How would truck lose air pressure in the engine intake?

[SUPERSPORT]

1991 M923A2.

Replaced my rubber fuel lines today. Started truck and let it run about 20 minutes while I packed up my tools. Went for a 30 to 40 minute drive. Everything was fine.

When I returned, I backed in from the road to park. It has been dumping snow all day. The rear wheels broke loose as I hit a slight incline so I flipped the switch to kick in the front wheels. About another 30 feet and I was in my spot.

I flipped the switch back and went to set brake. The low pressure buzzer went off. I throttled up and built pressure but it was slow and when I let off pressure dropped like a rock.

I shut off truck to jump out and see where I was losing air. I could hear it through the air intake and that's it. The mushroom intake stack was hissing like crazy.

 

[gimpyrobb]

Sounds like a frozen valve not closing.

 

[simp5782]

Yea the air valve going off the transfer case dumps into the intake tube. Probably just stuck. Flip the switch a few times back and forth. If not you may have to hit the valve a few times

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[doghead]

Have you serviced the air system lately?

 

[SUPERSPORT]

Have you serviced the air system lately?

Serviced in what way?

 

[SUPERSPORT]

Yea the air valve going off the transfer case dumps into the intake tube. Probably just stuck. Flip the switch a few times back and forth. If not you may have to hit the valve a few times

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I assumed it was transfer case valve but had no clue it dumped into air intake. Freaked me out when I stepped out door and heard it next to my head in the intake.

It's supposed to warm up, relatively, on Friday so I'll probably go out and get the truck then. It's supposed to snow again and my daughter wants me to pick her up from school.

 

[simp5782]

Serviced in what way?

Drain the the tanks or cleaned the tanks. Maybe run some airline anti freeze thru it. Replaced your receiver dryer filter and/or cleaned the pop valve. Replaced any bad or slow leaking diaphragms on the brake chambers

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[Jbulach]

I assumed it was transfer case valve but had no clue it dumped into air intake. Freaked me out when I stepped out door and heard it next to my head in the intake.

It's supposed to warm up, relatively, on Friday so I'll probably go out and get the truck then. It's supposed to snow again and my daughter wants me to pick her up from school.

Quite a few valves dump into the intake, but as simp said, start with the t-case

 

[gimpyrobb]

Wh3n was the last time th3 air dryer was rebuilt? If its been over a year, id start there.

 

[74M35A2]

I get the one on the right, you get the one on the left.

 

[Jericho]

Strange you had the same problem, was about to ask it when I saw your post, has been 30 below here, drove it from CT where it was warm and parked it for two days, now front wheels wont engage and air hissing in the Intake snorkel , But going to be 40 on Sunday so we shall see

 

[74M35A2]

30 below? No wonder why it is not behaving....

 

[Jericho]

No , normal for here this time of the year, Trucks just like aircraft do ok once they are Cold Soaked and you get the bugs out, Just tkes a few weeks, Fuel was jelled as well Gota ask two questions, Is it worth installing a No Reverse In LOw Range linkage . and If you have the A/c brackets whats a good source for an a/c unit. Have you looked at the stand alone units? Ive heard all the No reverse Hoopla, but hve used it with no problems, just don't horse it hard in low reverse. check out weather for the Mount Washington Observatory New Hampshire . I look out my kitchen window at it. Home to the worlds WORST weather !

 

[Shirehorse]

Time to rebuild the air dryer.

 

[74M35A2]

I don't supply the entire A/C unit. Different people want different things, so all I do is provide an easy way to put a conventional sanden ear mount compressor onto the factory 8.3L serpentine belt drive, which up until this point, was the hardest part. I knocked down that barrier, and now it is low cost and simple to do.


I took a detailed inventory of the Lo-Reverse breakage data, and 100% said it only breaks if pulling heavily or the pedal stomped, like you said. Light usage seems OK. If only you drive it, and nobody else, you should be OK.

"s" key broken

 

[Swamp Donkey]

"s" key broken

I'm parting out a keyboard and the "S" key is in good condition. PM if interested...

 

[infidel got me]

Good thing he don't need a t key---- I heard they are really expensive!

 

[SUPERSPORT]

Drain the the tanks or cleaned the tanks. Maybe run some airline anti freeze thru it. Replaced your receiver dryer filter and/or cleaned the pop valve. Replaced any bad or slow leaking diaphragms on the brake chambers

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I drain the tanks everytime I drive or run it. That would be it. Truck has been on sideline due to life last couple years.

Been looking into buying new dryer but don't have the money right now.

 

[simp5782]

I drain the tanks everytime I drive or run it. That would be it. Truck has been on sideline due to life last couple years.

Been looking into buying new dryer but don't have the money right now.

Main culprit tank is the wet tank right in front of the air dryer. Thay catches all the crap mostly. Pull its drain line off at the tank then let ur truck run. Close off the primary and secondary valves there. Hold finger over drain hole to gain pressure and see what kinda crap comes out.

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[SUPERSPORT]

Yea the air valve going off the transfer case dumps into the intake tube. Probably just stuck. Flip the switch a few times back and forth. If not you may have to hit the valve a few times

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Made it out there today but only had a few minutes.

Flipping switch didn't help. Where exactly is the valve I should hit?
It looked like 3 of them on transfer case but I don't know what one does what. Didn't have a hammer with me anyway.