Possible rod knock
 

Story time. I have a 13 FR-S with 140,000 on the engine to date. About a month and a half ago, I raced a Jaguar at around 120 for a good 3 solid hours down I-10, and when I finally slowed down, I heard a weird, throaty rattle coming from the engine. At first I thought it was related to the clutch, as it stopped when I was in neutral with my foot off the clutch. I then took my car into Toyota to have the valve-spring recall done, and got a call saying my engine has a rod knock, it has nothing to do with the clutch, and my engine needs replacing.

Now I trust this dealership, and have no reason to believe they are trying to hustle me (they know full well I know a lot more about cars than the average person, and have even told me to go away and do it myself when I brought it in for some other stuff). BUT, I am skeptical of their diagnosis, because I have heard many rod knocks before, even from other BRZs, and this sounds way less violent, is coming from the bottom of the engine not the top, and because the sound gets louder when I accelerate. I can't really get a good audio clip or video clip because the short shifter starts rattling whenever I'm going fast enough to hear it.

The sound is a deeper rattle, almost sounds like somebody gargling water, but more mechanical. It has gotten somewhat worse since it started, and it does get slightly worse when the engine warms up, but everything else points to it not being a rod knock. Any idea what else this might be, and any fixes I could attempt?

There are literally a million things it can be, so a diagnosis over the internet is going to be difficult. You could get a second opinion from another mechanic, or do an oil sample analysis which should show up bearing material in the oil if there is indeed a rod bearing issue.

If it's rod knock you'd hear it just as well racing the engine in neutral. Take a recording of that outside so we don't hear echo from the garage. Make sure the oil is up to temp.

Jaguar? I take it not a late model S Type with the supercharged V8

A rod knock is from the bottom end, not the top. They get much louder under load. A rod knock is a nice deep thunk thunk thunk, they don't always sound very metallic, and they usually sound "wet".

Basically, it sounds like you have a rod knock. But this is the internet. So it could really be anything.

https://youtu.be/aaK5e1S1Bak this was my rod knock. Spun #4 rod bearing

That’s not rod knock. That is just your flasher relay.







I kid I kid.

If it was rod knock you wouldn’t have a hard time reproducing it or hearing it. My car has had a faint rod knock like sound from the day I got the car. It’s a 2013 I picked up used with 83k. I did end up spinning a bearing and I replaced the short block but what do you know it still has this damn rod knock like sound when under light load at about 2500rpm. I’ve finally gotten used to the sound so it doesn’t trigged butterflies in my stomach anymore.