Tech Stuff

Cooling system service: Keep systems functioning at peak performance

Running a flush and fill machine with the engine off removes pulleys, belts and fans out of the safety equation. This RobinairCooltech 75700 unit features a “push/pull” exchange process, allowing the technician to safely remove high pressure in a hot system.
<p>Running a flush and fill machine with the engine off removes pulleys, belts and fans out of the safety equation. This RobinairCooltech 75700 unit features a &ldquo;push/pull&rdquo; exchange process, allowing the technician to safely remove high pressure in a hot system.</p>

Weber is president of Virginia-based Write Stuff. He is an award-winning freelance automotive and technical writer and photographer with over two decades of journalism experience. He is an ASE-certified Master Automobile Technician, and has worked on automobiles, trucks and small engines. He is a member of the Society of Automotive Engineers (SAE) and numerous other automotive trade associations. He has worked as an auto service technician, a shop manager and a regional manager for an automotive service franchise operation.

The automobile is slowly evolving into an appliance, at least in the minds of many motorists. Much like a refrigerator or microwave, owners tend to use the equipment and ignore service until something breaks.

Motor vehicles use less than a third of the energy from combustion to propel them. Roughly, another third of the heat must be carried away by the cooling system while frictional losses and exhaust account for the remainder.

To keep the system functioning properly and to prevent problems, the coolant (the mixture of water and antifreeze) must be replaced on schedule. In many car owners’ minds, that schedule is 100,000 or 150,000 miles because that is what the salesman touted. They forget that there is a time interval. People who do not drive very far may forget that the coolant must be routinely replaced and never do it. In reality, most vehicle owners likely ignore the importance of coolant replacement altogether, unless the system leaks or the engine overheats.

Neither appearance nor the freeze protection are measures of the coolant’s protective qualities. The additives that prevent corrosion and lubricate the water pump may be depleted. According to industry experts, over 75% of water pump failures are due to worn-out or contaminated coolant.

Inspecting belt condition is a routine part of maintenance but it’s sometimes easy to forget, especially during a rush job.
<p>Inspecting belt condition is a routine part of maintenance but it&rsquo;s sometimes easy to forget, especially during a rush job.</p>

Signs of trouble

Usually, the first sign of a water pump problem is coolant seeping from the weep hole on the bottom. Corrosion or debris can wear at the shaft seal. However, keep in mind that a small amount of initial seepage is completely normal. In fact, it may take a couple hours of running before a replacement water pump’s seal stops weeping, so don’t rush to send it back as defective.

If you must replace a water pump, the first step is not belt removal. It is system flushing. Get rid of any junk in the cooling system that could damage the replacement pump.

Before ordering the new pump from your jobber, determine if it is a standard rotation or reverse rotation pump. How? If the pump is driven from the front of the serpentine belt (the grooved side) it is standard rotation. If the pump is driven by the back of the belt, it is reverse rotation. They are not interchangeable.

After installing a new water pump, spin its shaft to make sure it rotates freely before installing the belt. Speaking of the belt, now is a good time to replace it along with its tensioner (for serpentine designs). If the water pump is driven by the timing belt, you could save your customer plenty of money for labor by replacing the timing belt now rather than later.

Always replace the coolant when replacing the water pump. That doesn’t mean a simple top-off — drain, flush and refill with a fresh mix.

As you know, the thermostat regulates the engine’s operating temperature. If it fails by staying open, the engine may run too cool. The heater output will probably be inadequate. If it fails by not opening, the engine will overheat.

Some people think that an engine that runs cool is a good thing. It isn’t. Cool running can contribute to oil sludging and reduced fuel economy. The engine management system uses coolant temperature as one of its vital inputs for fuel mixture enrichment. An engine running slightly cooler than normal may not set a trouble code or check engine light.

Thermostats can become sluggish or weaken over time. They are inexpensive and it makes sense to ensure your repairs by replacing them when other major cooling system service is performed.

Coolant hoses are often taken for granted. However, they should be visually and manually inspected at the very least. Check them for heat, oil and abrasion damage. Squeeze them to check for mushiness. Remember: Hoses degrade internally, so a visual inspection of only the outer surfaces isn’t adequate.

An engine block’s water passages (especially cast iron blocks) can become restricted over time by corrosion and rust deposits. A routine power flush and restoring with a fresh coolant mix is mandatory. The example seen here is an empty block simply to illustrate.
<p>An engine block&rsquo;s water passages (especially cast iron blocks) can become restricted over time by corrosion and rust deposits. A routine power flush and restoring with a fresh coolant mix is mandatory. The example seen here is an empty block simply to illustrate.</p>

Electro-chemical damage is public enemy number one. Automotive engines are a metallurgical mélange. There may be a cast iron block, aluminum head(s), copper/brass radiator and so on.

Electrical charges can be created and carried through the coolant hoses, especially if there are any loose or missing grounds in the engine compartment.

The hose degrades from the inside out as the inner tube beneath the reinforcement layer fails. When this happens, coolant seeps into the reinforcement and then, as pressure builds, creates a tiny hole in the cover creating a leak. Ultimately, the hose will burst and it usually happens while driving. The best case scenario is an inconvenienced motorist. The worst case is a damaged engine.

Squeeze the hoses with a finger and thumb near the end — close to the pipe to which it connects. Feel for gaps or soft spots. Next, squeeze near the middle of the hose’s length. If it feels firmer, electro-chemical degradation has begun. It starts at the ends of the hose.

Replacement hoses that are resistant to electro-chemical damage are readily available in the aftermarket.

Engine heat can damage the hose cover, especially if the hose is routed near a hot component like an exhaust manifold which also can damage the reinforcement layer. Look for hard, glossy areas on the hose surface. Replace marginal hoses and reroute them away from hot zones or wrap them in a heat-resistant sleeve if that is not possible.

A hose that rubs against a component can suffer abrasion damage. It is obvious when this happens. If the damage is minimal, reroute the hose and protect it from rubbing.

Tags: A/C  air conditioning 
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