Rep Power: 0

Hi there. I have a 99 Civic LX, stock d16y7 with 180k miles. Recently the car has been sounding extra noisy during idle and acceleration. Typically when I used to start the car, it would have a little engine noise that would resolve as the engine heated. Now it doesn't seem to go away unless I've been driving for a good 15 to 20 minutes or so. It almost sounds like the engine is running a little dry, as if there isn't enough oil, if that makes sense. It sounds like a knocking sound that increases in speed and intensity as I rev the engine.

I've owned the car since 120k miles. I did a timing belt / water pump / all belt replacement at 160k miles. During that time, I redid the valve lash at that time and noticed that one of the lock screws was seized completely, though the car made no odd noises or anything. At 165k I completely replace the whole rocker arm that had the seized lock nut, which is around the time the new noise began. I have since rechecked the lash twice and everything is at spec per manual. I've changed the oil 2-3 times since with no improvement. I have checked the timing with a timing light a couple times and everything is normal.

When I replaced the rocker arm, I marked the timing belt and gear to make sure I didn't skip a tooth. That said, might I have messed up the timing? Could this be a failing oil pump that is not adequately circulating oil? When I did my timing belt, I noticed one of the engine mounts has rotted, torn rubbed... Could this be it?

The car drives fine and there's no issues with horse power. I'm just worried that I'm causing damage to the engine. Any suggestions would be amazing. I'm hoping to get another 100k out of this sucker.

 
Rep Power: 518

A cracked exhaust manifold can make a helluva lot of noise, and those engines with a cast manifold will do that. Loud snapping noises, worse during acceleration. Exhaust smell.
Noise lessens or goes away after the manifold gets hot.


Listen around with a stethoscope, see if you can narrow down the area the noise originates from.

If it is exhaust manifold noise, stick a tube or hose in your ear to use as a stethoscope. Sometimes you can feel the air movement pulses in your ear when you get the end near the source of the leak/noise.




As far as engine internal noises go, most of the time, if the engine gets quiet after it warms up then noises are considered OK, they are usually related to the piston(s) growing to fit the cylinder(s) as it heats up to operating temperature.
(Is it taking longer than usual to warm up?)

Bearing problems normally get louder after warmup (and the oil thins out), so it's probably not bearings.
You could almost always find rod bearing noise by cancelling cylinders one at a time to see if noise is affected.

HTH

 
Rep Power: 0

Thanks much for the reply. Will definitely check for an exhaust manifold crack. I've had one in a different Civic as well... they seem to like to crack right at the center.

When you say "cancelling cylinders one at a time", how would one do that? I think that's my biggest concern is bearing issues.

 
Rep Power: 518

That means killing a cylinder on purpose, usually either by disconnecting a plug wire or by disconnecting a fuel injector.


Note: If you have an ignition coil that is already old and weak, disconnecting plug wires while it's running may push it over the edge.
If this happens.....you needed a new coil anyway.....count your blessings and be damn glad you or your dearly beloved didn't get stranded on a dark highway in BFE when it crapped out.

You said the engine gets quieter after it gets warmed up?
That is not consistent with typical bearing problems IMO.


If you have noise such as piston slap or carbon buildup knock, you might be able to notice that sound change as you cancel cylinders too.
Meaning, hearing noises that change does not automatically mean they are bearing noises.
There are lots of possibilities, there's a lot going on inside a running engine.