Cascadia DD13/DD15 compressor unloader valve

I could not find a video about this, so I made one. How to replace the unloader valve in your air compressor on a Cascadia with the DD engines without pulling the entire air compressor like Freightliner wants to do. They quoted a 10 hour job, I did it in two by removing the fender for access.

[@djibrilfall4030]

Hello! Did you solve your problem when you replaced the unloader vavle? Mine purge every 30 seconds too

[@cwmills76]

Yes it did.

[@djibrilfall4030]

@@cwmills76 I replaced the whole dryer assembly and it didn't fix the issues. Now the mechanic saying it seems normal. Mine is 2017 Freightliner

[@cwmills76]

@@djibrilfall4030 constant purging definitely isn't normal, but the unloader valve is on the air compressor. That constant Purge from your air dryer is due to an overbuild of air. The unloader valve is supposed to pop out when your air tanks are around 120 psi. If it is faulty, and it's not popping, your air dryer will Purge instead as a failsafe. You've already replaced the air dryer, so the unloader valve is your most likely culprit. After that, it's the entire air compressor, but that's pretty expensive so I would start with the unloader valve. As of right now your air compressor is constantly building air and under pressure, instead of relieving pressure through that unloader valve, and it will burn out your air compressor after a few months.

[@djibrilfall4030]

@@cwmills76 That is what I told him that it would be more wear and tear on the compressor. How long it took you to replace it? I am thinking about doing it myself best on your video

[@cwmills76]

@@djibrilfall4030 from start to finish it took right about an hour. That's including pulling off the fender and everything. Just make sure you get that right angle bit driver from Harbor Freight first. It's the only thing I found that you can use to remove the plate over the unloader valve. A screwdriver just won't fit with the way everything is stacked up above it.

[@nathanaeldiaz9036]

Hi thank you for this wonderful video , if you don't mind me asking where did you get the unloader valve from

[@cwmills76]

Picked it up from a little freightliner shop in Amarillo. Any freightliner should have them.

[@Ddprescot]

Thanks. Helpful video! Good bless!

[@vicpetrishak1077]

Yes , German over engineering at its finest ! Germans are capable of over engineering a toothpick .Replacing an air compressor on a (DD) is troublesome . They design the cabin and the engine without a floor plate to reach the air compressor .

[@ur_local_toodles]

Damn fix your steer tire man it’s worn out bad

[@cwmills76]

I have this set to not give me notifications, so sorry about this late reply. Meanwhile, 😒

[@TATEXPRESSINC]

I love the video

[@carloserazo4730]

Bro thanks so much for the video .. just finish working on my cascadia ..I fallow the video and I replaced the part and fix the problem

[@cwmills76]

Sure thing. Glad it helped.

[@platinimichel5067]

What if the purge valve is stuck open at 60 psi and wrong build? Just installed a new governor and air dryer unit. I’m suspecting unloading valve.

[@AmrikSingh-rw6ew]

I know they are pain to replace. Great video thanks .

[@mikerodr]

Thanks for the video

[@TATEXPRESSINC]

Great job on the video👍🏻

[@mikerodr]

Watch wes work also has a good video on the constant purging

[@mikep6014]

Do you clean the inside of compressor where the valve goes?

[@cwmills76]

Yes, as best you can. I used my air line with the spray gun attachment. Another guy commented regarding cleaning, as well, but I was only able to spray the valve seat. The primary reason these go bad is carbon build up, leaving them unable to properly seat, so you want to do whatever you can.

[@mikep6014]

@@cwmills76 thank you for the info.

[@cwmills76]

@@mikep6014 Anytime.

[@RayMuoio]

Here is a video of job

[@robertcussen8039]

oh my gosh, you just saved me from unbolting my air compressor. The longer screw is an awesome idea! Thanks!

[@cwmills76]

I called a mechanic, and he said the same thing. "Gotta pull out the compressor on those models." Or get creative. Either way.... 👍

[@truckerdaddy7124]

How did you get to the plate???

[@cwmills76]

I pulled the driver side fender, so I can get some space to get into there, and use a right angle bit driver to get to the screws.

[@The-tw3qg]

Where can I get the screws. Can you take a picture of the front of the box

[@cwmills76]

I don't think I have a set right now. It was the assorted screws and bolts from the T/A. The machined threads.

[@The-tw3qg]

OK thank you I like your video I will definitely try it out when I’m going to remove the unloader valve I started a new job as an apprentice so I’m trying to learn any tricks that makes my job easier

[@samvirginia4116]

Hey man thank you for the video ,I’m sitting on ramp having difficulty to open the plate screws which way should I go it’s impossible to get there please share your experience how you reached there 🙏

[@cwmills76]

That's what I used the right-angle wrench for. It's the only thing I could fit in to the plate. I pulled the fender to get the space to reach in.

[@samvirginia4116]

@@cwmills76 thank you brother for replying me back I’m gona search harbor freight near me sitting on exit 30 interstate 81 north Tennessee ,God bless you ✊

[@cwmills76]

@@samvirginia4116 Sure thing. That's where I got mine. It's a right angle bit wrench, for the T10(?) Bit to fit in.

[@samvirginia4116]

@@cwmills76 got it

[@sky2cpittman341]

​@@cwmills76h

[@makincash3337]

What does the unloaded value do

[@cwmills76]

Your air compressor fills the air tanks, and when they get to the correct PSI, the unloader valve pops to allow air to escape instead of going into the tanks. Once the pressure drops, the unloader valve seats and allows air to flow through, again. This is why the air dryer continually Cycles if your unloader valve is not working. Air keeps pumping into that air dryer, to go to the tanks, but once the pressure builds too high, the air dryer release valve pops if the unloader valve isn't working correctly.

[@bilalgorsi]

Thank you

[@joeyslaughter5791]

I’m getting a terrible rattling sound when my air compressor starts building pressure and it gets quiet once it tops off at 125 psi. Do you think that valve could be the problem?

[@cwmills76]

It is a distinct possibility. Your air compressor is always running, and it is the valve that directs that air. There are several other parts in that system that are only under load while it is building air into your tanks. It could be that valve, something with the air dryer, the lines, or something else. If the rattling is coming from the air compressor though, I would start with that valve.

[@joeyslaughter5791]

@@cwmills76 thanks for the quick reply.

[@cwmills76]

@@joeyslaughter5791 Sure thing. Hope it helps.

[@joeyslaughter5791]

@@cwmills76 you were right. My mechanic replaced that valve and it fixed the problem. Thanks for the video!

[@cwmills76]

@@joeyslaughter5791 sure thing. Glad I could help