer, could be a stuck purge valve like Mullaney suggested. What year truck and what type dryer. there is usually some form of cover or elbow over the actual purge valve. If that is where the air is coming from You will have to remove that cover and see if you can push the valve core in. since they blow oily snot out, they can become gummed/sticky and fail to reset after a purge.

If the air is coming from somewhere else, you will have to find and fix that leak...

 

[GeneralDisorder]

Compressor probably lost its exhaust valves. Bits of the valve springs can end up inside the dryer. The compressor can't unload to zero psi. It has to have wet tank pressure to operate the unloader pistons. If you have ~20 psi of air it might be able to unload if the regulator failed in the unloaded position but that's very unlikely IMO. If you have zero psi then the compressor has an internal mechanical failure or it's not being driven.

The dryer purge could be stuck. Stick a screwdriver up into the purge nipple and see if you can push it shut.

 

[LMTV89]

The truck is a 1998 M1078, not sure dryer model. Air is pretty steadily coming out of this elbow, if I put my palm over it the air will overpower me and still leak out so I think the compressor is working. Is that the thing I should disassemble?

 

[GeneralDisorder]

Yes. Or you could upgrade to a newer dryer. That model is deprecated and if it needs service it's probably worth upgrading instead. My advice about the screwdriver applies to the newer model not that antique. I'm sure you can clean the purge valve and get it working at least temporarily

 

[Ronmar]

Yep, remove the 3 screws holding that elbow on and push the purge valve back in And see if it seats.

that design although old has a lot going for it. Large heat exchanger area and oil separation area(narrow gap between outer heat-sync housing and inner aluminum canister), large coalescing media mass and blowdown storage area(area around media canister). They also have the advantage that the media can be cleaned and serviced by you…

I did a video on cleaning the unit… one thing I did not mention in the video is adding just a little silicone grease to the Orings in each housing end cap where that aluminum canister slides in…

 

[LMTV89]

Where should I be looking at dryers? Is that a surplus store or auto store type item?

 

[aw113sgte]

Yep, remove the 3 screws holding that elbow on and push the purge valve back in And see if it seats.

that design although old has a lot going for it. Large heat exchanger area and oil separation area(narrow gap between outer heat-sync housing and inner aluminum canister), large coalescing media mass and blowdown storage area(area around media canister). They also have the advantage that the media can be cleaned and serviced by you…

I did a video on cleaning the unit… one thing I did not mention in the video is adding just a little silicone grease to the Orings in each housing end cap where that aluminum canister slides in…

I found it kind of interesting that the MTVR uses this unit, but as an after cooler. Instead of desiccant media, it just has coalescing media.
After passing through this it goes to the air dryer (Pure Air plus) unit with the spin on element.

 

[Ronmar]

I found it kind of interesting that the MTVR uses this unit, but as an after cooler. Instead of desiccant media, it just has coalescing media.
After passing through this it goes to the air dryer (Pure Air plus) unit with the spin on element.

Dryers are rated by air volume, so if you used more air, you would want more capacity. I think the old unit does dissipate heat way better than the newer cartridge units.

all these dryers use coalescing media. I believe it is often mis-labeled desiccant Because it is removing moisture from the air stream. But “Desiccant” collects and holds moisture, so would quickly become saturated without some system to either heat or place it under a very low vacuum to force the moisture back out of the desiccant. Coalescing media separates and consolidates the moisture, but does not hold it, so gravity and an easily arranged reverse airflow can clear the moisture from the unit during a purge…

gotta change it, gotta change it, gotta put a new cartridge unit on, but the design and perfectly adequate performance speaks otherwise to me. Had someone give me 2 of them, overhauled them and put them on my shop air compressor, they work fantastic, never had such a dry shop airtank… fun to watch visitors to the shop jump when the twin units purge as I have not piped that exhaust all the way outside yet

 

[GeneralDisorder]

There was a time when I would bother with cleaning and baking media, etc to save a buck and part of me appreciates that level of maintainability with seemingly cheap and reusable media, etc. I'm that guy that will make a part on my lathe just to say I did and I won't make another because "you probably can't afford my time", and I'll take ANYTHING apart especially if it's broken - I may destroy it but I'll be having that tiny nugget of information that no one else has because they are scared of breaking it. I'll rebuild a water pump or an alternator or anything else that's "not user serviceable" if given half a chance to "get one over" on the man or the corporation or whatever. I enjoy that immensely.

As I get older though and my time is split between so many vehicles and properties, and work, and well...... everything.... I find I have less appetite for spending several hours saving a couple bucks when I could be having fun with my truck. It comes down to the cartridge dryer takes 15 minutes to service (if that), and the media bag monster takes AT LEAST TWO HOURS if you are dealing with brand new media from a kit, and quite a bit longer if you are washing the media and drying it in the oven or the sun on baking sheets, etc. The old dryer has to be serviced OFF The truck which means disconnecting every connection and then having yourself a big-ole mess on the floor and the bench..... it's just a whole production that doesn't need to even exist.

