VIDEO: Rod knock, piston slap, something else?

[tano9455]

So after months of trying to diagnose this tapping sound I am at a loss. Some shops say nothing is wrong while others say my engine will blow up any minute and others are searching but cant pin point the problem. The sound is definitely a cause for concern in my book since it is obviously not normal. The car as a whole drives great with no loss of power or [COLOR=blue !important][COLOR=blue !important]acceleration[/COLOR][/COLOR]. Really the only problem is the noise itself. This noise started maybe 5 months ago and has pretty much been the same since then. I attached the video and any help will be appreciated since I am on the verge of paying the shop to drop another engine in there. So my question is:

A. Drive it until it wont drive anymore
B. Pay to have [COLOR=blue !important][COLOR=blue !important]the [COLOR=blue !important]engine[/COLOR][/COLOR][/COLOR] broken down as far as possible to find out the cause, Ive already paid $600 in diagnosis/repair
C. Pay the $4000 to drop a new engine and other components ensuring years of worry free [COLOR=blue !important][COLOR=blue !important]vehicle[/COLOR][/COLOR] enjoyment

I know I could buy another one for around that but my car is complete and in great condition and if I did I dont want to go through the trouble of trying to sell the one I have etc. Ideas?

http://youtu.be/QdgrOENkfms

[bimmernutz]

is the noise coming from the front of the motor or back?

have you had the valves adjusted? sounds like its in the valvetrain to me..to slow to be piston slap. maybe worn cam, or eccentrics>> maybe a loose eccentric? I'd pull the valve cover and see if you have any obvious wear, and get a proper valve adjustment.

[DaveSmed]

A buddies car made almost that exact same sound. Ended up something was disintegrating in the timing area and it lunched the belt. New head, new waterpump and new belt+tensioner, it didn't make the noise anymore.


Not the most helpful info, but a start. I didn't personally work on it so I can't say for sure.

[Ceeker]

So after months of trying to diagnose this tapping sound I am at a loss. Some shops say nothing is wrong while others say my engine will blow up any minute and others are searching but cant pin point the problem. The sound is definitely a cause for concern in my book since it is obviously not normal. The car as a whole drives great with no loss of power or [COLOR=blue !important][COLOR=blue !important]acceleration[/color][/color]. Really the only problem is the noise itself. This noise started maybe 5 months ago and has pretty much been the same since then. I attached the video and any help will be appreciated since I am on the verge of paying the shop to drop another engine in there. So my question is:

A. Drive it until it wont drive anymore
B. Pay to have [COLOR=blue !important][COLOR=blue !important]the [COLOR=blue !important]engine[/color][/color][/color] broken down as far as possible to find out the cause, Ive already paid $600 in diagnosis/repair
C. Pay the $4000 to drop a new engine and other components ensuring years of worry free [COLOR=blue !important][COLOR=blue !important]vehicle[/color][/color] enjoyment

I know I could buy another one for around that but my car is complete and in great condition and if I did I dont want to go through the trouble of trying to sell the one I have etc. Ideas?

http://youtu.be/QdgrOENkfms

the bottom end on the m20 is bullet proof unless it was SEVERELY neglected and from the sounds of your story and u-tube vid I highly doubt it. I've worked on a good few cars with well over 200k miles on them and they bottom end was clean.

I would place my bet it is a loose rocker caused by eccentric loosening off.
Check your rocker to valve clearance and run the car with the cover off. Don't worry..you might get a bit of oil spitting around but at least you'll be able to see it. Do a valve adjustment and run it again with the cover off.

The previous post of the noise coming from the front end is either a timing belt tensioner failing or the free floating timing sprocket is making noise which could also be the bearing. I have this issue with one of my recent top end builds. I couldn't figure out what it was but narrowed it down to this because it was the only thing I didn't replace.

[jlevie]

A bit of investigation with a stethoscope should reveal whether the noise is from the head, block, or bottom end. That in turn will suggest the cause.

[jbshaw11]

Did you ever find out what that sound was? Mine sounds identical to your video.

[3vilE30]

That sounds quite nasty mine does make a similar sound but not quite as severe, but I know the cause of mine stupid fan keeps on hitting something happens only on the first start up. I'd say first check if your fan isnt hitting anything seems to me it only happens on engine decel?