Coolant or coolant

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Jan 13, 2005
I need to add a pint or two of coolant to my coach. The existing coolant is ethylene glycol based. The Cummins manual is adamant that it needs to be 'heavy duty' meeting some Cummins specs. I've driven around several auto parts stores today and all I can find is stuff that's rated for "automobiles and light duty trucks" with no mention of the Cummins specs. A NAPA parts store told me that there's a heavy duty version of one of the brands, but they don't stock it. I called in an RV repair shop and they told me "we just put in regular antifreeze".

What makes a coolant 'heavy duty' and where might I find it?

BTW the coach doesn't leak coolant. The only way to change the DCA filter is to clamp the hoses, but this doesn't totally stop the flow, so some escapes (I was prepared and caught it in a bucket, but the bucket wasn't clean).

Heavy duty usually means compatable with the DCAs and/or having some level of DCA included.  It sounds like your DCAs are added when you change the filter (it's inside the filter element and releases over time).  Almost any truck dealer will have Cummins spec coolant in stock.  I have a F-250 Ford with the International diesel and buy coolant for it at the International dealer in town.  Or try a truckstop like Flying J - they usually have coolant next to the diesel additives and motor oil.
Tom check this out this may or may not help


I found this because I have to get my radiator re-cored (don't ask this rust thing opened up a can of worms) :'(
Thanks Lou. Yes, I use a DCA filter. We'll be passing a Flying J on our way to our daughter's place in Nevada City for Christmas, so I'll stop in.
mfa said:
For the uninitiated...
What does "DCA" stand for?


That stands for Diesel Coolant Additive look at the web site that I posted above it has a lot of info.
Good information there Brian, thanks.
Tom   when You stop at the Flying J   before you leave make sure the lady and boss of you crew in in the RV  Don't need another  "He left me at the Flying J "  LOL
LOL Shayne. Since Chris does 95% of the driving, I'm the one who's likely to get left behind at Flying J  :(

What makes a coolant 'heavy duty' and where might I find it?


The heavy duty refers to the engine i.e. a heavy duty engine. The coolant may or not contain SCA's. If it does  - then it will say something like  heavy duty coolant/antifreeze with SCA's.  Heavy duty coolant is chemically different than the automotive coolant. I find that it can be bought at NAPA special truck stores, truck dealers like Freightliner or engine repair places like CAT, Cummins,etc. It is very seldom seen in regular type stores or gas stations because they volume of sales doesn't justify the space required.
Hi Tom  This doesn't have much to do with a diesel motor home but it's interesting. When we were building some high performance 2 stroke engines for snowmobiles, cooling was a problem because of piston seizure. Someone recommended we use Water Wetter made by Redline. So I did some testing with an infrared thermometer and sure enough it would reduce the coolant temp about 20 degrees. I'm not a big additive fan but this stuff worked. It would also stop the corrosion that happens between the cadmium plated bolts and the aluminum casting parts of the engine. Anyway theres some good reading in that link.

It also makes you realize all coolant isn't created equally.
Water Wetter works well in specific applications. Race cars use them to help keep the coolant temperature down (Karl, please correct if wrong, I can't remember whether WW leaks on the track are a real pain to clean). On the other hand, IIRC someone asked about WW at a Cummins engine seminar and was told it was incompatible with diesel engines, may affect the DCA protection.
(Karl, please correct if wrong, I can't remember whether WW leaks on the track are a real pain to clean).
Water wetter compounds (decreases surface tension) are o.k. to use and don't present any significant clean-up problems. Anti-freeze, on the other hand, is as bad or worse than oil, and is banned in racecars.

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