HOW NOT TO LOSE YOUR COOL: Cooling System Preventative Maintenance

After eighteen years in service, my 2005 Ram’s cooling system was due for a thorough check and periodic coolant change. The cooling system has always functioned reliably. Given the track record for Cummins water pumps, two water pump replacements over the span of 185,000 miles is not unusual. Fortunately, each water pump failure came with ample warning and telltale symptoms. Neither pump change was on the road.

Protecting the cooling system is a concern. I replace parts before they fail. During the first belt change, the belt tensioner and idler pulley were replaced. At the current mileage, the hoses and radiator are due for pressure testing. I changed the coolant and thermostat at the last water pump replacement. The thermostat has maintained normal opening and closing temperatures.

I watch the temperature gauge under all driving conditions. Recently, the engine has been running just a few degrees warmer while trailer pulling on grades. A cooling system flush and coolant change is due. Pressure testing, inspection, flushing and fresh coolant will keep the cooling system reliable and protected.

COOLANT FLOW, ANALYZING OLD COOLANT AND PRESSURE TESTING

A cooling system’s pressure affects the boiling point of the coolant. To assure a safe boiling point, the thermostat and radiator cap must be in good condition. The current thermostat opens at exactly 195° and holds this temperature at cruise speeds under normal load. The cold coolant level in the overflow tank has been fluctuating slightly, which suggests that the radiator cap may not be holding the rated 16psi pressure. The cap and entire cooling system need a pressure check.

Before draining the cooling system, I wanted to know the overall condition of the system. If there is an issue with the heater temperature or the engine’s operating temperature, I will replace the thermostat. If the engine shows a normal operating temperature, and the heater is not blowing hot air, I will troubleshoot the coolant flow through the heater core and the HVAC blend door control system. Since the heater core is buried within the HVAC plenum behind the dash, the easiest check is the heater core inlet and outlet pipe temperatures. These pipes are readily accessible in the engine bay.

Here is a picture of how I test for radiator or hose leaks, coolant flow, the old coolant’s condition and the radiator cap performance. These tests take place before draining the system:


With the engine running at operating temperature and the coolant circulating, use an infrared non-contact thermometer to check for uniform temperatures across the radiator core. A distinctly cooler section in the radiator core indicates a radiator tube blockage. Compare temperatures at the end tanks of the radiator. Check across the core where accessible and safe. Stay well away from the engine cooling fan.


Next, I checked the coolant flow through the heater core at the heater inlet and outlet hoses. Ram does not use a coolant shut-off valve in the heater system. With the engine running, heater on and fan blowing high, there should be a drop in temperature between the inlet and outlet tubes of the heater core. (When the blower fan pulls air through the heater core, the heater core cools some.) Reducing the heater fan speed should raise the outlet tube temperature closer to the inlet temperature. If the engine is running at normal operating temperature and coolant is not hot at the outlet side of the heater core, the heater core is clogged. Heat is directed into the cabin by the HVAC air flow blend doors.


Once coolant flow was checked, I let the engine cool down completely before removing the radiator cap. Always use hand protection and be sure the top of the radiator is cool. An infrared non-contact thermometer helps here. With the cap removed, check the engine coolant for signs of debris, scale, and engine oil. (Engine oil in the coolant would be a sign of internal engine problems.) Here, the coolant looks clean, and I test it with my inexpensive hydrometer for specific gravity. The tester reads degrees of protection, mine being lower than -45°. Coolant concentration also shows the boiling point with a radiator cap that seals properly.


An anti-freeze hydrometer is not an indicator of coolant condition. These Fleetguard 3-Way Test Strips for commercial engine testing show 1) ethylene glycol or propylene glycol freeze point, 2) molybdate level and 3) nitrite level. The test is run at the radiator filler neck with coolant at the full level and cold.


Aluminum radiator solder seams can be damaged by too much nitrite. For our cast iron engine blocks, iron heads and an aluminum radiator core, a Hybrid Organic Acid Technology (HOAT) anti-freeze like Valvoline’s Zerex G-05 or a Fleetguard recommended coolant works best. Here I test the used ethylene glycol antifreeze. Nitrite level is good, molybdate reads normal range and freeze point protection is 60% range. I use antifreeze concentrate mixed with distilled water only. No well water or city tap water has entered this system since the truck was new.


