I’ve been surprised on a lot of things over the decades. It could be a rod bearing failure – but I just don’t see that that often with 318’s. If engine has been using oil and there is a possibility of engine running out of oil, then the likelihood does start shooting upwards for the rod bearing – but you know your engines oil consumption better than I do.
To be honest, I do have oil consumption issues with both of my 318’s, currently. Both cars need valve seals replaced. Let’s face it, I would say that 90%+ of all the engines FMJ’s used need valve seals (unless you have had recent engine work performed). Those rubber umbrella seals get rock hard and crumble which allows engine oil to get sucked right down the valve guides. I’ve seen them crumble when five to six years old, and most Chrysler engines need valve seals replaced after 10-15 years old. I might have to do a writeup on how to change valve seals with cylinder heads on car (not that difficult for most of us).
Every seal/gasket on my Volare wagon is leaking – which I suspect is from age. Most likely because of gasket shrinkage. Just think about a seal or gasket not leaking after 42.5 years of service (in the case of my Volare).
My Fifth Ave has an excessive blowby problem because the piston rings not sealing (or broken). The PCV valve just can’t keep up when on the gas petal is down (which is more often down than not, for city driving). I have taken the car for a couple long distance driving which helped – but not enough. Fixing valve seals (only) will not make a difference on it. It really needs an engine overhaul – but I'm not going to do that. The big blocks I’m working on will make a nice replacement.
Getting back to your issue. If engine oil level is fine and oil consumption hasn’t been an issue (or is, but you stay on top of it), then I would say it is unlikely it is a rod bearing.
There is a way to test for a rod bearing problem you can do yourself - but there is a small bit of personal risk involved. Pull the spark plug wire off each plug with engine running. Just keep the time the plug wire is off to a minimum (unburnt fuel collecting in exhaust is not good for converters). The problem you face is you could get shocked with 30 to 40,000 volts. Getting shocked will not hurt you (unless you have a pacemaker), but it will generally cause you to jerk violently. When a person jerks suddenly, you can easily get hurt (elbow contacts hood hinge, head hits hood, slip and fall backwards, etc. so just be careful. When the plug wire is removed to the cylinder with bad rod bearing the noise will immediately change to a much lower tone and resume noise level when plug wire is reattached.
If you are concerned about a rod bearing, that is a good way to check. Some shops have a special tool one can use that will disable a cylinder at a time, but I hadn’t seen one, that fits our cars, in many moons.
BudW
