3.1L has rod knock. I have 20yrs of auto mechanic and built a few engines, but retired now.
If the knocking is from the bottom of the engine, it may be the big end bearings have worn.
Replace them or not? Difficult question.
Replacing the big end (crankshaft/piston rod) bearings may stop the knocking/rumble noise. It depends on the crankshaft..
If the crankshaft has worn oval on its journals, fitting new bearings is unlikely to achieve anything as the bearings may break up due to the oval of the crankshaft. Removing the crankshaft and checking the journals for ovality/regrinding if necessary isn't a 5 minute job.
You say you have good oil pressure. That's a positive.
Personally, in your situation, I would try an engine oil additive that's designed to eliminate knock provided the main bearings haven't worn down to base metal. It's the cheapest option.
Failing that - and again, personally - I would remove the oil pan and fit new big end bearings in the hope that it would work.
The next step, if that doesn't work - would be to remove the crankshaft and have it reground and fit oversize bearings. Or get a 2nd hand engine...
You say the car was given to you for free .. you have nothing to lose. Try an additive first.. molyslip/molybdenum or whatever...
Good luck ...
May 21, 2016 |
Cars & Trucks