Frequently Asked Questions

Whether you have a trusted technician who works on your vehicles or you prefer to do the work yourself, ACDelco wants to help you keep your cars and trucks running strong, long and efficiently. Use the links below to identify car noises, smells and leaks, as well as access frequently asked questions about car care and performance problems.

What’s your vehicle trying to tell you when it clicks, clunks or grinds? Translating these car noises is key for automotive technicians who are trained to identify problems via sound. The important thing to remember is to be specific. Narrow that rattle down and then document when it happens – details such as when the car is hot, cold, at idle, moving at 55 mph, etc. can go a long way in helping to diagnose the problem.

Type of Car Noise and Possible problem

• Squeaky brakes - Dirt in the lining of the pads or hardening of the pads and shoes

• Grinding brakes - Worn pads and shoes

• Metal on metal when braking - Worn-out pads

• Metal on metal when encountering bumps - Worn-out shocks

• Growling from air conditioner - Worn compressor

• Squealing windshield wipers - Worn wiper blades

• Whining from tires when turning a corner - Dry or worn-out wheel bearings

• Squealing from tires when turning a corner - Tires low on air or worn

• Grinding while shifting gears - Worn clutch or clutch that needs adjustment

• Screeching under the hood - Loose or worn belt

• Popping from engine - Dirty air filter or bad spark plugs, wires or ignition components

• Scraping or buzzing from transmission - Transmission needs new fluid

• Squeaking noise when shifting - Manual transmission needs lubrication

• Clunking under hood when gears change - Worn joints or engine’s idle speed may be set too high

• Knocking under hood - Clogged air filter, timing off or needs higher gas octane rating

• Clicking when idling - Needs oil

• Clunking that worsens as speed increases - Broken or worn engine parts

Learning to pinpoint strange vehicle odors can help your automotive technician sniff out the real cause of the problem. Here are a few common odiferous car complaints.

Type of Car Smell and Possible Problem

• Sweet smell, usually accompanied by steam from under the hood - Antifreeze or coolant leak

• Clear liquid with a smell - Brake fluid leak

• Heavy, thick smell, possibly accompanied by smoke from under the hood or from the exhaust - Burning oil

• Acrid smell, like burned toast - Electrical short

• Continuous, heavy sulfur smell, like rotten eggs - Emissions

• Burning material or rubber smell - Overheated brakes or clutch

• Metallic smell, usually accompanied by antifreeze/coolant smell - Overheating

If your vehicle is leaving strange stains or other visual signs behind on the driveway, use the chart below to pinpoint the cause

• Type of Car Leak and Possible Problem

• Black stains with a heavy, thick consistency - Axle leaks

• Clear liquid with a smell - Brake fluid leak

• Yellow, green, pink or orange-coloredstains that are lighter and thinner than oil - Coolant leaks

• Brownish-colored stains - Crankcase or power steering leaks

• Clear liquid with no smell - Just dripping water that has condensed on your air conditioner

• Black fluid - Motor oil leak

• Greasy fluid that is pink, red or clear - Power steering or transmission fluid leak

• Reddish-colored splotches - Transmission fluid leaks

Not everyone who drives is an expert on auto performance, and that’s why ACDelco offers you this handy reference guide. Knowing something about how your vehicle performs and handles will make communicating with service advisors and technicians fast and easy.

Performance Problems and How to Describe it

• Cuts out - Temporary, complete loss of power. Engine quits at sharp, irregular intervals. May occur repeatedly or intermittently. Usually worse under heavy acceleration.

• Detonation - Mild to severe ping, usually worse under acceleration and load. Engine makes sharp, metallic knocks that change with throttle opening. Sounds like marbles rattling around.

• Dieseling - Engine runs after ignition switch is turned off. Runs unevenly and may make knocking noises.

• Hesitation - Momentary lack of response as accelerator is pressed. Can occur at all speeds. Usually most severe when starting from a stop. May cause engine to stall.

• Missing - Pulsation or jerking that changes with engine speed. Exhaust has a steady spitting sound at idle or low speed. Not normally felt above 30 mph.

• Rough idle - Engine runs unevenly at idle. Car may also shake.

• Sluggish - Engine delivers limited power under load or at high speed. Won’t accelerate as fast as normal. Loses too much speed going up hills. Has less speed than normal.

• Spongy - Less-than-anticipated response to increased throttle opening. Little or no increase in speed when accelerator is pushed down to increase cruising speed. Continuing to push pedal down will finally give an increase in speed.

• Stall - Engine stops running or dies out. May occur at idle or while driving.

• Surge - Vehicle speeds up and slows down with no change on accelerator pedal. Can occur at any speed.

ACDelco Professional A/C Compressors pump refrigerant through the system and are the ideal high-quality replacement for your GM and non-GM vehicle. The compressor is typically engine driven via the accessory belt, and a clutch on the compressor is used to engage and disengage the compressor. Hybrid vehicles are typically equipped with an electric motor-driven compressor. The compressor draws in cool refrigerant gas from the evaporator and pumps it to a much higher pressure. The high-pressure gas travels on to the condenser. The compressor is lubricated by refrigerant oil. These Professional, premium aftermarket replacement components are manufactured to meet or exceed your expectations for fit, form and function.

