Subaru News (BLOG)

Welcome to Subaru News, Suburb Service’s monthly blog! Subaru News is meant to educate, entertain, and engage you in monthly musings on such topics as auto mechanics, Subarus, travel, auto repair, and driving and living in the Lake Forest Park and Shoreline area. Our blogs are released on the first day of each month!

How to Service a Subaru Coolant System

Driving a Subaru is a bit like driving a tank. You have the best of all-wheel drive, incredible safety standards, high quality materials, and a comfortable amount of space. They are among the safest road vehicles in rain, ice, and snow. With proper maintenance, a Subaru will run for a lifetime. Subaru parts are durable, but like all mechanical things,they will eventually wear out. We are addressing the coolant system here. Because of the way Subaru engines are structured, performing maintenance on the coolant system can be a bit difficult but extremely necessary. Here's a run down of what it takes to service the Subaru coolant system. Understand this is a basic overview of issues and possible cures. Your car may or may not need this described work or may need more in depth diagnosis or inspection, each model of Subaru has its specialized procedures.


To start, pressure testing the cooling system is the first step. If there's a specific problem, either a leak, the sweet smell of burning coolant,or overheating, this will help us with the basic diagnosis. We add a special dye and monitor the coolant system under pressure to see if liquid is circulating as it should, the dye will show us where the leak is at. The dye is visible using a black light to pin point the leak. If coolant is not circulating properly, we may be able to locate the issue without having to dig all the way in to the water pump. We check all hoses, and the thermostat to see if they are allowing the coolant to circulate properly.

At this time we would connect our latest model of the Subaru Select Monitor, the factory diagnostic tool, to monitor the electric fan operation, known as fan rational. This monitor will tell us the constant temperatures as the motor is running. This will also tell us the exact temperatures the fans turn on and cycle off. Our monitor will show is how your fans are operating as compared to exact factory specifications all on the lap top computer in live time.

All hoses and connections will be inspected at this time. any issues, leaks or loose fitting hoses will be detected by the dye added earlier. Hoses should be replaced at specific intervals as noted by the hose and belt manufactures. We recommend hoses be replaced at 24 month intervals as do most manufacturers. We only use Subaru hoses, not cheaper fitall flex hoses. We do this as preventative maintenance rather than as reactive replacement. In winter or summer the amount of internal pressure on your cooling system hoses is greatly increased, that's when a weakened older hose will rupture and break. Of course they only give out when you can least afford the down time and inconvenience. Be proactive, not reactive.

The Head Gasket

In the event that your head gaskets have failed, we would recommend head gasket replacement and cylinder head resurfacing. We hate delivering news that head gaskets need to be replaced, but catching this problem early may save you the cost of replacing the motor. We don't have to recommend engine replacement very often, but if necessary this option will give you thousands and thousands of additional miles from your Subaru. Head gasket or motor replacement is far less expensive than purchasing a new car. If you are considering the purchase of a used car instead, you may just be buying someone else's problem child. In most cases its better to repair than replace.

The Water Pump

The water pump is located on the right hand side of your Subaru engine, behind the black plastic timing covers on the front of the motor. About the size of a grown man's fist, the water pump works incredibly hard. Everytime your motor is running so is the water pump. Under 12-16 pounds of pressure constantly forcing the coolant through the motor and radiator. The seals will occasionally fail, allowing coolant to excape and splash onto engine components, that's most damaging to the timing belt, idlers and tensioners inside the timing case. If it is leaking onto the exhaust and burning up, you may be noticing the sweet smell as you drive. You may not notice the colored fluid(coolant)on the ground under your motor because most Subaru's have a belly pan that traps and absorbs the excaping coolant. Before we replace a leaking water pump, we will pressure test the entire cooling system to see where coolant is actually leaking - that way we can alert our client if something else is going to need replacing at the same time, to properly resolve the overheating issue.

Timing Belt

A Subaru timing belt is located on the front of the motor inside the black plastic timing case, and it drives the water pump. If your motor develops either oil or coolant leaks either or both will contaminate the timing belt. Prolonged coolant exposure to the timing belt may cause it to weaken, strech or fray, causing the belt to fail. If you are driving when the belt breaks serious damage may occur to your valves and cylinder heads. This is the very reason we replace all timing belts when it has been exposed to either oil or coolant. We never use a timing belt over, once it is removed we replace it with a new one.

The radiator is the last component of the cooling system. We have already added dye to the cooling system and now we can inspect the seams and tanks with the black light to check on the integrity of the radiator. We will do an internal visual inspection of the radiator tank with our bore-a-scope. This is a very small television camera on a flexible shaft. Connected to a big screen television in our service floor,this allows us to see inside the radiator and judge the internal condition of the radiator. While this is somewhat limited due to the ability of the hand held bore-a-scope, it is part of the lengthy process we will go through. We also have the ability to flow test the radiator. This test will tell us the gallons per minute of coolant flow of the radiator. Flow is the amount of coolant that runs through the radiator under pressure while the car is being driven. We will compare the factory specifications to the flow rate of your radiator, to determine if it needs replacement.

If we have to replace the radiator we only use quality original equipment radiators. There are less expensive ones on the market but in the 24 years we have been servicing Subaru's we have found OE units are the best. they cool the best and have the best flow rate and dissipate your engines heat better.

The last and most important piece of the cooling system is the radiator cap. Subaru engineers have spent millions of dollars designing your Subaru. They provide a specific cap for your car. The genuine Subaru radiator cap controls the pressure and quantity of coolant running through the system. We ONLY use genuine Subaru radiator caps for that very reason. Yes we can buy a $4.00 cap while a Subaru cap costs $14-19 dollars. The radiator cap is really the control valve for the cooling system of your motor, would you want to take a chance with an inferior cap, we think not.

If you have any questions about Subaru coolant system services, don't hesitate to contact us. We work exclusively on Subarus - we know them inside and out. If you just want a tune-up, or you have a repair that needs doing, we would love the opportunity to work on your vehicle. Make an appointment today!