Brake Fluid

Brake Fluid

The hydraulic brake system is the single most neglected part of your vehicle. The master cylinder, brake lines, and calipers are rarely ever inspected unless there’s a problem. And the weakest link in this critical component is arguably the brake fluid.

The primary function of brake fluid is to transmit force applied to the brake pedal to the brake pads. It is designed to withstand high boiling points and repel moisture absorption, while simultaneously inhibiting corrosion. But if the brake fluid becomes contaminated, it can compromise your automobile’s hydraulic system with potentially disastrous results. Even a small amount of water can reduce braking force – water boils at much lower temperatures than brake fluid – which is why we recommend that you flush the brake system in your car, truck, SUV or minivan at least every 24 months.

Brake fluid service Manassas, VA

Brake Fluid Fundamentals

There have been a number of technological advances in brake fluid development since the 1920s, when auto manufacturers changed from mechanical brakes to hydraulic brakes. As our cars, trucks, SUVs and minivans have become faster and heavier, manufacturers have had to keep pace with the extra demands required of hydraulic brake systems. Brake fluid is an integral part of this system and must work in extreme cold temperatures without thickening or freezing, as well as in extreme heat without boiling.

Brake fluid and brake repair in Manassas, VA.As it relates to heat, brake fluids are engineered to resist boiling for two reasons. First, boiling creates vapor and air bubbles, which are not compressible. This means that pressing on the brakes will not exert pressure on the brake pads. The second reason is that if allowed to boil, the physical and chemical properties of brake fluid changes and it will boil at lower temperatures going forward. This is why moisture contamination is so detrimental, especially with glycol-ether based brake fluids which are hygroscopic (meaning they absorb water from the atmosphere).

Moisture can access your vehicle’s hydraulic system and contaminate brake fluid in a number of ways. Microscopic water molecules can enter through the vent in the master cylinder, pores in the brake hose, seals in wheel cylinders and calipers, and simply through condensation in the air space above the fluid. Water contamination from any source will lower the boiling point, increase viscosity at low ambient temperatures, and cause corrosion of brake cylinder bores and pistons. This will ultimately compromise the efficiency and safety of a vehicle’s brake system.

Classification of Brake Fluids

Brake fluids are non-petroleum and are classified by their physical properties – they are either glycol-ether based (DOT 3, 4, and 5.1) or silicone-based fluids (DOT 5). Quality standards refer to a brake fluid’s dry and wet boiling points. The wet boiling point, which is usually much lower, refers to the fluid’s boiling point after absorbing a certain amount of moisture. Non-hygroscopic fluids (e.g. silicone/DOT 5-based formulations) are hydrophobic and can maintain an acceptable boiling point over the fluid’s service life (although at the cost of potential phase separation/water pooling and freezing/boiling in the system over time – the main reason single-phase hygroscopic fluids are used).

Brake fluid boiling points.

It should also be noted that not all brake fluids are compatible with one another. The chart below shows which are interchangeable. Just remember that when you mix brake fluids with different specifications, you risk lowering the boiling point.

Closing Thoughts and Suggestions

  • Adding brake fluid is usually not part of routine vehicle maintenance. Low brake fluid typically means that your brake pads are low and need to be changed. If you notice a sudden drop in the brake fluid level, it means there’s a problem with your brake system, or that you need to change your brakes.
  • NEVER substitute any other fluid for brake fluid.
  • Old glycol brake fluid invariably contains moisture and should never be used, as it won’t be nearly as effective as an unopened bottle.
  • Changing glycol-based brake fluids renews the anti-corrosion protection that can only be accomplished with fresh brake fluid.
  • If you are thinking about making a change from glycol-based fluid to silicone brake fluid, make it part of a total brake system overhaul.
  • Finally, recognize the important role that your hydraulic brake system plays and change the brake fluid at least every other year.

Replacing Engine Coolant

Replacing Engine Coolant

Cooling system failure is the most common cause of engine-related breakdowns. A few things that can help prevent this from happening is replacing engine coolant regularly, keeping the radiator’s coolant filled, using the right type of coolant (whether regular or the extended life kind) and knowing the precise application of coolant:water ratio. But before we continue, here’s a brief summary on how a cooling system works.


