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Old 02-18-2007, 10:02 PM   #1
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Joy....Elation.....Uggghhhh!

I was up north for my neice's birthday today and decided to go start the bus. It has been 3 months since the thing last ran . Before I put it away, I did run it with some good additive long enough to get it fully circulated through the fuel system. So here it goes....

It was 15 degrees today and 10 when I went to the bus. It is 500 feet from the nearest outlet so the block heater and a battery charger were not an option. I opened the hood and checked the fluids. I gave it a 2 second blast of ether in the air filter housing (there is no convenient ether port) and pumped the injecter pump primer about 5 times just to make sure it was good and solid. I also broke the rules and connected my house batteries since I only have a Group 27 starting battery rated at 750 cold cranking amps. One crank on a deep cycle can draw it down to 50%, but I wanted one good crank. I climbed in the seat and turned the key.

5 seconds...cranking SLOW

10 seconds...picking up steam

15 seeconds...almost there is seems

20 seconds...BOOM! She fired!

It was grumpy for the first 20 seconds or so, but immediately built oil pressure and smoothed out pretty quick. I let it idle for a minute or two and then slowly started to bump the idle up to 1300 rpm or so.

Oh sweet success! Remember...it's been sitting for 3 months without a block heater, glowplugs, or intake heater. I honestly don't even think the ether did anything. That was pure compression! I've developed a liking for the 6.6 Ford.

I let the thing run for 10 minutes and then started to go through some fairly normal procedures. I preheated the transmission per the Allison owners manual. I also completely filled the valvebody by shifting N-1-N-2-N-3-N-4-N-R-N.

Then I moved on to the brakes. I had stored it with the tanks drained, but it had built pressure up just fine. I shut the engine down and fanned the brakes down to 0 psi. I then started it back up and set the throttle at 1200 RPM while I timed the pressure build. It took exactly 3 minutes to go from 0 to 120 psi. I backed the parking brakes off with a clunk (it sits on an ever so slight incline where it is parked), and pulled the bus forward and back a few times just to get things moving. Then I put the parking brakes back on and tested leakdown.

It holds pressure just fine during an apply. It does use what seems like a high volume of air (2 applications take it from 120 psi to 90 psi), but I know a chamber is out of adjustment. It's stroke is 1.5 inches and goes just over 90 degrees whereas the rest go about 3/4 of an inch and stop at 90, just like they should.

However.....something goofy started happening. As I watched the pressure gauge, it started to dance a little. I went from 125 psi down to 115. The compressor kicked in and brought it back up to 120. Weird, right? I decided to fan the brakes down until the pop out released and watched again. It built pressure at what seemed like an inconsistant speed. It went from 65-90 rather quickly. Then it slowed down from 90-115 and sped up again from 115-125 before the air dryer kicked it out and it went back to 120. Then it went down to 115 again, followed by cut in to 125 and kick out. It then held at 120. I fanned the brakes a few more times. Sometimes it would cut in at 115. Sometimes it would cut in at 90. Sometimes it would cut in at 85.

My plan of attack is to adjust the pot that out first of all. Then I was thinking I would replace the governor though that really doesn't seem like a governor issue because it does build good pressure and it does kick out. I know I want some new petcocks on the tanks as mine just feel like they might be leaking very slowly and I want air chucks anyway. Is this just the cold and the sitting time making things finicky? Do I really have anything to worry about? It passes all the leakdown tests, pressure build test, etc, but the governor is weirding me out. One other noteworthy point. It will go from 120-~80 psi overnight. A leak obviously, but nothing horrible. However, it will hold at 80 psi then for a long time. Is it time to look at the checkvalves at the tanks? Is there a chance that diaphragm in the front chamber has a pinhole leak that requires over 120 psi to leak down? If that's the case, why is it doing it without the treadle applied?

I think I might just be paranoid about the whole thing. I pass all the test, aside from the brake being out of adjustment, but I knew about that when I parked it and it should only take 5 minutes to fix. Does anyone have any ideas? The bus isn't going to move until Spring anyway, but I would like to have a heads up here and I would REALLY like to have reliable brakes. I guess I'm just old fashioned that way...
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Old 02-18-2007, 11:25 PM   #2
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Is your air dryer functioning? sounds to me as though you may have got a little moisture in the governor, and it froze.

chances are real good that come spring time, drain the air tanks, adjust the chamber, and you will be fine.

