06 Monaco (Cummins 400) Coolant change

[716OutWest]

I know this topic has been beat to death on here, BUT looking for opinions / insight on changing the coolant on my 06 Diplomat with a Cummins 400 ISL.

A little context. I just purchased the unit 6 months ago, the previous owner converted the coolant to a NOAT by fleet rite. I drove the MH cross country with no issue but getting ready to do the annual maintenance and I noticed in the records the coolant has not been flushed / changed in about 8 years (which exceeds the recommended 6 years on the bottle).

My Question - since I am NOT changing the coolant type can I skip the whole flushing process (distilled water 4 times over, etc) and just drain the current coolant in there and then replace with new pre-mixed coolant (same type / brand) to give it a refresh? I know there will still be some that I won’t get out of the front end hoses, etc. Also, if this is the route I go, will I still need to account for air in the lines? And how do I mitigate / work those out?

Thank you in advance!

[bentjm]

That is what I would do. You might also send a sample out to be tested first - the current coolant may be fine.

[wolfe10]

The problem with not flushing (at least the last one with distilled water before adding coolant concentrate to make 50% coolant) is that you have many gallons of coolant in the lines to the dash heater core, the heater core itself and if a motor-aid water heater to it as well.


So, yes, IMO, at least one rinse is needed or you will have a mixture of new and 8 year old coolant in there.

[Dutch Star Don]

When I did the flush in my 2005 Monaco Diplomat 400ISL, I warmed up the coach and drained the coolant. I then filled with tap water and drained again. I did one fill and flush and with distilled water.

When I refilled the system with coolant, I added to two gallons of OAT concentrate and then the rest was a 50/50 mix. This way I knew that any water left in the system was mixed with the concentrate. I used Final Charge.

[wolfe10]

Originally Posted by Dutch Star Don

When I did the flush in my 2005 Monaco Diplomat 400ISL, I warmed up the coach and drained the coolant. I then filled with tap water and drained again. I did one fill and flush and with distilled water.

When I refilled the system with coolant, I added to two gallons of OAT concentrate and then the rest was a 50/50 mix. This way I knew that any water left in the system was mixed with the concentrate. I used Final Charge.

Yup.


Another way to insure the proper 50/50 mix is IF (OK, may be big IF) you know the total system capacity, after the final distilled water rinse, just add 50% of capacity in concentrate and top off with distilled water. Most accurate way IF you know the system capacity.


Note: system capacity is quite a lot more than what you just gravity drain because of lines from engine to front for the dash heater core and heater core itself.

[716OutWest]

Thank you all for the quick replies! Very helpful, so last question, reading the book it says to (after flushing) fill with new coolant and leave the cap OFF and start the engine. I'm assuming this is to help work out the air pockets? How long should I let the engine run before replacing the cap?

Thank you again!

[153stars]

Usually the cap loose until the thermostat opens for a while. Just monitor the level in the tank until it it's stable. Probably get flamed but.....These coolants say around 6 yrs 300k-600k miles use. I doubt a second flush is really necessary in MH use.

[Dutch Star Don]

You may find after your first trip that it will take some more fluid. Sometimes it takes a little time to eliminate the air pockets.

[Gary RVRoamer]

I'd draw a sample and have it tested - since it is OAT it may still be fine. Even if it tests ok, you could still drain the radiator and refill with 50/50 OAT. That would give you a refresh (partial fill).


Blackstone Labs, Fluid Life, etc can give it a thorough analysis.



[Don't bother to flame me - I'm impervious to it]

[716OutWest]

Well good news I tested the fluid and it looks pretty darn good on the strips but I noticed have a leak in the hose from the surge tank running down into the engine, so I guess I will be forced to drain now! Anyone have any advice on where to find a replacement hose? Generic at Napa or an automotive store?

Thanks!

[153stars]

I'm just guessing hose the to the tank is just off a roll and does not have special bent/formed kind. Any quality coolant hose should be okay. Gates green stripe is a higher quality. I know it's available in 1/2" I didn't look for smaller.

[moisheh]

AFAIK you cannot test OAT coolant with strips. I bought a cheap refractometer from Amazon and it works well. When I changed my coolant the first time I called Old World Industries. They make most antifreezes including Final Charge. I spoke with one of their engineers. He told me that there is no reason to change your coolant based on time in a motorhome. But he also stated that if you are worried just drain a gallon and add a fresh gallon of coolant. The
suggestion to send a sample for testing is a good idea.

[Cat320]

I sent my coolant sample to JG Labs...they also do my annual transmission testing. They will furnish a detailed chemical analysis with a recommendation regarding changing.

http://www.jglubricantservices.com/

[153stars]

Thought I seen shared strips for OAT not sure if one size fits all chemical wise.