Bus Conversions dot Com Bulletin Board
December 19, 2014, 08:24:20 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: New ownership began September 1st 2012!  Please send any comments to info@busconversions.com
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1]   Go Down
  Print  
Author Topic: Engine Vibration  (Read 1082 times)
TEAKNE
Newbie
*
Offline Offline

Posts: 20





Ignore
« on: July 15, 2010, 03:33:23 PM »

I have been working on my bus (PD4106 w/8V71 and 4 speed spicer) for several years now and recently I have been getting engine vibration at low to mid RPM but not noticeable at high RPM.  I have also noticed a “flat spot” when I press the accelerator petal. It will build RPM for the first half inch of petal travel then nothing for another half inch. After that the bus builds RPM normally. I have not noticed any loss of power or oil usage.  It is really noticeable when warmed up and attempting a dead throttle start.  Then the whole bus will shake.  It is also noticeable when shifting up through the gears.  I first thought I had a clutch issue, but I still have the vibration with the clutch pushed all the way in. Could I have clogged injectors and how do I find out which ones are plugged or do I have bigger problems?
Thanks
Logged
Lin
Hero Member
*****
Offline Offline

Posts: 4603

1965 MC-5a




Ignore
« Reply #1 on: July 15, 2010, 03:40:42 PM »

Could be several things I would guess.  Does is happen in reverse also? 
Logged

You don't have to believe everything you think.
TEAKNE
Newbie
*
Offline Offline

Posts: 20





Ignore
« Reply #2 on: July 15, 2010, 03:52:52 PM »

Lin,
 It will also do it in rev.
 Just a note..No strange sounds are noted and have not noticed any oil smoke or black smoke (unless I'm pushing it a little on a grade).
Thanks!
 Todd
Logged
Dreamscape
Dreamscape
Global Moderator
Hero Member
*****
Offline Offline

Posts: 3322


1968 Silver Eagle Model 01 8V71 Allison 740 #7443


WWW
« Reply #3 on: July 15, 2010, 05:32:27 PM »

We have an 8v17 in our Eagle. Have you checked your engine cradle? This is just a wild guess.
Vibration is not normal.

Maybe Clifford or Geoff will chime in.

Our foot feed is giving us a similar result, but I've dealt with it so far. It doesn't respond for about 1" of travel, then all is normal. The linkage is 42 years old and joints are worn. I'm assuming you have linkage.

Paul
Logged

Becky and Paul Lawry, On The Road
Travel Blog - http://dreamscapetravels.wordpress.com/
Bus Blog - http://dreamscapesilvereagle.wordpress.com/
______________________________________________________

Our coach was originally owned by the Dixie Echoes.
Bill B /bus
Sr. Member
****
Offline Offline

Posts: 267





Ignore
« Reply #4 on: July 15, 2010, 05:39:39 PM »

Replace the engine mounts on the cradle. The leaking DD engines soak the mounts in oil and they slowly deteriorate. Changed the engine mounts on a Buffalo and cured the vibration problem that was evident on take off and low to mid RPM. Another thing to check is the driveshaft and u joints. Bolts tight the rear end and joints tight and properly greased.

Bill
Logged

Bill & Lynn
MCI102A3, Series 50 w/HT70
luvrbus
Hero Member
*****
Offline Offline

Posts: 13121




Ignore
« Reply #5 on: July 15, 2010, 08:56:35 PM »

Could be the pilot bearing in the flywheel has gone bad also over time the flywheels will warp and the clutch will break springs causing the vibration doesn't sound like a engine problem too me

good luck
Logged

Life is short drink the good wine first
OneLapper
Hero Member
*****
Offline Offline

Posts: 561



WWW

Ignore
« Reply #6 on: July 16, 2010, 08:19:16 PM »

Teakne,

My 4106 had an engine vibration when i got it.  It eventually just got worse and worse.  I knew I had a "wet" cylinder, either from a cracked oil ring or a low compression. I never determined exactly what it was.  Injectors can easily give a vibration and are the one of the "cheaper" items to replace.

People are right in saying that a healthy 8V71 is very smooth at all rpms.  I have run my new engine on the garage floor several times to test things, and it was smooth with the original injectors in it, but even smoother with the new N65's I installed (I also advanced the timing, that might have affected things, but advancing usually makes engines run a bit rougher).

Good luck!  Let us know what you find.
Logged

OneLapper
1964 PD4106-2853
www.markdavia.com
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!