I have an older Stant pressure tester and a newer OTC 6977 pressure test kit. Here, I pressurize the system to 16psi (never over 20psi) with the OTC tool. A quality tester that seals well should hold the system pressure steady for 20-30 minutes. This test held 16+psi, indicating no leaks or sealing issues. I watched the water pump, radiator tanks, hoses and clamp ends during this test. The system is secure, hoses remain firm, no cracks, and in good condition.


The Stant kit has a radiator cap adapter sleeve. Using the newer OTC 6977 pump with the adapter, the cap would not hold its 16psi rating. I tested several times at 16psi. The pressure dropped slowly to 5-6psi and held there. Holding there and not dropping to zero indicates a balance spring issue and time for a new radiator cap. This defective cap accounted for the recovery tank coolant level variation. Cap pressure should be tested routinely.


A 16psi system with a 5psi cap has a much lower boiling point than the advertised coolant protection. Coolant boiling point is always listed for a specific psi cap pressure and antifreeze-coolant concentration. This new Murray aftermarket cap tests okay and will work until the next system service or water pump replacement. The cap’s metal shell stamping is lighter gauge than the OEM Mopar, and the locking tabs are not as wide. I will get a Mopar cap next time.


COMPLETE DRAIN AND FLUSH WITH DISTILLED WATER

There are several ways to drain the coolant. The common method is to open the radiator drain petcock and drain the radiator and engine. Leave the radiator cap in place while draining. This should draw out coolant from the overflow tank. (If the overflow tank does not drain completely, see my steps for siphoning coolant from the tank.) Once the overflow tank is empty, remove the radiator cap to complete the draining.

Drain coolant into a large drain pan. I use a plastic cement mixing tub with a stable, flat bottom. This pan is rugged and easy to clean thoroughly after oil or coolant changes. With 30 or so quarts involved, draining the Ram’s coolant will take a while.

On the 2003-2005 Ram radiators with the plastic threaded drain valve, I do not unthread the plug completely or remove it. Open the petcock just enough for coolant to flow well from the down spout. A later twist type barrel plug can be removed for draining. Often, the barrel plug’s O-ring will need replacing. 3M Silicone lubricant or paste can help get the O-ring into the bore.

There are several flushing methods. On my well-maintained system, without signs of scale or a bad strip test reading, a quality flushing compound will loosen any gel or normal scale. I use Rislone Hyper-Cool Cleaner and Super Flush. The product removes deposits, neutralizes acids, and prevents corrosion, scale and deposits. It also contains water pump lubricant. Some flushing compounds are harsh acids or abrasives that can damage the water pump’s seal or the bushing in an old-style pump. For Cummins water pumps, premature pump failure needs no encouragement. This level of preventive care is valuable.

Tap water should not be used in a cooling system. Nevada’s city water and well systems are typically hard, mineralized water. I installed a whole house and shop water filtration system with a softener. The system reduced water spotting on glass when I wash vehicles. Despite this, I still flush cooling systems with pure distilled water. Tap or garden hose water has never been used in the Ram’s cooling system.

Simply draining the radiator and refilling the system will not remove all of the old coolant. Draining the block, heater core and hoses can be challenging. Few modern engines will drain completely without removing block plugs. The plugs on a Cummins block are not easy to reach or remove. A sensible alternative is pressure flushing or reverse flushing the system. Volume shops use a coolant exchange machine.

The shop manual method of flushing and refilling is sufficient if the system shows no sign of scale buildup. Following those steps, I go further with an extra round of draining, filling and flushing with a distilled water rinse. Here is my approach for a conventional drain, flush, refill and rinse.

The engine and cooling system are allowed to cool completely before loosening the radiator drain petcock. For a threaded stem plug (Ram models built during 2003-2005), I highly recommend not unthreading the plug stem completely. The threads are plastic and act like it. Once removed, the plug is difficult and often impossible to start back into the radiator drain seat threads. I drain the system in two cycles. This takes more time than a dealership or most shops will allot. The engine and cooling system must cool down completely between each draining.


This is the pesky ’03-’05 radiator plug.

It is also necessary to drain the coolant recovery tank. I accomplished this task by siphoning the old coolant. The drained system gets filled with distilled water and two bottles of Rislone flushing solution to handle the large cooling system capacity. Radiator cap in place, start the truck. To be clear, there is no shut-off valve on the truck’s heater core; hot coolant circulates through the core whether the heat is turned on or off. (You can turn on the heater if you need heat.) At thermostat opening temperature (195°), coolant fully circulates through the system. The truck is driven an additional fifteen minutes at cruise speed to flush the system.


