20 August 2005
COOLING SYSTEM SERVICE UPDATE BY PAUL WEISSLER There s no sense longing for the good old days. Today s cooling system service requires specialized equipment, an understanding of coolant/antifreeze compositions and compatibilities and knowledge of specific vehicle requirements. Photo courtesy Wieck Media In the old days, if a cooling system didn t leak or overheat, we used to ignore it at this time of year. Today, the system has to operate year round within very precise ranges, as if it were an emissions control. Well, it is an emissions control, and a cooling system problem can turn on the MIL before it ever illuminates the overheat lamp. In fact, the diagnostics are aimed at finding the engine that warms up slowly, takes too long to go into closed-loop and doesn t run warm enough for lowest emissions. When that happens, there ll usually be a trouble code, such as P0128, which indicates failure to reach normal operating temperature in a specified time. Often the reason is a thermostat that was removed (and not reinstalled after the system was flushed during the spring). More often there s a problem because the cooling system hasn t been touched at all, many motorists believing extended-life coolants are a life of the car deal they can forget about. It s no secret that many car manufacturers have been extending coolant service intervals. Reducing maintenance is just fine with motorists who would normally ignore it anyway. And environmentalists like the idea of dumping less antifreeze, even though much of it would be recycled. But the extended intervals are really a mixed bag, and not everyone has adopted them. General Motors has a 150,000-mile interval, but sets a fiveyear limit, the same as Ford and Chrysler Group, which have a 100,000- mile limit. Toyota went to a 10-year interval, also with a 100,000-mile limit. Honda has a 10-year/120,000-mile interval. Mercedes really raised the bar to 15 years/150,000 miles. But these intervals don t apply to August 2005 21
Could the thermostat have been removed from this vehicle and left out during spring cooling system service done elsewhere? If the cooling system logs a slow warmup diagnostic trouble code, don t be surprised if there s no thermostat in place. A simple check with an infrared thermometer should tell you for sure, so you won t needlessly pull the housing. This Honda label identifies the type of coolant as recommended for 10 years/120,000 miles on the factory fill, so don t even look at the dye color. It was deep green for several years (same color as the conventional Japanese antifreeze), but was recently changed to blue. Photos: Paul Weissler older models. Toyota, for example, had a 60,000-mile coolant-change interval through its 2003 models, and Honda recommended 3 years/45,000 miles through 2000. Mercedes began its changeover from four years to 15/150 on some models in 2003, completing it during the current model year. In the meantime, such high-volume lines as BMW, Nissan and Subaru have not extended their intervals nearly as far. Even Nissan s extended interval (4/60) is a one-shot deal for new models. The second flush & fill is scheduled after 2/30, which is the only interval recommended by Subaru. BMW uses a 4/50 recommendation. It s important to note that these intervals extended or not are based on a properly maintained system. If the coolant mix is kept at about 50/50 and the system is always topped up, the recommendations apply. Otherwise, all bets are off. Furthermore, the long intervals were validated only with specific antifreeze formulas used by the OEMs. If you change to an antifreeze with inhibitors that provide a different type of protection (such as silicates vs. phosphates or organic acids), On-Engine Pressure Cap On-Engine Pressure Cap Radiator Pressure Cap To simplify bleeding, Subaru s turbo engine compartment has two pressure caps one on the radiator and another on the engine next to the intercooler. 22 August 2005
the system may not continue to be protected under severe conditions. System neglect is the big issue, however low concentration from top-ups with water, or a low coolant level. The plain fact is that we re seeing a lot more corrosion damage. Once corrosion builds up in a system, electrolysis indicated by.3 volt or higher in the coolant may occur and accelerate deterioration. The most effective cure for voltage in the coolant, except in special cases reported in service bulletins, is an effective flushing of the system, not a string of additional ground straps. There certainly has been enough publicity about GM s problems with low coolant levels and reduced antifreeze concentrations from normal seepage (and water top-ups). The extended-life antifreezes, particularly organic acid technology (OAT) types like DexCool, protect the system most effectively when the coolant is in continuous contact with the cooling system passages. That means a full system, with a 50/50 concentration. Sure, you can do a complete coolant change without a machine, but it may take repeated draining and filling, thermocycling and topping off. There are more efficient ways to earn a dollar. Getting 90% of the coolant out (the necessary minimum) is really tough without a machine, even if you drain To help the motorist keep the cooling system properly topped up, mix the antifreeze remaining in a jug with an equal amount of distilled water. the engine block, disconnect hoses, etc. On many GM 3.8 V6s, for example, removing the knock sensor will let a surprising amount of coolant drain from the block. Topping Up the System As for topping up the cooling system without a machine, or at least a vacuum fill kit, you ve got to do a lot more than just fill the radiator and reservoir, then hope that engine thermocycling You may know if you have hard water in your area of the country, but not corrosive water. The shaded portions of this map indicate the areas where water from underground aquifers may be corrosive. If the water in your area is corrosive, use distilled