Have a 3.5 engine in 05 MDX, horrible noisy, hot and cold. We can hear it in our building from out in the parking lot. First thoughts were valves, despite these usually going tight. Listened to it with stethoscope. Was quite clear in both valve covers, maybe more in the front one. Took off covers, adjusted valves, were not really out of adjustment. Looked for broken springs and felt all of the rockers in an unloaded position. Then went into timing belt and tension system. Replaced leaking oil seals and installed new tensioner. Changed oil and filter. Same noise. Used stethoscope at oil pan and transmission. Definitely loud in engine oil pan. Listened at starter as well, was much less noise. Took off oil pan, no goodies at bottom. Carefully looked at flexplate and bolts. Then looked up into cylinders and pistons. Did not notice any cracked pistons but really difficult to see even with fibre optics. Can see three cylinders with very shiny wear patterns at bottoms. Think it must be piston noise. Reassembled and tried listening under load and free. Noise definitely diminishes with load.

Customer says unit has been like this for many months. The noise is not like just one per revolution but more continuous, but not thumping like a diesel nor quite ticking like lifters or rockers. Customer says we could put in a used unit if we can find one. Seems to be a bit rare. So.. the question is could we make an Odyssey engine work? I think this MDX has the A6 engine but do not know Honda well enough. What do all my IATN Honda friends think?

David Robin
Owner
Robin's Precision Auto Care Ltd.
St Albert, Alberta, Canada