5 Tricks To Solving Belt Noise

Engineering a belt system is one of the most difficult jobs for OEMs. There are contact, frictional, centrifugal and peripheral forces that must be taken into account. If they get it right, the belt will be quiet, efficient and last 100,000 miles. If they get it wrong, the belt will be noisy or rob the engine of power. For technicians, the job is even tougher. Variables that the engineer did not factor in can put the belt and your diagnostic skills to the test. But there are four techniques you can use to solve belt noise problems.

1. Remove the Belt

If you have a hard-to-isolate accessory drive belt noise, try removing the belt and running the engine. If the noise is still present after the belt is removed, it might be an issue with the motor mounts or the timing chain/belt. With the belt off, it is also a great chance to examine the pulleys and belt for potential problems like worn bearings inside the idler pulleys.

2. Tensioner Twist

Place a wrench on the tensioner and move the arm its entire range of motion at least three times. Feel for spring tension along with a fluid motion throughout. Any sticking or notching movement may indicate a problem with the spring or pivot bearing. The arm should move up and down. Any lateral movement could indicate a bad bearing or spring. Inside some belt tensioners, unseen to most technicians, is a dampening mechanism that absorbs shock. Excessive chattering or tensioner arm movement is not only the result of weak spring tension but also a worn dampener. This makes the tensioner a wear part with a limited life span.

3. Spray it Down

In the 1950s, the sales trick to sell a new belt was to spray a running belt to show that it was slipping or that the noise went away when wet. This trick went away when serpentine belts became more popular. But, this test can be used to isolate worn pulley bearings by eliminating belt noise that could be caused by an alignment problem. Use only water; old-school belt dressing will damage modern EPDM belts and cause more noise.

4. Get in the Groove

Like a tire, the friction between the belt and pulleys wears away at the belt, usually on the tops and walls of the ribs. Eventually, the grooves of the pulleys will bottom out on the grooves of the belt, and then the belt will start to slip.According to one belt supplier, as little as 5% of rib material loss and surface wear can affect how the belt performs, and just 10% belt slippage can affect the overall drivability of a vehicle. Belt manufacturers have simple gauges that can measure groove depth, overall thickness and cracks to quantify wear.

5. Check the Alignment

Pulley alignment tools can help you rule out alignment issues. They can give you the peace of mind that there is a pulley that is out of alignment. It is also a great tool to have if you do a lot of power steering pump or A/C compressor replacement jobs.  

Article courtesy Underhood Service.


Auxiliary Water Pump Diagnostics

A car or truck comes into your shop with a complaint of poor heater performance. The driver complains that on cold mornings the heater will blow cold during the drive to work in rush hour traffic. The car is not overheating and the air is coming from the correct ducts.

Your first reaction might be to install a new thermostat and inspect the heater core for a blockage. On the test drive, the system may perform great for you. Is the customer just cold blooded?

The issue could be the auxiliary water pump. This pump is not connected to the cooling of the engine. Its primary function is to circulate warm coolant to the heater core. If too little coolant is circulated, the blower fan will pull enough heat out of the coolant and cause the heater core to get cold.

These pumps were first used on luxury and diesel vehicles in the 1990s. Most diesel engines typically do not generate a lot of heat when running or idling. Coupled with the lower engine speeds, the coolant in the heater core would lose most of its heat before it passed through to the outlet. This would frequently cause drivers to complain about insufficient heating if they drove in stop-and-go traffic or cruised at speeds with lower RPM. So, adding an auxiliary coolant pump would provide enough volume of coolant to keep the heater core warm.

Engineers then started to use these pumps on gasoline-powered vehicles for the same purpose. This allowed vehicle designers to use larger heater cores to provide better passenger comfort.

The control of the pump as part of the automatic temperature control system keeps the cabin heated even after the driver has turned off the ignition. The system can keep the interior warm for short periods of time while the driver goes shopping or grabs a bite to eat.

