My 04 Forester developed a VERY high frequency low volume scream under the hood after a recent 300 mile run through cold/icey roads. It has not abated since. It is electrical in nature as it will subside somewhat when I challenge the electrical system (such as press door locks).

 

I can hear it when the engine is off, key out. Low volume but very high pitch. Definetly coming from the engine. Diffiuclt to pinpoint due to the frequency.

 

Check engine light is not on. 137K miles. Running about 700-800 miles per week. Most of that is at highway speeds: 50-70 mph.

 

No other symptons. Runs fine.

 

Any ideas?

I can hear it when the engine is off, key out.

 

Is this only just after turning the engine off?

Or does the noise persist for a while? Overnight, for instance?

My 04 Forester developed a VERY high frequency low volume scream under the hood after a recent 300 mile run through cold/icey roads. [...]

 

I can hear it when the engine is off, key out. [...]

 

Any ideas?

I can't say for sure, but there's a common cause of that noise. It's typically due to a corroded connection at the keyless remote entry "beeper". That's located just behind the grill, where it's vulnerable to road salt, and the cold weather can make a poor connection worse due to metal contracting.

 

If you have a couple feet of rubber or plastic tubing around, you can use it as a stethescope -- put one end to your ear, and the other near the beeper. If that's the culprit, you can try unplugging the connector and cleaning the connection. If it's badly corroded, you might have to replace the beeper and/or the connector.

Is this only just after turning the engine off?

Or does the noise persist for a while? Overnight, for instance?

 

It persists. I hear it all the time now.

I can't say for sure, but there's a common cause of that noise. It's typically due to a corroded connection at the keyless remote entry "beeper". That's located just behind the grill, where it's vulnerable to road salt, and the cold weather can make a poor connection worse due to metal contracting.

 

If you have a couple feet of rubber or plastic tubing around, you can use it as a stethescope -- put one end to your ear, and the other near the beeper. If that's the culprit, you can try unplugging the connector and cleaning the connection. If it's badly corroded, you might have to replace the beeper and/or the connector.

 

I like the theory. We don't salt the roads here in the PNW but I will pursue it. All my tools are at home so I'll have to wait.

 

It does not sound like it threatens draining the battery or causing a road side failure. Thanks for the idea.