Coolant Check

Remember somewhere I said that if we feed our diesel clean fuel, clean air, keep the oil fresh and don’t overheat it it will run a loooong time? This is part of the not overheating: ….Item # 20-03 on your maintenance checklist….

It says to replace the coolant every 100,000 miles IF the heavy duty SCA (Supplemental Coolant Additive) is in there….. which, according to Mike Cody at Camp Freightliner, it is.

It also says to test the SCA levels every 25,000 miles. So, also per Mike, I ordered the Fleetguard 3 way heavy duty coolant test kit:

Test Kit 1.jpg

Tesst Kit 2.jpg

So, we’re checking the freeze point, the Molybdate level, and the Nitrite level…. What do these do? They fight rust, scale and corrosion — and in diesel engines protect wet cylinder sleeves from cavitation. Google that, you’ll be reading for a while.

The instructions say to collect a sample. NOT from the expansion tank….but from the radiator or petcock. Oh dear, here we go again. Back to the world of “I can barely see it, let alone get to it….” So under there we go….. Well….. pleasant surprise. Passenger side bottom corner of the radiator there’s the petcock…..

Radiator Petcock.jpg

Squirt it with a little happy juice, let it sit for a minute and (regular lefty loosey) drain a little to flush out any crud, throw it out and then get sample….. Easy peasy.

Coolant Test 1.jpg

And do the test, per the instructions…..

Coolant Test 2.jpg

Tip nice and dark….. -30ºF protection. That’s enough. If it gets colder than that I got bigger problems. Middle pad… Molybdenum: Hmmm, that’s a little light. Gonna call that “Row 2 or 3″…… Nitrite: Nice and dark purple. Call it H. So, that puts me in the 3.5 to 3.8 SCA units per gallon. Carry on!

All that said, these test strips are not the MOST accurate thing out there. And since this actually matters a lot for the longevity for our engines I am considering sending it in for testing. Found this place… Will call and see what that that sets me back. Maybe around 50K miles or so, may throw in an oil analysis while I’m at it. Right before the warrantee runs out maybe? Meanwhile I’ll do another test in 10K or so…. see how it trends.

And of course we check the level. There’s a “cold min” and “cold max” on the expansion reservoir. It was a little low so I decided to add some….

What to add? The world of coolants is, to say the least, confusing. Specs, colors, additives you can read for days. After a LOT of searching I ended up on the Cummins Quickserve site and figured out that their highest spec coolant is CES 14603 And we’re looking for an SCA pre-charged. Prestone Command HD seemed to meet these requirements and I added about 2 quarts.


April 2021, about 45,000 miles.

The block heater died and during the repair of same I had a bucket of coolant sitting out. Perfect opportunity for a test, it was time anyways. Turned out I was a little “light” on SCA. Somewhere around 1.9 units per gallon. Hard to judge those colors accurately. So, time to add some, and the big tub full going back in was a perfect place to mix it. First….. What? Well, this seems to be a pretty secret process because NAPA gave me the deer in the headlight look, and the Kenworth dealer down the road barely remembered that he had it on the shelf, but he did. DCA4 and that’s what the test card mentions. Bingo.

Now the big question: How much? Well first you have to know how much coolant you have. The book is very non-committal. Best answer came from social media from someone who got an email from FL and the answer was: 38QTS. Call it 10 gallons. So to get from 2 to 3 units per gallon I needed to add 10 units. Bottle says 1 pint is equal to five units, so two bottles is 10. So that’s what I put in. Will test again in a few miles.