Free 7 Day Trial RV GPS App RV Trip Planner Campground Reviews RV Maintenance Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
 
Old 06-18-2021, 04:23 PM   #1
Skoolie
 
Join Date: Jun 2015
Location: Toledo OH
Posts: 103
Year: 2006
Coachwork: Thomas
Chassis: Saf-T-Liner EF
Engine: Cat C7 + Allison MD3060
Cat C7 rattling/knocking at specific throttle level

Caterpillar C7 engine owners: do any of you have issues with a knocking/rattling sound at certain levels of throttle? This only seemed to happen when going up a slight incline at 65mph, the top speed of the governor.

https://youtu.be/4mCHMME9N0A

dbsoundman is offline   Reply With Quote
Old 06-18-2021, 05:15 PM   #2
Skoolie
 
Join Date: Oct 2018
Location: Central Alabama
Posts: 220
Year: 1998
Coachwork: Blue Bird
Chassis: TC/2000
Engine: 5.9 Cummins 12-valve
Rated Cap: 1
The idler pulley would be the first thing I would check. Or the fan bearings since it's when the fan should fully engage.
BamaBus is offline   Reply With Quote
Old 06-19-2021, 10:20 AM   #3
Mini-Skoolie
 
DtotheAmbrose's Avatar
 
Join Date: Feb 2020
Location: Way Out West
Posts: 38
Year: 1990
Coachwork: Century
Chassis: C5500, Bus not a School Bus
Engine: 3116 9YN, CAT, 250HP
Rated Cap: 30k
Quote:
Originally Posted by BamaBus View Post
The idler pulley would be the first thing I would check. Or the fan bearings since it's when the fan should fully engage.
I had the tensioner pulley do something similar only under heavy load pulling hills. It looked fine visually when the truck was idling, when the belt was removed you could really tell it was dying.
DtotheAmbrose is offline   Reply With Quote
Old 06-19-2021, 11:54 PM   #4
Bus Nut
 
Simplicity's Avatar
 
Join Date: Aug 2019
Location: Auburn, WA
Posts: 682
Year: 2000
Coachwork: IC / Amtran
Chassis: 3000 / 33' Flat Nose
Engine: IC T444E / Allison MT643
Rated Cap: 72 Kids / 48 Adults
Once it has started to knock, what do you do to make it stop?

What speed does it start to happen?

While it could be a pully, I'm wondering, since you said it starts knocking at it's governed speed, if it's trying to "govern" the speed and it's "knocking" against that governor limit??
__________________
Steve
Simplicity is offline   Reply With Quote
Old 06-20-2021, 09:21 AM   #5
Skoolie
 
Join Date: Jun 2015
Location: Toledo OH
Posts: 103
Year: 2006
Coachwork: Thomas
Chassis: Saf-T-Liner EF
Engine: Cat C7 + Allison MD3060
Quote:
Originally Posted by Simplicity View Post
Once it has started to knock, what do you do to make it stop?

What speed does it start to happen?

While it could be a pully, I'm wondering, since you said it starts knocking at it's governed speed, if it's trying to "govern" the speed and it's "knocking" against that governor limit??
I think itís more of an RPM/torque level combination. It will happen briefly when accelerating from a stop to say 35-45 mph. It happens consistently when climbing small inclines at the governor limit I think just because I hit that magic RPM level. My tach doesnít work but I have a BlueFire so I plan to monitor it next time I go for a drive.

Basically, the way to get it to stop is to take my foot off the gas, or get the transmission to downshift.
dbsoundman is offline   Reply With Quote
Old 06-20-2021, 01:42 PM   #6
Skoolie
 
Join Date: Oct 2018
Location: Central Alabama
Posts: 220
Year: 1998
Coachwork: Blue Bird
Chassis: TC/2000
Engine: 5.9 Cummins 12-valve
Rated Cap: 1
Quote:
Originally Posted by DtotheAmbrose View Post
I had the tensioner pulley do something similar only under heavy load pulling hills. It looked fine visually when the truck was idling, when the belt was removed you could really tell it was dying.
You're right. The tensioner and/or it's pulley is more likely.
BamaBus is offline   Reply With Quote
Old 06-21-2021, 07:24 AM   #7
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 23,293
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
sounds like a pulley or engine accessory to me.
__________________
.
Wear A Mask- Stop the Spread!
EastCoastCB is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 08:48 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.