I've had the infamous Honda cold engine knock for awhile, but tonight was the coldest night so far this winter and the engine knocked half way back to the house. [edit] And I did let it warm up for a bit before I drove it. [/edit] I figured it would sound "best" when I first started it up after my shift at around 7 this morning so I went ahead and recorded it.



It only does this when it's cold. Never does it in the summer.

 

Is the engine oil low? Based on your reading, what are the ideas about what causes cold-engine knock?

Use a length of rubber hose to localize the knock. Place one end at your ear and the other at various locations in the engine. Start by listening at the block versus head. If the noise specifically comes from the block, then you may have rod knock, which is caused by a bad bearing between the crankshaft and piston rod.

 

The engine oil is fine. I'm due for an oil change in around 400 miles (3000), but the level is still fine.

Using my stethoscope, I localized the noise to right around cylinders 1 and 2 on the block. Could have been one or the other, could have been both.

 

Well, that sure fits with rod knock. What type of stethoscope do you have?

Do you hear the knock when the engine is idling and does it get louder with higher rpm? Does the knock cease after the engine has warmed up in cold weather? Has the noise steadily worsened over time?

 

I have a Coreg stethoscope. It's purple and a bit cheap. Drug rep item. Don't know the brand. (Medical family. We have tons of free junk.) We also have a red one somewhere that is equally cheap.

Yes, the knock is there when the engine is idling. Yes, it gets more noticeable with higher rpms. Yes, the knock goes away completely once the engine is warm. Once its warm the car runs like a champ. (Well, a middle aged, past its prime champ with arthritis.) And yeah, it started last winter and wasnt so bad. This year it's much worse.

 

If the rod knock diagnosis is indeed correct (likely), then you may soon throw a rod through the block if the situation is not remedied.

Where have you read that engine knock is a common Civic problem?

 

oil changes should never be done at 3000 miles, that's just wasting money.

 

Well, if you have the money, it couldn't hurt.

 

Piston slap is a more likely cause. I'm not 100% sure but don't civics have Hypereutectic pistons? It does sound a bit louder on your car but when it's cold out they all seem to do it a little. I think it has something to do with the aluminum pistons and the iron block expanding and contracting at different ratios. causing a little more space between the piston and the block when they are really cold, and making the piston "slap" slightly against the block upon combustion. But once it warms up and the metals expand properly the issuse goes away.

 

I did a search and there were lots of threads about cold start knock. Apparently it applies to most Hondas. Well, most cars in general. That's what a guy said on a local forum.

Interestingly enough, the guy also mentioned piston slap as a possible diagnosis...

(I don't change oil at exactly 3000. I get it done when I have free time between 3000-5000. Religiously means that it's usually done between 3K and 4K, not 3K and 4K past due.)