Green engine coolant being poured into engineSome of the heat created from an engine’s combustion process is expelled into the exhaust system, and any heat that was not dispersed in this way stays in the car engine. Engineers devised liquid-cooling and air-cooling, two kinds of cooling system that reduces residual heat, keeping the temperature balanced. Some older model of cars, but only very few of the modern ones, are air-cooled. The engine block has some kind of fins that convey the heat off the cylinder instead of having the fluid circulate through the engine. A powerful fan, ala 1965-1989 Porsche 911s, is often used to force the air over the fins, cooling the engine when heat transfers into the air.

A radiator is used conversely in liquid-cooled cars for heat dissipation. A type of heat exchanger, a radiator is designed to shift heat from the engine when the coolant flows through it passing to the radiator and then dissipating to the air. The coolant passes from the inlet into the outlet through some of the tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

A car can function in varying temperatures, ranging from below freezing to heat about over 100 F (38 C) . The fluid to be used in cooling the engine should have a high boiling point, as well as a very low freezing point, and should have the capability to handle a lot of the heat.

While water is an effective fluid and is most commonly used in holding heat, it shouldn’t be used by itself in the engine because it can easily be susceptive to freezing. Most cars use antifreeze, a kind of fluid consisting of ethylene glycol and water. Adding water and ethylene glycol significantly improves the freezing and boiling points of the fluids. The cooling system also uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of the water is higher in a pressure cooker, the boiling temperature of the coolant is higher if you pressurize the system.

Temp Warning LightAntifreeze serves three purposes: It helps to keep the engine from overheating; it keeps the coolant from freezing and it helps keep cooling system components from corroding. Most of the Manufactures recommend a coolant mixture of 50% antifreeze and 50% water (preferably distilled water). A 50/50 level the antifreeze will protect the system from freezing down to –34 Fahrenheit and boil over to 265 degrees. The boil over point will depend on the pressure rating of the radiation cap. The higher the pressure rating of the radiator caps the higher the boil over temp.

For those wanting an even wider range of temperature variation, higher concentrations of antifreeze can be used to protect the cooling system in extreme conditions (for this area, CoHo Auto only uses a 50/50 mix). A 70% antifreeze and 30% water solution will protect the cooling system down to –84 degrees and boil over up to 276 degrees. But using anything higher than 70/30 should never be used since antifreeze does not carry heat as well as water and a higher level of a concentration could create an overheating condition. It should also be noted that antifreeze by itself will freeze at –8 degrees.

Car RaceEthylene Glycol, however, does nothing to prevent corrosion in the system. For that reason, corrosion-inhibiting chemicals are added to the antifreeze. In conventional phosphates, antifreeze, silicates and or borates are used in combinations to form a protective coating on the cooling system surfaces. Eventually heat and other conditions dissolve these inhibitors. Once these inhibitors are gone, the electrolytic corrosion begins to accelerate very quickly. The electricity flowing through the coolant system can cause pinholes to form in the heater core and/or the radiator. The first thing the electrolysis process will attack are aluminum components of the cooling system such as cylinder heads, intake manifolds, water pumps etc. Proper servicing of the coolant and correct installation of engine grounds can greatly reduce the electrolysis process. Generally speaking, the coolant needs to be replaced about every two years. Postponing this maintenance will actually accelerate the corrosion process rather than inhibit it.

Recently, some manufacturers have been installing extended life coolant in many of their vehicles cooling systems. This type of coolant contains special additive packages that can extend coolant life up to five years or 100,000 miles. These types of coolants can be used in any vehicle application old or new where long-term protection is desired – providing that the old coolant is completely flushed out the system before you install the extended life coolant. Volvo, for instance, uses a special phosefate free coolant in its cars even though it is green like conventional coolant. But when in doubt, check with the manufacturer. We don’t guess, and you shouldn’t either.

