Running Cool

Words By: Mark Yanochko

The earliest gasoline engines were air-cooled, but it wasn’t long before these powerplants required water cooling. Over the years, the cooling system has remained basically the same, with few changes. It should be mentioned, though, that its importance has remained critical to the operation and longevity of the internal combustion engine.

The life blood of the cooling system is the coolant, a specially-blended liquid. The boiling point is higher than that of water; conversely, its freezing point is lower than water. As a result, mixed with the proper ratio of distilled water, coolant is used for all driving conditions.

With summer approaching, now is a good time to check that coolant and, perhaps, change it. Regardless of where you live, summertime brings with it the hottest temperatures of the year. The coolant in your engine must be ready to meet the challenge. With that in mind, let’s review a general cooling system drain/fill procedure.

Drain and Refill

Before you drain the coolant from the radiator, raise the vehicle and remove the splash shield. A typical splash shield, A, is shown in Figure 1. Most vehicles today have some sort of shield to reduce drag on the underside of the chassis. Usually there are about 8 to 10 small screws that hold it in place.

Once the splash shield is removed, place a drain pan under the radiator. Remove the cap from the coolant reservoir and/or the radiator. Rotate the petcock, B, one-half turn counter-clockwise. Be sure the drain pan is under the drain hose, C (Figure 2). Remember, wait until the engine is at ambient temperature before draining the coolant. Never drain the coolant when it is hot.

While the coolant is draining, check the condition of all the hoses, D, looking for any cracks or splits. Check the heater hoses, too. Also, check the condition of all the hose clamps, E (Figure 3).

Chrysler recommends replacing the petcock. This part should be replaced because the sealing O-ring will likely leak if you close the petcock (the O-ring is not a serviceable part). To remove the petcock, rotate it an additional one-half turn and pull it out.

After the new petcock has been installed and closed, fill the engine with new coolant. On most vehicles, the coolant, F, is poured into the coolant reservoir, G, as shown in Figure 4 (fill almost to the top). On vehicles that are equipped with radiator caps, fill the radiator through the filler neck up to the top edge of the neck. In either case, be sure to use a 50/50 mixture of coolant and distilled water.

Note: Most automotive applications use either an ethylene glycol or propylene glycol formulation. Propylene glycol coolants are not recommended by Chrysler LLC as they provide less freeze and boiling protection than the recommended ethylene-glycol-based coolants. Older Chrysler vehicles use traditional “green” coolant, while later vehicles require extended life “orange” coolant with hybrid organic corrosion inhibitors, a.k.a. Hybrid Organic Additive Technology (HOAT). These coolants MUST NOT BE MIXED. Doing so will reduce the corrosion protection and may result in premature water pump seal failure.

The Mopar® part number for the “orange” extended-life coolant is 68048953AA. It should be noted that the service life of this coolant exceeds that of conventional coolant. While “green” coolant is limited to three years of service, the extended-life coolant is formulated to last 5 years/100,000 miles.

After the cooling system has been filled, start the engine and bring it to operating temperature to check the coolant level. On vehicles in which the engine is higher than the radiator, excess air has to be removed from the cooling system. On such vehicles, there is a plug, H, which is removed with an Allen wrench, J (Figure 5) or a bleeder screw, K, as shown in Figure 6 (loosen the screw 2 turns). When a steady stream of coolant flows from the hole or screw, install the plug or close the screw (have a small pan or jar to catch this coolant). This indicates all the air has been removed from the system.

Once operating temperature is reached, the coolant level should be between the MIN line, L, and the MAX line, M, on the coolant reservoir, N (Figure 7). If the system was filled by pouring the coolant into the radiator filler neck, the level of the coolant should drop.

After the coolant level has been checked, check the specific gravity of the coolant. This will ensure that the new coolant can protect the engine through all extremes of weather, hot or cold. Simply insert a hydrometer, O, into the coolant reservoir, P, as shown in Figure 8.