Loud hum from intake pipe. Possible cam timing off?

Posts specific to the 2.5 litre NA engine

Loud hum from intake pipe. Possible cam timing off?

Postby Lavalamp » Fri May 20, 2022 8:00 am


I'm looking at buying an Outback with the EJ25 DOHC, no VVT engine. There's something odd about how it sounds when it's running. I can best describe it as a 'hum' sound. I removed the pipe where it connects to the airbox, bypassing the air filter. It got WAY louder.

The owner has receipts for work done, including head gaskets, cam belt and other bits and pieces. I noticed that the pipe that runs from the driver's side rocker cover to the airbox was disconnected, as was an earth wire on that side of the engine. I reconnected them for the owner to see if they fixed the problem but didn't make any difference.

It drives OK, idles fine, although misses occasionally. I had a thought that if the standard of work evidenced by the disconnected pipe and earth wires, might also be responsible for something like the timing for one of the four cams being one tooth off, and that this incorrect cam timing might be the cause of that noise.

There's also some exhaust work that's been done, with a larger cat back system installed. The owner THINKS that one of the cats has been deleted but can't be sure. Might this exhaust mod be the cause of the sound, by somehow changing how the exhaust gas flows on these boxer engines? Or, is this normal for these engines? Can't say as how I've ever struck anything like this and I've been messing around with cars for quite a few years.

Any help or insights would be appreciated.
Posts: 3
Joined: Tue Jan 28, 2014 7:58 pm

Re: Loud hum from intake pipe. Possible cam timing off?

Postby Gyro10 » Fri May 27, 2022 1:46 pm

Check fuel consumption. If something is out it will use more fuel.
Posts: 18
Joined: Sun Jun 06, 2021 3:36 pm
Car: Liberty 2002 Manual

Return to 2.5i engine specific

Who is online

Users browsing this forum: No registered users and 0 guests