Subaru sounds like a diesel when starting up

starting
engines
noises

#1

My son recently bought a 97 Legacy Subaru that has the 2.5 liter engine in it. The car was recently replace with a short block before he bought it. The car’s engine sounds like a diesel engine starting up when it is cold. It take a couple of minutes of idling before the noise starts going away. I couldn’t find any record of the oil pump being replaced. Not sure if it is low oil pressure or something else. Any ideas where to start?


#2

If someone replaced the engine with a “short block” this means the original cylinder heads, along with the valve train, were re-used. The cylinder heads ecompass the entire valve train including camshafts, lifters, etc. If this is the case, hopefully the heads were resurfaced and a valve job performed (that’s a no-brainer) and the lifters should have been replaced.

The heads are overhead cam with hydraulic adjusters and it’s possible that one or more of the lifters could be faulty. I’m going on the assumption here that the noise is lifter related due to it taking a few minutes to quieten down and the noise being more of a rattling sound.

It’s doubtful that an oil pump or low oil pressure would cause this.
I would try adding a can of SeaFoam to the engine oil and see if the problem goes away. The SF could clear up a sticking or gummed up lifter but would not affect a defective one.


#3

Thanks for your reply. We couldn’t find anything in the shop receipts that the owner provided indicating that any head work was done. I guess I will assume that the lifters were not replaced. I will have my son call the shop and see if they will confirm. We will try your suggestion too.


#4

Since I can’t hear the noise, this is just a shot in the dark, but is it possible that you are hearing piston slap? Some Subaru engines are subject to this before they warm up.