Where is the unlaoder valve on the cummins 250?

[Hammer]

My unloader valve is bad. I get constant bleed off of air from behind the dash. To be expected there, but I am unsure of where the unloader valve IS on the cummins motor.
I know where it is on the multi fuel. Seen a few posts on that in the deuce sections. But the air compressor on the 250 doesn't look like that.

Unless I am just missing something, and it's right there in front of my face.

 

[bigelk50]

Ed, I am not sure where it is, my 818 does the same as yours. I also have to drop my lower air tank and fix one last leak. I thought that way why it bleeding off from behind the dash. Guess not.

 

[Hammer]

My paperwork shows the defects found on the truck when it was inspected for 'release'. It lists it as 'Unloader valve leaking - C2'.
And cost of parts as $3.43, and 2 hours of labor to repair (not replace). So it sounds like it either needs a little work, or it's a gasket issue maybe.

 

[bigelk50]

Yeah that could be. I have not located mine but can hear it. Sounds like it is near the firewall and probably easy to get to. I just have not tackled it yet.

 

[doghead]

The unloader valve is part of the compressor(just follow the smallest line connected to the air governor). The air governor, is the part that is mounted on the firewall.

 

[Hammer]

Thanks, will do.

 

[groundog]

Hammer--I just re-placed my air govenor--it was clicking pretty loud when it shut off compressor---also check low air pressure switch mounted on inside of firewall just to right of steering column---they leak air thru a smaal hole in the side of switch----Groundog

 

[Hammer]

Well, just got back in from completely pulling the unloader valve apart, cleaning it up, sanding down some parts, and putting it back together.

Then, guess what, I traced the 'final' (I hope anyways), air leak to....

the low air pressure switch.

Is that the same part that is used on the deuce?

 

[groundog]

yes---they are the same---note in previous reply i suggested checking low pressure switch----bendix makes the part as well as a couple of other suppliers----groundog

 

[Hammer]

Yeah, you got that one right!
The unloader valve did need work though.

 

[groundog]

Hammer--glad to hear yours had a fresh engine--did you preview it or a stroke of luck/----groundog

 

[Hammer]

Luck based on a guess on the pictures of the engine, and the spedo reading 26 miles and only 7 hours.

 

[vinny-socom1]

I'd like see what was fixed & cleaned!!!

Vinny

 

[Hammer]

Not much to talk about.
Two bolts with washers hold the setup down. And undo the air line.
There are a few things that come out, have o rings on them, and have washers between the parts.
Was that vague enough?
Honestly though, pull it apart and just clean up the rusty stuff.
If the O-rings are bad, or the parts are too rusted, then you need some new parts. Otherwise cleaning it up should make things work OK. Mainly the sitting for long periods with junk in them makes things not move well.

 

[Hammer]

yes---they are the same---note in previous reply i suggested checking low pressure switch----bendix makes the part as well as a couple of other suppliers----groundog

And I pulled that apart as well. Cleaned it up, made sure the diaphragm was in good shape, put back together, tested with air pressure.
All works good now!

You should see the SLUDGE that is in the air tanks! I guess 700 miles of constantly running will blow a bit of oil into the tanks because of the crusted up unloader valve.

 

[groundog]

glad to hear things are shaping up---all of the trucks usually need a little work---have been cleaning axles and drive shafts with engine cleaner and wire brush befor re-paint---my low pressure valve also leaks---will disassemble and clean like you did and hope it works----Groundog

 

[Hammer]

Funny thing, the low pressure setup wasn't really that dirty. A little grime in there (probably from the sticking unloader valve). Otherwise it was in good shape. I just pulled it apart, wiped it all down, inspected for cracks in the rubber, and put back together.
Hardest part was laying on my back to get that sucker out of there!

 

[groundog]

you are so right-----hard to get to---have you ever re-placed the rubber brake hose from the frame to the top of the front axle---I replaced all rubber brake lines and wheel cylinders on my m-813A1---not fun------Groundog