Flushing Coolant:

As is the case when changing brake fluid, there is a difference between a “drain and fill” and a complete coolant flush. We do not advocate just draining old antifreeze and then topping off the radiator. In brief, the effects of the “new” fluid will quickly loose their effectiveness because the “old” fluid will contaminate it.

carCoHo Auto uses a state-of-the-art BG CT2 Coolant Transfusion System to completely flush old coolant from the radiator, engine block and all hoses. We first add a cooling system flush additive to the existing coolant and let it circulate throughout the entire system for about 20 minutes (the additive essentially removes tough organic deposits that result from oil fouling, grease and glycol oxidation residues). After it has circulated through the entire cooling system, the old antifreeze is then back-flushed. This is the preferred method of replacing the old fluid since it removes scale and debris not accessible when the coolant flows in the normal direction. As the old antifreeze is forced out of the cooling system, the BG machine simultaneously introduces new fluid. Once all the old antifreeze has been replaced, we reconnect the hoses and thoroughly inspect the radiator cap, drain valve, overflow reservoir, and all connections for deterioration.

As a matter of routine, CoHo Auto also adds a cooling system conditioner to the new coolant. This conditioner contains a balanced combination of pH buffering ingredients that act as acid neutralizers, thus preventing corrosive damage to cooling system components. It also contains anti-foaming agents that help prevent bubbling in the system as well as oxide-forming ingredients that prevent corrosion of aluminum surfaces such as the radiator and the cylinder heads.


As part of our customer service program, CoHo Auto inspects and tops off all vital fluids on every car we work on – including the antifreeze or replacing engine coolant id necessary. But we usually don’t test the coolant unless asked. If you don’t remember when you last changed the antifreeze, or if you recently acquired a used car with no maintenance history, then we recommend having the fluid tested with a hydrometer. Hydrometers measure the specific gravity of the coolant, or in layman’s terms, tells you how acidic the antifreeze is and if it needs to be replaced. You can stop by virtually any automotive shop to have the coolant tested. This time of year is a good time to check the condition of this vital fluid – before the heat of the summer impacts us all.



Gas Saving Myths

10 Gas-Saving Myths

By the CoHo Team

Ideological blind spots exist in every culture.  After some time, these ideas become so profoundly rooted in its psyche that they’re rarely debated and are eventually accepted as fact. Such is the case with a number of questionable and even humorous gas-saving myths.  So we decided to compile a list of the 10 most commonly held misconceptions:

Gas saving myths Manassas VA
Myth #1 – Accurate Pumps Can Only Be Found in Newer Gas Stations:
The age of the pump used in gas stations does not really matter. Each state has a Weights and Means department that is responsible for setting the standard when it comes to measurement and the quality of the fuel. Officers regularly inspect dispensers. When a dispenser passes an inspection, a sticker is placed on it; if it doesn’t, then measures will be taken to make sure that it is repaired properly.


Myth #2 – Gas is Denser in the Morning:  The time of day has absolutely no effect on the volume of gas a pump dispenses.   Density is defined as the ratio of mass to volume and while it’s true the density of a liquid will increase when temperatures drop below 40 degrees F, the gasoline being pumped out of the ground is dispensed at a uniform (ground) temperature which is independent of the ambient air temperature.  Also, gas pumps do not measure the density of fuel concentration, instead it measures the volume of gas.  In other words, you are charged not on the density, but on the volume of measurement of the liquid.

Myth #3 – Utilizing the AC Will Reduce Fuel Economy:  Your father might have told you to turn off the A/C in the past. While it is true that the A/C can eat up power, the effect is minimal when it comes to modern vehicles. Then there is the fact that when you put the windows of your car down, that would increase the drag which would take away any gain that you might have from turning off the A/C. Driving with open windows is just the same as driving with the A/C on according to Edmunds.Com.

Gas Saving Myths Empty TankMyth #4 – Avoid Filling Up When a Tanker is On Site:  There’s no arguing that when a tanker fills a station’s underground tanks, it’ll stir up any deposits at the bottom of the tank.  However, the gas station’s filters should remove any sediment well before it reaches the nozzle, meaning it will not clog your car’s gas filter.  Also and as described in Myth #1, the Department of Weights and Means not only inspects the pumps, but it periodically takes fuel quality samples for chemical analysis to ensure that the station meets state and national legal requirements.

Myth #5 – Only Buy Brand Name Gas:  It’s important to note even before addressing this myth that simply stated, octane is a measurement of how hard it is to ignite the gas and has nothing to do with the quality of the gas.  With that said, one prevailing Internet theory holds that “top tier gasoline stations” provide a higher quality gas which will yield better economy.  The fact is that most brands of gas come from the same refinery for a given region – only the company’s specific additives are different.  So check with GasBuddy.Com and buy from the least expensive source, which is usually found at an independent station.

