Steven P Posted November 27, 2021 Share Posted November 27, 2021 Noticed I was dropping air (about 20psi) over a couple of hours while parked. I could hear air hissing from rear, driver's side and found air leaking from the back side of the air dryer. See pics. It's the piece behind the 2 fittings in front. I circled and drew arrows to the part. I'll be able to get a better look today as it was getting dark when I parked and found it. (I did do a brake test before traveling onwards.) Link to comment Share on other sites More sharing options...
Bob Jones Posted November 27, 2021 Share Posted November 27, 2021 If it's the aluminum boss that the hoses screw on to it makes me wonder if it might be cracked 😞 I'd take a really good look at it. In a worst case scenario, if it is cracked, or cracking all the way around, if you lost a chunk you could have a very serious problem. Not trying to scare you, just concerned about it possibly being cracked and what the implications could be. There also appears to be a bolt or hole in that area, maybe it's there? If so, then it might be as easy as removing a bolt and resealing? I'm curious to see what you find. If my memory is correct, I don't think entire dryer assemblies are cost prohibitive. 1 Link to comment Share on other sites More sharing options...
Jdw12345 Posted November 27, 2021 Share Posted November 27, 2021 One thing to always carry along is a connection fitting to totally bypass the air drier in an emergency.. Just connect the two big air lines and your back up and rolling! Jmo 1 1 Link to comment Share on other sites More sharing options...
96 EVO Posted November 27, 2021 Share Posted November 27, 2021 Top photo is the regeneration valve. Link to comment Share on other sites More sharing options...
Bob Jones Posted November 27, 2021 Share Posted November 27, 2021 42 minutes ago, Jdw12345 said: One thing to always carry along is a connection fitting to totally bypass the air drier in an emergency.. Just connect the two big air lines and your back up and rolling! Jmo That's a good work-around - I need to get one for the just in case bin. Link to comment Share on other sites More sharing options...
JohnC3 Posted November 28, 2021 Share Posted November 28, 2021 The Air Dryers are Easy to replace. You can get one from either a place like anythingtruck.com (a wabco OEM replacement for about 350) or go on amazon and get a chinese clone for about 120 (The clone performed as well as the OEM replacement, but I believe I was getting teflon in the diaphragm. I have been having an ongoing issue with different parts leaking on the air dryer and have tried 2 of both (One original and one replacement under warranty). Takes about 1 hr to pull and replace and you need to drain your air before you start. For me, it was only the hoses and 3 bolts. Longest time was cleaning up the threads. On my last replacement a shop tech suggested I don't use teflon tape, but a liquid thread sealant (Formula 32??? kind of like red thread lock, but specific for this type of seal.) for hydraulic and pneumatic connections. Had a cummings tech look it over in Coburg and he told us that if you have oil splatter under your purge valve, its a sign of compressor blowby (ie new compressor or rebuild) ours didn't need that. Sorry to overload you, but your replacement regen valve kit is around 130 and looks like you might have a structural issue. I am not an expert but would suggest replace the complete unit. Don't over tighten (especially if you use Teflon tape it can stress your casting. Hope this helps, John 1 Link to comment Share on other sites More sharing options...
Steven P Posted November 28, 2021 Author Share Posted November 28, 2021 Thanks to all the responses and here's an update. I removed the 4 hex head bolts on the backside of the dryer holding this part on. I found no cracks in any of the housing areas. I cleaned up the mating surfaces and reinstalled and tightened the bolts pretty tight. Still have the same leak. However, there is a small rubber O ring at the place where it's leaking. There appears to be no gasket between these 2 surfaces and my theory is the O ring needs replacing. The air leaks right at that spot. That I can do later. Today we have a long drive home. But I feel good about the trip. Link to comment Share on other sites More sharing options...
Jdw12345 Posted November 28, 2021 Share Posted November 28, 2021 after trucking for myself to California from Minnesota for the better part of 20 years I always used OE parts on the air system fwiw! This may help, https://www.wabco-customercentre.com/catalog/docs/mm34_web.pdf 1 Link to comment Share on other sites More sharing options...
Jdw12345 Posted November 29, 2021 Share Posted November 29, 2021 Also found this for anyone looking for a complete air dryer assembly, very reasonable for new non after market! IMO https://www.finditparts.com/products/11751232/wabco-r955205?srcid=CHL01SCL010-Npla-Dmdt-Gusa-Svbr-Mmuu-K11751232-L565&srcid=CHL01SCL004&promo=CYBER15&gclid=EAIaIQobChMI2LzJ5tS89AIV33FvBB2FwgFTEAQYBSABEgIudvD_BwE#description 1 Link to comment Share on other sites More sharing options...
Steven P Posted November 29, 2021 Author Share Posted November 29, 2021 @Jdw12345 thank you very much for the document and the site. Very helpful info! 1 Link to comment Share on other sites More sharing options...
Steven P Posted December 11, 2021 Author Share Posted December 11, 2021 Update: I found an O ring at O'Reillys today that was a close fit. Changed out and reinstalled and so far, so good, no leak as before. I'll keep an eye on it though. Thanks all for your help. Link to comment Share on other sites More sharing options...
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