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bluebirdvision
Top Member
USA
1081 Posts |
 Posted - 02/16/2012 : 1:53:15 PM
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I work in the commercial bus industry. The fleet is comprised of almost all Thomas EFs. This particular bus has a Cummins ISB 5.9L engine. On low idle, the bus vibrates so bad that you can't hear ANYTHING. If the high idle switch is turned on, the vibrating quiets a little. Is there possibly something in the engine that is out of balance? It literally sounds like this bus is going to vibrate itself apart.
We have another (same year, MORE mileage) that doesn't vibrate at all. I thank the bus gods for the upgraded ISB-07 engine, as they are quieter! |
Edited by - bluebirdvision on 02/16/2012 1:55:10 PM
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08 Thomas EF
Top Member
533 Posts |
Posted - 02/17/2012 : 3:02:20 PM
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Our '01 TC with the ISB tends to vibrate a lot at the beginning of the school year when it sits over the summer. After a few weeks, it gets used to running again and smooths out. I observed this one year when I rode it, and its new driver observed it at least one year after that. I know it sounds strange.... It wasn't a constant vibration but it caused surges, or waves, of vibration. As time went on, the waves wound get farther apart and less severe until they disappeared altogether.
Our '91 TC vibrated the same way this towards the end of its life as a spare 3 years ago, too.
I guess they just don't like to sit around and do nothing, but that doesn't mean there isn't a problem. Is that bus infrequently used? |
Edited by - 08 Thomas EF on 02/17/2012 3:04:12 PM |
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bluebirdvision
Top Member
USA
1081 Posts |
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overbyja
Senior Member
USA
123 Posts |
Posted - 02/17/2012 : 6:23:06 PM
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| What year is the bus? We have quite a few 2005 All Americans (built in Canada in '03) with that engine that do the same thing. It's really bad when you first start them up, especially in cold weather. Things improve as the engine warms up, but they still vibrate some and sound like a deisel-electric locomotive chugging away. And I will also add that some are worse than others from the same year. It's unlike any Cummins I've ever heard, and I've driven buses as old as 1989 until the switch to the 6.7L. Maybe it was just that particular year as no other bus I've driven does that. |
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Edited by - overbyja on 02/17/2012 6:35:10 PM |
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bluebirdvision
Top Member
USA
1081 Posts |
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Thomas Ford 85-16
Top Member
USA
4177 Posts |
Posted - 02/19/2012 : 4:04:09 PM
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| Is there a low idle adjust switch? Our 1999 Blue Bird TC2000 FE has an electronic Cummins ISB, probably similar to your '07, and it has a low idle adjust switch. On the Blue Bird dash, it is located next to the high idle switch. The low idle adjustment allows you to vary the low idle between 500 and 900 or so RPM on this bus. That way if there is a speed that rattles the mirrors, you can adjust the low idle to move it out of that range. |
Mike's Bus Yard - http://buses.zwebpages.com - Since 1999
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bluebirdvision
Top Member
USA
1081 Posts |
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C24U
Advanced Member
United States
220 Posts |
Posted - 03/16/2012 : 07:11:37 AM
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| I bet if you remove the grille and put your hand back to the left of the radiator tank, you will find your vibration. There may be a rubber mudflap type splash shield in the way but reach past that and feel the panel to the left. Probably vibrating a nice tune for ya! |
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07 Thomas EF vibrating