Lack of or insufficient cooling, excessive clicking sounds, unusual noises or growling when using the A/C system could be a sign of a worn A/C compressor or components. This could be due to:

• Internal compressor fault
• A/C clutch or electrical circuit failure
• A broken or loose drive belt

Your A/C system must be maintained with the correct level of refrigerant and appropriate pressure to work properly. An A/C system leak, which could result in incorrect fluid or pressure levels, could potentially harm or interfere with the performance of your A/C system. This would result in lack of or insufficient cooling performance. Common causes of A/C system leaks include:

• Worn or damaged service valves and caps
• Worn hoses
• Loose connections
• Seal failures
• Damaged components
• Worn or damaged compressor shaft seal
• Worn or damaged evaporator
• Worn or damaged condenser
• Worn or damaged compressor seals
• A/C system component corrosion
• Missing service cap

To check your A/C system for leaks:

• Use a leak detection dye, such as ACDelco Fluorescent Tracer Dye. Be sure to use the dye that is specified for use with your system’s oil and refrigerant type.
• Look for dirt or containment build-up around hose or line connections. This could be a sign that oil, which would attract and hold contaminants, is leaking out of the connection.

If your engine begins overheating while driving in heavy traffic, the following steps can help alleviate the condition:

• Set the climate control system to “Heat” or “Vent.”
• Set the blower fan on “High” (roll down your windows if the interior becomes too warm).
• Allow more distance between your vehicle and the one in front of you; this enables more air to enter the radiator easily.

These steps will help reduce heat within the system. If the overheating condition persists, pull over to the shoulder of the road and allow the engine to cool. As a precautionary measure, have your vehicle checked by a professional technician as soon as possible.

The Heating and Air Conditioning System heats and cools the vehicle’s cabin and defrosts the windows.

Your vehicle’s air conditioning (A/C) system should be routinely checked by a professional technician. This should occur approximately every 12 months, though you should check your Owner’s Manual for more specific recommendations. Any related maintenance should be handled only by professionals. If you notice any of the following conditions, have your vehicle checked right away:

• Musty smell when the air conditioning or heating system is activated
• Inadequate cooling or heating temperatures when using the air conditioning or heating system
• The vehicle’s temperature gauge indicates a “red” condition
• Steam coming from the engine compartment
• Unusual smells inside or outside the vehicle

Your A/C system requires proper air-flow to operate effectively. Poor air-flow across the condenser will impact system performance and can increase refrigerant system pressure. Make sure air-flow into your system is not obstructed by bugs, leaves, dirt or other contaminates in between tune-ups.

Your A/C system is a sealed system, which includes different components connected by hoses, tubes or lines. To keep the system leak free, inlet and outlet fittings have O-rings or seal washers, and the lines have leak-free fittings. To help prevent leaks in the A/C system, follow these guidelines when servicing connections:

• Use the proper O-ring for the system
• Thoroughly clean all fittings and do not over torque beyond what is recommended
• Always lubricate O-rings with clean refrigerant oil
• Always replace sealing caps on service ports
• Recover refrigerant from the system when or if necessary
• Keep dirt and foreign material from all sealing surfaces

When replacing your compressor, it is very important to use suction screens and inline filters on liquid lines. These filters and screens will catch any debris in the system to avoid damage to the new compressor. ACDelco also recommends system flushing using native refrigerant before installing a new compressor.

Yes. Consult the product’s fitment information to see if it will fit the year, make, and model of your vehicle.

ACDelco GM Original Equipment Transfer Case Assemblies are GM-recommended replacements for your vehicle’s original components. An important part of the drivetrain for four-wheel drive systems, transfer cases are responsible for engaging and disengaging four-wheel drive. This two speed, part time, electric shift transfer case is for a four-wheel drive system, and has been updated with the latest GM engineering enhancements. It comes with pad inserts, an actuator motor, and an aluminum vent instead of plastic. It also features no hassle core return and is available in heavy duty and super heavy duty applications. These original equipment transfer case assemblies have been manufactured to fit your specific GM vehicle, providing the same performance, durability, and service life you expect from General Motors.

No. Transfer cases are used in vehicles with four-wheel or all-wheel drive systems.

Yes. Four-wheel drive transfer cases give the option of two-wheel drive or four-wheel drive, and engage when activated electronically or manually by the driver. When engaged, power is split evenly between front and rear wheels, and when not engaged, the vehicle is in two-wheel drive. All-wheel drive systems are always on, getting information from the wheels, and sending power to the wheels with the most traction at the time of slippage. This happens automatically and requires the driver to do nothing to engage it.

Yes. Part time transfer cases have a main mode of two-wheel drive, usually with the rear wheels powered. When needed, four-wheel drive can be engaged, and the front wheels are powered. Front wheel binding can occur on dry pavement when in four-wheel drive. Full time transfer cases have constant four-wheel drive, with all four wheels powered all the time. Differential (planetary gears) are incorporated into the transfer case so binding does not occur on dry pavement.

