What is wrong in a Camry engine if after being sometime on the road randomly during ignition starts but makes a rattling or clunky noise right after starting the engine but goes away once running?

Answer 1

Engines will sometimes make a little rod or lifter noise when starting if all oil has drained from either the hydraulic lifter or the crankshaft. If the engine has been running a while and the oil is hot it drains easier from the bearing "journals". Typically, if everything else is ok, that does not turn out to be a problem nor does the engine make any different noise. But once the main and/or rod bearings start to wear, the bearings will "pop" against the crankshaft until oil pressure is built up. It can take a couple seconds and sound quite bad. In fact, it isn't very good for the engine. Next time you change the oil, try a heavier grade oil. If you've been using a 5 W 15, try a 10 W 30. If you've already been using a 10 W 30, try a 15 W 40. That's just the nature of running an older engine that has a little wear on it. It's essential that you keep the oil and filter changed and the oil level up to avoid costly engine damage. I've seen engines go more than 300,00 and 400,000 miles when properly maintained. I've also seen engines fail after 30,000 because the oil was never changed. A little prevention goes a long way with engine maintenance.