Myth #6 – Parking in the Shade Will Stop Gas from Evaporating:  We don’t know where this one originated, but it’s totally bunk too.  Modern cars have closed loop systems so gas from a regularly used vehicle will not evaporate from the tank resulting in poorer gas mileage.

Myth #7 – Using a Higher Octane Will Improve Fuel Economy:  When deciding on what grade of gasoline to use, we recommend first reading the owner’s manual to determine if a particular grade of gasoline is “required” or if it’s “recommended.”  If it is recommended, a lower grade of gas could be used if you’re willing to accept a slight reduction in performance.  Most modern cars have a sophisticated engine management system that is the equivalent of having a laptop under the hood your car.  The EMS controls the knock sensors and will protect the engine from pre-detonation that can cause internal damage.  Therefore, we recommend using the lowest octane gas that won’t make your engine knock.

Myth #8 – Keep Wheels Aligned for Better Mileage:  It is important to regularly inspect suspension and chassis parts for damage and misalignment, and get a wheel alignment to save your tires.  In addition to just being unsafe, bent wheels, axles, bad shocks, broken springs, etc. will increase fuel consumption by creating a drag on the engine.  But while a misaligned car will ruin a perfectly good set of tires, it has minimal affect on fuel economy.

Gas Saving Myths Saving MoneyMyth #9 – Additives Don’t Work:  For the most part, this is a true statement.  However, bogus gas additives that promise phenomenal performance and improved gas mileage – often referred to as “snake oils” – should not be confused with legitimate products like Chevron’s Techron or BG’s 44K, which are designed to clean the entire fuel system.   Normal wear and tear, high temperatures and poor quality gasoline can contribute to a buildup of olefin wax, dirt, and carbon on the fuel injectors, all of which inhibit performance.  Using a proven fuel injection cleaner at least once a year will remove these deposits and help improve the efficiency of your engine.

Myth #10 – A Clean Car Will Provide Better Gas Mileage:  While the remains of a thousand bugs plastered across the front of your car isn’t very attractive, it really won’t adversely affect the aerodynamics or the fuel economy.  As an aside, by regularly cleaning your car, hopefully you will notice things like underinflated tires, dirty or clogged air filters, or other gas-robbing issues which will ultimately affect fuel economy.

Vehicle Warning Lights Explained

Your Vehicle Warning Lights

All late model cars, trucks, minivans, and SUVs are controlled by sophisticated computer systems vehicle warning lights that monitor an assortment of critical components that include, but are not limited to, the engine, drivetrain, emission’s system, electrical system, tire pressures, brakes, airbags, cooling system and suspension. These components are constantly being monitored and adjusted by the computer according to speed, load, engine temperature, gasoline quality, ambient air temperature, road conditions, etc.

When the computer “senses” the car is operating outside of standard parameters, it stores the corresponding trouble code(s) in its memory and triggers a light that appears on the dash to indicate that there is a problem. A technician then needs to connect a scanner to the car’s computer in order to retrieve the fault. This code, however, doesn’t tell exactly what’s wrong or what component is faulty; it only indicates what system is malfunctioning and where the technician needs to start looking.

Knowing what to do when a light appears on your dash can make the difference between a quick and easy diagnosis, and an expensive repair. Here are some of the more important warning lights every driver should be aware of:


Check Engine Light

This light simply means that your vehicle’s on-board computer system detected a problem and stored a fault code. In this respect, there are literally hundreds of reasons why a Check Engine light icon might appear on your dash, but if it’s there, it’s on for a reason and needs to be addressed as soon as possible. Depending on the year, make, and model, it may be related to the engine, emission’s system, or the transmission. More often than not, the fault code points to a problematic circuit, as opposed to a specific component, sometimes resulting in a lengthy process to identify, diagnose, repair. This is also why each car requires an individual approach before the root cause of the problem can be identified and fixed. To avoid potential long-term issues, we strongly recommend that you get it checked at your earliest convenience or risk damaging the engine or expensive emissions components.

