Subaru engine tapping

I have a 01 Legacy 2.5liter engine that taps when first starting and remains until warmed up. It taps louder when in gear in contrast to being in park or neutral. I bought this car with 89000 miles and only had it for three months. I’m wondering if this is a serious problem or something minor? The dealer is replacing one of the head gaskets so what else should be considered? I already spent $1000. on a catalytic converter that required replacement.

Is the dealer currently replacing the head gasket or have they done so already? O blown head gasket can make a tapping sound when it actually is air violently hissing out the hole then closes after the engine heats up and swells the hole shut. My gut leans to a stuck hydraulic lifter in the valve train. First check the oil level and make sure you are using the right viscosity 5W 10 vs 10W 30, and check the oil pressure if there is no oil pressure gauge have the dealer check it. It could possibly be a weak or bad oil pump. If the engine is worn the oil might not be able to build pressure due to internal leaks between the bearings and connecting rods. Still my gut says lifter.

It could also be excessive valve lash that tightens up due to thermal expanion of the metal when hot.
Subaru, like Honda, etc. recommends valve lash checks at a 100k miles + and this is not a very wise recommendation at all. Every 30k miles is more like it.

JMHO here, but head gaskets are generally replaced in pairs on Subarus because the odds are that if one is going the other is not far behind.

After having done a lot of Subaru head gaskets I’ve often found the “good” one was in pretty sad shape also and there is something else that needs to be considered.
Logic might dictate that a short hunk of aluminum won’t warp but after having done a lot of Subaru head gasket replacements I would estimate that the vast majority of those cylinder heads were warped beyond what Subaru recommends and that is .002 of an inch.

With .002 of an inch, head bolts will flatten them out some but when one gets into the .004 or better range there is a chance the new head gaskets might not last if this is overlooked or ignored. Hope this helps anyway.

In addition to OK4450’s comprehensive response, I want to add another possbility. The OP may be hearing piston slap, which is characteristic of some 2.5 liter Subaru engines, prior to warm-up. While it is not dangerous, it can be alarming if you don’t know what you are hearing.

I’ll second OK4450 here . . . the valve lash should be checked first . . . easy enough to do and could cause the noise on start-up, which will go away as oil pressure comes up and the parts expand upon warm-up. Even before checking the valve clearance, I think I’d check the oil level and viscosity. Do this now as you may be saving yourself $$$$ and loss of use for some time with your subie. Rocketman

The noise you hear is piston slap likely. It is not known to cause any real problem or longevity issues. Its mainly annoying. Of my family’s 10 Subaru’s, one does it and started at 80k miles. It now has 250k+ without any mechanical failure and the sound remains on cold starts.

I would have the dealer have a listen to it while its in as they can test it easily with a cold start(morning).

They haven’t done the work yet and I wanted to avoid taking things apart twice… Someone also mentioned that when the converter was replaced there could be a leak from the manifold if not replaced properlyand this could cause the noise as well. So you think the thinner oil is better. The dealer suggested 10-30W?? I will get the oil pressure checked.

Doesn’t the piston slap occurr briefly? My tapping continues until the guage gets to its normal position.

My own cars have not had this problem, but to the best of my knowledge, the noise from piston slap does usually continue until the engine is fully warmed up. Perhaps someone who has experienced it firsthand can comment.

Oil level is fine and assume there is a 10-30W in the engine.