How do I tell if my main or con-rod bearings are gone in a 97 Mustang 3.8L?

I have a low end clattering / rumble noise which is intermitent coming from the bottom of the engine. It does not significantly change with RPM, and is not constant. Some times it seems like the engine is going to fall apart, other times it just sounds like a loose exhaust joint.



It is almost like a diesel when it gets bad, and like an older car when it is good. No engine lights, good oil pressue, no fluctuating RPM's or shudders, stable vibrations with no crazy things going on.



I really do not want to rip things apart if I do not need too, but I am more of a transmission person and engines are not what I diagnois on a regular basis. New oil with a viscosity modifier helps so I am leaning to bad bearings. Any help would be appreciated greatly. Likewise any help with transmission problems I am glad to share.How do I tell if my main or con-rod bearings are gone in a 97 Mustang 3.8L?
Are you sure its not just detonation and/or carbon build up on the pistons? Does it do it under load or just idling? Also make sure your crank pulley is tight, a loose crank pulley can cause all kinds timing issues (its where the crankshaft position sensor is, the computer uses this signal to time the ignition). Other than that, the other information given is also good, and its really not hard to pull the oil pan, then you can get your fingers on crank and rod bearings, and even (one at a time now) take off bearing caps and inspect. You may be able to isolate it to a certain cylinder and save some time, especially if its rod bearings, by pulling a wire off a cylinder at a time and seeing which cylinder affects the noise.How do I tell if my main or con-rod bearings are gone in a 97 Mustang 3.8L?
Normally the main bearings will leak oil fluid from the front of the engine.



Check the crank play.



Pull the calve covers and see if it is getting oil..



Prob con bearings - diesel sound.
if you take an oils sample to your local Caterpillar dealer they can analyze it and tell you if it is the bearings or it might be a cracked piston..

i am surprised the oil pressure is good.

.that is why i think it may be a piston.

pulling the pan off is really not that hard..

take a look inside
it kinda sounds like the engine module is going out.it regulates the timing,and if an engine has bad timing ,it will sound like this at times.. and if you checked the oil pressure with a manual guage,instead of looking at the electric one.it's not the mains or rod.brings,the rod brings will knock all time. and you might just check the air cleaner element.if that thing is plugged up.no air to engine,and it will have all fuel and no air.justl like the old nose,when it's pluged ,just cant get a good breath.. this cleaner is one of the most neglected thing on vehicles today.
puting the vehicle in gear putting your foot on the brake a prees the gas to create a load......if its bearing you can tell as the noise will increase drasticly......sounds to me like it could possibly be another problem such as your crank....your motor shouldnt be gone unless you have dogged it like it was a cobra.....v-6 models need to be driven like they are v-6s....most teen-ages ruin these motors thinking these models are true sports cars, but they are all looks and no bottom...
A bad timing chain can make this sound also. As the chain stretches, the cam timing is off, creating interesting pressures in the cylinders. Had a Pontiac that did this once...scared me to death, until I realized what the problem was.