So, my 4.0 started making this knocking/rattling a few weeks ago. I can't tell what it is, it is everywhere when I try to listen. Can a water pump make that sound? Or is it more likely valvetrain related. There is an exhaust leak at the manifold, and I get an occasional misfire, but other than that there has been nothing wrong with this engine.


Second, how difficult would it be for me to convert my '89 to a COP (coil on plug) type setup? I like the simplicity of it. Much less to go wrong than in a cap and rotor setup. Some people have a very negative opinion on the COP setup, but the way I see it, newer is better. Less maintenance is required with coil on plug systems.

 

Forgot to mention!

5 speed, so it isn't the flex plate bolts. 227,500 miles on it. No oil leaks, oil level good, no noticeable changes in performance since the rattle began.

 

I'd remove the serpentine belt and start it and see if the noise is still there. Also a good time to check the water pump for looseness in the shaft and the bearings in the idler pulley and alternator.

 

x1
And if it is still making the noise, look very carefully at the balancer pulley.