Hello, Just had the head gaskets replaced on my 2007 Subaru Impreza 2.5i. Vehicle drove great for the first two days, but has now developed a ticking sound at idle/low rpms. Have checked oil... lots there. No smoke from exhaust. Ticking sound seems to be coming from the top of the engine, near the alternator. Pulleys and belts seem solid and tight, but the mechanic mentioned they would replace the timing belt. When I rev up to ~3000 rpms, the noise seems to go away (or just becomes too faint to hear over the engine... see video). I plan on taking the car back to the mechanic that did the gaskets, but they don't open until next week. I was hoping to get some ideas about the cause before then so I can decide whether to leave the car parked or if we can still use it. Video here: http://youtu.be/A99Cz3vsAN8 Thanks.
Hello and welcome to JustAnswer!
The noise is pretty bad, I wouldn't recommend driving it before it's repaired unless absolutely necessary. Is the oil light coming on? If the oil light is coming on then I wouldn't recommend running the engine at all.
The noise sounds a lot like a rod or wristpin knock where a lifter should give more of a lighter ticking type noise, but it can be a little hard to tell without hearing it in person. Valvetrain noise should appear to come from the extreme left and right sides of the engine from under the valve cover area.
One thing you can try is disabling each cylinder one at a time by unplugging the fuel injectors and see if the noise lessens, if it does then you know it's a deeper issue than a lifter. This takes away combustion pressure and will lessen or stop a wristpin and should lessen a rod knock also.
Since major engine work was just done I hope that the shop will make this right since you weren't having any problems before. If it's a bottom end issue then that wouldn't likely be related to the work they did, but if the noise is coming from the valvetrain or even foreign debris that made it into the engine (dropped bolt, etc) then it should be related.