I just don't have time for it. I like the idea. It doesn't fit my requirements when $100 every 6-12 months buys back 4 hours of my time that I am billing out at a considerably higher rate for what I consider to be easier work.

To each their own and maybe I'll come back around to doing stuff like this and shaking my fist at the children playing on my lawn when I'm almost ready for the rocking chair on the porch.

No offense to Ronmar who is an amazingly knowledgeable individual and for those that WANT to do this stuff and learn the magic of recharging media, etc he is an amazing resource. I'm just offering the other perspective. Neither is wrong, and both have perfectly acceptable results.

I also worked in the compressor and vacuum pump industry for a couple years and did a lot of work with dual-tower desiccant dryers - BIG stuff for use in high tech. I recall filling the desiccant towers on one unit that was special ordered by Intel from ZEKS - it was so tall it had to be shipped on it's own flatbed and then we had to use a 18k forklift to stand it upright for filling the tanks. IIRC that unit was something like $750,000 in 2008 or so. Mostly because it was 100% stainless construction since it was going into a chip fab to provide extremely low dew-point air for high tech manufacturing that could not have ANY moisture in their process. All that is to say that the "magic" of something like servicing a desiccant/coalescing filter and it's media has long since lost it's mystery and shine for me. Cartridge. 15 minutes. Done and onto the next adventure.

I highly encourange anyone that still finds all this fascinating to give it a go though. The learning experience is worth the time. Then go buy the new one so you never have to experience that again. Secure in the knowledge that you have the experience and understanding now.

 

[Ronmar]

absolutely none taken, i agree, time is a valuable commodity, lost track of how many desiccant batches I have baked(toaster oven) to dry them out for re-install on waveguide dryers over the years. I guess for me its habit and these are actually pretty easy to service as you are simply trying to remove any oil that has made its way to the media.

The cartridge units work just fine, and service is WAY easier... Many here are hobbyists, so a little time for this type maint is probably available. It takes about an hour of work to disassemble, wipe out the sludge and re-assemble, I probably left the media soak in soap solution for an hour or so while I had it apart. I dried it in the video, but you don't have to, just rinse it a few times and you can put it back wet, the water will drain out the bottom and the system will self purge...

 

[aw113sgte]

Dryers are rated by air volume, so if you used more air, you would want more capacity. I think the old unit does dissipate heat way better than the newer cartridge units.

all these dryers use coalescing media. I believe it is often mis-labeled desiccant Because it is removing moisture from the air stream. But “Desiccant” collects and holds moisture, so would quickly become saturated without some system to either heat or place it under a very low vacuum to force the moisture back out of the desiccant. Coalescing media separates and consolidates the moisture, but does not hold it, so gravity and an easily arranged reverse airflow can clear the moisture from the unit during a purge…

gotta change it, gotta change it, gotta put a new cartridge unit on, but the design and perfectly adequate performance speaks otherwise to me. Had someone give me 2 of them, overhauled them and put them on my shop air compressor, they work fantastic, never had such a dry shop airtank… fun to watch visitors to the shop jump when the twin units purge as I have not piped that exhaust all the way outside yet

I figured it was desiccant due to the need of being dried - I suppose it could be coalescing media. The one in the MTVR uses these aluminum pieces instead.

 

[Ronmar]

I figured it was desiccant due to the need of being dried - I suppose it could be coalescing media. The one in the MTVR uses these aluminum pieces instead. View attachment 941707

It doesn't have to be dried. After rinse you can put it back wet and it would drip dry/purge same as it does in service…

aluminum is interesting, could also probably use sintered bronze, same principal as the porus beads, lots of small convoluted passages that force the water from Vapor back into droplets to then combine and fall to the bottom…

 

[canadacountry]

regarding @GeneralDisorder you know what, some people can say the same thing about these old furnaces that came "bundled" with steel mesh filters instead of being expected to use separately purchased throwaway paper filters .. the former requires a good deep soakwash to be "refreshed" to use again and again for as long as you wanted to keep that furnace going while the latter is literally just 'pull it out, kick new one in, chuck the dirty one into big garbage bin, and uhh well thats it!'

 

[GeneralDisorder]

regarding @GeneralDisorder you know what, some people can say the same thing about these old furnaces that came "bundled" with steel mesh filters instead of being expected to use separately purchased throwaway paper filters .. the former requires a good deep soakwash to be "refreshed" to use again and again for as long as you wanted to keep that furnace going while the latter is literally just 'pull it out, kick new one in, chuck the dirty one into big garbage bin, and uhh well thats it!'

That's true though I have seen electrostatic furnace filter elements (the metal mesh panels) catch fire when neglected and I have not seen such behavior from the paper panel filters.

So trade offs again. But you're right there are serviceable options. How much is the soap and water and labor vs. the paper element? Economies of scale make the paper elements really cheap and convenient so......