Skip to main content ↑ ↓
Topic: Changing Coolant In Cummins 400ISL Important Question  (Read 422 times) previous topic - next topic

Changing Coolant In Cummins 400ISL Important Question

According to everything I've read my Cummins ISL400 cooling system has a 15 gallon capacity.

I have flushed it twice now and am planning to do a 50/50 final fill of the same coolant that has been in the system, Rotella ELC.

I have only been able to drain about 10-1/2 gallons of coolant the three times I've tried, and the coolant is not getting significantly paler red in color.  Is it possible that because our FT is only 36' that it doesn't have the coolant capacity of 15 gallons?

I probably need to know the answer to my question before I add the ELC concentrate at the rate of 50% coolant capacity.

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #1 –
The coach length would have nothing to do with it. I don't think you can drain all the coolant out of the system. I would allow for the missing 4 1/2 gal by putting in 2 gal of the concentrate, then do the 50-50 mix to top off.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #2 –
The heater hose length, engine pre-heat and Aqua Hot must all have an effect on the capacity.
Ours is a 36 footer with AH and engine pre-heat.

If it is indeed a 15 gallon system then I need to add 7.5 gallons of concentrate and top off with distilled water.
If it isn't a 15 gallon system then I need to find out what it is and adjust the concentrate amount.

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #3 –
Quote from: Travelin' Man –
The heater hose length and Aqua Hot must have an effect on the capacity.
Ours is a 36 footer with AH.
It would have some effect, but and extra 8 ft. of 5/8 heater hose compared to a 40 ft. coach wouldn't hold but a quart.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #4 –
After your first drain and fill did you run the unit with the heater on high and again with with each flush.
The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #5 –
Did you remember to turn on the dash heater to circulate the coolant out of those lines and the heat exchanger?  That might account for it.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #6 –
It will never all come out. Thats why its so important to do multiple flushes and then check concentration with a refractometer after refilling. Use your best guess to get it close to 50/50, run it to get everything well mixed, test and if you arent close to your ideal mix, drain some off and refill with concentrate or water to achieve desired results.
95 U300SE

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #7 –
Yup, you will never get it out.  Length matters only in additional volume in two 5/8" heater hoses off additional length. Pretty much noise level when talking about 20 gallon system.

If total system capacity is 20 gallons, merely do the last rinse (including dash heater ON) with distilled water.  Add 10 gallons of CONCENTRATE, NOT PREDILUTE and just top off with distilled water.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020
 

Re: Changing Coolant In Cummins 400ISL Important Question

Reply #8 –
OK guys, thanks. 
I did have the heater on for both flushes, and now headed out to get some more distilled water.