The products I use to flush with Rislone.

Back at the shop and cooled down, I drain and check the flush water with a hydrometer. It does not show any antifreeze protection, indicating that most of the original coolant is gone. Many would stop here and refill the system with fresh coolant. I can tell by the coloration that there is still some old coolant present. I now refill the system with pure distilled water for the rinse cycle.

I drive the truck for fifteen minutes after a warmup. This is the third and final draining. The distilled water runs clear with the truck parked on a downward slope to fully drain the engine. Rislone Hyper-Cool Cleaner and Super Flush is not harmful to the cooling system or water pump. The cooling system is now ready for a fresh refill with coolant.

As you know, coolant is toxic. Dispose of coolant properly. Waste transfer stations and local auto supply stores often accept drained coolant. Make sure you have an outlet for the used coolant before draining the system. Follow regulations and labels when handling coolant and additives.


THE DRAIN PETCOCK DETOUR

Stripped threads on early radiator petcocks have been a popular forum topic. Tightening the drain for the last time, I felt the stem threads strip. The petcock needed replacing. A service kit is readily available and includes the plastic plug stem and the threaded seat. The kit is available from Mopar and the aftermarket.

Some owners stop using these drain petcocks, opting to evacuate coolant from the filler neck side of the radiator or disconnecting the lower radiator hose. I went for restoration, as the petcock is easier to use than these options. Before panicking because the petcock has stripped, here are the steps for installing a new assembly:


The drain petcock’s plastic threads were stripped. This stem should be not be cinched with pliers. Even with snug finger tightening, the threads will eventually strip. As a Mopar replacement drain petcock assembly, use is limited to 2003-2005 Ram trucks. For Mopar the part number is 52029087AA. Limited use usually leads to discontinued parts. For expediency, I looked further at the NAPA online national website.


Searching at NAPA turned up an illustration for part number NOE6051278. This is a new GM part. I bought the one drain petcock at our local NAPA store and ordered two spares. Not to worry, if you have a 2003-05 Ram with this threaded stem drain petcock, the part is for GM back to 1987 plus Ford and Toyota. Mopar used this petcock briefly. It is apparent why: You loosen it, attempt to pull it out, but the “tangs” prevent it from removal.

The new kit comes with a plastic stem and plastic threaded seat. The easiest method for removing the old seat is needle nosed pliers. Slide the pliers deeply enough to capture one lock tab then bend that flange inward. Tilt the piece to release the other tab. Use care not to scratch the ring seat where the rubber gasket seats and seals. Fortunately, despite this marginal design, the item is serviceable. $6.79 at NAPA is a lot cheaper than replacing the whole radiator!


The marginal design is removed!



Note the shoulder on the threaded stem. I start two threads and keep the lock tab flanges just below the stem shoulder. This allows the flanges to squeeze inward for inserting the lock tabs. Since the stem threads are already started, there is no risk of cross threading the stem after the threaded seat snaps in place. There are notches in the drain seat that align with the tabs. I push the stem and seat into position together, making sure both flange tabs snap into place. Once in place, the stem and seat fit squarely and snugly.

This is the stem with the seat snapped in place and the few threads caught. Turning the stem inward (clockwise) will spread the flanges onto the stem’s shoulder. This secures the threaded seat in the radiator. If you only screw the stem out this far to drain the radiator, you will avoid trouble. The coolant will drain straight down and well. Do not unscrew the stem all the way! You may not get it threaded back in place. Have a stem and seat kit on hand before draining the radiator.


There should be a decal on the radiator. Do not remove the stem.



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FINAL FILL WITH COOLANT AND “SUPER COOLANT”

The last decade has seen a push toward “wetting” additives. Wetting agents reduce surface tension between coolant and the cooling system components. The aim is to eliminate minute bubbles, enable better heat transfer and enhance the coolant’s ability to dissipate heat. Diesel engines are all about heat, and I have been intrigued with the claims of lower cylinder head temperatures. With this flush and a clean cooling system, the timing is right for testing a quality wetting product.

I again gravitated to Rislone. Hy-Per Cool Super Coolant is described as “very high cloud point surfactants” aimed at wetting to reduce surface tension. Tests show reduced engine temperatures, a lower risk of overheating, general lubrication, and protection of the water pump. The product also claims to prevent corrosion, erosion and electrolysis on aluminum, plastics, and rubber in the cooling system.

