b17 knock noise?

After replacing a leaking coolant hose and trying to get rid of air bubbles out of the cooling system, I hear this noise. My guess is a knock but after seeing other people’s videos, mine isn’t as loud as theirs. So what could this be?


Just FYI, you can’t make a fair comparison of how an engine sounds using two different cameras w. different microphones, different distance/angle from the engine, different frequency response etc. Even the reflected sound from a bare hood makes a difference compared to a hood liner.

understood. do you hear the tapping noise right before i rev it or starting to rev?

[QUOTE=iogearz;2278843]understood. do you hear the tapping noise right before i rev it or starting to rev?[/QUOTE]I hear it.

What coolant hose did you replace, and did it definitely START after that, OR, do you think you just noticed it b/c the hood was open?

Where I am going with this, if it was the top coolant hose or something in that area, is it possible you bumped the distributor and messed up the timing?

I replaced #9

Well, I haven’t been keeping up to date with my weekly checks as I used to and I just noticed it after replacing that hose. However, I do noticed when I start my car, there’s a quick SQUEAK. But I’m always in a hurry to go somewhere so I forget about it quickly after.

Any other ideas? Would you rule out knocking?

Thanks for helping so far.

Any other ideas? Would you rule out knocking?[/QUOTE]No, I would not rule it out, but there are lots of causes for an engine sounding “rough”, and people often lump them all under “knock”.

Here is another interesting youtube video I came across where someone is trying to localize it to one cylinder:
(I do NOT recommend pulling individual wires on this engine, but you can compare the sound).

I’ve done it before to find out which spark plug was dead. Thanks for the vid

maybe LMA’s

I hear two different sounds in the video. There is the tapping or muffled knocking sound.

There is also a whistle or whine as you let of the gas after revving the engine. That second sound seems familiar, like something I have heard before, but can’t remember the cause.

It sounds a bit like the sound a timing belt makes when it is rubbing on something, or too loose. Unfortunately I do not have enough experience with this car to say that definitely. Maybe welfare knows, or someone else with a good ear for engine sounds can listen to this and tell you. The sound occurs each time when you let off the gas, lasts less than a second, and changes pitch from high to low as the rpm drops.

Oh, that’s my power steering pump. Im slowly leaking fluid.

In that case, I think I might take the p/s and ac belts off before I tried to diagnose it. After that, check the timing with a timing light, and on from there…