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Author Topic: Help needed - frozen air valve, not building pressure  (Read 4553 times)
Tenor
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« on: December 07, 2008, 12:29:27 PM »

I need to take the bus to Detroit tomorrow, so on Wed. I aired up the bus with my air compressor to check for leaks.  Everything aired up fine.  Today, I fired up the bus to get some diesel, and it will not air up.  I have a large air leak/release either above the wet tank, or on top of the brake relay valve.  I have pressure at the dry air tank and I confirmed that by checking the pop valve that has a wire to pull.  I get no pressure to the air gauge, no air to any of the accessories and no air to the engine shutoff system and no air to the rear airbags.  The front airbags have never come down.  Where should I look to clear the blockage?  Thanks!
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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
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« Reply #1 on: December 07, 2008, 12:44:24 PM »

I would suggest letting it high idle for awhile, with luck the heat from the engine will warm things up enough to clear whatever.  if there is anyway to cut the supply to the area that is leaking that would help too as the air rushing by will keep thing too cold.  BTW in Canada when I want things to warm up I block of the rad with a piece of plywood or carpet or whatever  between the fan and rad. 
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Tenor
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« Reply #2 on: December 07, 2008, 01:18:41 PM »

Some more info - the air leak is the safety valve  on the wet tank.  There seems to be very little air getting into that tank.  Any thoughts?
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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
niles500
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« Reply #3 on: December 07, 2008, 01:58:13 PM »

Did you try a light touch with a hot wrench?
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- Niles
Tenor
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« Reply #4 on: December 07, 2008, 04:25:50 PM »

More update - installed the alcohol mister, and I'm putting air line antifreeze into the system after the dessicant canister, based on the advice of a long time trucker.  Any other ideas? 

I'm not sure where I would put a hot wrench...
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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
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« Reply #5 on: December 07, 2008, 05:40:12 PM »

Do you have an automatic drain valve or dryer, it may be frozen.
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PD4107-152
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« Reply #6 on: December 07, 2008, 07:00:47 PM »

There is an old air dryer, it has a 24v connection, but I have no idea how it works.  This particular one is not in my manual.  It is a welded unit that I have not seen how to open. 

More update, I am getting air to the brakes, but not the parking brake release valve.  No acessories work yet and the airbags are still down in the rear.  The fronts have never come down.
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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
Sojourner
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« Reply #7 on: December 07, 2008, 07:08:52 PM »

Old Post About Frozen Air System (Left Click)

BTW...even if you install the alcohol system now while below 32F, it will not always get thorough the blocked air line passage until air is flowing to let alcohol work and it will not fully removed water from tank until in warmer melting temperature.

The Bottom-Line is to always manually drain all tanks before stored in freezing climate or stored in a above freezing temperature building.

FWIW

Sojourn for Christ, Gerald
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« Reply #8 on: December 07, 2008, 07:18:24 PM »

Bendix Air Dyer (left click)

About the 24v connection....that is heater next to the purger valve to keep it from sticking open and frozen shut.
The 24v is connect to engine run switch.

FWIW

Sojourn for Christ, Gerald
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Ps 28 Blessed be the LORD, because he hath heard the voice of my supplications. The LORD is my strength and my shield; my heart trusted in him, and I am helped: therefore my heart greatly rejoiceth; and with my song will I praise him
makemineatwostroke
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« Reply #9 on: December 07, 2008, 07:26:23 PM »

How much pressure is showing on your gauge, if it is frozen it should read 0 sounds like the air dryer to me remove the 1/4 inch line for a few seconds then reconnect and see if that helps   have a great evening
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Tenor
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« Reply #10 on: December 08, 2008, 06:01:22 AM »

Thanks for the tips guys!  The air dryer is not frozen up.  My air dryer is in line between the compressor and the discharge muffler and is plumbed with at least 3/4 inch hose and then 1 inch output.  I am getting air into the service brake system, but the parking brakes do not release. 

I did drain the system this fall, but I believe my garage air compressor pumped condensation into the bus on Wed. when I aired it up.

Makemine, the air gauge is staying at 0, and I think you meant for me to try disconnecting the air gauge line? 

Thanks again!

Glenn
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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
makemineatwostroke
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« Reply #11 on: December 08, 2008, 06:23:00 AM »

No, Tenor disconnect the 1/4 inch line on the dryer from the compressor governor for a few seconds ,have you tried using a large space heater the forced air type   
have a great day
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Tenor
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« Reply #12 on: December 08, 2008, 06:54:05 AM »

Makemine, there is no 1/4 inch line on the air dryer.  The only lines are the main input about 3/4 and the output which is about 1 inch.  There is a fitting on the bottom of the dryer that an air line could be attached to, but I assumed it really was there as a drain.  The compressor has 3 lines, one to the alcohol dispenser, one to the air line right above on the ceiling and another heading to the clutch assist.  It seems that all of the items that are not functioning are from the circuit running from the clutch assist.  Gerald, thanks for sending the pictures, but mine is different

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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
luvrbus
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« Reply #13 on: December 08, 2008, 07:30:38 AM »

Tenor, reading here maybe some of the guys could answer a question for me because I have never saw a air dryer that did not have a governor line ran to it how does it work ? do you have a photo because this sounds more like a filter or a ping tank. good luck and I hope you solve your problem
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« Reply #14 on: December 08, 2008, 10:51:54 AM »

I'd dump more alchol in, although I've never done this to my bus, therefore I'm not sure where to dump it. I have although taken the main line off of the compressor on big trucks several times and dump in as much as it will take, restart the engine a wait. Has worked for me each time.
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