We sometimes have problems with the check valves too, but thats usually in the winter time... such as now. and since the vehicle hadn't been run for a while, I'm sure its just something simple like frozen moisture somewhere.

I take it your bus is not equipped with automatic slack adjusters?



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Old 02-18-2007, 11:27 PM   #3
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That's what I'm hoping. Never once have I had water in my tanks. I have a heated air dryer that has always SEEMED to work great. I've never had a frozen line, or water in the tanks and it always gives me that reassuring "psshhhht" at 120 psi so I THINK it's working just fine. I guess we'll see what happens this spring. I just want to be prepared should I need to shell out some cash.
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Old 03-03-2007, 12:48 AM   #4
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Just reading through all the older posts. I would agree and see what warmer weather brings.
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Old 03-03-2007, 01:43 AM   #5
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automatic slack adjusters on a bus.....does anybody have those? Our fire trucks have them and they are a pain to try and adjust manually when the automatic gizmo doesn't do it's job because the truck sits most of it's life. After 15 or 20 years our trucks usually have about 10k original miles on them. Lots of sitting.

manual slack adjusters are fast and easy to adjust. I was going to put together a photo tutorial all about how to adjust air brakes.....but i don't think i ever got around to it.
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Old 05-06-2007, 02:12 AM   #6
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Ok...so the bus came down to Duluth with me this weekend.

The air brakes, aside from needing a good cleaning and lube seem ok. The compressor built just fine and didn't cycle obnoxiously. However, my air dryer seems to be at fault for my problems. It keeps purging every 1minute or two. The compressor isn't coming on at all...it's just purging from the air dryer. The tanks are still dry which is reassuring.

So...do I need to find a new cartidge for the dryer or is it possible that the purge valve is just bunk or what? How much do the cartridges run? Are the purge valves replaceable? Should I just be looking to buy a new air dryer?
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Old 05-07-2007, 03:19 PM   #7
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TTT

No ideas anyone? Do I really have to break down and crawl under there to look at tags and start calling around?
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Old 05-07-2007, 09:45 PM   #8
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New update....

I adjusted all the brakes (only one was out, but I checked all 4) and drained the tanks. There was no noticeable moisture in the tanks. The bus still builds pressure fine and within time limits and everything seems to be ok. Except....

The air dryer continues to do its rapid cycling. However, I noticed when I had the hood open that the compressor kicks back on right after the dryer purges. It doesn't run for long....not enough to even notice on the air gauge inside, but it certainly is running. It kicks out and the air dryer purges and the process starts over again.

Fanning the brakes down and the compressor won't cycle on until 90 psi and will kick out at 120, just like it's supposed to....then it will start doing the purge-kick in thing again...unless I fan the brakes down to say 100 psi where it will stay until until I use enough air to kick the compressor back in again.

I'm at a loss here. I'm not sure if it's the air dryer or more likely my governor. I hate to start just replacing parts until the problem is solved. Does anyone have some input?
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Old 05-09-2007, 04:18 PM   #9
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The dryer is supposed to spit each time the compressor cycles. So the dryer is fine.

Sounds like the regulator on the compressor is "short cycling" (if that's the term?).
You might want to ask a mechanic about that. I've lost a couple of regulators
on the road over the years, so we know they can go bad.

(I've also had one freeze, which resulted in uncontrolled pressure and a loud bang,
but that's a story for another time. )
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Old 05-09-2007, 06:09 PM   #10
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Well I went to NAPA and a new governor for my compressor (Bendex p/n 104433) is $18 so it's not going to break the bank. They even had one in stock...they just couldn't find it. When they find the one I needed or get another one in I'm going to go pick it up and try that out. The old one is heavily corroded and just plain nashty looking anyway on the outside so it makes me wonder about the inside.

Any special precautions for the removal of this thing besides discharging the air in the system and taping the connections when I put it back together?
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