Yes. Electric shift operates by activating a motor on the transfer case, which rotates a linkage to engage the main shaft. The main shaft transfers power to the front driveshaft for four-wheel drive. Manual shift operates by moving a lever attached to a linkage on the transfer case, which manually engages the main shaft. The main shaft transfers power to the front driveshaft for four-wheel drive.

The Cold Cranking Amps (CCA) test is the number of amps required to crank an engine for 30 seconds at 0 degrees Fahrenheit. Due to lower viscosity engine oils, gear reduction starters and smaller engines having the right amount of CCA is required but not too much. More CCA will not start your car faster. The Reserve Capacity test is the number of minutes that a battery will last with the headlights left on or at a 25 amp draw. Due to the increased electronics in a vehicle, having as much Reserve Capacity as possible is now more important than having the excessive CCA.

Most Battery Manufacturers put the "CCA" rating right on the label of the battery. Be careful when shopping for batteries as some manufacturers put on the label a reference to "CA". This is a reference to "Cranking Amps" this test is done at 32 degrees Fahrenheit and not a 0 degrees like the Cold Cranking Amp (CCA) test.

This should be on the label right under the CCA rating of the battery.

It is important to have the right battery for your vehicle. Refer to OEM specifications in your Owner's manual or an OEM driven supplier such as ACDelco.

All batteries need to be maintained. Parasitic drains in a vehicle can deplete a battery in 2-4 weeks. To be safe, vehicles should be started once a week or once every other week and idled for 5 minutes to ensure that the battery retains a reasonable state of charge.

Batteries that are Accessible Maintenance Free or Sealed Maintenance Free have a Calcium Additive to the plate material inside the battery that helps to prevent the gassing off of electrolyte. These types of batteries should never need to have water added. Vent caps on these batteries should not be removed at any time as this breaks the seal and could allow seepage or water loss. Low electrolyte in these batteries is an indication of overcharging. Filler Cap batteries have an additive in them that requires the checking and refilling of the battery with distilled water.

In the case of GM vehicles AGM batteries are required for Start Stop vehicles. Use of a flooded battery will result in the life only being about 4-6 months. Most other vehicle manufacturers are using AGM for these vehicles as well.

No. The Chevrolet Volt requires this unique AGM battery.

• Check the auto battery as part of regular vehicle maintenance.
• Keep auto battery terminals clean and free of corrosion. To remove corrosion from terminals use a terminal brush.
• Check the alternator and make sure that it is not charging too high or low – if the alternator is not charging properly it will cause the battery to not charge correctly and cause deterioration.
• Avoid exposing the auto battery to extreme heat whenever possible.
• Turn off other electrical accessories (stereos, internal lights, etc.) as soon as they are no longer required to save electrical energy.

Fully charged ACDelco Batteries (OCV is >12.7) should be stored in an upright position at temperatures between 32°F and 70°F. When a battery is stored, a very slow chemical reaction takes place between the plate materials and the electrolyte, causing a slow discharge. This reaction, called a self-discharge, occurs more rapidly at higher temperatures. Therefore, it is not recommended to store next to a furnace or other heat source. If an ACDelco Battery is completely discharged, the electrolyte will freeze when stored below 30°F. To prevent electrolyte freezing and battery damage, do not store ACDelco Batteries below 30°F if their OCV is less than 12.5 volts.

Yes. It is included where the design of the starter requires a solenoid.

No, not always. However a shim may be required at the starter’s mounting surface to align the starter, so the starter drive can make appropriate contact with the flywheel. Consult a technician to determine if your starter requires a shim.

Yes. ACDelco starters are designed to withstand a wide range of temperatures.

• Check electrical connections, making sure they are kept clean.

• Make sure all connections to the battery are firmly attached and in good condition.

• Keeping all connections clean and tight can help make sure your starter will crank with full power.

• It is very important to try and keep the starter area clean from leaking car fluids or any other debris that may be near it.

Yes. ACDelco GM OE alternators are designed to withstand a wide range of temperatures.

No. Some vehicles require more amperage than others depending on the amount of electronics that need to be operated. Consult the vehicle information for proper application.

There is a cooling fan in most alternators to keep it from overheating. Making sure that the fan is clean can help the fan and alternator run properly.

It is also important that all electrical connections are kept clean and firmly attached, which can help make sure the battery is being properly charged by the alternator.

Spark plug wire sets, battery cables, and pigtail connectors.

You should always look for the Original Equipment Cable or one that is designed to the original fit, form and function.

Not always, battery cables should be inspected and changed if damaged or excessive corrosion is found.

Yes, you should only use the wire or cable that is designed to meet the original equipment fit, form and function.

Inspect the battery cables and posts for good connections and/or signs of corrosion. Clean them if needed. When working around a battery, always make sure to take the appropriate safety precautions.

WARNING: Battery posts, terminals, and related accessories contain lead, lead compounds, and cadmium chemicals known to the State of California to cause cancer and reproductive harm. Wash hands after handling!