Has anyone faced a similar overheating problem with a Subaru Legacy?
- Started ~9 months, 5-10k miles ago
- Enging overheating at higher engine loads (either speeds > 60mph or longer uphill stretches)
- temperature gauge goes beyond center towards the red area, ECU reading confirms temperature going beyond 105C (I never went beyond 110C before taking action)
- in such situations, reducing speed and putting heating on full blast cools down the engine in a few minutes to nominal
- behaviour strongly dependent on outside temperature,
e.g. on a cold winter day going 90-100mph is no issue,
on hot days with AC on, 45mph can already be a problem.
This makes it difficult to decide whether problem is becoming worse over time.
Problems considered so far:
- ECU reports fans switching on
- visual check confirms both fans are running
- no obvious oil in coolant
- no obvious coolant in oil
- mechanic tested twice with sniffer for exhaust in coolant (negative)
- no significant loss of coolant
- cleaned and shortened reservoir hose according to Subaru TSB -> no change
- replaced radiator cap -> no change
- mechanic replaced thermostat -> no change
- hoses appear firm and in good condition
System not properly “burped”:
- radiator flushed and refilled by mechanic -> no change.
Thermal sensor broken:
- measured engine block temperature near thermal sensor location and it is close to ECU read-out
- how to check best?
Radiator (currently my prime suspect):
- lower hose is hot
- difficult to check radiator temperature by hand since fans and AC heat exchanger block access.
- checked the temperature on the left and right edge of radiator and it appears substantially coolr at bottom end
actually it feels cooler than lower radiator hose
- how can one check whether the cooling capability of the radiator is degraded?
Crack in engine block:
- hairline crack that only opens when engine is hot?
- how can one check this?
Any recommendations or suggestions would be great.