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Open Roads Forum  >  Class A Motorhomes

 > 300HP CAT running hot

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wolfe10

Texas

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Posted: 11/25/11 08:04am Link  |  Print  |  Notify Moderator

sowego wrote:

When we were newbies our 1st year out...our CAT 330 got hot on hills...even smaller hills. After going through the whole process to rule out mechanical problems and cleaning the radiator...it still ran hot.

The simple answer was - we were not manually downshifting on grades to keep the rpm up, therefore improving the airflow through the cooling system to prevent overheating. We thought that Allison would take care of all that. The transmission will downshift somewhat on hills but not enough to keep you running cool. Drop down 2 or 3 gears upshifting as you crest the hill.

If that does not solve your issue then it will take further investigation.


Good advice IF the ambient temperature is high (over 90 degrees F) combined with a grade that is really long and steep. But, if you need to downshift to keep it cool under less severe conditions, it is almost always an indication of a cooling system with compromised capacity.

Most common cause is blockage of air flow to the CAC and radiator. Sure, there are lots of other causes, but this is the common one, particularly if the CAC is not cleaned once a year.

Said another way, if you have to gear down to keep the engine cool, you may be "driving around" the problem rather than addressing it.

BTW, this has nothing to do with brand of engine-- it has to do with cooling system capacity/ability to reject XX BTU's of heat per minute.

* This post was edited 11/25/11 08:18am by wolfe10 *


Brett Wolfe
1997 Safari Sahara 3540
EX: 1993 Foretravel 36' U-240


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BIGGDOGG

Alberta

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Posted: 11/25/11 02:50pm Link  |  Print  |  Notify Moderator

After reading this post, I'm embarrassed to say that same situation happened to us heading south last month. Got a Cat 300, and after three days driving without the gage ever getting over 190, we eventually starting pulling some longer hills and the alarm started to flicker. I remembered once reading that hills should be taken WOT, so that's what I did: pinned it thinking that would get the RPM's up. Well it does, but it also raises the temperature. We got to the tops of these grades, pulled over and let the engine cool down at high idle and off we went.

Re-reading the many posts here, I will be having the CAC area cleaned thoroughly, and will lay off the accelerator and downshift as needed when coming home. Am I on the right track here, or should I be looking harder at this?

wolfe10

Texas

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Posted: 11/25/11 03:05pm Link  |  Print  |  Notify Moderator

BIGGDOGG wrote:

Am I on the right track here, or should I be looking harder at this?


Yup, cleaning the front of the CAC is ALWAYS the place to start when you have overheating on a rear radiator DP.

This should be part of the routine annual maintenance. No special tools needed. Once you access the fan area from bedroom/closet, a garden hose with garden nozzle is all you need if it is just dirt. If the deposits are really thick or oily, use a good detergent such as Dawn dishwashing liquid. Flush until the effluent runs clear. No rocket science here.

Gearing down and raising RPM is a reasonable "work around" until you get your cooling system back up to snuff. But you will loose MPG and performance in this "work around".

wolfe10

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Posted: 11/29/11 08:26pm Link  |  Print  |  Notify Moderator

Joeycockerspaniel wrote:

I am yet to read, how hot is it running?


You are correct, but hot enough to trigger the engine's overheat alarm (unrelated to gauge package) IS hot-- too hot.

sowego

northwestern corner of the Nebraska panhandle

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Posted: 11/25/11 07:26pm Link  |  Print  |  Notify Moderator

Thanks, it is true our overheating situation only occured in quite warm weather not winter. The coach was new, cleaned the system anyway.


2002 Tiffin Phaeton
2005 Malibu Maxx toad


Joeycockerspaniel

Cumming, GA

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Posted: 11/29/11 08:22pm Link  |  Print  |  Notify Moderator

I am yet to read, how hot is it running?


Hank & Winde
Cumming, GA.
2006 Forest River Charleston
CAT C7


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