Low End Rattle = Main Bearings?

Hi,

I am hoping some one can shed some light on my problem before I spend the time or money figuring out only to have done the wrong thing. I have a '97 with 140k on it and for the most part have had no problems. Recently (2 weeks) there has been a low end knock which seemed like an exhaust leak and was localized around the muffler area. There was a small rip/tear/hole so I chaulked it up to that and figured with the salt on the roads I would get to it in the spring. Now the loud knock has migrated to the engine bay?? I get a low knock/rattle from the bottom under load (up hills etc.) which is just spark knock because high octanes normally kill that right off fast. This new rumble knock is not the spark knock.

The noise seems to be localized around the water pump / crank area and is almost like a motorcycle rumble. Kind of like a Harley clunk. I was out yesterday and at idle the noise was like the exhaust leak and when I was doing 90 the noise was not there or so quiet that the wind noise covered it up. When I got off the highway and into stop and go it was a loud "rumble/knock" and would get louded and quieter without any pattern. I shut it down and when I did it sputtered and sounded terrible, just like a diesel with that sick run on gurggle and die kind of chug. I turned it back on and off and it was even worse! Well I said enough of this and headed home just in case. 80 miles back doing 70 and then I idled in the drive way and it sounded a lot better. Shut it off and no rumble or diesel. Turned if over 30 minutes later and shut it down again and no noise??

This morning started it and it was not bad, backed out of the garage and it sounded sick, drove 5 miles and stopped at a light, no strange noises, 2 more miles and at the next light it was back but not bad. Got to work, parked it and wound it up several times to 2500 rpm. No noises?? RPM steady, no lights, good temps and pressures. Nothing "funny".

Is it the mains, or am I crazy? If it was those I would figure I would hear the noise all the time. What about a bad plug and injector? I am at a stuck and really do not want to tear things a part as it is a daily driver and that would be a pain. I have the full shop manuals so if anybody has ideas or can give me a hint I will go from there.

Thanks!!
 
  • Sponsors (?)