Question: This question came from the OOIDA Members Only Maintenance Forum on the Internet: My Cummins N-14 has 566,000 miles. The extended life coolant (ELC) antifreeze was flushed and changed at 335,000. It tests all right for freeze point, but it has a brownish color to it. No oil or anything else could be detected. Should I be worried? Should I replace the antifreeze? If I do, should I use ELC or go back to regular (green) antifreeze?
Answer: Replies on the Member Forum page included several possibilities. One poster suggested the water pump could be resting and recommended antifreeze analysis, always a good idea. Another suggested changing water filters every 24,000 to 30,000 miles. It should be done every second preventive maintenance (PM) or every extended PM, except if the coolant or filter system are designed for extended life. Even then, additive strength should be checked at each PM. You should check acid/alkaline balance (pH) and adjust it with additives.
Coolant conducts electricity, so stray current from a poor ground may be running through the engine and cooling system. One member corrected similar symptoms with a ground strap from the radiator to the frame. Suggestions included changing brands of antifreeze and changing the radiator, too. One highly respected frequent poster, an ASE Certified Master Technician, suggested sticking with “the old fashioned stuff, regular antifreeze and water. Check the additive specs and change the water filter every other oil change.”
Penray’s Darrell Hicks (www.penray.com) is an expert on coolants, so I checked with him. He replied:
“A weak head gasket may be letting exhaust gas into the coolant. Check the coolant for nitrite level at least every 50,000 miles. ELC has additives that creep and leak more than conventional ones. A few years ago, Cummins had issues with ELC and gaskets. Cummins has documented how to handle this. If your truck dealer can’t help, try a Cummins distributor.
“Brown coolant is evidence of rust, so start by cleaning and flushing the cooling system thoroughly. The best products are chelant cleaners. They can be used while the truck is working. Penray 2001 cleaner can be used over 30 days or 10,000 miles. It has a full SCA package to protect the system.”
Another good coolant cleaner is made by another active TMC and SAE member, George Sturman of Enviro-Cool (1-877-741-2111, www.ecfilter.com). The Cooling System Cleaning Filter chemically cleans and captures the residue. The Enviro-Cool system also restores radiator flow.
Darrell said that once the system is clean, you can select between alternative systems: conventional coolant, extended life coolant or, what in my opinion is the best of both worlds, conventional coolant with an extended service coolant filter. Baldwin makes a timed release (of SCAs) filter, and Penray’s Need Release has membranes that react to coolant chemistry and dissolve to release a premeasured quantity of additive precisely when needed.
The benefit of ELCs using organic acid technology is that they should be able to go 300,000 before needing their inhibitors replenished, and 600,000 before needing to be replaced. They work well provided they are not contaminated, either by exhaust and combustion byproducts or by conventional antifreeze. If enough regular coolant is mixed in (most often when coolant is topped off during preventive maintenance), the ELC must be treated with SCAs just like regular coolant. If you do use ELC, make sure you keep the right kind of coolant with you, and top off the coolant yourself before turning the truck over to the shop.
Darrell mentioned test kits that will detect exhaust in coolant. NAPA BK 700-1006 or Cummins 382298 will work. By the way, Darrell is an OOIDA member. He volunteered to help any member with any coolant-related questions. Call 1-800-322-2143 and make sure you mention you’re an OOIDA member.
Question: Here’s another Cummins engine question from the Forum. Does anyone know what to do about an intermittent rough idle, rough enough to shake the whole truck? It won’t act up at Cummins, and no fault codes show up. There’s no rhyme or reason. It does it cold, hot, parked and pulling up to a stop sign.
Answer: The first reply suggested a bad load of fuel, but this is unlikely if the condition persists. A suggestion from another ASE Certified Master Technician was to check for aging fuel lines that might be swelling shut or drawing in air. Another post cautioned that if the fuel filter had recently been changed, the old gasket might not have been completely removed. The new gasket may not be seated properly. One poster suggested checking for air in the fuel by installing a sight glass to see whether bubbles are in the fuel.
Again, a great deal of good information on the forum, but to be sure, I checked with Mike Bradford, OEM service account manager at Cummins. Mike said it does, indeed, sound like air in the fuel system. If it were a hard component failure, it would not be intermittent.
The problem may be occurring at all engine rpm, but it would not be as noticeable at 1,200 up. It could, as was posted, be a bad filter seal or even a bad filter. A good possibility is dirt under the seal, or a filter just not seated well.
Mike offered another possibility not mentioned in the posts, a restriction in the fuel return line. If it has collapsed inside, you won’t notice it inspecting the outside of the line. That’s true of the suction side, too. The only way to tell is with a restriction gauge. Place one on the suction side of the fuel delivery line. Check the pressure of the return line as close to the engine as possible. If suction is weak or return pressure is excessive, you’ve isolated a problem.
Mike also suggested the cause might be electrical. Dirt or corrosion on EMC or sensor connectors can affect idle, as can any moisture in the connectors. Pressure washing can force moisture past the connector seals. It’s probably a good idea to check all the connections anyway. Inspect, clean and dry. Then before replacing, put in an adequate amount of dielectric grease. I keep Truck-Lite NYK in my toolbox and use it on all connections.
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