Air Dryer Problems

Brandy

Expert Expediter
I had this problem once before but after a few days it seemed to fix it's self. I drive a '97 Freightliner FLC 112 and last week I started it up and then went out side to do a walk around truck inspection. When I got back into the truck I noticed that the air tanks weren't filling up. At 50psi you could hear the purge valve on the airdryer open sputtering the air out untile the psi in the air tanks went down to 40 psi and then the valve would close. Does this airdryer need to be replaced or can it be rebuilt, and how much would either cost?

Thanks
Sean
 

Weave

Veteran Expediter
Charter Member
Either way it sounds like your dryer needs some attention. Shops usually opt to replace it, as it is cheaper that way for the customer saving them the labor costs to rebuild one. They run about $350-450 for a new one. If you are ambitious mechanically and have the time, you can buy a rebuild kit (around $100) and rebuild your old dryer, it's really not hard to do on a nice warm weekend day. The dessicant cartridges in air dryers should be replaced every three years to keep moisture from damaging other stuff in the air brake system. For a quick breakdown repair, it sounds like the dryer on your truck needs a new pressure valve and cartridge, a less than $100 project. Also check your air compressor governor, it can cause similar problems. It's only about $20 to replace.
-Weave-
 

NEVERHOME247

Veteran Expediter
Charter Member
Air dryer rebuild kit is fairly inexpensive. But when you figure in your time rebuilding it. Your better off to buy a reman dryer. I replaced mine earlier this year. Reman was like $225.00 All you have to do is swap over the fittings from your old dryer. You can have the new one on in half and hour. And have peace of mind when your done.
 

Big Scooter

Veteran Expediter
Charter Member
Hey Weave, Can you help me with this one? I recently had my dessicant cartridge replaced at Freightliner in Salt Lake City. Afterwards, I noticed a loud thumping/knocking noise when the pressure is building which quits as soon as the pressure release valve activates. If pressure is building while I'm accelerating the knocking increases in speed as acceleration increases as well. My wife calls it our "woodpecker" noise. Called Salt lake City and the Service Manager suggested that the Air Dryer mount must have broken. It isn't. El Paso Freightliner said it was the Air Dryer check valve gone bad and put a new one on. Same noise. I can hear it a little while standing next to the air compressor with the hood open, but the noise is most pronounced when sitting in the cab or sleeper with the cab doors closed and seems to come from the air dryer. I can even feel the knock in the floorboard. Any ideas?
 

streetsweeper

Expert Expediter
Hey Big Scooter!

Get it to a QUALITY repair shop ASAP. Dont pass Go any more.

The 'woodpecker' knock you hear is the air compressor itself. Cause of it is one of these items: piston slap, bent connecting rod, or the con rod bearing/journal.

The exception could be, you have a Holset air compressor (Cummins)& the unloader kit in the head could be bad. Those can also make a knocking noise.

Bendix TrueFlow 500 or 501? ID tag on side of compressor will tell you the model & serial. Used on Cat & Detroit Diesel.

If it was knocking when air dryer was serviced, they should not have let you out the door with it. Get it checked out POSITIVELY ASAP!

Then call Fruitliner of SLC, let the SM know what was found after, Ok?
Maybe he'll help with the bills? *hint hint*
 

Big Scooter

Veteran Expediter
Charter Member
Thank you very much, Streetsweeper. I'm heading home right now and will have it in the shop tomorrow. And you can bet I'll give SLC Fruitliner a "heads up" as soon as the problem is diagnosed. The problem began 7 Sep 02 and nobody has been able to tell me me what it is. Thanks for your help. Wish I'd come to EOL earlier. Count myself lucky. Wish you the best. Will let you know what it is.:7 :7
 

Weave

Veteran Expediter
Charter Member
I just question why the compressor wasn't making the noise until the dessicant cartridge was replaced. Anyway, there is definitely something wrong, it sounds like something is REALLY loading down the compressor, and if it wasn't damaged before, it probably is now. I'm going to guess there is something wrong with the dryer/cartridge installation too. It's amazing how some shops can turn something simple in to a multi-million dollar nightmarex(
-Weave-
 

streetsweeper

Expert Expediter
Weave,Big Scooter,Everyone;

Any tme you are in a BIG shop, their ultimate motive is PROFIT, same as you and me. Simple but sad fact of life.


Scooter; You need to get that unit in NOW, not later. PERIOD. Far as the unit making noise sooner? Due to tendencies of any system to transmit noise, it may be a while before you know about it.

It is very easy to mistake regular noise as being something else. Since your life & safety are dependant upon knowing your VEHICLE, dont take the chance of it being incorrectly diagnosed.

I cannot express it more firmly. All mechanics are human & make errors. If any of you all are ever stranded out here in Seattle, Wa I will be glad to help out however I can. Peace!
 

Big Scooter

Veteran Expediter
Charter Member
Thanks for the help, again. The loud knocking began suddenly the day after the dessicant cartridge was changed and it is very noticable. It will be repaired tomorrow in Jacksonville, Fla. I really appreciate the help I can depend on at EOL.
 

Weave

Veteran Expediter
Charter Member
I like streetsweeper's comment on "quality shop." That is the place to find. I have not had too much luck myself at the shops of big dealerships when desperate to use them. If I can't handle something myself, I'm glad to know I have an independent shop near my home that is honest and accurate. These are the people you should get to know somewhere near your home town, as most of them don't have any trucks to sell and are only interested in repeat service, which will only come about by doing the job right the first time, which is what a professional is paid to do. How many second chances do we drivers get to deliver freight on time, undamaged, and in a courteous manner with all the variables we have? That is where streetsweeper is right again.. it is best to know your specific vehicle in and out, as all of its variables become yours, and drivers should take specific note of things they see and hear, or changes in performance, and write them down. That way a quality local mechanic (who will become a friend and know the history of your vehicle) can not only find things that may cause an on the road breakdown, but will also listen to your concerns. Best of all, they most likely won't try to rip you off.
Plus, if they are an ASE certified shop, their diagnosis will be accepted by dealerships for vehicles that are under warranty. That in itself prevents a lot of run-around and gives you a little peace of mind.
-Weave-
 

Shoreland

Active Expediter
I have a problem with a 2006 International day cab. It is freezing up all the time. There is always a lot of moisture in the tank. The air dryer is working perfectly. (just replaced). The tanks are drained daily but when it gets cold the moisture freezes before you can drain the tanks.
Any ideas?
 
Top