My concern for Cummins water pumps is reason enough to try the product. Although I have never overheated the engine, reducing cylinder head temperature on any engine is a good idea. With a ‘Long Haul’ goal of 500,000 or more miles from the engine, there is plenty of time to real world test this Rislone wetting additive.

There are options for the coolant refill procedure. The use of a vacuum filling tool is now popular and does save considerable time. I use this method when practical or necessary. The cooling system becomes a vacuum chamber, drawing down at the radiator filler neck until the system is under a negative pressure (vacuum) of 18-20 in/hg vacuum. The typical tool uses compressed air to create the vacuum. This method has the advantage of quickly siphoning liquid into the cooling system.

The vacuum/siphon method also eliminates “burping” the system. Vacuum removes the nuisance air in the system. Without a vacuum fill tool, it can sometimes take several full engine warmups and cooldowns to replace air with coolant from the overflow tank. This is why the Ram Shop Manual recommends filling the overflow tank for the first run of the engine and checking the tank’s coolant level afterward. Two or more adjustments of the overflow tank’s coolant level are not uncommon. Vacuum filling eliminates that need. After vacuum filling the radiator to full, a normal amount of mixed fresh coolant can be added at the empty overflow tank.

A downside is that the 20 in/hg vacuum at the radiator filler neck will collapse the radiator hoses. If the hoses are older like my system, this is a strain on them. While it looks amazing to watch gallons of fresh antifreeze coolant mix siphon from a clean drain pan directly into the radiator and cooling system, weakening an older radiator hose may not be worth the time savings. If you use a quality vacuum refill system, follow the instructions carefully.

A Ram/Cummins engine is easier to fill with antifreeze-coolant mix than most systems. The challenge when filling any cooling system at the radiator filler neck is leveling coolant in the engine block and head. On many engine designs, air gaps remain in the engine, heater core and hoses. Only the radiator gets full. The Cummins engine has the advantage of two one-way check valves or “jiggle pins” that help vent air as you fill the cooling system. Unlike some cooling systems, the Cummins engine should be filled without the engine running.

When I renew the radiator hoses, I will use my vacuum refill tool to fill the cooling system. This time I used the conventional fill method: Since the system lists as 29.5-quart capacity, I will use 16 quarts (four full gallons) of concentrated coolant. By using concentrate, I can adjust the coolant concentration for more than 50%. I run 60% concentration. A 60/40 concentration with Zerex G-05 lowers the freeze protection to -62° and raises the boiling point to 270° with a 16psi pressure cap that holds.


It is now time to add the “good stuff.”

Thoroughly cleaned, with fresh coolant, super coolant and a new radiator cap installed, coolant inspection can now take place at the recovery tank. I will watch for normal hot and cold coolant levels in the tank and check coolant concentration with a hydrometer and test strips. Concentration and protection level can be adjusted, if needed.

FOOTNOTES AND TAKEAWAYS

A topic that comes into modern cooling system care is electrolysis. The cooling system is conductive, and the Ram’s electrical system is direct current (DC) with a ground circuit. If the radiator is not properly grounded or there is a faulty engine or chassis ground, the coolant can act like an electrolyte. This causes pinholes in the radiator, galvanic corrosion, and other damage. One cure, of course, is proper grounding of the entire electrical system, including the chassis, engine, body and radiator.

Chrysler and FCA have done a good job around grounds. Problems usually occur with aftermarket modifications or accessories that are not properly grounded. Additional causes of radiator electrolysis range from bad pH balance in the coolant to stray alternator voltage. This is one more reason to periodically flush the cooling system and change coolant. You can check for electrolysis with straightforward volt/ohmmeter tests. An excellent article on the subject with test steps is at: https://ve-labs.net/electrolysis-101/how-to-test. The information is valuable.

Another topic that comes up is cavitation erosion. Cavitation is air bubbles in coolant caused by pressure fluctuations. But let’s be clear, this is not a problem with the Cummins engine in our Ram pickup trucks.

The best example of cavitation is a diesel engine with removable cylinder liners. The power stroke and compression stroke force cause the liner to vibrate, creating air bubbles between the liner and coolant. Changing pressure causes these bubbles to implode and hammer against the liner. These shock waves bore pits in the liner. Our Ram/Cummins engine does not have removable cylinder liners.

Moses Ludel
www.4WDmechanix.com
TDR Writer