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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3325
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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I have 2010 freightliner century last six of the vin#AN2005.

Customer Question

I have 2010 freightliner century last six of the vin#AN2005. Air dryer has excesive sneezing(bursting air out) changed whole air drier. The valve on the bottom of the air drier keep bursting(loosing) air continues. Swap air drier with other new one samething. Changed air governor no luck. No idea what is wrong. Air tank not getting air.
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you.

Do you have the Bendix module style where the drier mounts right to the tank? If so, drain the air, then pull the module from the tank and start the truck. If there is air, the issue is the tank itself. You most likely have something caught in the check valve inside the tank. Most times when that occurs, you have to replace the tank.

If you are not getting air out of the module, then it is bad. The module is the square part the air dryer mounts to, then mounts to the tank.

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Customer: replied 1 year ago.

It's in the hood compartment near steering gear box right by bumper. Tank is new left tank had problem so we replaced it four months ago.

Expert:  Jeremy replied 1 year ago.

You have the one without the module.

If you break the line going to the tank, are you getting air out of that line? You did mention that the air is purging so that tells me the compressor is working and the unloader valve is allowing air to go to the drier. So that can be eliminated in the chase. Now it needs to be determined if air is leaving the drier to the tank or not. This will rule out that part of the system. Based on what I read, I'm presuming you are getting no build up at all?

Do this check right quick, If you have an air gauge, put it on the line that feeds the air drier and see if it builds up to at least 110. Shut the truck down if so and bleed that line off, then do the same on the line that feeds the tank from the air drier. This will help determine if the unloader springs are weak and it is going to unload mode or if the governor is set wrong on the system.

I would do that. If no gauge, then check for air on line from drier to tank. If air, then on the other side of the tank you have a 2 way check valve. It will have 2 lines, one going left and one going right out of the tank. Remove those lines and then start again to see if air is going out those lines. If not, the valve in the wet tank is plugged and not allowing air out of it to feed the two tanks. I have a feeling that your wet tank, the one on the right, is bad or plugged up and not allowing air to feed the tanks. The wet tank has a small tank in front of the main tank. It is part of the same tank. It is welded to it and you only know it is there by the weld marks on the tank. It is to keep the tanks from getting "shocked" by the air pressure from the air going to the tanks to keep them from blowing up. I bet that valve in it is messed up. It is only a 1/8 inch hole in the middle.

Customer: replied 1 year ago.

No if i take the line out that comes from air drier it is not getting air. But if I fill air in the same line from external air it fills the tank. Governor is new.

Expert:  Jeremy replied 1 year ago.

You already tried another air drier as well? Were the tanks filling prior to the air drier change out? If so, then I'm leaning towards the issue being at the unloader vavle or something connected wrong. It throw me off that you are getting air to the drier though telling me there is an issue with it, but if doing the same thing with another one, then it can only be something isn't connected properly or the unloader valve is sending air to the drier making the air purge instead of fill the tanks. I'm going to think thought that everything is connected properly since the issue was going on before and blame the unloader valve for the issues you are having.

Take the unloader valve off the top of the compressor, taking caution on the spring under the plate, and remove the parts to see if the o-rings on the valve are damaged or if the pistons look worn on it. If so, replace it with the kit. The kit is very inexpensive. It will be around $40 for the kit. Usually less. Then install the kist and you should get normal operation back instead of the valve sending air to the purge valve on the drier and evacuating all the air out.

Expert:  Jeremy replied 1 year ago.

What were you able to find out with this issue?

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