knocking/ ticking

[Joel]

🙁 I have a 2001 Subaru Forester with 219,000 miles. The engine knocks or ticks almost like a diesel around 2-3k rpms. It makes me uneasy and it’s borderline embarrassing. I take good care of it and want to solve this issue. Some may term it ‘piston slap’, but I am not sure if that’s what I am hearing. I am not sure what it is, though. And my gas mileage is not where it should be. Basically, my questions are these.

First and foremost, what the heck is it?

Should I be worried?

How can I fix it?

Is my gas mileage being affected from whatever this problem is?

Any input would be graciously accepted!

Topic

[dan]

alright bud, for me to tell you what it is i need to hear this noise, if you can provide a video that would be awesome.

a ticking noise like a loose rocker or lifter tick makes a slight ticking noise “tick tick tick tick.” this noise decreases or increases in frequency with the speed of the engine, this is commonly fixed buy replacing a collapsed lifter or a bent pushrod in the case of a pushrod engine, or making adjustments to valve clearance in the case of a engine that needs adjustment and i am sure your engine does not require adjustment…

Piston slap is a ticking or slight almost dieseling knocking noise that is heard on a cold start, common in 3100SFI engines, and i have owned a buick century that had piston slap… and i can tell you its annoying, but with piston slap sometimes its nothing to be worried about, sometimes it is, it can becaused buy a cracked piston skirt or excessive warn pistons or cylinder walls, as the piston is fired down on its compression stroke it bangs or slaps agents the side of the cylinder wall… once the engine warms up and oil flow starts a little more typically this slapping noise quiets down next to nothing or completely goes away! to fix it you would require new pistons, or hone or re sleeve the cylinders or even bore the cylinders out and put over sized pistons in.

lastly the worst… Rod Knock… to me it is the worst sound in the world, above taking your finger nails and scraping them across a chalk board, it is a “Knock Knock Knock Knock!” noise like you are describing, that almost sounds like dieseling, and this is caused buy warn out or spun rod bearings or a bent rod… what happens is as the piston is fired during the combustion stroke, excessive clearance between the crankshaft journal and the rod bearing cause too much play, and as a result when the piston is fired the rod bearing knocks agents the crank journal, sometimes there is even sort of a squeaking noise heard with the knock, and sometimes the noise is made louder and louder when you quickly blip the throttle up to 2-3grand revs… sometimes at idle is suppressed, then once you bring the revs up and put load on the engine it sounds… in bad cases the excessive clearance between bearings can cause low oil pressure, and fragments of bearing can be found settling to the bottom of your oil pan, or even in really bad cases like i have seen, the bearing can literally get so hot it can melt apart. this is the worst to fix because you will need to get the crank re surfaced or replaced, and new bearings…. some cases depending on how old the engine is its better just to get a newer or new engine.

[EricTheCarGuy]

Yea, it’s difficult to tell you what the noise is without hearing it. I’ve actually written an article on finding issues like this that you might find helpful. Here’s a link.

http://www.ericthecarguy.com/faq/diagnosing-noises-in-your-car

Perhaps give that a read and see if you can come up with a video for us in the mean time.

Good luck and keep us posted.

[Mike]

It’s unusual that an internal engine noise, caused by loose/worn parts, would occur only within a certain rpm range.

Perhaps it’s transmission related to a specific gear?

[dan]

i have seen Rod Knock show up at spacific RPMs many times, on my old Buick it would show up at about 1,500RPM.

here is a Subaru with Rod Knock

[zero]

WAY back in late 2000, early 2001 I did a couple rotations of work experience at a Toyota/Subaru dealer. They were having troubles with engines knocking in almost new cars. So it’s completely possible that there is some kind of “bottom end” knock, bottom end being things attached to the crankshaft. A lot of the Subarus from that era I’ve come across, which isn’t a whole lot, exhibit some kind of bottom end knock sound.

[Author]

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