Air dryer purge valve leaking...help please!

[Michaelwnc]

Hey all, hoping for some advice. 93 international w/ DT 360 here. Stuck in a parking lot in Tucson, with a leaking air dryer purge valve. Not building pressure past about 30psi says my mechanical gauge... low pressure alarm going off. This problem seems to have been getting progressively worse over the last month while traveling. Been taking longer and longer to build pressure upon first start in the a.m. Attached photo. Is this thing an AD 9? Can't find any info on it except a tiny Bendix stamp on the purge valve assy. Can I adjust the nut that is visible in the valve? Can/should I replace only the valve assy. It looks as though there is a torn diaphragm inside.Pretty sure I can pick one up nearby from Napa today. Part # TWD H 800405. This thing doesn't appear to have a cover/dust cover on it. Is that normal? First time doing any extensive repair work on the air system other than just fixing some minor leaks. So go easy on me here, I'm learning. I know I should consider replacing the desiccant cartridge, as I don't know it's history ( just acquired this bus back in October) but I'm traveling, in a parking lot, with minimal tools.
Any advice as well as help confirming if it's an AD 9 would be greatly appreciated by myself and family!

[Michaelwnc]

If anybody picks up on this thread, just wanted to give a little more info. I messed around with the valve and was able to get my system to pressurize so that I could drive the short distance to Napa ( thankfully). Here are my options at Napa. Haldex purge valve replacement with thermostat and heater $214 and get it today. Bendix same as above $270 or a reman Haldex complete dryer unit for $170 after core charge with no bracket, get it tomorrow. Any ideas or experience with this conundrum. What is my best option? Again, keep in mind I have been traveling now for over two months, I'm parked in a parking lot with only basic hand tools and no friends around to help out...except for skoolie.net of course. Are Haldex parts dependable? Will the reman Haldex dryer be compatible with my existing bracket? How much harder is it to change the whole unit vs just the purge valve and heater assembly? Also, keep in mind that I don't know the history of the current Bendix air dryer or it's maintenance schedule. Thanks in advance. What would y'all do?

[Booyah45828]

Purge valves can be rebuilt. Numerous fleets do this as part of an annual maintenance schedule. Drier maintance has been gone through on a few different posts on here. You can search to find them, I don't have the time to look for you at the moment. However, with no experience doing one and limited tools and space I wouldn't recommend you try it though.

Honestly, 170 for an entire drier over 214 for just the valve seems like a no-brainer to me. The bracket should swap over no problem. You'll have to swap the fittings over as well.

Haldex is an okay brand, I've used them before.

If you're in the napa parking lot, any additional tools that you need you can likely borrow or "rent". Use teflon paste thread sealer on the pipe fittings.

[Michaelwnc]

Thanks Booyah, every bit of info is super helpful at this point. Yes, I am in the Napa parking lot so I'm gonna try and see if I can get the drier loose and if so just order the whole unit I guess, and hope the bracket and fittings are compatible. Much appreciated, I'll keep things posted.

[ewo1]

Originally Posted by Michaelwnc

Hey all, hoping for some advice. 93 international w/ DT 360 here. Stuck in a parking lot in Tucson, with a leaking air dryer purge valve. Not building pressure past about 30psi says my mechanical gauge... low pressure alarm going off. This problem seems to have been getting progressively worse over the last month while traveling. Been taking longer and longer to build pressure upon first start in the a.m. Attached photo. Is this thing an AD 9? Can't find any info on it except a tiny Bendix stamp on the purge valve assy. Can I adjust the nut that is visible in the valve? Can/should I replace only the valve assy. It looks as though there is a torn diaphragm inside.Pretty sure I can pick one up nearby from Napa today. Part # TWD H 800405. This thing doesn't appear to have a cover/dust cover on it. Is that normal? First time doing any extensive repair work on the air system other than just fixing some minor leaks. So go easy on me here, I'm learning. I know I should consider replacing the desiccant cartridge, as I don't know it's history ( just acquired this bus back in October) but I'm traveling, in a parking lot, with minimal tools.
Any advice as well as help confirming if it's an AD 9 would be greatly appreciated by myself and family!

I posted the air dryer service manual here, chapter 8 of post #1.

I hope this helps you out.

[David from Ontario]

For what it's worth, I recently had the same issue on my Thomas bus. I have no experience working on anything under the hood. I take it to the Thomas dealer for that. But the bus was going nowhere with no air pressure to release the parking brake. So I bought a new purge valve and replaced it myself, with much trepidation. Worked out fine. I expect it will for you, too. I made a 5 minute video about the process:
https://youtu.be/XF2UtW2lrxs

[Booyah45828]

Oh I'd say the problem is definitely the purge valve. They get gummy and stick and will also leak too. That's why I mentioned the annual maintenance part.

Last time I priced a rebuild kit it was about 30 bucks or so, and fresh cartridge kit was another 30. With that said, I'd never spend 214 on a valve when a reman dryer costs 170. When we service an ad9 drier on a bus we remove it from the bus entirely anyways, so remove/replace a reman dryer over remove/rebuild/replacing the current one would be less work. Most buses you can't get the top cover off an ad9 to replace the dessicant with it installed on the bus, which is why we remove it.

[musigenesis]

I had the same problem, called a mobile mechanic to come fix it, he replaced the purge valve and I paid $750. Since you're DIYing you're way better off than me no matter what option you go with.