or deionized (softened) water in the cooling system. will clear out the air bubbles. Some engines have two fill necks, maybe one on the radiator or pressurized reservoir and a second on a neck on the engine. On Subaru turbos, there s a pressure cap on a housing with hoses to the reservoir. Even with all the bleed valves opened and a jack under the fill neck location, there are no guarantees that you ll get all the old coolant out. Ask anyone who s ever tried to manually top up such classics as the Toyota MR2, Volkswagen Eurovan and Pontiac Fiero, plus various Nissan vehicles. Establishing long-life protection with a specific type of antifreeze creates an inventory problem for the independent shop. When coolant service intervals were 5/50 or shorter, a good rinsing of the system made it possible to switch to good old conventional American green. That antifreeze contains two popular inhibitors silicates and phosphates so it worked in European cars with silicated antifreezes and in Japanese cars with phosphate antifreezes. Now many systems contain the organic acid technology antifreeze/coolants that provide a different type of protection, and work far more slowly. GM, VW/Audi and some European makers use OAT coolants with no silicates or phosphates. Japanese companies have been moving to an OAT with phosphates, but oppose a key organic acid in GM DexCool. Chrysler Group, Ford U.S.A. and BMW use basically the same antifreeze as Mercedes, a low-silicate hybrid formula. As another indication of the meaninglessness of antifreeze dye colors, Honda just switched from green to blue, with no change in the formula. If you see an extended-life coolant label under the hood and the coolant is the original stuff, it could be green if it s pre-2005. And we hope you know that despite the orange color of the Chrysler coolant, it s exactly the same formula as the yellow coolant in Ford products, or the usually yellow but sometimes blue antifreeze in Mercedes-Benz models. Mercedes is an easy-to-understand example of why you shouldn t change types of extended-life coolants. Mercedes coolant jug contains a silica gel continued on page 31 24 August 2005
With all the cosmetic plastic covering on this Lexus RX 400h hybrid (left), all you can see is a coolant reservoir at the back of the radiator and a pressurized reservoir cap visible through an opening at the left rear of the powertrain compartment (right). However, that second reservoir and pressurized cap are for the hybrid electronics cooling system. bag (yes, something similar to the packets designed to absorb moisture in camera cases, etc.). However, with a coolant containing silicate inhibitors, the silica gel helps maintain a stable level of silicate protection over the years. Mercedes has long used the silica gel bag, and the protection level is supported by field experience. The packet is built into the jug and is a life-of-the-car item. Because each extended-life antifreeze provides a specific type of protection, you should stick with the original type. Under severe conditions, such as a low antifreeze concentration, there might not be enough of the needed additives (silicates, phosphates or other inhibitors) to do a good job. Given the variety of individual vehicle requirements and the specific antifreeze/coolants developed to fulfill those requirements, it would be foolhardy to top off with whatever is handy. Even Texaco, which once promoted its DexCool formula as a one-for-all, has introduced Havoline Custom-Made, a low-silicate formula for Ford U.S.A., Chrysler Group, Mercedes and BMW vehicles. Phosphates and silicates perform similar functions, and protecting water pumps from corrosion after cavitation erosion is a job they do better and faster than the OAT inhibitors. So how do you deal with this problem? Stock a half-dozen or more antifreezes? It depends on the vehicle mix in your shop. If you get in a lot of older cars, a conventional American green antifreeze, which contains both silicates and phosphates, still is needed. With a good rinsing, it can be used in import nameplates with intervals of 2/30 to 3/45. But for extended life, you need at least three antifreeze types: a low-silicate hybrid, such as Zerex G-05 or Havoline Custom-Made, for Radiator Reservoir Radiator Pressure Cap Ford, Chrysler, Mercedes and BMW products. a nonsilicate, no-phosphate OAT for GM, VW/Audi and Jaguar vehicles. There are several aftermarket brands, including Texaco Havoline DexCool, Prestone orange or yellow and Zerex ExtremeLife. Japanese phosphate-oat. We haven t seen an aftermarket brand yet, so shop the Toyota or Honda parts departments for the best deal. Electronics Cooling System Reservoir With the plastic panels removed, you can see a second pressure cap on the radiator. August 2005 31
Engine Coolant Temperature Sensor Water Valve Outlet Temperature Sensor To/From Heater Core Water Pump (for Heater) This illustration of the Prius so-called third cooling system shows an appendage to the engine cooling system featuring a vacuum container that keeps three liters of coolant hot for days. This is designed to reduce emissions by preheating the engine intake ports during cold-engine startup. Yes, that s four different antifreezes, and even they won t cover replacement of Japanese conventional antifreeze (Toyota Red and other makes that are typically deep green). Although we re sympathetic, we don t have a researchvalidated alternative answer to suggest, unless you want to switch the cars to conventional American green and 2/30 to 3/45 service intervals. Of course, getting motorists to bring their cars in for a coolant level check isn t easy in the first place... One consideration: If a customer had been topping up with water, you might want to increase the initial antifreeze concentration to 60%, after making sure you ve found and fixed any leaks. Then, if you re left with some antifreeze, add an equal amount of water to the jug, cap tightly and give it to the motorist for topping up. If you re in an