Note: Leaving the gas cap off or failing to securely tighten it after filling up is the most common, and inadvertent, customer-induced issue and happens more often than you’d think.


Service Reminder Lights

Also called a Change Oil Soon or Service Soon light, these are as common as check engine lights. The computer’s on some cars track when the oil and filter needs to be changed, which is most often calculated on time and/or mileage and how your vehicle is driven. While there is a lot of debate whether it’s best to regularly change the oil and filter or rely on the computer to tell you, the system should still be reset after each oil change so the computer is reset. In this respect, each manufacturer has a specific method to reset this light; some cars require expensive diagnostic tools, and some require the technicians to simply follow a specific procedure. It’s best to call or visit a reputable shop like Coho if you have any questions.


Other Oil Lights

A steady (non-flashing) or yellow engine oil light icon typically means that there is a general fault within your engine’s oil lubrication system such as a malfunctioning oil pump. Vehicles that do not have an oil level monitoring function should have the oil checked during the next gas stop. If, however, you get a flashing or red oil warning light on your dash, pull your vehicle over immediately and shut the engine off. The best-case scenario is that your engine oil is low or there is a problem with the circuit. The worst-case scenario is you have no oil pressure and risk complete engine failure by driving the car any farther. In this case, it’s best to have the car towed to us.


SRS Light (Supplemental Restraint System)

The supplemental restraint system is your airbag system and is monitored with a variety of active, passive, or pre-safe sensors. The slightest malfunction in this system illuminates the SRS light and if activated, can mean any number of things. For instance, it could be alerting you that a broken part needs to be repaired, or is indicating that a critical circuit was temporarily disconnected (e.g., while you were installing a stereo, alarm, aftermarket seat or steering wheel). Since the SRS system is an important safety feature, it needs to be diagnosed, repaired and reset as soon as possible.


ABS Lights

This warning lamp means your antilock brake system – which keeps you from skidding out of control during braking by limiting your wheels from locking up/skidding – has detected a fault. Simply put, it temporarily disables your ABS system. You can continue driving and still brake and stop normally, but the antilock braking system will not work if you need to make a sudden panic stop or brake on wet or slick surfaces. But you should have the problem diagnosed and repaired at your earliest convenience.

Note: The ABS Warning System does not monitor disc brake pad or disc brake rotor wear. Also, the system is often integrated with traction control and stability systems, all of which are designed to keep you safe during panic stops.


Low Coolant Light

The low coolant Light will come on when the coolant drops below the sensor – generally one to two quarts; i.e., low coolant level. If this light is on, there are a number of possibilities. The most common is a coolant leak. Other common causes include: an electrical fault in the warning lamp circuit, a stuck thermostat, a cooling fan that is not working, a failed water pump, obstructions that block airflow through the radiator, a buildup of scale or sludge inside your cooling system, or overworking your engine or air conditioning system during unusually hot weather. Towing a heavy trailer or prolonged mountain driving may also cause your engine to run hotter than normal. The best course of action is to stop as soon as possible, park it in a safe place, and call for a tow truck.


Charging System

The generator (GEN) or alternator (ALT) warning light is usually an icon of a battery and means there’s a problem with the charging system. While you do not have to stop driving immediately, the time you have left is limited – possibly 30 minutes during the day, or less after dark. The reason is that your car is running exclusively off the battery, so as long as the battery lasts, you will be able to drive. However when the battery’s charge is depleted, the fuel pump, ignition and other powered systems will stop working. The cause may be a failed alternator or generator, a failed voltage regulator (if separate from the alternator), loose or corroded battery cables, or a broken or slipping drive belt. Regardless, your car needs to be inspected and repaired by a professional.


Brake Warning Light

The light usually means you forgot to release the parking brake, or your brake system has a potentially serious hydraulic problem that may make your vehicle unsafe to drive. If the light comes on only while pressing the pedal, one of the hydraulic circuits in the brake system has lost pressure because of a leak with the brake hose, at the disc brake caliper or drum brake wheel cylinder, or there’s a problem with the master brake cylinder reservoir. Many vehicles have a fluid level sensor that will also come on if the fluid level gets too low. If the pedal feels unusually soft or goes to the floor, do not drive the vehicle. Have it towed to us immediately and do NOT attempt to drive it further.