Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
Thread Tools Search this Thread Display Modes
Old 10-07-2012, 03:08 PM   #1
jmarmor's Avatar
Join Date: Sep 2012
Posts: 80
Running engine temperature

Cummings 400hp diesel. What temperature should it run at at around 1500-1700 rpm. Around 85 degrees outdoor temp. I run about 195 degrees ferh. Is that too hot? A few times this summer it was hitting 202 and the beeper was just starting to beep. This was uphill. If its too hot should I change the coolant and thermostat. The coolant was last changed 25000 (2008) miles ago but not the thermostat. Thanks

jmarmor is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 10-07-2012, 03:33 PM   #2
Senior Member
Cat320's Avatar
Fleetwood Owners Club
American Coach Owners Club
Join Date: Mar 2011
Posts: 4,977
I normally run a shade under 200 in all temps.

2014 American Eagle 45T
DD 500
Pulling a Honda CRV
Cat320 is offline   Reply With Quote
Old 10-07-2012, 04:23 PM   #3
Join Date: Jul 2012
Posts: 86
That is a perfect temp. I would worry and shut down around 220, dont let it run any warmer than that.
We had a fleet of large diesel pusher 84 passenger school buses here that ran the 5.9 Cummins, way too small for that size of bus and they tended to run real hot in the summer.
You also dont want a diesel that runs too cool either, it causes incomplete combustion and the unburned fuel can washdown cylinder walls. I say this if you have run that runs less then 160 degrees.
vegas39 is offline   Reply With Quote
Old 10-07-2012, 04:32 PM   #4
Senior Member
Tony Lee's Avatar
Join Date: Sep 2012
Location: Tasmania now, USA/Canada/Alaska in April
Posts: 2,419
Main cure for getting hot on long uphill grades is to turn off the aircon, manually drop back a gear to raise the revs to 1900 to 2000 and slow down.

Apart from that, it sounds as if there may be nothing at all wrong and in any case there are a couple of things that need to be checked before spending money replacing parts. Cleaning the radiator for one.
Tony Lee - International Grey Nomad. Picasa Album - Travel Map
RVs. USA - Airstream Cutter; in Australia - MC8 40' DIY Coach conversion & OKA 4x4 MH; in Germany - Hobby Class C; in S America - F350 with 2500 10.6 Bigfoot camper
Tony Lee is offline   Reply With Quote
Old 10-07-2012, 07:48 PM   #5
Senior Member
monkey's Avatar
Join Date: Sep 2011
Location: Arkansas
Posts: 2,390
We have Thousands of the 400 Cummins at work,,although in big trucks,, the engines are basically the same as yours. 195-200 degrees is perfectly normal...
Monkey, pilot of a Great Dane hauler,
2015 Silverado 2500 Duramax/Alison 4x4 CrewCab 2016 Cougar 28SGS
monkey is offline   Reply With Quote
Old 10-07-2012, 08:19 PM   #6
Senior Member
siggyd's Avatar
Freightliner Owners Club
Join Date: Aug 2005
Location: Chicagoland
Posts: 695
Compared to my 40' MH, 400 ISL,EPA 07,yours is running about 5~10 degrees high.
Have you checked / cleaned the radiator?
Siggy & Ursula.
2011 Newmar DSDP 4020 (no Tag, no DEF, 07 emission),
FTL XCR ,ISL 400,2015 Jeep Cherokee Limited, 4x4, V6, Active Drive II, BrakeBuddy
siggyd is offline   Reply With Quote
Old 10-08-2012, 06:11 AM   #7
jmarmor's Avatar
Join Date: Sep 2012
Posts: 80
when you say clean the radiator the inside or outside?
Outside via power washer?
Inside via change the coolant and flush out ?
jmarmor is offline   Reply With Quote
Old 10-08-2012, 06:28 AM   #8
Senior Member
SVTotem's Avatar
Winnebago Owners Club
Freightliner Owners Club
Join Date: Feb 2010
Location: Orlando, FL
Posts: 626
Siggy is probably referring to the exterior of the radiator and CAC. Oil vapor from the engine and road grime get pulled into these items and clog the vanes. Spraying with a cleaner like Simple Green Extreme (purple in color) and flushing with a garden hose will do the trick. There are threads explaining this in detail on the forum.

Do not use a pressure washer as that is too powerful and may damage the fins. Steam cleaning can work too, but it is usually just done from the outside and may not be as effective.

Check the engine breather tube to be sure it extends well aft of the fan housing to minimize clogging the radiator.
Bill Burgner, '05 Journey, 350 CAT
'05 Wrangler LJR, Blue Ox Aventa, Air Force One
SVTotem is offline   Reply With Quote
Old 10-08-2012, 02:40 PM   #9
Senior Member
MDPD's Avatar
Tiffin Owners Club
Join Date: Apr 2011
Location: Stuart, Florida
Posts: 203
I have the 400 ISL in my '09 Winn Tour. When we got it I felt that the temp was running too high and took it to a Cummins repair station. They discovered that the fan was programed to start at 212 degrees and cut off at 195. Contacted the factory and were told that the engine was designed to run hotter than earlier years and that it could go as high as 220 before any alarms were sounded and even at that 230 would not damage the engine. There are several threads about the 400 ISL running temps in the Cummins section, one in particular written by a former Cummins engineer. Do a search there and you will feel a little better about the high temps. I did!

MDPD is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
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

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 04:14 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.