Intermittent AIR Problem

bevans6 · January 14, 2010, 07:11:11 AM

We're having a heat wave up here, forecast is up to 35 degrees today. Fahrenheit. All of a sudden the difference between Celsius and Fahrenheit really means something...

Brian

Ed Hackenbruch · January 14, 2010, 07:16:40 AM

Well i just checked the forecast for here and we are supposed to be a little cooler today, and we do have a wind advisory which means we are likely to have a dust storm later today.

luvrbus · January 14, 2010, 07:17:28 AM

Brain, I'll stick with 130 #per Eagle if you check most air brake chambers are good up to 120 or 125 # max depending on the manufacture.As per my instructor in the Bendix school follow your manufactures recommendations so if MCI says 150 # so be it.
FWIW some Eagles are a 150 # for the dual air system and are regulated to the brake chambers but mine is 130 #

good luck

bevans6 · January 14, 2010, 07:40:00 AM

I'm curious now, what is the governor cut-out pressure normally set to on the Eagles? MCI calls for 115 - 118 psi, the bendix data sheet referenced 125. Mine is actually set to 118. I wonder what pressures the non-adjustable ones (the ST-3) are available in? the sheet doesn't mention, it just says the pressure setting is stamped on them.

I guess I should take mine off and test it. You are supposed to maintain it every 50 K miles. I wonder what the true average maintenance interval in practice is?

Brian

John316 · January 14, 2010, 08:16:16 AM

Quote from: Ed Hackenbruch on January 14, 2010, 07:06:53 AM
Rain? ...you got rain up there? Really? clear skies and 85 degrees here in the Foothills yesterday, and clear skies again this morning. Only had rain one day since we got here on the 27th of Oct.

Just quit raining in Tucson. Now the sun is coming back out. Outside it smells so good and clean...very nice.

God bless,

John

Busted Knuckle · January 14, 2010, 08:31:59 AM

I haven't read the manual on either MCI or Eagle in so long I could not quote it word for word.
But I learned a lot from a guy who had & maintained 13-14 MCI's at a time (yeah he had poor taste, but knew his stuff!) and you could jump in any one of his MCI's and fire it up and in just a couple minutes it would be up to around 140 and spitting and would run right at 140 all day long! He has been around buses much longer than I have and has "been doing it this way for ever!" in his own words.

Personally I usually set mine up for 125-140. FWIW

Also we could not find anything wrong with Nellie's bus except it would not build air and or first thought after adjusting the governor. And pulling the hose off the intake and finding it wasn't drawing any air either was that #1 it either had hung unloader valves or had broken or stripped the fiber drive gear, or sheared the key!
But when driving it back to Jack's and it went to 150-160 I knew the drive gear and key way were fine! So I'm still guessing unloaders, but once I thought I was wrong, and it turned out I was mistaken!

Jack shouldn't need much more than an inch to remove the intake manifold if you can get the bolts out. The hardest part would be getting in there with your needle nose pliers to swap parts (if you can get a kit that is!). But then again, I'd think that a guy who retired from being an EMT might have some hemostats with curved ends laying around somewhere!

BK

Jerry32 · January 14, 2010, 09:57:45 AM

I have put air to my air system and when trying to go over 130 lbl it starts dumping air continuosly. The weather is sunny every day in Yuma. Jerry

Lin · January 14, 2010, 10:24:06 AM

The governor is certainly cheap enough to just change out on suspicion. Although I have heard of cleaning the old one up and keeping it as a spare, I am not sure it is worth doing. I did do that with my last bus, but it had a governor that is no longer manufactured and cost over $100. if you could find someone with old stock. I would think that most of the time, if you are going to the trouble of changing out a part, you might as well use a new one instead of one that will just probably be okay. That is, of course, unless you really want to set yourself up for another repair since that is part of the hobby. I bet there are some busnuts that would find a lack of failures and problems terribly frustrating.

bevans6 · January 14, 2010, 10:32:52 AM

"I have put air to my air system and when trying to go over 130 lbl it starts dumping air continuosly."

If you air up your system with external air, and go past the cut-out pressure of the governor, the governor will sense that and signal the air dryer to purge. The air dryer purge valve opens and dumps air. Since the governor can't signal the external compressor to stop supplying air the way it does to the bus compressor, the air feed continues and the air dryer continues to purge all of the supplied air. It will continue to do so until the supply pressure falls below cut-in pressure, when the governor tells the air dryer to stop purging. I set my compressor that I use to externally fill the bus to below cut-out pressure so that this doesn't happen. In other words, it's normal.

Brian

Busted Knuckle · January 14, 2010, 11:13:46 AM

Quote from: Lin on January 14, 2010, 10:24:06 AM
The governor is certainly cheap enough to just change out on suspicion. Although I have heard of cleaning the old one up and keeping it as a spare, I am not sure it is worth doing. I did do that with my last bus, but it had a governor that is no longer manufactured and cost over $100. if you could find someone with old stock. I would think that most of the time, if you are going to the trouble of changing out a part, you might as well use a new one instead of one that will just probably be okay. That is, of course, unless you really want to set yourself up for another repair since that is part of the hobby. I bet there are some busnuts that would find a lack of failures and problems terribly frustrating.

Lin while it is true that it is cheap enough to replace them with a new one.
#1) it's not always practical. Say at midnight on a lonely stretch of hwy, or out in the backwoods miles & miles from nowhere. Or in bad weather where it's easier to pull one out of a bay and change it than to unhook a toad and go find a new one (or worse yet find a ride if you don't have a toad)
#2) even new ones can be bad. (we had one go back on the way to FL and had it replaced by WW Williams $260.00 w/service call to McDonald's where we were and group could get off the bus! And then once in Florida it had to be replaced again by Orlando Detroit Diesel Allison for another $58.00 parts & labor total)

Also they can be remote mounted to make them easier to get to and replace or adjust! (our Setra's come that way from the factory!)
FWIW

BK

gus · January 14, 2010, 04:53:30 PM

When my governor failed it would build up air just fine but to 150psi when it should have been 82!

Lin · January 14, 2010, 05:57:42 PM

BK,

Agreed, having a spare part can be useful. However, since even a new governor can be bad, it would seem that one is being particularly optimistic in a believing the bad one you removed, cleaned, and never tested is a dependable backup. It may be better than having nothing, but it would be better to keep another new one as spare. I realize it is highly unlikely that anyone would do it. I know that if mine failed I would do exactly as you say, but when the time came to use it, I would only do so if it was unavoidable.

DaveG · January 15, 2010, 04:22:38 PM

Bryce, when you replace D-2s do you use reman or new, OEM or aftermarket?

Busted Knuckle · January 15, 2010, 04:44:26 PM

Quote from: DaveG on January 15, 2010, 04:22:38 PM
Bryce, when you replace D-2s do you use reman or new, OEM or aftermarket?

Yes.

OK yes all of the above mostly depending on what is readily available at the time. If I can get new I try to get NEW regardless of OEM or after market. If all I can get is re-manned then re-manned is what I get! HTH FWIW

BK

gus · January 15, 2010, 08:51:23 PM

I agree with Lin, new ones are only $20.