area with hard water (a lot of mineral content) or corrosive water (it may be soft but you see the blue stains), you don t want to use it in a cooling system. Most tap water in municipal systems is good enough for automotive use, but if you have well water or another source that isn t chemically neutral, use distilled water or even deionized (softened) water. Ion exchange substitutes some salt for A Coolant Heat Storage Tank Coolant Heat Storage Tank Outlet Temperature Sensor To/From Water Valve Coolant Heat Storage Water Pump View From A To/From Engine Block the calcium and other minerals, but overall, it s a good choice. A typical cooling system will need a gallon or so (at about 60 cents); it s definitely a value-added product that motorists will pay for. The Second Cooling System A second cooling system? Yes, and a simple example is the Mercedes V12 biturbo, which has a separate one for the twin turbochargers. Although the cars in which they re installed carry the 15/150 service interval for the regular system, the second one has just a fouryear service interval. Okay, so you don t see many twinturbo V12 Mercedes in your shop. But you are likely to start seeing some of the gasoline/electric hybrid vehicles with a separate (second) cooling system just for the electronics. If you don t think that can be very significant, just take a look under the hood. Don t be surprised if you see a pair of coolant reservoirs. The full hybrid cooling systems (the vehicle can run on electricity alone) are complete systems, needed just to cool all the electronics and, in the case of the Prius, also a motor generator. The Ford Escape full hybrid has a pair of reservoirs at the right front of the Illustration courtesy Toyota Motor Sales U.S.A. powertrain compartment. The Lexus RX 400h and Toyota Highlander hybrids have a pair of reservoirs and two pressure caps. We should warn you, they use extended-life Toyota pink antifreeze, a very different formula from the more familiar Toyota Red. Both Toyota and Ford use fan-driven air cooling for the battery packs behind the rear seats. The 2004-on Prius actually has a third cooling system well, really more of a second heating system and it s truly an emissions control. An additional circuit for the engine cooling system opens when engine coolant exceeds 197 F, to fill a heat storage jug a 3- liters vacuum bottle, much like the Thermos containers used to keep coffee hot. The jug maintains the coolant temperature for a long time even after three days in a vehicle parked in temperatures of about 75 F, the coolant in the jug still is over 120 F. At that temperature or higher, the coolant can quickly preheat the intake ports of the cylinder head, which reduces wetting of injected fuel on the port wall. This permits a reduction in the amount of fuel that has to be injected for a cold start, and reduces hydrocarbon emissions during that critical period by 20%. This system helped enable the Prius to meet California s stiff PZEV (partial zero emission vehicle) standards. It takes 7 to 12 seconds for the ports to warm up, but because the Prius is a full hybrid, it can be driven off on electricity alone, and the gasoline engine started after the ports are warmed. The coolant is circulated by the vehicle s electric water pump with the engine in that prestart mode. Clearly, it s important for the pump to run, but on a more basic note, the engine has to warm up properly to fill the vacuum jug with hot coolant for later reuse. The GM Silverado and Sierra pickups, so-called mild hybrids with 42-volt systems that handle just the stop-start function, still have a lot of electronics and therefore a complete second cooling system (like the Ford Escape hybrid, with two adjacent reservoirs), including an electric water pump like the full hybrids. The Honda system is not a full hy- 32 August 2005
brid. The car can t run on electricity alone, but uses the hybrid system for acceleration assist only. But like the full hybrid, the Honda system features regenerative braking and engine stopstart. So it s very sophisticated, and gets fuel economy close to that of the full hybrids. (We got 45 mpg in a Civic hybrid, 46 in a Prius.) It has the electronics together with the battery pack at the rear, and uses a large air cooling system for everything. In fact, Honda warns against putting anything on top of the air inlets, which are on the cabin package shelf, or perishables against the air outlet in the trunk, which could go over 100 F. Pressures Are Up If you re just pumping up a pressure cap or cooling system to 15 psi, you should take a look at the markings on the cap first. More and more systems are running higher pressures than the traditional 14 psi; in fact, pressures into More and more cooling systems are running with higher pressures than the traditional 14 to 17 psi. This one (on a Volvo) reaches 21 psi, and there are some with even higher ratings. Unless your pressure tester can test at these pressure levels, a system might pass, yet overheat without turning on the warning light. the 20s are not unusual. Cooling system engineers select the pressures necessary to meet no-overheat targets and set the hot coolant warning light accordingly. Each psi raises the boiling point of a 50/50 mix by about 2 1 2 F, so a system with a cap that holds only to about 14 to 15 psi instead of a specified 21 would boil coolant at about 15 to 18 F below specs. Because the hot coolant warning light likely wouldn t come on in this case, the engine could suffer damage. You may long for the days when one coolant actually did fit all, service intervals were shorter and systems were a lot easier to drain and refill. You didn t need a scan tool to check a radiator fan, either. And in those olden days, 80% of antifreeze was installed by DIY motorists and everyone (thought he) could service a cooling system without making a mistake or a misstep. It s not that simple anymore. Visit www.motor.com to download a free copy of this article. Circle #13 August 2005 33