• A Plus Truck Repair

Clogged Air Compressor Lines

Updated: Jun 23

I had a road call from Freightliner truck driver with air brakes "not able to release" issue and came right onto him, where I have found the truck being stuck on the hard shoulder of I-5 freeway with air tanks pressure not being able to "build up" above 65psi mark. I inspected the truck while the engine running and noticed very "audible" hissing pulsating noise coming from under the cab on the driver's side right below the edge of entrance door. Sure enough:the metal jacketed main air supply line from air compressor to the air dryer blew up and air was escaping from it. Unfortunately, for such metal jacketed hoses there is no "quick connect" coupler like there are ones for regular rubber or nylon air brake lines where there is an option just to cut the hose on two halves and join the two pieces together. In this particular air line failure I had to go ahead and replace the complete hose running from compressor all the way up to air dryer.

Driver also told me that the air dryer was replaced just two months ago, as a reply to my initial troubleshooting thought process which led me to the thought that there had to be a "clogged" air dryer cartridge. Right after when I have disconnected the air lines (one metal jacketed and the other one regular nylon thread cloth rubber cased) I have found that these lines are all clogged up with cooked and baked oil coming from the compressor (oil bypass). The air passageway in these two hoses to the air dryer was completely "blocked off" to the point that even if I had replaced the air line without clearing out all the "crystallized carbonated gunk" from another hose that joins the one that raptured and leads to air dryer, the newly installed hose would not provide adequate air supply to the air dryer and will just rapture again. This is basically what had caused the original hose to blew a hole - the restricted and completely clogged air line, and I am not talking here about just some sort of small "plug" of crystallized oil, I am talking COMPLETE 100% BLOCKAGE!!! As I have tried to "unclog" the other rubber hose (shown on the picture below), the one I didn't have, since the Freightliner Dealership was closed on Sunday, i have tried to puncture that crystallized "matter" with heavy duty pick tool and screwdriver and about 7" of that pick went into this "matter" by forcing it really hard in. I also was folding the hose in a different directions in order "to loosen up" a "carbon gunk", but the thing would not give up. Finally, after about 25 minutes of "struggle" and blowing through the other end with compressed air the passageway was cleared out and I have attached the hose back to the air dryer. The air pressure started to build up again and after checking the system for air leaks (where non were found) I was satisfied with this truck's repair I have completed that day and advised to the driver about future repairs that should be carried out on elements of air foundation brakes.

For all of you techs involved in the heavy duty road repair and maintenance industry I would highly recommend replacing (or at least checking and blowing through them with shop air) the air lines from air compressor to the dryer once the dryer gets replaced every 24 months or 200,000 miles, since those lines are usually getting quite hot and with addition of oil creates a "perfect environment" for complete blockage of air supply to an air dryer and thus ultimately leading to a foundation brakes failure. Below are some pictures of hoses clogged lines along with the one that I have found raptured during my service call and was cut by me to examine how far the blockage went, also the link on recommended service interval for air dryers.



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