These pumps will show up on more and more vehicles as engines become more efficient and generate less excess heat. Also, new technologies like hybrid drives and stop/start systems need auxiliary pumps to not only improve driver comfort, but also to keep the batteries at a constant temperature.

Modes of Operation

Note that the auxiliary pump is not running all the time. The BCM or controlling module will control and regulate the pump using information like:
• Vehicle speed;
• Engine RPM;
• Coolant temperature;
• The temperature selected on the control head;
• Blend door position;
• Fan speed; and
• Exterior and interior temperatures.

If the vehicle has key-off control, there are additional parameters that must be met to activate the pump. These include:
• Battery voltage;
• Supply voltage to blower motor;
• Recirculation flap position;
• Security module input; and
• Keyless entry fob location.

A scan tool can test the pump function in most vehicles, but it is also possible to test the system by pressing an HVAC control head button sequence listed in the service information.

Causes of Failure

The main reason why these pumps fail is age and wear of the electric motor. Like all rotating electrical devices, brushes wear and windings short. Overheating can hasten the electric pump’s failure because increased cooling system pressures can force coolant past the shaft seals. Low coolant can also cause a pump to fail because of its position, which is typically high in the system, either on the firewall or strut tower.

Failure Modes

A failed pump will almost never cause the vehicle to overheat. If the auxiliary coolant pump is inoperative, the customer might notice reduced heater performance at low speeds and at idle.

Your first instinct might be to replace the thermostat, the water pump or the heater core, but if the vehicle is equipped with an auxiliary coolant pump, you will need to dig a little bit deeper with your diagnostic process.


The tools needed to diagnose an auxiliary coolant pump include scan tool, meter and service information, with scan tools and service information being most important for late-model vehicles. The operation of the pump is dependent on several modules and numerous sensors that are networked.

The first step in the diagnostic process is to check for codes with a scan tool. Unrelated codes for collision detection, door module operation and loss of communications incidents can cause the deactivation of the pump. This is where service information can make the difference between a quick diagnostic process and parts swapping.

Newer vehicles may vary the voltage to control pump speed. Like all electrical devices on a vehicle, the operation is a balancing act between driver comfort and minimizing electrical loads on the alternator.

The cooling circuit on some vehicles with electric pumps may be called an auxiliary cooling circuit in the service information. The coolant may travel through the transmission cooler and windshield washer fluid bottle as part of the circuit on some Mercedes models.


Hybrids almost always have an electric water pump to cool the battery packs and inverters, and some hybrids will have a second pump for the heater core in the cabin. Hybrids or mild hybrids with stop/start systems not only have an auxiliary cooling pump, but also electric pumps for the oil and transmission fluid.

If a pump fails on some hybrids, the system will disable the hybrid drive system or put the vehicle into a limp mode. Most hybrids also have an insulated coolant reservoir or jug that may have a pump of its own to help warm up the engine faster or keep the batteries at a constant temperature.

Not every car has an auxiliary water pump, but those that do can throw a monkey wrench in your normal diagnostic logic when solving cooling system problems.


Diagnosing Intelligent Cooling Systems

You might be seeing a trend on late-model water pumps, such that an undersized mechanical pump being augmented by an electric pump with an electronic thermostat. These components, combined with the cooling fans, are working together to manage heat loads instead of reacting to them.

The majority of cooling systems on the roads react to what is happening inside the combustion chamber. After the engine is stressed, the heat causes the thermostat to open. Increases in temperatures will also cause the cooling fans to come on. The heat carried by the coolant is the trigger for operation of the fans and thermostat.

But, while the engine is waiting for the thermostat to open and the fans to come on, the heat could be changing efficiency and economy inside the combustion chamber.

Intelligent cooling systems can identify events as they happen. Instead of a thermostat opening, these smart systems will look at calculated load and throttle position to determine a course of action. These real-time countermeasures are an effort to keep the cylinder head and walls at the correct temperatures for the best possible combustion event.

