What this sound?

2001 sonoma with 4.3. Just replaced intake manifold gaskets, water pump and took the starter out and put it back in.

Today I started it up and it made a god awful noise. My first thought was rod knock. From the examples I’ve seen rod knock is cyclical and constant. I ran it without the belt, but nothing changed.

Maybe a lifter? Starter alignment off?

The youtube link is bellow. Thanks for any help.

Sounds more like an exhaust leak but the video clip wasn’t long enough to really tell.

Maybe the heat riser passage isn’t sealed. That is a little opening between the intake ports that allows exhaust heat to warm the intake. If it isn’t sealed, you’ll hear an exhaust leak.

Thanks. I’ll get a better recording today.

My bet is something you touched,

Sounds like the timing chain is rubbing.



Is that likely to happen while changing the distributor? I did have to turn the crankshaft.

Noise, can’t tell where it is coming from… no stereo… can’t feel the vibration because I am not there… you should be able to feel where that is coming from…

Bit of a snide answer BUT, that is very likely. It didn’t do it before your work and now it does. Pretty high likelihood it is something you touched.

If you rotated the engine in reverse…you could have damaged the timing chain.

Pulling distributor does not affect timing chain crank/cam physical timing. You did not touch pushrods with intake off? Or drop anything in intake ports?

No I didn’t touch the pushrods and I’m 99% sure I didn’t drop anything. I forgot too mention that I did replace the valve cover gaskets if that makes a difference.

Remove the spark plugs and look into the cylinders to see what fell through the intake port when you had the intake manifold off.

I’ll do that when I get out of class. You’ve seen that happen before?

My first impression was an exhaust leak and repeatedly listening to the link only confirms my opinion. But noises like that have thrown me before and that’s why I own several stethoscopes with various attachments.

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Not that I know anything but I have had a few noises. First thing is to try to localize a little where it is coming from. If not from the timing chain area or deep in the engine, is anything hitting anything like the fan blades? The other thing is a leaky or misplaced plug wire can cause a tapping noise but usually with the resulting rough idle. Hard to tell from a couple thousand miles away though.

The first thing I would do is pull off the valve cover and see what tool I left in there.

I think you might be right

I’m going to pull them here in a bit