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Blown head gasket

I have a Subaru Lecagy L wagon. Its engine temperature is fluctuating as I drive. I’m worried that it is a blown head gasket. I have already replaced the viscous coupler on the car, and I am thinking about selling it if it is a blown head gasket. I was just wondering if I could get some response about head gaskets and the reliability of a Subaru after their replaced.

Fluctuating temp, but no overheat, leads me to believe it is a bad thermostat or low coolant level. Have you checked the coolant level in the radiator and the reservoir? What levels are they at? What range does the temperature fluctuate between? Cold and warm, or warm and hot, or cold and hot?

Give the year of manufacture of this Subaru and the engine size, example 2.5 liter. Some years and engines had worse head gasket problems than others. Also the year and the general condition of the Legacy factors into whether you should fix, sell, or junk this.

Hope to help.

My first guess would be a simple sticky thermostat…assuming you’ve already checked your coolant level…have you?

Having said that, you didn’t say the year and mileage of the car, but there are a number of possible causes other than a headgasket. They include but are not limited to a partially clogged headgasket, a worn water pump, and a collapsed hose inner lining.

If it were me I would not make any assumptions. I’d go through the steps. A leakdown test of the cylinders and a new T-stat (about $20) are good steps to start with. If the leakdown test shows no headgasket problem, I’d probably perform a “thermal mapping” of the radiator. Using a pyrometer, one can “map” the radiator looking for temperature anomolies that indicate clogged tubes. If there are any, I’d put a new radiator in. The radiator can also be checked for free flow, and the water pump can be tested for flow. Hoses should just be changed if in doubt. Like the T-stat, they’re cheap.

And let’s not forget the cooling fans…are they working properly?

I’ve already had the water pump and the timing belt replaced. I added coolant to the car and its still running hot. When I put a load on the engine the temperature increases almost to the red mark. It calms when I shift into a higher gear or decrease the load on the engine.

With that additional clarification added, I’d go to the cylinder leakdown test as a first step.

Question: did this problem exist prior to having the water pump and timing belt done, or did it sudden occur after the work was performed?

If this Subaru Legacy is 1999 or less than the chance it is head gasket is not that high. The 1999 and before use a 2.2L flat four that has few issues with head gasket. Subaru is not better or worse than average car in regards to head gaskets except for the 2.5L non-turbo engine.