The Water Pump

The conventional water pump has one fatal flaw – the shaft speed tied to the speed of the engine. This means that an engine controls the speed, rather than the demands, of the cooling system. It is also a parasitic power draw on the engine.

During cold operation, the pump is still moving the same amount of coolant as if it were warm. It might be bypassing the radiator, but the rapid movement could extend warm-up times.

Since the engine turns the water pump, it will have to turn at speeds from idle to redline. Designing an impeller that works efficiently at this wide variety of speeds is next to impossible.

At some higher speeds, tiny “bubbles” of water pump cavitation can damage the pump. While you will never actually see these tiny bubbles, you can see the damage of cavitation that looks like metal eaten by termites.

By combining a conventional water pump and electric water pump, it is possible to create a more efficient system that has less parasitic draw and can cool the engine on demand.

The Thermostat

A conventional thermostat is like a carburetor in that they only respond to throttle and engine vacuum signals. As such, a conventional thermostat can only respond to changes in temperature caused by heat from the engine and cooling from the radiator.

By being able to actively control the temperature of the coolant, the engine management system can optimize engine performance so leaner combustion events can take place and cold start periods are minimized. It does this by minimizing sudden surges of cold coolant from the radiator side of the cooling system. This helps to keep a more consistent temperature for the engine. Most of all, this minimizes the sudden need to make the fuel mixture richer because there is a sudden drop in block temperature.


Diagnosing electric water pumps and electronic thermostats requires a scan to ensure the components are functioning and there are no codes. Sensors inside these components monitor operation of these systems, as well as look for specific outcomes when the components are activated.

The other diagnostic challenge will be the “limp home” modes these systems will use to prevent the engine from overheating and causing engine damage. This is why studying the service information will be critical.

Article courtesy Underhood Service.

Automotive Featured

Truck Stop: Heavy-Duty Coolant Maintenance Tips

More than half of heavy duty engine failures due to improper maintenance.

The coolant system is responsible for removing approximately 30 percent of combustion heat of heavy duty engines, while more than 53 percent of premature engine failures are due to improper maintenance.

coolingmaintentProper understanding of coolant types and adherence to vehicle manufacturers’ requirements are essential to ensuring that antifreeze effectively maintains engine temperature and helps protect the cooling system from rust and corrosion.

WIX Filters, a global manufacturer of filtration products celebrating its 75th anniversary, has developed the following coolant maintenance tips:

Start clean and keep it clean – Make sure the entire system is clean – inside and out. Replace corroded and damaged components and use appropriate flush. Balanced coolant prevents – but does not fix – problems.

Use deionized or distilled water – Never use sodium “softened” water.

Use quality EG or PG – It is important to know the chemistry of your coolant; pay attention to whether you are using traditional IAT coolant or organic acid technology.

Select the proper supplemental coolant additives – If you are using IAT, there are three ways to protect traditional coolant with supplemental coolant additives – standard service intervals, slow release and extended service interval.

Ensure proper balance – In order to effectively maintain engine temperature, coolant must be correctly diluted – usually in a 50/50 mixture with acceptable water.

Practice proper top-off – Do not overdo your coolant by topping it off with water or coolant. You must use the correct 50/50 mixture.

Diagnose after use –The coolant filter catches dirt, debris, chemical precipitation and other contaminates – all things you can see. Review the filter closely after removal to determine whether debris or other contaminates are penetrating the filter and entering the coolant system.

Replace coolant when it’s time – Adhere to your vehicle’s change intervals. Also refer to the vehicle manufacturer’s and the coolant manufacturer’s recommendations. Coolant manufacturer’s recommendations should be followed especially if you have replaced the original equipment manufacturer’s coolant or specified something other than original equipment manufacturer’s default.  As a result, replace your coolant when recommended by the coolant manufacturer.

Test, inspect and detect – Coolant should be tested regularly to check its freeze protection capabilities. Use coolant test strips or refractometers to determine the concentration ratio of coolant to water.

Practice proper handling and storage – Handle and store your coolant in a clean, temperature-controlled environment.