Help!- I need to identify a "knock" in my motor!

[efhughes3]

I started the car to take it for a short spin today. I've got a subtle knock seemingly from the upper LH side of the motor. It definitely is on the LH side. I can't hear anything under the motor. It is louder or more pronounced than valve noise I've heard before. I'd equate it to the sound of two marbles knocking together, like those silver metal marbles that hang in those kinetic energy conversation pieces. It does indeed change with RPM's

I did a valve adjust about 400 miles ago, and have done a DE since. I drove the car yesterday, and can't remember hearing this.

NOTE: The knock is in the upper LH side of the engine, and it doesn't sound like a rod knock in an american V8.

1. Could a valve nut have backed off and make this much noise? 2. If I pull the upper valve cover to check the valves, can I do it without draining the oil?

I'm BUMMED

[jluetjen]

I just tore apart a 2.4 TK that had a knock. The number 4 rod had noticable play when I was taking the top-end apart. When I finally go the case apart, I found that the big-end bearing had oozed out of rod and the #4 crank throw was undersized. From what I've seen, here's what I'd do to determine if you have a similar problem...

1) Drain the oil for an oil change.
2) Remove the sump plate and see if there is any junk in there. In the motor that I just took apart there was a ton of copper colored swarf collected there around the screen. If you find the same thing it is time for a motor rebuild before the problem gets worse and contaminates the rest of the engine.
3) If sump is clean, put a new gasket on and reinstall the sump plate and keep looking for the problem elsewhere.

Good Luck!

[tgarnoldo]

Had the same thing happen on my 3.2 l. #3 rod bearing was shreaded, rod and crank are scrap... Rebuilding now.

Check the sump, if it is clean, count your blessings.

Good luck,


Arnie

[efhughes3]

John:

What did your knock sound like, and could you discern where it came from?

[Tim L]

tgarnoldo

What was wrong with your crank? Where did you find a replacement and for how much?

Tim

[emarsh]

Rod knocks typically start out at high engine speeds and work their way to lower speeds and get louder as they get worse. Piston slap is most noticable at low speeds and tends to become less noticable at higher speeds. Pin knocks seem to be most noticable with the engine lightly or not at all loaded at higher speeds.

When is the noise most noticable and does it change at different engine speeds? Does it seem to be at engine speed or half engine speed?

Eric

[efhughes3]

Eric:

The knock is most noticeable at idle and low engine speed most likely due to that is when the engine is quietest. It doesn't seem to get louder or more pronounced with RPM's or load.

As I stated earlier, I can't hear it down below, only on the top LH side of the motor. I'm not sure if this would make a difference in telling if it's rod bearing, wrist pin, or piston slap.

It also sounds fairly "light", as in the two marble scenario described above.

[jluetjen]

'Sorry Ed, I never heard the engine with the knock. I bought it as a rebuildable core.

[emarsh]

Doesn't sound like a rod and if it were pistion slap I'd figure that you could hear it from below. Probably not a bad idea to pull the upper cover and see what there is to be seen.

[jriera]

Bummer!! no experience with engine knocks... but let me know if you need any help

[Bones]

This must be an American/English thing...just for future ref. you are talking about the connecting rod when you say 'rod' ?

[emarsh]

Originally posted by Bones
This must be an American/English thing...just for future ref. you are talking about the connecting rod when you say 'rod' ?

Yes.